Climate Change and Human Health - Risks and Responses

SUMMARY

WHO WMO UNEP

1900 1950 2000 2050 2100

WHO Library Cataloguing-in-Publication Data

Climate change and human health : risks and responses. Summary.

1.Climate 2.Greenhouse effect 3.Natural disasters 4.Disease transmission5.Ultraviolet rays - adverse effects 6.Risk assessment I.World Health Organization.

ISBN 92 4 159081 5 (NLM classification: WA 30)

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Climate Change and Human Health - Risks and Responses

SUMMARY

WHO WMO UNEP

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 04

SUMMARY05

Over the ages, human societies have altered local ecosystems and modified regionalclimates. Today, the human influence has attained a global scale. This reflects therecent rapid increase in population size, energy consumption, intensity of land use,international trade and travel, and other human activities. These global changes haveheightened awareness that the long-term good health of populations depends on thecontinued stability and functioning of the biosphere's ecological, physical, andsocioeconomic systems.

The world's climate system is an integral part of the complex of life-supportingprocesses. Climate and weather have always had a powerful impact on human healthand well-being. But like other large natural systems, the global climate system iscoming under pressure from human activities. Global climate change is, therefore, anewer challenge to ongoing efforts to protect human health.

This booklet is a summary of the book Climate Change and Human Health - Risksand Responses, published by WHO in collaboration with UNEP and WMO. Thecomplete volume seeks to describe the context and process of global climate change,its actual or likely impacts on health, and how human societies and their governmentsshould respond, with particular focus on the health sector.

Preface

1Global climate

change andhealth:

an old storywrit large

Climate change poses a

major, and largely

unfamiliar, challenge. This

publication describes the

process of global climate

change, its current and

future impacts on human

health, and how our societies

can lessen those adverse

impacts, via adaptation

strategies and by reducing

greenhouse gas emissions.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 0620 000 10 000 2000 1000 300 100 Now +100

Number of years before present (quasi-log scale)

5

4

3

2

1

0

-1

-2

-3

-4

-5

Av º

º

erage temperature over past 10 000 years = 15 C

Agricultureemerges

Mesopotamiaflourishes

Vikings inGreenland

HoloceneOptimum Medieval

WarmLittle ice agein Europe

(15th–18thcenturies)

1940

IPCC (2001) forecast:+2–3 C, with band

of uncertainty

End oflast

ice ageYoungerDryas

21stcentury:

very rapidrise

Tem

pera

ture

cha

nge

(ºC

)

In 1969, the Apollo moon shotprovided extraordinary photographsof this planet, suspended in space.This transformed how we thoughtabout the biosphere and its limits.Our increasing understanding ofclimate change is transforming howwe view the boundaries anddeterminants of human health.While our personal health may seemto relate mostly to prudentbehaviour, heredity, occupation,local environmental exposures, andhealth-care access, sustainedpopulation health requires the life-supporting "services" of thebiosphere. Populations of all animalspecies depend on supplies of foodand water, freedom from excessinfectious disease, and the physicalsafety and comfort conferred byclimatic stability. The world’s climatesystem is fundamental to this life-support.

Today, humankind’s activities arealtering the world’s climate. We areincreasing the atmosphericconcentration of energy-trappinggases, thereby amplifying the natural"greenhouse effect" that makes theEarth habitable. These greenhousegases (GHGs) comprise, principally,carbon dioxide (mostly from fossilfuel combustion and forest burning),plus other heat-trapping gases suchas methane (from irrigatedagriculture, animal husbandry andoil extraction), nitrous oxide andvarious human-made halocarbons.In its Third Assessment Report(2001), the UN’s IntergovernmentalPanel on Climate Change (IPCC)

stated: "There is new and strongerevidence that most of the warmingobserved over the last 50 years isattributable to human activities."1

During the twentieth century, worldaverage surface temperatureincreased by approximately 0.6ºC,and approximately two-thirds ofthat warming has occurred since1975. Climatologists forecast furtherwarming, along with changes inprecipitation and climatic variability,during the coming century andbeyond. Their forecasts are basedon increasingly sophisticated globalclimate models, applied to plausiblefuture scenarios of globalgreenhouse gas emissions that takeinto account alternative trajectoriesfor demographic, economic andtechnological changes and evolvingpatterns of governance.

The global scale of climate changediffers fundamentally from themany other familiar environmentalconcerns that refer to localisedtoxicological or microbiologicalhazards. Indeed, climate changesignifies that, today, we are alteringEarth’s biophysical and ecologicalsystems at the planetary scale – as isalso evidenced by stratosphericozone depletion, acceleratingbiodiversity losses, stresses onterrestrial and marine food-producing systems, depletion offreshwater supplies, and the globaldissemination of persistent organicpollutants.

Human societies have had longexperience of naturally-occurringclimatic vicissitudes (Figure 1.1).The ancient Egyptians,Mesopotamians, Mayans, and

Figure 1.1. Variations in Earth's average surface temperature, over the past

20,000 years

SUMMARY07

European populations (during thefour centuries of the Little Ice Age)were all affected by nature's greatclimatic cycles. More acutely,disasters and disease outbreaks haveoccurred often in response to theextremes of regional climatic cyclessuch as the El Niño SouthernOscillation (ENSO) cycle.2

The IPCC (2001) has estimatedthat the global average temperaturewill rise by several degreescentigrade during this century. Asis shown in Figure 1.2, there isunavoidable uncertainty in thisestimate, since the intricacies of theclimate system are not fullyunderstood, and humankind’sdevelopmental future cannot beforetold with certainty.

World temperature has increasedby around 0.4ºC since the 1970s,and now exceeds the upper limit ofnatural (historical) variability.Climatologists assess that most of that recent increase is due to human influence.

Potential health impacts of climate change

Change in world climate wouldinfluence the functioning of manyecosystems and their memberspecies. Likewise, there would beimpacts on human health. Some ofthese health impacts would bebeneficial. For example, milderwinters would reduce the seasonalwinter-time peak in deaths thatoccurs in temperate countries,while in currently hot regions a

further increase in temperaturesmight reduce the viability ofdisease-transmitting mosquitopopulations. Overall, however,scientists consider that most of thehealth impacts of climate changewould be adverse.

Climatic changes over recentdecades have probably alreadyaffected some health outcomes.Indeed, the World HealthOrganisation estimated, in its"World Health Report 2002", thatclimate change was estimated to beresponsible in 2000 forapproximately 2.4% of worldwidediarrhoea, and 6% of malaria insome middle-income countries.3

However, small changes, against anoisy background of ongoingchanges in other causal factors, arehard to identify. Once spotted,causal attribution is strengthened ifthere are similar observations indifferent population settings.

The first detectable changes inhuman health may well bealterations in the geographic range(latitude and altitude) andseasonality of certain infectiousdiseases – including vector-borneinfections such as malaria anddengue fever, and food-borneinfections (e.g. salmonellosis) whichpeak in the warmer months.Warmer average temperaturescombined with increased climaticvariability would alter the pattern ofexposure to thermal extremes andresultant health impacts, in bothsummer and winter. By contrast,

the public health consequences ofthe disturbance of natural andmanaged food-producingecosystems, rising sea-levels andpopulation displacement forreasons of physical hazard, landloss, economic disruption and civilstrife, may not become evident forup to several decades.

Conclusion

Unprecedentedly, today, the worldpopulation is encounteringunfamiliar human-induced changesin the lower and middleatmospheres and world-widedepletion of various other naturalsystems (e.g. soil fertility, aquifers,ocean fisheries, and biodiversity ingeneral). Beyond the earlyrecognition that such changeswould affect economic activities,infrastructure and managedecosystems, there is nowrecognition that global climatechange poses risks to humanpopulation health.

This topic is emerging as a majortheme in population healthresearch, social policy development,and advocacy. Indeed,consideration of global climatic-environmental hazards to humanhealth will become a central role inthe sustainability transition debate.

1850 1900 1950 2000 2050 2100

Year

20

19

18

17

16

15

14

13Ave

rage

tem

per

atur

e (

C)

of e

arth

’s su

rface

High

Low

Centralestimate

º

Figure 1.2 Global temperature record, since instrumental recording began in

1860, and projection to 2100, according to the IPCC

Source: reference 1

Weather is the continuouslychanging condition of theatmosphere, usually considered on atime scale that extends fromminutes to weeks. Climate is theaverage state of the loweratmosphere, and the associatedcharacteristics of the underlyingland or water, in a particular region,usually spanning at least severalyears. Climate variability is thevariation around the averageclimate, including seasonalvariations and large-scale regionalcycles in atmospheric and oceancirculations such as the El Niño/Southern Oscillation (ENSO) or theNorth Atlantic Oscillation.

Climate change occurs over decadesor longer time-scales. Until now,changes in the global climate haveoccurred naturally, across centuriesor millennia, because of continentaldrift, various astronomical cycles,variations in solar energy outputand volcanic activity. Over the pastfew decades it has becomeincreasingly apparent that humanactions are changing atmosphericcomposition, thereby causing globalclimate change.1

The Climate System

Earth’s climate is determined bycomplex interactions between theSun, oceans, atmosphere,cryosphere, land surface andbiosphere. The Sun is the principaldriving force for weather andclimate. The uneven heating of

Earth’s surface (being greater nearerthe equator) causes great convectionflows in both the atmosphere andoceans, and is thus a major cause ofwinds and ocean currents.

Five concentric layers of atmospheresurround this planet. The lowestlayer (troposphere) extends fromground level to around 10-12 kmaltitude on average. The weatherthat affects Earth’s surface developswithin the troposphere. The nextmajor layer (stratosphere) extends toabout 50 km above the surface. Theozone within the stratosphereabsorbs most of the sun’s higher-energy ultraviolet rays. Above thestratosphere are three more layers:mesosphere, thermosphere andexosphere.

Overall, these five layers of theatmosphere approximately halve theamount of incoming solar radiation that reaches Earth’s surface. Inparticular, certain "greenhouse"gases, present at traceconcentrations in the troposphere(and including water vapour, carbondioxide, nitrous oxide, methane,halocarbons, and ozone), absorbabout 17% of the solar energypassing through it. Of the solarenergy that reaches Earth’s surface,much is absorbed and reradiated aslong-wave (infrared) radiation. Someof this outgoing infrared radiation isabsorbed by greenhouse gases inthe lower atmosphere, which causesfurther warming of Earth’s surface.This raises Earth’s temperature by33ºC to its present surface averageof 15ºC. This supplementarywarming process is called "thegreenhouse effect" (Figure 2.1).

2Weather and

climate:changing

humanexposures

In discussing "climate change

and health" we must

distinguish between the

health impacts of several

meteorological exposures:

weather, climate variability

and climate change.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 08

Figure 2.1. The greenhouse effect (reference 2)

Solar radiationpasses through

the clearatmosphere.

Some solarradiation is

reflected by theEarth and theatmosphere.

SUN

Most radiation is absorbed by the

Earth’s surface and warms it.

Infrared radiation isemitted from theEarth’s surface.

Some of the infrared radiationpasses through the

atmosphere, and some isabsorbed and re-emitted in all

directions by greenhouse gasmolecules. The effect of this is

to warm the Earth’s surfaceand lower the atmosphere.

ATMOSPHERE

EARTH

SUMMARY09

Greenhouse Gases

Human-induced increases in theatmospheric concentration ofGHGs are amplifying thegreenhouse effect. In recent times,the great increase in fossil fuelburning, agricultural activity andseveral other economic activitieshas greatly augmented greenhousegas emissions. The atmosphereconcentration of carbon dioxide has increased by one-third since theinception of the industrialrevolution (Figure 2.2).

Table 2.1 provides examples ofseveral greenhouse gases andsummarizes their 1790 and 1998

concentrations, their rate of changeover the period 1990 to 1999 andtheir atmospheric lifetime. Theatmospheric lifetime is highlyrelevant to policy makers becausethe emission of gases with longlifetimes entails a quasi-irreversiblecommitment to sustained climatechange over decades or centuries.

Studying the Health Impacts ofClimate

Studying the impact of weatherevents and climate variability onhuman health requires appropriatespecification of the meteorological"exposure". Weather and climate

can each be summarized overvarious spatial and temporal scales.The appropriate scale of analysis,and the choice of any lag periodbetween exposure and effect, willdepend on the anticipated nature ofthe relationship. Much of theresearch requires long-term datasets with information aboutweather/climate and healthoutcome on the same spatial andtemporal scales. For example, it hasproven difficult to assess howclimate variability and change hasinfluenced the recent spread ofmalaria in African highlandsbecause the appropriate health,weather and other relevant data(e.g. land use change) have not

been collected in the same locationsand on the same scales.

In all such research, there is a needto accommodate the several typesof uncertainty that are inherent inthese studies. Predictions abouthow complex systems such asregional climate systems andclimate-dependent ecosystems willrespond when pushed beyondcritical limits are necessarilyuncertain. Likewise, there areuncertainties about the futurecharacteristics, behaviours andcoping capacity of humanpopulations.

Figure 2.2. Atmospheric concentration of CO2 from year 1000 to year 2000

1000

Ice core data

1200 1400 1600 1800 2000

1000

900

800

700

600

500

400

300

200

100

0

Projections

Directmeasurements

ppm

high

medium

low

2100

1000

900

800

700

600

500

400

300

200

100

0

ppm

Source: Watson et al, 2001.3 (The data are from polar ice cores and from direct atmosphericmeasurements over the past few decades. Projections of CO2 concentrations for the period 2000 to2100 are based on the IPCC’s six illustrative SRES scenarios and IS92a.)

Table 2.1: Examples of greenhouse gases that are affected by human activities

CO2 CH4 N2O CFC-11 HFC-23 CF4

(Carbon (Methane) (Nitrous (chloroflu- Hydrofluoro- (Perfluorom-

Dioxide) Oxide) oro-carbon-11 carbon-23) ethane)

Pre-industrial ~280 ~700 ~270 Zero Zero 40 concentration ppm ppb ppb ppt

Concentration 365 1745 314 268 ppt 14 ppt 80 pptin 1998 ppm ppb ppb

Rate of 1.5 7.0 0.8 -1.4 0.55 1 Concentration ppm/yra ppb/yra ppb/yr ppt/yr ppt/yr ppt/yrchange b

Atmospheric 5-200 12 114 45 260 >50,000 lifetime yrc yrd yrd yr yr yr

a Rate has fluctuated between 0.9 ppm/yr and 2.8 ppm/yr for CO2 and between 0 and 13 ppb/yr for CH4 over the period 1990 to 1999.

b Rate is calculated over the period 1990 to 1999.c No single lifetime can be defined for CO2 because of the different rates of uptake by different

removal processes.d This lifetime has been defined as an "adjustment time" that takes into account the indirect effect

of the gas on its own residence time.ppm: parts per million. ppb: parts per billion. ppt: parts per trillion.

Sour

ce: r

efer

ence

1

3International

consensus onthe science of

climate andhealth: the

IPCC ThirdAssessment

Report Through recent research, our

understanding of

climate-health relationships

has increased rapidly, largely

due to the stimulus of the

IPCC and other policy-related

reviews at regional and

national levels.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 10

In the early 1990s there was littleawareness of the health risks posedby global climate change. Thisreflected a general lack ofunderstanding of how thedisruption of biophysical andecological systems might affect thelonger-term wellbeing and health ofpopulations. There was littleawareness among natural scientiststhat changes in their particularobjects of study – climaticconditions, biodiversity stocks,ecosystem productivity, and so on –were of potential importance tohuman health. Indeed, this was wellreflected in the meagre reference tohealth risks in the first major reportof the UN’s IntergovernmentalPanel on Climate Change (IPCC),published in 1991.

Subsequently, the situation haschanged. The IPCC SecondAssessment Report (1996) devoteda full chapter to the potential risksto health. The Third AssessmentReport (2001) did likewise, this timeincluding discussion of some earlyevidence of actual health impacts,along with assessing potentialfuture health effects. That reportalso highlighted the anticipatedhealth impacts by major geographicregion.

The IPCC was established byWMO and UNEP in 1988. TheIPCC’s role is to assess the world’spublished scientific literature on: (i) how human-induced changes tothe lower atmosphere, via theemission of greenhouse gases, have

influenced and are likely toinfluence world climatic patterns;(ii) how this does, and in futurewould, affect various systems andprocesses important to humansocieties; and (iii) the range ofeconomic and social responseoptions available to policy-makersto avert climate change and tolessen its impacts.

The IPCC’s work has been done bymany hundreds of scientists, world-wide. On a five-yearly basis,national governments proposescientists with expertise in the manytopic areas included within thiscomprehensive review task. Topicreview teams are then chosen toensure proper geographic anddisciplinary representation.Excluding the small number ofscientists working at IPCCsecretariat level, all this work ofreviewing, discussing and writing iscontributed voluntarily.

The IPCC’s draft assessments aresubject to a series of internal andexternal peer-review processes.The final wording of IPCC reportsummaries are subject, via formalinternational conferences, todetailed and systematic scrutiny bygovernments.

The IPCC’s assessment of healthimpacts

In its Third Assessment Report theIPCC concluded that: “Overall, climate change is projected to

increase threats to human health,particularly in lower income populations,predominantly withintropical/subtropical countries.”

That summary went on tostate:“Climate change can affecthuman health directly (e.g., impactsof thermal stress, death/injury infloods and storms) and indirectlythrough changes in the ranges ofdisease vectors (e.g., mosquitoes),water-borne pathogens, waterquality, air quality, and foodavailability and quality. The actualhealth impacts will be stronglyinfluenced by local environmentalconditions and socio-economiccircumstances, and by the range ofsocial, institutional, technological,and behavioural adaptations takento reduce the full range of threats tohealth.”1

Broadly, a change in climaticconditions can have three kinds ofhealth impacts:

• Those that are relatively direct, usually caused by weather extremes.

• The health consequences of various processes of environmental change and ecological disruption that occur in response to climate change.

• The diverse health consequences – traumatic, infectious, nutritional, psychological and other – that occur in demoralizedand displaced populations in the wake of climate-induced economic dislocation,

SUMMARY11

environmental decline, and conflict situations.

These several pathways areillustrated in Figure 3.1.

Our understanding of the impactsof climate change and variability onhuman health has increasedconsiderably in recent years.However, several basic issuescomplicate this task:

• Climatic influences on health are often modulated by interactions with other ecological processes, social conditions, and adaptive policies. In seeking explanations, a balance must be sought between complexity and simplicity.

• There are many sources of scientific and contextual

The IPCC concluded, with highconfidence, that climate changewould cause increased heat-relatedmortality and morbidity, decreasedcold-related mortality in temperatecountries, greater frequency ofinfectious disease epidemicsfollowing floods and storms, andsubstantial health effects followingpopulation displacement from sealevel rise and increased stormactivity.

For each potential impact of climatechange, certain groups will beparticularly vulnerable to diseaseand injury. The vulnerability of apopulation depends on factors suchas population density, level ofeconomic development, foodavailability, income level anddistribution, local environmentalconditions, pre-existing healthstatus, and the quality andavailability of public health care.5

For instance, those most at risk ofbeing harmed by thermal extremesinclude socially isolated citydwellers, the elderly and the poor.Populations living at the presentmargins of malaria and dengue,without effective primary healthcare, will be the most susceptible ifthese diseases expand theirgeographic range in a warmerworld.

The IPCC report also underscoresthat our understanding of the linksbetween climate, climate changeand human health has increasedconsiderably over the last ten years.

However, there are still many gapsin knowledge about likely futurepatterns of exposure to climatic-environmental changes, and aboutthe vulnerability and adaptability ofphysical, ecological and socialsystems to such climate change.

Health effects

Temperature-relatedillness and death

Extreme weather-related health effects

Air pollution-relatedhealth effects

Water and food-borne diseases

Vector-borne androdent-borne diseases

Effects of food andwater shortages

Mental, nutritional,infectious and other

health effects

CLIMATECHANGE

Modulatinginfluences

Humanexposures

Regional weatherchanges

• Heatwaves• Extreme weather

• Temperature• Precipitation

Contaminationpathways

Transmissiondynamics

Changes inagro-ecosystems,

hydrology

Socioeconomicand demographic

disruption

uncertainty. The IPCC has therefore sought to formalise the assessment of level of confidence attaching to each health impact statement.

• Climate change is one of several concurrent global environmental changes that simultaneously affect human health – often interactively.3 A good example is the transmission of vector-borne infectious diseases, which is jointly affected by climatic conditions, population movement, forest clearance and land-use patterns, biodiversity losses (e.g., natural predators of mosquitoes), freshwater surface configurations, and human population density.4

Figure 3.1. Pathways by which climate change affects human health (modified

from reference 2)

4Looking tothe Future:

Challenges forScientistsStudyingClimate

Change andHealth

Research on climate change

and health spans basic

studies of causal

relationships, risk assessment,

evaluation of population

vulnerability and adaptive

capacity, and the evaluation

of intervention policies

(Figure 4.1).

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 12

The challenges in identifying,quantifying and predicting thehealth impacts of climate changeentail issues of scale, “exposure”specification, and the elaboration ofoften complex and indirect causalpathways.1 First, the geographicscale of climate-related healthimpacts and the typically wide time-spans are unfamiliar to mostresearchers. Epidemiologists usuallystudy problems that aregeographically localised, haverelatively rapid onset, and directlyaffect health. The individual isusually the natural unit ofobservation.

Second, the “exposure” variable –comprising weather, climatevariability and climate trends –poses difficulties. There is noobvious "unexposed" group to actas baseline for comparison. Indeed,because there is little difference in

weather/climate exposures betweenindividuals in the same geographiclocale, comparing sets of personswith different “exposures” is usuallyprecluded. Rather, wholecommunities or populations mustbe compared – and, in so doing,attention must be paid to inter-community differences invulnerability. For example, theexcess death rate during the severe1995 Chicago heatwave variedgreatly between neighbourhoodsbecause of differences in factorssuch as housing quality andcommunity cohesion.

Third, some health impacts occurvia indirect and complex pathways.For example, the effects oftemperature extremes on health aredirect. In contrast, complex changesin ecosystem composition andfunctioning help mediate theimpact of climatic change on

transmission of vector-borneinfectious diseases and onagricultural productivity.

A final challenge is the need toestimate health risks in relation tofuture climatic-environmentalscenarios. Unlike most recognizedenvironmental health hazards,much of the anticipated risk fromglobal climate change lies years todecades into the future.

Research strategies and tasks

While much health-impactsresearch focuses on future risk,empirical studies referring to therecent past and present areimportant. Standard observationalepidemiological methods canilluminate the health consequencesof local climatic trends in pastdecades – if the relevant data-setsexist. Such information enhancesour capacity subsequently toestimate future impacts.Meanwhile, we should also seekevidence of the early health effectsof climate change, since change hasbeen underway for several decades.

The health impacts of futureclimate change, including changesin climatic variability, can beestimated in two main ways. First,we can extrapolate from analoguestudies that treat recent climaticvariability as a foretaste of climatechange. Second, we can usepredictive computer models basedon existing knowledge about

Public health research

Baseline relationships• Dose-response

Evidence of early effects,including monitoring

Scenario modelling

Adaptation options

Co-benefits ofmitigation

Assessments of• vulnerability• adaptation

Questions to address?Information sufficient?

Communication to• Policy-makers• Stakeholders

• Other researchers

Other disciplines

Policy formulation process

Figure 4.1 Tasks for public health science

SUMMARY13

relationships between climaticconditions and health outcomes.Such models cannot predict exactlywhat will happen, but they indicatewhat would occur if certain futureclimatic (and other specified)conditions were fulfilled.

The five main tasks for researchersare:

1. Establishing baselinerelationships between weatherand healthThere are many unresolved

questions about the sensitivity ofparticular health outcomes toweather, climate variability, andclimate-induced environmentalchanges. For example, the majorpathogens that cause acutegastroenteritis multiply faster inwarmer conditions. Do higherambient temperatures cause moreillness? Apparently so – as isevident from the monthlysalmonella infection count in NewZealand in relation to averagemonthly temperature (Figure 4.2).

2. Seeking evidence of earlyeffects of climate change There have been many, coherent,observations on physical andecological changes attributable torecent global warming – but fewindications yet of human healtheffects. Amongst these are changingpatterns of infectious disease (suchas tick-borne encephalitis2 andcholera3). Health researchers mustallow for the fact that humans havemany coping strategies, ranging

from planting shade trees, tochanging work-hours, to installingair-conditioning.

The challenge is to pick thesettings, populations and healthoutcomes with the best chance of:(i) detecting changes, and (ii)attributing some portion of these toclimate change. Impacts are likelyto be clearest where the exposure-outcome gradient is steepest, thelocal population’s adaptive capacityis weakest, and when there are fewcompeting explanations forobserved relationships.

3. Scenario-based predictivemodelsUnlike most other environmentalexposures, we know that the world’sclimate will continue to change forat least several decades.Climatologists now can satisfactorilymodel the climatic consequences of

future scenarios of greenhouse gasemissions. By linking these climatescenarios with health impactmodels, we can estimate the likelyimpacts on health.

Some health impacts are readilyquantified (deaths due to stormsand floods for instance); others aremore difficult to quantify (e.g., thehealth consequences of foodinsecurity). We need models withsufficient representation of themulti-faceted future world toprovide useful, or credible,estimates of future health risks.Where possible, we should use ahigh level of “integration” toachieve realistic modelled forecastsof impact in a world that will haveundergone various otherdemographic, economic,technological and social changes.

4. Evaluating adaptation optionsAdaptation means taking steps toreduce the potential adverse impactof environmental change. (Seesection 11 below).

5. Estimating the co-incidentalbenefits and costs of mitigationand adaptation. Steps to reduce GHG emissions(mitigation) or to lessen healthimpacts (adaptation) may have othercoincidental health effects. Forexample, promotion of publictransport relative to private vehiclesmay not only reduce CO2 emissions,but also improve public health inthe near-term by reducing airpollution and road traffic injuriesand increasing physical activity.Information about these "ancillary"costs and benefits is important forpolicy-makers. Note, however, forimpacts that are either deferred intime or that extend into the distantfuture, the costing is notstraightforward.

General issues concerninguncertainty

Researchers should describe,communicate and explain allrelevant uncertainties. This gives thedecision-maker important insightinto the conditions needed for aparticular outcome to occur. Sinceenvironmental risk perception varieswith culture, values and social status,“stakeholders” should assist both inshaping the assessment questionsand in interpreting the risk.

Average monthly temperature (Centigrade)

0

50

100

150

200

250

300

350

400

10 11 12 13 14 15 16 17 18 19 20

Num

ber

of S

alm

onel

la c

ases

/mon

th

Figure 4.2 Relationship between mean temperature and monthly reports of

Salmonella cases in New Zealand 1965 - 2000

5Health

impacts ofclimate

extremesClimatic factors are an

important determinant of

various vector-borne diseases,

many enteric illnesses and

certain water-related

diseases. Relationships

between year-to-year

variations in climate and

infectious diseases are most

evident where climate

variations are marked, and in

vulnerable populations. The

El Niño phenomenon

provides an analogue for

understanding the future

impacts of global climate

change on infectious

diseases.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 14

Extreme climate events are expectedto become more frequent withclimate change. These disruptiveevents have their greatest impact inpoor countries. The two categoriesof climatic extremes are:

• Simple extremes of climatic statistical ranges, such as very lowor very high temperatures

• Complex events: droughts, floods, or hurricanes

The Pacific-based El Niño-Southern Oscillation (ENSO), anapproximately semi-decadal cycle,influences much of the world’sregional weather patterns. Climatechange is likely to increase thefrequency and/or amplitude of ElNiño.1 It illustrates well howclimatic extremes can affect humanhealth.

Climate, weather, El Niño andinfectious diseases

Both temperature and surface waterhave important influences on theinsect vectors of vector-borneinfectious disease. Of particularimportance are vector mosquitospecies, which spread malaria andviral diseases such as dengue andyellow fever. Mosquitoes needaccess to stagnant water in order tobreed, and the adults need humidconditions for viability. Warmertemperatures enhance vectorbreeding and reduce the pathogen’smaturation period within the vector

organism. However, very hot anddry conditions can reducemosquito survival.

Malaria, today, is mostly confinedto tropical and subtropical regions.The disease’s sensitivity to climateis illustrated by desert and highlandfringe areas where highertemperatures and/or rainfallassociated with El Niño mayincrease transmission of malaria2.In areas of unstable malaria indeveloping countries, populationslack protective immunity and areprone to epidemics when weatherconditions facilitate transmission.

Dengue is the most importantarboviral disease of humans,occurring in tropical and subtropicalregions, particularly in urbansettings. ENSO affects dengueoccurrence by causing changes inhousehold water storage practicesand in surface water pooling.Between 1970 and 1995, the annualnumber of dengue epidemics in theSouth Pacific was positivelycorrelated with La Niña conditions(i.e., warmer and wetter).3

Rodents, which proliferate intemperate regions following mildwet winters, act as reservoirs forvarious diseases. Certain rodent-borne diseases are associated withflooding, including leptospirosis,tularaemia and viral haemorrhagicdiseases. Other diseases associatedwith rodents and ticks, and whichshow associations with climaticvariability, include Lyme disease,

tick borne encephalitis, andhantavirus pulmonary syndrome.

Many diarrhoeal diseases varyseasonally, suggesting sensitivity toclimate. In the tropics diarrhoealdiseases typically peak during therainy season. Both floods anddroughts increase the risk ofdiarrhoeal diseases. Major causes ofdiarrhoea linked to heavy rainfalland contaminated water suppliesare: cholera, cryptosporidium, E.coliinfection, giardia, shigella, typhoid,and viruses such as hepatitis A.

Temperature extremes: heatwavesand cold spells

Extremes of temperature can kill.In many temperate countries, deathrates during the winter season are10-25% higher than those in thesummer. In July 1995, a heatwavein Chicago, US, caused 514 heat-related deaths (12 per 100,000population) and 3300 excessemergency admissions.

Most of the excess deaths duringtimes of thermal extreme are inpersons with preexisting disease,especially cardiovascular andrespiratory disease. The very old,the very young and the frail aremost susceptible. In terms of theamount of life lost, the mortalityimpact of an acute event such as aheatwave is uncertain because anunknown proportion of deaths arein susceptible persons who wouldhave died in the very near future.

SUMMARY15

Global climate change will beaccompanied by an increasedfrequency and intensity ofheatwaves, as well as warmersummers and milder winters.Predictive modelling studies, usingclimate scenarios, have estimatedfuture temperature-relatedmortality. For example, the annualexcess summer-time mortalityattributable to climate change, by2050, is estimated to increaseseveral-fold, to between 500-1000for New York and 100-250 forDetroit, assuming populationacclimatisation (physiological,infrastructural and behavioural)4

Without acclimatisation the impactswould be higher.

The extent of winter-associatedmortality directly attributable tostressful weather is less easy todetermine. In temperate countriesundergoing climate change, areduction in winter deaths mayoutnumber the increase in summerdeaths. Without better data, the netimpact on annual mortality isdifficult to estimate. Further, it willvary between populations.

Natural disasters

The effects of weather disasters(droughts, floods, storms and bush-fires) on health are difficult toquantify, because secondary anddelayed consequences are poorlyreported. El Niño events influencethe annual toll of persons affectedby natural disasters.5 Globally,

disasters triggered by droughtsoccur especially during the yearafter the onset of El Niño.

Globally, natural disaster impactshave been increasing. An analysisby the reinsurance companyMunich Re found a tripling in thenumber of natural catastrophes inthe last ten years, compared to the1960s. This reflects global trends inpopulation vulnerability more thanan increased frequency of extremeclimatic events. Developingcountries are poorly equipped todeal with weather extremes, even asthe population concentrationincreases in high-risk areas likecoastal zones and cities. Hence, thenumber of people killed, injured ormade homeless by natural disastershas been increasing rapidly.

Table 5.1. shows the numbers ofevents, deaths and people affectedby extreme climatic and weatherevents in the past two decades, bygeographic region.

Conclusion

The increasing trend in naturaldisasters is partly due to betterreporting, partly due to increasingpopulation vulnerability, and mayinclude a contribution fromongoing global climate change.Especially in poor countries, theimpacts of major vector-bornediseases and disasters can limit oreven reverse improvements in socialdevelopment. Even underfavourable conditions recovery frommajor disasters can take decades.

Short-range climatic forecasts mayhelp reduce health impacts. Butearly warning systems must alsoincorporate monitoring andsurveillance, linked to adequateresponse capacities. Focusingattention on current extreme eventsmay also help countries to developbetter means of dealing with thelonger-term impacts of globalclimate change, although thiscapacity may itself decline because

Table 5.1. Numbers of extreme climatic/weather events, people killed and affected, by region of the world, in the 1980sand 1990s

1980s 1990sEvents Killed Affected Events Killed Affected

(thousands) (millions) (thousands) (millions)

Africa 243 417 137.8 247 10 104.3

Eastern Europe 66 2 0.1 150 5 12.4

Eastern Mediterranean 94 162 17.8 139 14 36.1

Latin America and Caribbean 265 12 54.1 298 59 30.7

South East Asia 242 54 850.5 286 458 427.4

Western Pacific 375 36 273.1 381 48 1,199.8

Developed 563 10 2.8 577 6 40.8

Total 1,848 692 1,336 2,078 601 1,851

of cumulative climate change. Forexample, increased food importsmight prevent hunger and diseaseduring occasional drought, butpoor, food-insecure, countries maybe unable to afford such measuresindefinitely in response to gradualyear-by-year drying.

6Climate

Change AndInfectious

Diseases Today, worldwide, there is an

apparent increase in many

infectious diseases, including

some newly-circulating ones

(HIV/AIDS, hantavirus,

hepatitis C, SARS, etc.).

This reflects the combined

impacts of rapid

demographic, environmental,

social, technological and

other changes in our ways-

of-living. Climate change will

also affect infectious disease

occurrence.1

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 16

Humans have known that climaticconditions affect epidemic diseasesfrom long before the role ofinfectious agents was discovered,late in the nineteenth century.Roman aristocrats retreated to hillresorts each summer to avoidmalaria. South Asians learnt earlythat, in high summer, stronglycurried foods were less likely tocause diarrhoea.

Infectious agents vary greatly insize, type and mode oftransmission. There are viruses,bacteria, protozoa and multicellularparasites. Those microbes thatcause “anthroponoses” haveadapted, via evolution, to thehuman species as their primary,usually exclusive, host. In contrast,non-human species are the naturalreservoir for those infectious agentsthat cause “zoonoses” (Fig 6.1).There are directly transmittedanthroponoses (such as TB,HIV/AIDS, and measles) andzoonoses (e.g., rabies). There arealso indirectly-transmitted, vector-borne, anthroponoses (e.g., malaria,dengue fever, yellow fever) andzoonoses (e.g. bubonic plague andLyme disease).

Vector-borne and water-borne diseases Important determinants of vector-borne disease transmission include:(i) vector survival and reproduction,(ii) the vector’s biting rate, and (iii)the pathogen’s incubation ratewithin the vector organism. Vectors,pathogens and hosts each surviveand reproduce within a range of

optimal climatic conditions:temperature and precipitation arethe most important, while sea levelelevation, wind, and daylightduration are also important.

Human exposure to waterborneinfections occurs by contact withcontaminated drinking water,recreational water, or food. Thismay result from human actions,such as improper disposal ofsewage wastes, or be due to weatherevents. Rainfall can influence thetransport and dissemination ofinfectious agents, while temperatureaffects their growth and survival.

Observed and predictedclimate/infectious disease links

There are three categories ofresearch into the linkages betweenclimatic conditions and infectiousdisease transmission. The firstexamines evidence from the recentpast of associations between climate

variability and infectious diseaseoccurrence. The second looks atearly indicators of already-emerginginfectious disease impacts of long-term climate change. The third usesthe above evidence to createpredictive models to estimate thefuture burden of infectious diseaseunder projected climate changescenarios.

Historical EvidenceThere is much evidence ofassociations between climaticconditions and infectious diseases.Malaria is of great public healthconcern, and seems likely to be thevector-borne disease most sensitiveto long-term climate change.Malaria varies seasonally in highlyendemic areas. The link betweenmalaria and extreme climatic eventshas long been studied in India, forexample. Early last century, theriver-irrigated Punjab regionexperienced periodic malariaepidemics. Excessive monsoonrainfall and high humidity was

Figure 6.1: Four main types of transmission cycle for infectious diseases (reference 5)

AnthrAnthroponosesoponoses

HUMANS

HUMANS

ANIMALS

ANIMALS

HUMANS

Zoonoses

Direct transmission

HUMANS

HUMANS

ANIMALS

ANIMALS

Indirect transmission

VECTOR/VEHICLEVECTOR/VEHICLE

VECTOR/VEHICLEVECTOR/VEHICLE

HUMANS

SUMMARY17

identified early on as a majorinfluence, enhancing mosquitobreeding and survival. Recentanalyses have shown that themalaria epidemic risk increasesaround five-fold in the year after anEl Niño event.2

Early impacts of climate changeThese include several infectiousdiseases, health impacts oftemperature extremes and impactsof extreme climatic and weather events (described in section 5 above).

Predictive Modeling The main types of models used to

forecast future climatic influenceson infectious diseases includestatistical, process-based, andlandscape-based models.3 Thesethree types of model addresssomewhat different questions.

Statistical models require, first, thederivation of a statistical (empirical)relationship between the currentgeographic distribution of thedisease and the current location-specific climatic conditions. Thisdescribes the climatic influence onthe actual distribution of thedisease, given prevailing levels ofhuman intervention (diseasecontrol, environmental

management, etc.). By thenapplying this statistical equation tofuture climate scenarios, the actualdistribution of the disease in futureis estimated, assuming unchangedlevels of human intervention withinany particular climatic zone.Thesemodels have been applied toclimate change impacts on malaria,dengue fever and, within the USA,encephalitis. For malaria somemodels have shown net increases inmalaria over the coming half-century, and others little change.

Process-based (mathematical)models use equations that expressthe scientifically documentedrelationship between climaticvariables and biological parameters– e.g., vector breeding, survival, andbiting rates, and parasite incubationrates. In their simplest form, suchmodels express, via a set ofequations, how a givenconfiguration of climate variableswould affect vector and parasitebiology and, therefore, diseasetransmission. Such models addressthe question: “If climatic conditionsalone change, how would thischange the potential transmissionof the disease?” Using morecomplex “horizontal integration”,the conditioning effects of humaninterventions and social contextscan also be incorporated.

This modelling method has beenused particularly for malaria anddengue fever.4 The malariamodelling shows that smalltemperature increases can greatly

affect transmission potential.Globally, temperature increases of2-3ºC would increase the numberof people who, in climatic terms,are at risk of malaria by around 3-5%, i.e. several hundred million.Further, the seasonal duration ofmalaria would increase in manycurrently endemic areas.

Since climate also acts byinfluencing habitats, landscape-based modeling is also useful. Thisentails combining the climate-basedmodels described above with therapidly-developing use of spatialanalytical methods, to study theeffects of both climatic and otherenvironmental factors (e.g. differentvegetation types – often measured,in the model development stage, byground-based or remote sensors).This type of modelling has beenapplied to estimate how futureclimate-induced changes in groundcover and surface water in Africawould affect mosquitoes and tsetseflies and, hence, malaria andAfrican sleeping sickness.

Conclusion

Changes in infectious diseasetransmission patterns are a likelymajor consequence of climatechange. We need to learn moreabout the underlying complexcausal relationships, and apply thisinformation to the prediction offuture impacts, using morecomplete, better validated,integrated, models.

Environmental changes Example diseases Pathway of effectDams, canals, irrigation Schistosomiasis Snail host habitat, human contact

Malaria Breeding sites for mosquitoes

Helminthiasies Larval contact due to moist soil

River blindness Blackfly breeding, disease

Agricultural intensification Malaria Crop insecticides and vectorresistance

Venezuelan rodent abundance, contacthaemorraghic fever

Urbanization, Cholera sanitation, hygiene; water urban crowding contamination

Dengue Water-collecting trash, Aedesaegypti mosquito breeding sites

Cutaneous leishmaniasis proximity, sandfly vectors

Deforestation and new Malaria Breeding sites and vectors, habitation immigration of susceptible people

Oropouche contact, breeding of vectors

Visceral leishmaniasis contact with sandfly vectors

Reforestation Lyme disease tick hosts, outdoor exposure

Ocean warming Red tide Toxic algal blooms

Elevated precipitation Rift valley fever Pools for mosquito breeding

Hantavirus Rodent food, habitat, pulmonary syndrome abundance

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Table 6.1: Examples of how diverse environmental changes affect the occurrenceof various infectious diseases in humans (Refernce 5)

increase reduction��

7How much

disease wouldclimate

change cause?

To inform policies, an

estimation of the

approximate magnitude of

the health impacts of climate

change is needed. This will

indicate which particular

impacts are likely to be

greatest and in which

regions, and how much of

the climate-attributable

disease burden could be

avoided by emissions

reduction. It will also guide

health-protective strategies.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 18

The global burden of diseaseattributable to climate change hasrecently been estimated as part of acomprehensive World HealthOrganization project.1 This projectsought to quantify disease burdensattributable to 26 environmental,occupational, behavioural and life-style risk factors in 2000, and atselected future times up to 2030.

Disease burdens and summarymeasures of population health

The disease burden comprises thetotal amount of disease orpremature death within thepopulation. To compare burden-fractions attributable to severaldifferent risk factors requires, first,knowledge of the severity/disabilityand duration of the health deficit,and, second, the use of standardunits of health deficit. The widely-used Disability-Adjusted Life Year(DALY2) is the sum of:

• years of life lost due to prematuredeath (YLL)

• years of life lived with disability (YLD).

YLL takes into account the age atdeath. YLD takes into accountdisease duration, age at onset, and adisability weight reflecting theseverity of disease.

To compare the attributable burdensfor disparate risk factors we need toknow: (i) the baseline burden ofdisease, absent the particular risk

factor, (ii) the estimated increase inrisk of disease/death per unitincrease in risk factor exposure (the“relative risk”), and (iii) the currentor estimated future populationdistribution of exposure. Theavoidable burden is estimated bycomparing projected burdens underalternative exposure scenarios.

Disease burdens have beenestimated for five geographicalregions (Figure 7.1). Theattributable disease burden hasbeen estimated for the year 2000.For the years 2010, 2020 and 2030,the climate-related relative risks ofeach health outcome under each

climate change scenario, relative tothe situation if climate change didnot occur, were estimated.3 Thebaseline scenario is 1990 (the lastyear of the period 1961 to 1990 –the reference period used by theWorld Meteorological Organizationand IPCC).

The future exposure scenariosassume the following projectedGHG emission levels:

1. Unmitigated emission trends(approximating the IPCC "IS92a"scenario)

2. Emissions reduction, achievingstabilization at 750 ppm CO2-equivalent by 2210 (s750)

Figure 7.1 Estimated impacts of climate change in 2000 by region

* without developed countries; ** and Cuba

Region Total DALYs DALYs(1000s) / million

population

Africa region 1894 3071.5Eastern Mediterranean region 768 1586.5Latin America and Caribbean region 92 188.5South-East Asian region 2572 1703.5Western Pacific region* 169 111.4Developed countries** 8 8.9WORLD 5517 920.3

SUMMARY19

3. More rapid emissions reduction,stabilizing at 550 ppm CO2-equivalent by 2170 (s550).

Health outcomes assessed

Only some of the health outcomesassociated with climate change areaddressed here (Table 7.1). Thesewere selected on the basis of: (a) sensitivity to climate variation,(b) predicted future importance,and (c) availability/feasibility ofquantitative global models.

Additional likely health impacts thatare currently not quantifiableinclude those due to:

• changes in air pollution and aeroallergen levels

• altered transmission of other infectious diseases

• effects on food production via climatic influences on plant pests and diseases

• drought and famine

• population displacement due to natural disasters, crop failure, water shortages

• destruction of health infrastructure in natural disasters

• conflict over natural resources

• direct impacts of heat and cold (morbidity).

All independently-published modelslinking climate change toquantitative, global, estimates ofhealth impacts (or health-affectingimpacts – e.g. food yields) werereviewed. Where global models donot exist, local or regionalprojections were extrapolated.Models were selected according totheir assessed validity. Linearinterpolation was used to estimaterelative risks for inter-scenario years.

Summary of results

Climate change will affect thepattern of deaths from exposure tohigh or low temperatures.However, the effect on actualdisease burden cannot bequantified, as we do not know towhat extent deaths during thermalextremes are in sick/frail personswho would have died soon anyway.

In 2030 the estimated risk ofdiarrhoea will be up to 10% higherin some regions than if no climatechange occurred. Since few studieshave characterized this particularexposure-response relationship,these estimates are uncertain.

Estimated effects on malnutritionvary markedly among regions. By2030, the relative risks forunmitigated emissions, relative tono climate change, vary from asignificant increase in the South-East Asia region to a small decreasein the Western Pacific. Overall,although the estimates of changesin risk are somewhat unstablebecause of regional variation inrainfall, they refer to a majorexisting disease burden entailinglarge numbers of people.

The estimated proportionalchanges in the numbers of peoplekilled or injured in coastal floodsare large, although they refer to lowabsolute burdens. Impacts ofinland floods are predicted toincrease by a similar proportion,and would generally cause a greater

acute rise in disease burden. Whilethese proportional increases aresimilar in developed and developingregions, the baseline rates are muchhigher in developing countries.

Changes in various vector-borneinfectious diseases are predicted.This is particularly so for malaria inregions bordering current endemiczones. Smaller changes wouldoccur in currently endemic areas.Most temperate regions wouldremain unsuitable for transmission,because either they remainclimatically unsuitable (e.g., most ofEurope) or socioeconomicconditions are likely to remainunsuitable for reinvasion (e.g.,southern United States).Uncertainties relate to how reliableis extrapolation between regions,and to whether potentialtransmission will become actualtransmission.

Application of these models tocurrent disease burdens suggeststhat, if our understanding of broadrelationships between climate anddisease is realistic, then climatechange may already be affectinghuman health.

The total current estimated burdenis small relative to other major riskfactors measured under the sameframework. However, in contrastto many other risk factors, climatechange and its associated risks areincreasing rather than decreasingover time.

Table 7.1. Health outcomes considered in this analysis

Type of outcome Outcome Incidence/Prevalence

Food and water-borne disease Diarrhoea episodes Incidence

Vector-borne disease Malaria cases Incidence

Natural disasters* Fatal unintentional injuries Incidence

Risk of malnutrition Non-availability of Prevalencerecommended daily calorie intake

*All natural disaster impacts are separately attributed to coastal floods and to inland floods/landslides

8Stratospheric

ozonedepletion,ultraviolet

radiation andhealth

Strictly, stratospheric ozone

depletion is not part of

“global climate change”,

which occurs in the

troposphere. There are,

however, several recently-

described interactions

between ozone depletion

and greenhouse

gas-induced warming.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 20

Scientists 100 years ago would havebeen incredulous at the idea that,by the late twentieth century,humankind would be affecting thestratosphere. Yet, remarkably,human-induced depletion ofstratospheric ozone has recentlybegun – after 8,000 generations ofHomo sapiens.

Stratospheric ozone absorbs muchof the incoming solar ultravioletradiation (UVR), especially thebiologically more damaging,shorter-wavelength, UVR. We nowknow that various industrialhalogenated chemicals such as thechlorofluorocarbons (CFCs – usedin refrigeration, insulation andspray-can propellants) and methylbromide, while inert at ambientEarth-surface temperatures, reactwith ozone in the extremely coldpolar stratosphere. This destructionof ozone occurs especially in latewinter and early spring.

During the 1980s and 1990s atnorthern mid-latitudes (such asEurope), the average year-roundozone concentration declined byaround 4% per decade: over thesouthern regions of Australia, NewZealand, Argentina and SouthAfrica, the figure approximated 6-7%. Estimating the resultantchanges in actual ground-levelultraviolet radiation remainstechnically complex. However,exposures at northern mid-latitudes, for example, are likely topeak around 2020, with anestimated 10% increase in effective

ultraviolet radiation relative to1980s levels.1

In the mid-1980s, governmentsrecognised the emerging hazardfrom ozone depletion. TheMontreal Protocol of 1987 wasadopted, widely ratified, and thephasing out of major ozone-destroying gases began. Theprotocol was tightened in the1990s. Scientists anticipate a slowbut near-complete recovery ofstratospheric ozone by the middleof the twenty-first century.

Main types of health impacts

The range of certain or possiblehealth impacts of stratosphericozone depletion are listed in Table8.1, with a summary evaluation ofthe evidence implicating UVR intheir causation.

Many epidemiological studies haveimplicated solar radiation as a causeof skin cancer (melanoma andother types) in fair-skinnedhumans.2 Recent assessments bythe United Nations EnvironmentProgram project increases in skincancer incidence and sunburnseverity due to stratospheric ozonedepletion1 for at least the first halfof the twenty-first century (andsubject to changes in individualbehaviours).

The groups most vulnerable to skincancer are white Caucasians,especially those of Celtic descent

living in areas of high ambientUVR. Further, culturally-basedbehavioural changes have led tomuch higher UV exposure,through sun-bathing and skin-tanning. The marked increase inskin cancers in western populationsover recent decades reflects,predominantly, the combination ofbackground, post-migration,geographical vulnerability andmodern behaviours.

Table 8.1 Summary of possible effects

of solar ultraviolet radiation on

human health

Effects on skin

• Malignant melanoma

• Non-melanocytic skin cancer –

basal cell carcinoma, squamous

cell carcinoma

• Sunburn

• Chronic sun damage

• Photodermatoses

Effects on the eye

• Acute photokeratitis and

photoconjunctivitis

• Climatic droplet keratopathy

• Pterygium

• Cancer of the cornea and

conjunctiva

• Lens opacity (cataract) – cortical,

posterior subcapsular

•Uveal melanoma

• Acute solar retinopathy

• Macular degeneration

SUMMARY21

Effect on immunity and infection

• Suppression of cell mediated

immunity

• Increased susceptibility to

infection

• Impairment of prophylactic

immunization

• Activation of latent virus infection

Other effects

• Cutaneous vitamin D production

- prevention of rickets,

osteomalacia and osteoporosis

- possible benefit for hypertension,

ischaemic heart disease and

tuberculosis

- possible decreased risk for

schizophrenia, breast cancer,

prostate cancer

- possible prevention of Type 1

diabetes

• Altered general well-being

- sleep/wake cycles

- seasonal affective disorder

- mood

Indirect effects

• Effects on climate, food supply,

infectious disease vectors, air

pollution, etc

Scientists expect the combined effectof recent stratospheric ozonedepletion and its continuation overthe next 1-2 decades to be (via thecumulation of additional UVBexposure), an increase in skin cancerincidence in fair-skinned

populations living at mid to highlatitudes.3 The modelling of futureozone levels and UVR exposuresstudy has estimated that, inconsequence, a ‘European’population living at around 45degrees North will experience, by2050, an approximate 5% excess of total skin cancer incidence(assuming, conservatively, no changein age distribution). The equivalentestimation for the US population isfor a 10% increase in skin cancerincidence by around 2050.

Laboratory studies demonstrate thatexposure to UVR, in particular toUVB, in various mammalian speciesinduces lens opacification. Theepidemiological evidence for a roleof UVR in human lens opacities ismixed. Cataracts are more common

in some (but not all) countries withhigh UVR levels.

In humans and experimentalanimals, UVR exposure, includingwithin the ambient environmentalrange, causes both localised andwhole-body immunosuppression.4

UVR-induced immunosuppressioncould influence patterns ofinfectious disease. It may alsoinfluence the occurrence andprogression of various autoimmunediseases and less certainly, vaccinefficacy.5

Finally, there is a wider, ecological,dimension to consider. Ultravioletradiation impairs the molecularchemistry of photosynthesis bothon land (terrestrial plants) and atsea (phytoplankton). This could

affect world food production, atleast marginally, and thuscontribute to nutritional and healthproblems in food-insecurepopulations. However, as yet thereis little information about this lessdirect impact pathway.

Conclusion

Encouraging total sun avoidance(with the related notion of solarradiation as a “toxic” exposure) is asimplistic response to the hazardsof increased ground-level UVRexposure due to stratosphericozone depletion, and should beavoided. Any public healthmessages concerned with personalUVR exposure should consider thebenefits as well as the adverseeffects. Nevertheless, we must bealert to the potential increase insome particular risks to healthposed by stratospheric ozonedepletion.

Figure 8.1. Estimates of ozone depletion and skin cancer incidence to examine the

Montreal Protocol achievements. (Source: Adapted from reference 6)

1950 1975 2000 2025 2050 2075 2100Year

1500

1250

1000

750

500

250

100

Exce

ss c

ases

of s

kin

canc

er p

er m

illion

per

yea

r

Peak excess =10% in 2050

No CFCrestrictions

MontrealProtocol(original)

CopenhagenAmendments

(’92)

US baseline rate = 110 cases/million/year

Now

9National

assessments ofhealth impacts

of climatechange

Estimates, even if approximate,

of the potential health impacts

of climate change are an

essential input to policy

discussion on reducing

greenhouse gas emissions and

on social adaptation to climate

change. Societies must respond

despite the unavoidable

uncertainties. Indeed, national

governments have a

responsibility, under the UN’s

Framework Convention on

Climate Change (1992), to carry

out formal assessments of the

risk to their population’s health

posed by global climate change.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 22

Health impact assessment (HIA) hasbeen defined as “a combination ofprocedures, methods and tools bywhich a policy, project or hazardmay be judged as to its potentialeffects on the health of a population,and the distribution of those effectswithin the population”.1 Despiterecent advances in health impactassessment methods, its integrationinto mainstream policy-making hasyet to be satisfactorily achieved.Besides, impact assessments typicallyrefer to health impacts over the next10 to 20 years (e.g. due to currentsmoking rates, obesity levels, orpopulation ageing), rather than the50 to 100 year time-scaleappropriate to climate changeprojections. So there is need forscenario-based impact assessmentsthat incorporate, and communicate,a higher level of uncertainty. Thesteps in climate change impact andadaptation assessment are shown infigure 9.1.

Several types of national healthimpact assessments have beenundertaken. A basic assessmentidentifies the types, but not muchabout the magnitudes, of potentialimpacts. In contrast, comprehensivewell-funded and well-supportedassessments are undertaken. Forexample, in the United Statesassessment, published in 2000,population health was one of thefive target sectors included in the16 detailed regional assessmentsand in the overall assessment. TheUS assessment involvedstakeholder participation andextensive consultation and peerreview.3 Further Comparativedetails of two national assessmentsare shown in the box.

Comprehensive multi-sectoralassessments have been conductedby the USA, Canada, the UK andPortugal. Assessments indeveloping countries have been

undertaken only under the auspicesof donor-funded capacity-buildinginitiatives. (Other sub-national orlocal assessments of potentialhealth impacts may have beenundertaken for climate change, but,if so, such studies are in the “grey”literature, not widely available.)The outcomes listed refer to thelikely health impacts reported onfor that particular country. Thelevel of uncertainty accompanyingthese estimates is usually notdescribed. Vector-borne diseases,particularly malaria, have beenwidely addressed. Other potentiallygreater impacts, such as fromweather disasters, have been lesswell addressed.

Out of these experiences, severalconclusions can be drawn:

• Assessments should be driven by region and country priorities in order to determine which health impacts are considered. No singleset of guidelines covers all health and institutional situations.

• HIA is a policy tool, therefore theactual process of conducting assessments, particularly the involvement of stakeholders, is very important.

• Assessments should set an agenda for future research. Nearly all the assessments done to date have identified research gaps, and they often specify detailed research questions.

• Assessment should be linked to follow-up activities such as monitoring and updated reports.

Figure 9.1. Steps in climate change impact and adaptation assessment (reference 2)

Regionalassessments

Scenarios

Climatescenario

Socio-economicscenario

Impacts

Agriculture

Fisheries

Forestry

Coastal zones

Industry• Energy• Tourism• Insurance

Human health

SUMMARY23

Box: Comparing Assessments: UKand Fiji

The UK assessment concentratedon producing quantitative resultsfor the following health outcomes4,for three time periods and for fourclimate scenarios:

• Heat-related and cold-related deaths and hospital admissions

• Cases of food poisoning

• Changes in distribution of Plasmodium falciparum malaria (global) and tick-borne encephalitis (Europe), and in seasonal transmission of P. vivax malaria (UK)

• Cases of skin cancer due to stratospheric ozone depletion.

The large uncertainty surroundingthese estimates was acknowledged.The main conclusions of the reportwere the impact of increases in riverand coastal flooding, and severewinter gales. This report also clearlyaddressed the balance between thepotential benefits and adverseimpacts of climate change: thepotential decline in winter deathsdue to milder winters is muchlarger than the potential increase inheat-related deaths. Climate changeis also anticipated to lessen airpollution-related illnesses anddeaths, except for those associatedwith tropospheric ozone, which willform more readily at highertemperatures.

The Fijian assessment addresses health impact in the context of

current health services. Fiji’s mainconcerns were dengue fever (recentepidemic in 1998), diarrhoealdisease and nutrition-related illness.The islands are malaria free and ananopheline mosquito vectorpopulation has not beenestablished despite a suitableclimate. Hence, the risk ofintroduction and establishment ofmalaria and other mosquito-bornediseases due to climate change wasconsidered to be very low. Filariasis,an important vector-borne diseaseon the islands, is likely to beincreased by warmer temperatures.The distribution of the vector(Aedes polynesiensis) may also beaffected by sea level rise, since itbreeds in brackish water. A denguefever transmission model wasincorporated into a climate impactsmodel developed for the PacificIslands (PACCLIM). The modellingindicates that climate change mayextend the transmission season andgeographic distribution in Fiji.

Diarrhoeal disease may increase inFiji because of increasedtemperature and altered patterns ofrainfall. However, no evidence waspresented on the associationbetween flooding or heavy rainfall and cases of diarrhoea. The1997/998 drought (associated withEl Nino) had widespread healthimpact, including diarrhoealdisease, malnutrition andmicronutrient deficiency in childrenand infants.5

The development of formalguidelines for the nationalassessment of health impacts willimprove methods used, will achievesome standardization, and willfacilitate the development ofrelevant indicators. Health Canadahas prepared an initial framework6,proposing that there are threedistinct phases to the assessmenttask:

1. Scoping: to identify the climatechange problem (concerns ofvulnerable groups) and its context,describe the current situation(health burdens and risks) andidentify key partners and issues forthe assessment. 2. Assessment: estimations offuture impacts and adaptivecapacity, and evaluation ofadaptation plans, policies andprogrammes. 3. Risk management: actions tominimize the impacts on health,including follow-up assessments.

This type of health impactassessment, in relation to large-scale climatic-environmentalchanges, requires guidelines thataccord with the mainstream HIAframework of WHO and otherinternational agencies. Achievingthis would help to move the climatechange policy discussion beyondthe environmental impact domainand into the social and publichealth impacts arenas. Currently, inmost countries, sectordifferentiation and the associated

policy environment neitherfacilitates nor fosters intersectoralcollaboration. Within the healthsector, resources are allocatedprimarily in relation to dealing withexisting problems, taking someaccount of the relative burden ofdisease.

A major shortcoming of manyclimate change health impactassessments has been thesuperficial treatment of thepopulation’s adaptive capacities andpolicy options. Strategies toenhance population adaptationshould promote measures that arenot only appropriate for currentconditions, but which also build thecapacity to identify and respond tounexpected future stresses/hazards.The restoration and improvementof general public healthinfrastructure will reducepopulation vulnerability to thehealth impacts of climate change.In the longer-term, and morefundamentally, improvements inthe social and material conditionsof life and the reduction ofinequalities within and betweenpopulations are required forsustained reduction in vulnerabilityto global environmental change.

10Monitoringthe HealthEffects of

ClimateChange

Both the detection and

measurement of health

effects of climate change are

necessary as evidence

underpinning national and

international policies relating

to measures to protect public

health. Those measures

include mitigation of

greenhouse gas emissions.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 24

Good evidence requires good data.The climate varies naturally as wellas in response to human influences,and, in turn, climate is only one ofmany determinants of populationhealth. Therefore, assessing thehealth impacts of climate changeposes challenges. Further, theprocess of climate change isdetectable only over decades, andthe resultant health impacts will besimilarly slow to emerge.

Monitoring is “the performance andanalysis of routine measurementsaimed at detecting changes in theenvironment or health ofpopulations”1. In many publichealth investigations, it is possible tomeasure changes in a defined healthimpact and to attribute this trend tochanges in a directly-acting riskfactor. However, the monitoring ofthe impacts of climate change onhealth is more complex. There arethree main issues:

(i) Distinguishing apparent from real“climate change”Climate is always fluctuatingnaturally, and many indices ofhealth show seasonal and inter-annual fluctuation. Thedemonstration of such arelationship provides no directevidence that climate change per sehas occurred — rather, it merelyconfirms that these diseases have aseasonal or climatic dependence.An excess of heat-related deaths in aparticularly hot summer, or even asuccession of hot summers,indicates the potential for climatechange to increase mortality, but it

does not prove that mortality hasincreased as a result of climatechange. That would requireevidence of a change in the'baseline' climate conditions – i.e.that the sequence of hot summerswas exceptional, and due to climatechange rather than randomvariation.

(ii) AttributionSince climate is one of manyinfluences on health, the attributionof an observed change in populationhealth to an associated change inclimate is not straightforward. Theinfluence of concurrent changes inother environmental, social orbehavioural factors must be firstallowed for.

(iii) Effect modificationOver time, as the climate changes,other changes may also occur thatalter the population’s vulnerabilityto meteorological influences. Forexample, vulnerability to extremeweather events, including floods andstorms, will depend on where andhow residential housing is built,what flood protection measures areintroduced, and how land-use ischanged. Effective monitoring mustinclude parallel measurements ofpopulation and environmental data,to allow study of potentialmodifying influences.

General Principles

The principal criteria for selectingdiseases and settings for monitoringshould include the following:

• Evidence of climate sensitivity - tobe demonstrated through either observed health effects of temporal or geographical climate variation, or evidence of climate effects on components of the disease transmission process in the field or laboratory.

• Significant public health burden -monitoring should be preferentially targeted towards significant threats to public health. These may be diseases with a high current prevalence and/or severity, or considered likely to become prevalent under conditions of climate change.

• Practicality – logistical considerations are important given that monitoring requires dependable and consistent long-term recording of health-related indices and other environmental parameters. Monitoring sites should be chosen where change is most likely to occur, but where appropriate capacity for reliable measurement exists.

Data Requirements and Sources

The data needed for monitoringclimate effects on health comprise:(i) climatic variables; (ii) populationhealth markers; and (iii) other non-climatic explanatory factors (Table10.1).

The choice of non-climatic variableswill depend on the specific disease,but the principal categories ofconfounding or modifying factorsinclude:

SUMMARY25

• age structure of population

• underlying rates of disease, especially cardiovascular and respiratory disease and diarrhoeal illness

• level of socio-economic development

• environmental conditions, e.g. land-use, air quality, housing conditions

• quality of health-care

• specific control measures, e.g. vector control programmes.

Specific Categories of HealthImpacts: Data Needs, Opportunities

To monitor the health effects ofthermal extremes, reliable long

and most vector-borne disease.Assessment of the climatecontribution to long-term trendsrequires linked data on factors suchas land-use, host abundance andintervention measures. Clearerunderstanding of relationshipsshould result from high-qualityserial data on vectors at a modestnumber of sites within or at themargins of endemic areas. Datafrom sites along specified transectscould indicate changing vectordistributions (including altitude).Geographical comparisons based onremote sensing data may giveadditional insights into diseasetrends.

Conclusion

With all forms of monitoring,interpretation of evidence will bestrengthened by procedures forstandardization, training and qualityassurance/quality control. Longtime-series of health changes inpopulations in relation to steep (i.e.sensitive) climate-diseaserelationships will be the mostinformative. Such monitoring willbecome more effective throughinternational collaboration andintegration with existing surveillancenetworks.

Principal health outcomes

Which populations/locations to monitor

Sources and methods foracquiring health data

Meteorologicaldata

Other variables

Thermal extremes

Extreme weather events(floods, highwinds, droughts)

Food- & water-borne disease

Vector-bornedisease

Daily mortality; hospital admissions;clinic/emergency roomattendance;

Attributed deaths;hospital admissions;infectious disease surveillance data; (mentalhealth); nutritional status

Relevant infectiousdisease deaths &morbidity

Vector populations;disease notifications;temporal andgeographical distributions

Urban populations, especially in developingcountries

All regions

All regions

Margins of geographicaldistribution (e.g: changes withlatitude, altitude) andtemporality in endemic areas

National and sub-national deathregistries (e.g. city specific data)

Use of sub-national death registries; local public health records

Death registries; national & sub-national surveillance notifications

Local field surveys; routinesurveillance data (variable availability)

Daily temperatures(min/max or mean) &humidity

Meteorological eventdata: extent, timing &severity

Weekly/dailytemperature; rainfall forwater-borne disease

Weekly/dailytemperature, humidityand rainfall

Confounders: influenza & other respiratoryinfections; air pollution

Modifiers: housing conditions (e.g.household/workplace air conditioning),availability of water supplies

Disruption/contamination of food & watersupplies; disruption of transportation.Population displacement

The above parameters will have an indirectimpact on health

Long term trends dominated by host-agentinteractions (e.g. S enteritidis in poultry)whose effects are difficult to quantify.Indicators may be based on examination ofseasonal patterns.

Land use; surface configurations offreshwater

Figure 10.1 Data required to monitor climate impacts on health

time-series of temperature andmortality/morbidity data areavailable in many countries. Animportant focus of research datashould be the assessment of howthe temperature-mortality/morbidityrelationship is modified byindividual, social and environmentalfactors. Existing databases (e.g. EM-DAT) for extreme weather eventsmay be a key resource. To maximizetheir usefulness, complete andconsistent reporting of extremeweather events across a widegeographical area, along withstandard definitions of events andmethods of attribution, is needed. Current monitoring data canprovide only a broad quantificationof the relationship between climate

11Adaptation

and adaptivecapacity, to

lessen healthimpacts

Even if greenhouse gas

emissions are reduced in the

near future, Earth’s climate

will continue to change.

Hence, adaptation strategies

must be considered to reduce

disease burdens, injuries,

disabilities and deaths.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 26

The IPCC has defined the followingtwo closely-related terms1:

Adaptation: Adjustment in natural orhuman systems in response toactual or expected climatic stimulior their effects, which moderatesharm or exploits beneficialopportunities.

Adaptive Capacity: The ability of asystem to adjust to climate change(including climate variability andextremes) to moderate potentialdamages, to take advantage ofopportunities, or to cope withconsequences.

The extent to which human healthis affected depends on: (i) theexposures of populations to climate

change and its environmentalconsequences, (ii) the sensitivity ofthe population to the exposure, and(iii) the ability of affected systemsand populations to adapt (Figure11-1). We therefore need tounderstand how decisions are madeabout adaptation, including theroles of individuals, communities,nations, institutions and privatesector.

Adaptation and Prevention

Many adaptive measures havebenefits beyond those associatedwith climate change. The rebuildingand maintaining of public healthinfrastructure is often viewed as the“most important, cost-effective and

urgently needed” adaptationstrategy.1 This includes publichealth training, more effectivesurveillance and emergencyresponse systems, and sustainableprevention and control programs.

Extreme weather events can havevastly different impacts because ofdifferences in the target population’scoping capacity. For example,cyclones in Bangladesh in 1970 and1991 are estimated to have caused300,000 and 139,000 deathsrespectively.2 In contrast, HurricaneAndrew struck the United States in1992, causing 55 deaths (althoughalso causing around $30 billion indamages3). Climate-relatedadaptation strategies must thereforebe considered in relation to broadercharacteristics – such as populationgrowth, poverty, sanitation, healthcare, nutrition, and environmentaldegradation – that influence apopulation’s vulnerability andcapacity to adapt.

Adaptations which enhance apopulation’s coping ability mayprotect against current climaticvariability as well as against futureclimatic changes. Such “no-regrets”adaptations may be especiallyimportant for less developedcountries with little current copingcapacity.

Adaptive Capacity

Adaptive capacity refers to bothactual and potential features. Thus,it encompasses both current coping

Humaninterference

Exposure

Initial impactsof effects

Autonomousadaptation

Residual ornet impacts

IMPA

CT

S

VU

LN

ER

AB

ILIT

IES

Policy responses

Planned ADAPTATIONto the impacts and

vulnerabilities

MITIGATIONof climate changevia GHG sources

and sinks

CLIMATE CHANGEincluding variability

Fig 11.1. Relationships between vulnerability and impacts (including both risks and

opportunities) and society’s main response options – i.e., mitigation of greenhouse

gas emissions and adaptation (Source: reference 1)

SUMMARY27

ability and the strategies that expandfuture coping ability. For example,access to clean water is part of thecurrent coping capacity fordeveloped countries – butrepresents potential adaptivecapacity in many less developedcountries.

Highly-managed systems, such asagriculture and water resources indeveloped countries, are thought tobe more adaptable than less-managed or natural ecosystems.Unfortunately, some components ofpublic health systems are oftenrelaxed when a particular healththreat recedes. For example, thethreat of infectious diseasesappeared to be retreating thirty yearsago because of advances inantibiotic drugs, vaccines andpesticides. Today, however, there isa general resurgence of infectiousdiseases – and relevant public healthmeasures need to be reinvigorated.

The main determinants of acommunity’s adaptive capacity are:economic wealth, technology,information and skills,infrastructure, institutions, andequity. Adaptive capacity is also afunction of current populationhealth status and pre-existingdisease burdens.

Economic ResourcesWealthy nations are better able toadapt because they have theeconomic resources to invest, andto offset the costs of adaptation. Ingeneral, poverty enhances

vulnerability – and we live in a worldin which approximately one-fifth ofthe world’s population lives on lessthan US$1 per day.

TechnologyAccess to technology in key sectorsand settings (e.g., agriculture, waterresources, health-care, urbandesign) is an important determinantof adaptive capacity. Many health-protecting adaptive strategies involvetechnology – some of which is wellestablished, some new and stillbeing disseminated, and some stillbeing developed to enhance copingwith a changing climate.

The health risks from proposedtechnological adaptations should beassessed in advance. For example,increased air conditioning wouldprotect against heat stress, but couldincrease emissions of greenhousegases and other air pollutants.Poorly designed coastal "defences"may increase vulnerability to tidalsurges if they engender falsesecurity and promote low-lyingcoastal settlements.

Information and SkillsIn general, countries with more“human capital” or knowledge havegreater adaptive capacity1. Illiteracyincreases a population’svulnerability to many problems4.Health systems are labor-intensiveand require qualified andexperienced staff, including thosetrained in the operation, qualitycontrol, and maintenance of publichealth infrastructure.5

InfrastructureInfrastructure specifically designedto reduce vulnerability to climatevariability (e.g., flood controlstructures, air conditioning, andbuilding insulation) and generalpublic health infrastructure (e.g.,sanitation facilities, wastewatertreatment systems, laboratorybuildings) enhance adaptivecapacity. However, infrastructure(especially if immovable) can beadversely affected by climate,especially extreme events such asfloods and hurricanes.

InstitutionsCountries with weak institutionalarrangements have less adaptivecapacity than countries with well-established institutions.1 Forexample, institutional andmanagerial deficiencies contributeto Bangladesh’s vulnerability toclimate change.

Collaboration between public andprivate sectors can enhance adaptivecapacity. For example, theMedicines for Malaria Venture – ajoint public-private initiative todevelop new antimalarial drugs – isdeveloping new products for use indeveloping countries.

EquityAdaptive capacity is likely to begreater when access to resourceswithin a community, nation, or theworld is equitably distributed.6

Under-resourced and marginalpopulations lack adaptive resources.

While universal access to qualityservices is fundamental to publichealth, many still lack access tohealth care. Overall, the developingworld, with 10 per cent of theworld’s health resources, carries 90per cent of the disease burden.5

Health Status and Pre-existingDisease Burdens

Population well-being is animportant ingredient anddeterminant of adaptive capacity.Great progress has been achieved inpublic health, yet 170 millionchildren in poor countries areunderweight, of whom over threemillion die each year. Manycountries face the double burden ofincreases of non-communicablediseases, but with continuedprevailing infectious diseases.

Conclusions

Adaptive strategies intended toprotect public health will be neededwhether or not actions are taken tomitigate climate change. Buildingcapacity is an essential preparatorystep. Adapting to climate changewill require more than financialresources, technology, and publichealth infrastructure. Education,awareness-raising and the creationof legal frameworks, institutions andan environment that enables peopleto take well-informed, long-term,sustainable decisions are all needed.

12From Science

to Policy:Developing

Responses toClimateChange

Policy choices are guided by

several principles. These

include considerations of

equity, efficiency and

political feasibility. The usual

public health ethics

considerations may also

apply: respect for autonomy,

nonmaleficence (not doing

bad), and justice and

beneficence (doing good).

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 28

To make informed decisions aboutclimate change, policy-makers willneed timely and useful informationabout the possible consequences ofclimate change, people’s perceptionsof those consequences, availableadaptation options, and the benefitsof slowing the rate of climatechange.1 The challenge forresearchers is to provide thisinformation.

Once policy-makers have receivedinput from the impact assessmentcommunity, they must integrate thisinformation into a broader policyportfolio. Response options includeactions to mitigate greenhouse gasemissions to slow the rate of climatechange; measures to adapt to achanging climate in order toincrease society’s resilience to thechanges that are coming; activitiesto increase the public’s awareness ofthe climate change issue;investments in monitoring andsurveillance systems; andinvestments in research to reducekey policy-relevant uncertainties.

Climate change, however, shouldnot be considered in isolation fromother global environmentalstresses. Further, policy-makersusually deal with multiple socialobjectives (e.g., povertyelimination, promotion ofeconomic growth, protection ofcultural resources), whilecompeting stakeholder desirescompound the allocation of scarceresources. Climate change shouldtherefore be viewed as part of the

larger challenge of sustainabledevelopment.

Using the information provided bythe research community, riskmanagers must make decisionsdespite the existence of scientificuncertainties. Policy-focusedassessments analyze the bestavailable scientific andsocioeconomic information toanswer questions being asked byrisk managers. They characterizeand, if possible, quantify scientificuncertainties to the extent possible,and explain the potentialimplications of the uncertainties forthe outcomes of concern to thedecision makers. Ultimately, it is upto society to decide whether aperceived risk warrants action. Butthe scientific uncertainty, by itself,does not excuse delay or inaction.

Decision-making criteria.

Many different criteria exist formaking decisions about climatechange policy. Two approaches todecision making that are oftendiscussed are the “precautionaryprinciple” and “benefit-cost”analysis.

The precautionary principle is a riskmanagement principle applied whena potentially serious risk exists, butsignificant scientific uncertainty alsoexists.2 The precautionary principleallows some risks to be deemedunacceptable not because they havea high probability of occurring, but

because the consequences if theyoccur may be severe or irreversible.This principle was featured in the1992 Rio Declaration onEnvironment and Development asPrinciple 15, stating:“Where there are threats of serious orirreversible damage, lack of full scientificcertainty shall not be used as a reason forpostponing cost-effective measures toprevent environmental degradation.”

Another widely used approach isthe “benefit-cost” criterion,weighting the expected benefits andcosts of a proposed action.Questions arise about how benefitsand costs should be measured, andhow they should be comparedamong different societies. Thebenefit-cost criterion emphasizesthe efficient use of scarce resources– but does not deal with equity. Nordoes it deal well with consequencesthat are displaced into the future,and therefore, by economicconvention, often discounted.Climate change has the potential forcatastrophic outcomes in the distantfuture, the “present value” of whichwould be small if discounted.Despite these concerns, benefit-costanalysis should not be dismissed.This would only deprive decisionmakers of one set of insightfulinformation.

Response Options

The mitigation of greenhouse gasesprovides a mechanism for slowing,and perhaps eventually halting, the

SUMMARY29

buildup of greenhouse gases in theatmosphere. A slowing of the rate ofwarming could yield importantbenefits in the form of reducedimpacts to human health and othersystems; however, the inertia in theclimate system means that there willbe a significant temporal lagbetween emission reduction andslowing in the rate of warming.

Adaptation (discussed in section 11,above) is another importantresponse option. Such actionsenhance the resilience of vulnerablesystems, thereby reducing potentialdamages from climate change andclimate variability.

Communication of informationabout climate change, its potentialhealth impacts, and responsestrategies, is itself a public policyresponse to climate change. So, too,are the development andimplementation of monitoring andsurveillance systems, andinvestments in research. Monitoringand surveillance systems are integraland essential to providing theinformation needed to supportdecisions by public health officials.

Building the Bridge from Scienceto Policy: Policy-focusedAssessment

Policy-focused assessment is aprocess that can help resourcemanagers and other decisionmakers meet the challenge ofassembling an effective policy

portfolio. It is a process by whichthe best-available scientificinformation can be translated intoterms that are meaningful to policymakers. A policy-focusedassessment is more than just asynthesis of scientific information oran evaluation of the state of science.Rather, it involves the analysis ofinformation from multipledisciplines – including the socialand economic sciences – to answerthe specific questions being askedby stakeholders. And it includes ananalysis of adaptation options toimprove society’s ability to respondeffectively to risks and opportunitiesas they emerge. Formulating goodpolicy requires understanding thevariability in vulnerability acrosspopulation sub-groups, and thereasons for that variability.

In the assessment of adaptationoptions, a number of factors relatedto the design and implementation ofstrategies need to be considered.These include the fact that (1) theappropriateness and effectiveness ofadaptation options will vary byregion and across demographicgroups; (2) adaptation comes at acost; (3) some strategies exist thatwould reduce risks posed by climatechange, whether or not the effectsof climate change are realized; (4)the systemic nature of climateimpacts complicates thedevelopment of adaptation policy;and (5) maladaptation can result innegative effects that are as serious asthe climate-induced effects beingavoided.

Complicating the assessmentprocess is the fact that there aresignificant scientific andsocioeconomic uncertainties relatedto climate change and its potentialconsequences for human health.Uncertainties exist about thepotential magnitude, timing andeffects of climate change; thesensitivity of particular healthoutcomes to current climaticconditions (i.e., to weather, climate,and climate-induced changes inecosystems); the future health statusof potentially affected populations(in the absence of climate change);the effectiveness of different coursesof action to adequately address thepotential impacts; and the shape offuture society (e.g., changes insocioeconomic and technologicalfactors). A challenge for assessors isto characterize the uncertainties andexplain their implications for thequestions of concern to the decisionmakers and stakeholders. Ifuncertainty is not directly addressedas part of the analysis, a healthimpacts assessment can producemisleading results and possiblycontribute to ill-informed decisions.

Public Awareness: CommunicatingAssessment Results

Stakeholders should be engagedthroughout an assessment process.A communication strategy mustensure access to information,presentation of information in ausable form, and guidance on howto use the information. Risk

communication is a complex,multidisciplinary, and evolvingprocess. Often information has tobe tailored to the specific needs ofrisk managers in specific geographicareas and demographic groups. Thisrequires close interaction betweeninformation providers and thosewho need the information to makedecisions.

Conclusion

Some have argued that the existenceof scientific uncertainties precludespolicy makers from taking actiontoday in anticipation of climatechange. This is not true. In fact,policy makers, resource managers,and other stakeholders, despite theexistence of uncertainties, makedecisions every day. The outcomesof these decisions may be affectedby climate change. Or the decisionsmay foreclose future opportunitiesto adapt to climate change. Hence,the decision makers would benefitfrom information about the likelyimpacts of climate change. Aninformed decision is always betterthan an uninformed decision.

Care must be taken to respect theboundary between assessment andpolicy formation. The goal ofpolicy-focused assessment is toinform decision-makers, not tomake specific policyrecommendations.

13Conclusions

andRecommend-

ations forAction

Sustainability is essentially

about maintaining Earth’s

ecological and other

biophysical life-support

systems. If these systems

decline, human population

wellbeing and health will be

jeopardised. Technology can

buy time, but nature’s

bottom-line accounting

cannot be evaded. We must

live within Earth’s limits. The

state of human population

health is thus a central

consideration in the

transition towards

sustainability.1

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 30

Climate change, like other human-induced large-scale environmentalchanges, poses risks to ecosystems,their life-support functions and,therefore, human health (Figure13.1).2,3 WHO, WMO and UNEPcollaborate on issues related toclimate change and health,addressing capacity building,information exchange and researchpromotion.

Recommendations

• Climate-related exposuresThe IPCC’s Third AssessmentReport projected that, as we

continue to change atmosphericcomposition, global average surfacetemperature will rise by 1.4 to 5.8ºCin this century, along with changesin precipitation and other climaticvariables. Research needs includedeveloping innovative approaches toanalysing weather and climate inrelation to human health; setting uplong-term data sets to answer keyquestions; and improvingunderstanding of how toincorporate outputs from GlobalClimate Models into human healthstudies.

• Reaching consensus on the scienceThe science of climate change has

achieved increasing consensusamong scientists. There isincreasing evidence that humanhealth will be affected in many anddiverse ways. Knowledge is stilllimited in many areas, for exampleon the contribution of short-termclimate variability to diseaseincidence; on development of earlywarning systems for predictingdisease outbreaks and extremeweather events; and onunderstanding how recurringextreme events may weakenadaptive capacity.

• Challenges for scientistsClimate change poses some specialchallenges, including the complexityof causal process, the unavoidableuncertainties, and temporaldisplacement of anticipated impactsinto the future. Some key researchtopics to address include identifyingwhere first effects of climate changeon human health will be apparent;improving estimates of climatechange impacts; and betterexpressing the uncertaintiesassociated with studies of climatechange and health.

• Extreme climate eventsThe IPCC’s Third AssessmentReport projected changes inextreme climate events that includemore hot days and heat waves;more intense precipitation events;increased risk of drought; increasein winds and tropical cyclones (oversome areas); intensified droughtsand floods with El Niño events; andincreased variability in the Asian

Health effects

Temperature-relatedillness and death

Extremeweather-relatedhealth effects

Air pollution-relatedhealth effects

Water and food-borne diseases

Vector-borne androdent-borne

diseases

Effects of food andwater shortages

Mental, nutritional,infectious

and other healtheffectsHealth-specific

adaptationmeasures

Regionalweatherchanges

• Heatwaves

• Extremeweather

• Temperature

• Precipitation

CLIMATECHANGE

Greenhousegases (GHG)

emissions

Drivingforces

Populationdynamics

Unsustainableeconomic

development

Evaluation ofadaptation

Modulatinginfluences

Naturalcauses

Mitigativecapacity

Adaptivecapacity

Mitigationmeasures

Microbialcontamination

pathways

Transmissiondynamics

Agro-ecosystems,hydrology

Socioeconomics,demographics

Researchneeds

Figure 13.1. Climate change and health: pathway from driving forces, through

exposures to potential health impacts. Arrows under research needs represent input

required by the health sector. (Modified from reference 4)

SUMMARY31

summer monsoon. Research gapsto be addressed include furthermodelling of relationships betweenextreme events and health impacts;improved understanding of factorsaffecting vulnerability to climateextremes; and assessment of theeffectiveness of adaptation indifferent settings.

• Infectious diseasesInfectious diseases, especially thosetransmitted via insect vectors orwater, are sensitive to climaticconditions. Disease incidence datais needed to provide a baseline forepidemiological studies. The lack ofprecise knowledge of current diseaseincidence rates makes it difficult tocomment about whether incidenceis changing as a result of climaticconditions. Research teams shouldbe international andinterdisciplinary, includingepidemiologists, climatologists andecologists to assimilate the diversityof information from these respectivefields.

• The burden of diseaseThe stock of empirical evidencerelating climatic trends to alteredhealth outcomes remains sparse.This impedes estimating the range,timing and magnitude of likelyfuture health impacts of globalenvironmental changes. Even so, aninitial attempt has been made, withinthe framework of the WHO GlobalBurden of Disease 2000 project.Analyzing only the better studiedhealth outcomes, the climate changethat occurred since the climate

baseline period 1961-1990 wasestimated to have caused 150,000deaths and 5.5 million DALYS inthe year 2000.5

• Stratospheric ozone depletion, climatechange and healthStratospheric ozone depletion isessentially a different process fromclimate change. However,greenhouse-warming is affected bymany of the chemical and physicalprocesses involved in the depletionof stratospheric ozone.6 Also,because of changes in climate (inaddition to public information andeducation campaigns), patterns ofindividual and community sunexposure behaviour will change –duly affecting received doses ofultraviolet radiation.

• National assessmentsSeveral developed and developingcountries have undertaken nationalassessments of the potential healthimpacts of climate change, includingreference to vulnerable areas andpopulations. There is a need tostandardize the health impactassessment procedures, and toolsand methods are being developed.More accurate climate informationat the local level, particularly onclimate variability and extremes, isneeded.

• Monitoring climate change impacts onhuman healthClimate change is likely to affectdiseases that are also influenced byother factors. Monitoring to assessclimate-change impacts on health

therefore requires data-gatheringcoupled with analytical methods ableto quantify the climate-attributableportion of such diseases.Monitoring and surveillance systemsin many countries currently cannotprovide useful data on climate-sensitive diseases. Less developedcountries should strengthen existingsystems in order to meet currentneeds.

• Adapting to climate changeSince climate change is alreadyunderway, we need adaptationpolicies to complement mitigationpolicies. Efficient implementation ofadaptation strategies can significantlyreduce adverse health impacts ofclimate change. Human populationsvary in their susceptibility,depending on factors such aspopulation density, economicdevelopment, local environmentalconditions, pre-existing health statusand health-care availability.Adaptation measures usually willhave near-term as well as futurebenefits, by reducing the impacts ofcurrent climate variability.Adaptation measures can beintegrated with other healthstrategies.

• Responses: From science to policyThe magnitude and character ofglobal climate change necessitates acommunity-wide understanding andresponse, guided by policiesinformed by good scientific advice. Asuccessful policy-focused assessmentof the potential health impacts ofclimate change should include: i) a

multidisciplinary assessment team; ii) responses to questions asked byall stakeholders; iii) evaluation of riskmanagement adaptation options; iv) identification and prioritisation ofkey research gaps; v) characterizationof uncertainties and theirimplications for decision-making;and vi) tools that support decision-making processes.

Conclusion

International agreements on globalenvironmental issues such as climatechange should consider theprinciples of sustainabledevelopment proposed in Agenda 21and the UNFCCC. These includethe “precautionary principle”, theprinciple of “costs andresponsibility” (the cost of pollutionor environmental damage should beborne by those responsible), and“equity” – both within and betweencountries and over time (betweengenerations).

Adherence to these principles wouldhelp prevent future globalenvironmental threats and reduceexisting ones. With climate changealready underway, there is need toassess vulnerabilities and identifyintervention/adaptation options.7

Early planning for health can reducefuture adverse health impacts. Theoptimal solution, however, lies withgovernments, society and individuals– and requires changes in behaviour,technologies and practices to enablea transition to sustainability.

Glossary

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 32

adaptation: Adjustment in naturalor human systems to a new orchanging environment. Adaptationto climate change refers toadjustment in response to actual orexpected climatic stimuli or theireffects, which moderates harm orexploits beneficial opportunities.Various types of adaptation can bedistinguished, including anticipatoryand reactive adaptation, public andprivate adaptation, and autonomousand planned adaptation.

anthropogenic emissions:Emissions of greenhouse gases andaerosols associated with humanactivities. These include fossil fuelburning for energy, deforestationand land use changes that result innet increase in emissions.

atmosphere: The gaseous envelopesurrounding the Earth. The dryatmosphere consists almost entirelyof nitrogen and oxygen, togetherwith a number of trace gases such asargon, helium and radiatively activegreenhouse gases such as carbondioxide and ozone. In addition, theatmosphere contains water vapour,clouds, and aerosols.

biosphere: The part of the Earth’ssystem comprising all ecosystemsand living organisms in theatmosphere, on land (terrestrialbiosphere), or in the oceans (marinebiosphere), including derived deadorganic matter such as litter, soilorganic matter, and oceanic detritus.

carbon dioxide (CO2): A naturally

occurring gas as well as a by-productof burning fossil fuels and land-usechanges and other industrialprocesses. It is the principalgreenhouse gas which affects theEarth’s radiative balance and thereference gas against which othergreenhouse gases are measured.

chlorofluorocarbons (CFCs):Greenhouse gases which are usedfor refrigeration, air conditioning,packaging, insulation, solvents, oraerosol propellants. They are allcovered under the 1987 MontrealProtocol. Since they are notdestroyed in the lower atmosphere,CFCs drift into the upperatmosphere where, given suitableconditions, they break down ozone.These gases are being replaced byother compounds, includinghydrochlorofluorocarbons, coveredunder the Kyoto Protocol.

Climate: Usually defined as the‘average weather’ or more rigorouslyas the statistical description in termsof the mean and variability ofrelevant quantities over a period oftime ranging from months tothousands or millions of years. Theclassical period is 30 years as definedby the WMO. These relevantquantities are most often surfacevariables such as temperature,precipitation and wind.

climate change: Refers to astatistically significant variation ineither the mean state of the climateor in it’s variability, persisting for anextended period (typically decades orlonger). Climate change may be dueto natural internal processes orexternal forcings, or to persistentanthropogenic changes in thecomposition of the atmosphere. TheUNFCC defines climate change as ‘achange of climate which is attributeddirectly or indirectly to humanactivity that alters the composition ofthe global atmosphere and which isin addition to natural climatevariability observed over comparabletime periods’. See also climatevariability.

climate variability: Variations in themean state and other statistics (e.g.

standard deviations, the occurrenceof extreme events etc) of the climateon all temporal and spatial scalesbeyond that of individual weatherevents. Variability may be due tonatural internal processes within theclimate system or to variations innatural or anthropogenic externalforcing.

Disability Adjusted Life Year(DALY): An indicator of life

expectancy combining mortality andmorbidity into one summarymeasure of population health toaccount for the number of yearslived in less than optimal health. It isa health measure developed forcalculating the global burden ofdisease which is also used by WHO,the World Bank and otherorganizations to compare theoutcomes of different interventions.

El Niño/Southern Oscillation(ENSO): El Niño, in its original

sense, is a warm water current thatperiodically flows along the coast ofEcuador and Peru. This event isassociated with a fluctuation of theintertropical surface pressurepatterns and circulation in theIndian and Pacific Oceans, called theSouthern Oscillation. This coupledatmosphere-ocean phenomenon iscollective known as the El NiñoSouthern Oscillation or ENSO.During an El Niño event, theprevailing trade winds weaken andthe equatorial counter currentstrengthens, causing warm surfacewaters in the Indonesian area to floweastward to overlie the cold waters ofthe Peru current. This event hasgreat impact on the wind, sea surfacetemperature, and precipitationpatterns in the tropical Pacific. It hasclimatic effects throughout thePacific region and in many otherparts of the world. The opposite of

SUMMARY33

an El Niño event is called La Niña.greenhouse effect: Greenhouse gases

absorb infrared radiation, emitted bythe Earth’s surface, the atmosphereitself due to the same gases and byclouds. Atmospheric radiation isemitted to all sides, includingdownward to the Earth’s surface.Thus greenhouse gases trap heatwithin the surface-tropospheresystem. This is called the ‘naturalgreenhouse effect’. Atmosphericradiation is strongly coupled to thetemperature of the level at which it isemitted. An increase in theconcentration of greenhouse gasesleads to an increased infrared opacityof the atmosphere and therefore toan effective radiation into space froma higher altitude at a lowertemperature. This causes a radiativeforcing, an imbalance that can onlybe compensated for by an increaseof the temperature of the surface-troposphere system. This is the‘enhanced greenhouse effect’.

greenhouse gases (GHGs): Thosegases in the atmosphere whichabsorb and emit radiation at specificwavelengths within the spectrum ofinfrared radiation emitted by theEarth’s surface, the atmosphere andclouds. Water vapour, carbondioxide, nitrous oxide, methane andozone are the primary greenhousegases in the atmosphere. Moreover,there are a number of entirelyhuman-made gases in theatmosphere, such as the halocarbonsand others dealt with under theMontreal and Kyoto Protocols.

impacts: Consequences ofclimate change on natural systemsand human health. Depending onthe consideration of adaptation, wecan distinguish between potentialimpacts and residual impacts:• Potential impacts are all impacts

that may occur given a projectedchange in climate, with noconsideration of adaptation.• Residual impacts are the impacts ofclimate change that can occur afteradaptation.

Intergovernmental Panel onClimate Change (IPCC): A group of

experts established in 1988 by theWorld Meteorological Organization(WMO) and the United NationsEnvironment Programme (UNEP).Its role is to assess the scientific,technical and socio-economicinformation relevant for theunderstanding of the risk of human-induced climate change, basedmainly on peer reviewed andpublished scientific/technicalliterature. The IPCC has threeWorking Groups and a Task Force.

monitoring: Performance andanalysis of routine measurementsaimed at detecting changes in theenvironment or health status ofpopulations. Not to be confusedwith surveillance althoughsurveillance techniques may be usedin monitoring.

morbidity: Rate of occurrence ofdisease or other health disorderwithin a population, taking accountof the age-specific morbidity rates.Health outcomes include: chronicdisease incidence/prevalence,hospitalisation rates, primary careconsultations and Disability-Adjusted-Life-Years (DALYs).

mortality: Rate of occurrence ofdeath within a population within aspecified time period.

ozone: Form of the element oxygenwith three atoms instead of the twothat characterise normal oxygenmolecules. Ozone is an importantgreenhouse gas. The stratospherecontains 90 % of all the ozonepresent in the atmosphere which

absorbs harmful ultraviolet radiation.In high concentrations, ozone canbe harmful to a wide range of livingorganisms. Depletion ofstratospheric ozone, due to chemicalreactions that may be enhanced byclimate change, results in anincreased ground-level flux ofultraviolet-B-radiation.

scenarios: A plausible and oftensimplified description of how thefuture may develop, based on acoherent and internally consistentset of assumptions about key drivingforces and relationships. Scenariosare neither predictions nor forecastsand may sometimes be based on anarrative storyline.

sensitivity: Degree to which a systemis affected by climate-related changes,either adversely or beneficially. Theeffect may be direct (e.g. a change incrop yield in response to temperaturechange) or indirect (e.g. damagescaused by increases in the frequencyof coastal flooding).

stratospheric ozone depletion: Thereduction of the quantity of ozonecontained in the stratosphere due tothe release of greenhouse gases as aresult of human activity.

stratospheric ozone layer: Thestratosphere contains a layer inwhich the concentration of ozone isgreatest, the so-called ozone layer.The layer extends from about 12 to40 km. This layer is being depletedby human emissions of chlorine andbromine compounds. Every year,during the Southern Hemispherespring, a very strong depletion of theozone layer takes place over theAntarctic region, caused by human-made chlorine and brominecompounds in combination with themeteorological conditions of thatregion. This phenomenon is calledthe ozone hole.

surveillance: Continuous analysis,interpretation and feedback ofsystematically collected data for thedetection of trends in the occurrenceor spread of a disease, based onpractical and standardized methodsof notification or registration.Sources of data may be relateddirectly to disease or factorsinfluencing disease.

ultraviolet radiation (UVR): Solarradiation within a certainwavelength, depending on the typeof radiation (A, B or C). Ozoneabsorbs strongly in the UV-C (<280nm) and solar radiation in thesewavelengths does not reach theearth's surface. As the wavelength isincreased through the UV-B range(280nm to 315nm) and into the UV-A (315nm to 400nm) ozoneabsorption becomes weaker, until itis undetectable at about 340nm. Thefractions of solar energy above theatmosphere in the UV-B and UV-Aranges are approximately 1.5% and7% respectively.

UN Framework Convention onClimate Change (UNFCCC):

Convention signed at UnitedNations Conference onEnvironment and Development in1992. Governments that becomeParties to the Convention agree tostabilize greenhouse gasconcentrations in the atmosphere ata level that would prevent dangerousanthropogenic interference with theclimate system.

vulnerability: The degree to which asystem is susceptible to, or unable tocope with, adverse effects of climatechange, including climate variabilityand extremes. Vulnerability is afunction of the character, magnitudeand rate of climate variation towhich a system is exposed, itssensitivity and its adaptive capacity.

CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 34

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Chapter 61 Patz, J.A., et al., Effects of environmentalchange on emerging parasitic diseases. Int JParasitol, 30(12-13): p. 1395-405 (2000). 2 Bouma, M. and H. van der Kaay, The ElNiño Southern Oscillation and the historicmalaria epidemics on the Indiansubcontinent and Sri Lanka: an earlywarning system for future epidemics?Tropical Medicine and International Health,1(1): p. 86-96. (1996).3 Martens WJM, Rotmans J, Rothman DSIn: Martens WJM, McMichael AJ (eds).Environmental Change, Climate and Health:Issues and Research Methods. Cambridge:Cambridge University Press, 2002, pp. 197-225..

4 Hales, S., et al., Potential effect ofpopulation and climate changes on globaldistribution of dengue fever: an empiricalmodel. Lancet, 360: p. 830-834 (2002). 5 Wilson, M.L., Ecology and infectiousdisease, in Ecosystem Change and PublicHealth: A Global Perspective, J.L. Aron andJ.A. Patz, Editors. 2001, Johns HopkinsUniversity Press: Baltimore. p. 283-324.

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Chapter 81 Environmental effects of ozone depletion:1998 assessment. Nairobi, Kenya, UnitedNations Environment Program, 1998. Also:Kelfkens, G. et al. Ozone layer-climatechange interactions. Influence on UV levelsand UV related effects. Dutch NationalResearch Programme on Global AirPollution and Climate Change. Report no.:410 200 112.2 IARC. Solar and Ultraviolet Radiation.IARC Monographs on the Evaluation ofCarcinogenic Risks to Humans. Vol 55.Lyon, France, International Agency forResearch on Cancer, 1992.3 Madronich S, de Gruijl FR. Skin cancerand UV radiation. Nature, 366 (6450): 23(1993).4 Ponsonby A-L, McMichael AJ, van der MeiI. Ultraviolet radiation and autoimmunedisease: insights from epidemiologicalresearch. Toxicology; 181-182: 71-78 (2002).5 Temorshuizen F, et al. Influence of seasonon antibody response to high doserecombinant Hepatitis B vaccine: effect ofexposure to solar UVR? Hepatology, 32 (4):1657 (2000).5 Slaper H.et al. Estimates of ozonedepletion and skin cancer incidence toexamine the Vienna Convention

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Chapter 91 WHO Health impact assessment as a toolfor intersectoral health policy. WHO EuropeanCentre for Environment and Health/EuropeanCentre for Health Policy, 1999.2 Parry, M.L. & Carter, T. Climate impact andadaptation assessment. London, UK,EarthScan, 1998.3 Patz, J.A.et al. The potential health impactsof climate variability and change for the UnitedStates: executive summary of the report of thehealth sector of the US National Assessment.Environ Health Perspect 108: 367-376 (2000).4 Dept of Health (UK) Health Effects of ClimateChange in the UK. London: DoH 2002.5 OCHA. UNDAC Mission Report FijiDrought. UN Office for Co-ordination ofHumanitarian Affairs,1998.6 Health Canada. National Health Impact andAdaptation Assessment Framework and Tools.Ottawa: Climate Change and Health Office,Health Canada, 2002.

Chapter 101 Last, J. A dictionary of epidemiology. 2ndedition. New York: Oxford University Press,1988.

Chapter 111 IPCC, 2001. Climate Change 2001:Impacts, Adaptation, and Vulnerability.Contribution of Working Group II to theThird Assessment Report of theIntergovernmental Panel on ClimateChange. Cambridge University Press,Cambridge, UK.2 NOAA. NOAA releases century’s topweather, water, and climate events. 1999.http://www.noaanews.noaa.gov/stories/s334b.htm.3 US Centers for Disease Control (CDC).Rapid health needs assessment followingHurricane Andrew - Florida and Louisiana,1992. Morbidity and Mortality WeeklyReport, 41 (37): 685 (1992).4 UNDP. 2000 Human DevelopmentReport 2000: Human rights and humandevelopment. United Nations Development

Program. Oxford University Press, NewYork, NY, USA.5 WHO. 2000. World Health Report 2000:Health systems: Improving Performance.World Health Organization, Geneva,Switzerland. 6 Rayner, S. & Malone, E.L. Climatechange, poverty and intragenerationalequity: the national level. In: Climatechange and its linkages with development,equity and sustainability. Proceedings of theIPCC Expert Meeting held in Colombo, SriLanka, 27-29 April, 1999. Munasinghe, M.& Swart, R. eds. Colombo, Sri Lanka, LIFE;Bilthoven, The Netherlands, RIVM; andWashington D.C., USA, World Bank, pp.215-242, 1999.

Chapter 121 Scheraga, Joel D., and Anne E. Grambsch,“Risks, opportunities, and adaptation toclimate change,” Climate Research, Vol. 10,1998, 85-95.2 Tamburlini, G., and K. L. Ebi, “Searchingfor evidence, dealing with uncertainties, andpromoting participatory risk-management,” inChildren’s health and environment: A reviewof evidence, Tamburlini G., O.S. vonEhrenstein, R. Bertollini, editors. A JointReport from the European EnvironmentAgency and the WHO Regional Office forEurope, EEA, Copenhagen, 2002, 199-206.

Chapter 131 McMichael AJ et al. The SustainabilityTransition: A new challenge (Editorial). BullWHO, 78: 1067 (2000).2 R. Watson, et al. Protecting Our PlanetSecuring Our Future: Linkages AmongGlobal Environmental Issues and HumanNeeds. UNEP, NASA, World Bank, 1998. 3 McMichael, A.J. Population, environment,disease, and survival: past patterns, uncertainfutures. Lancet, 359: 1145-48 (2002).4 Patz, J.A. et al. The potential health impactsof climate variability and change for theUnited States: executive summary of thereport of the health sector of the U.S.National Assessment. Environ HealthPerspect,108(4): 367-76 (2000). 5 World Health Organization. World HealthReport, 2002.

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CLIMATE CHANGE AND HUMAN HEALTH - RISK AND RESPONSES 36

Project Coordinator: Carlos F. Corvalán. Editor: Anthony J. McMichael.

Based on the book "Climate Change and Human Health – Risks and Responses" (A.J. McMichael, et al, Eds.WHO, Geneva 2003). With contributions from: M. Ahern, London School of Hygiene and Tropical Medicine,London, UK; C. L. Bartlett, Centre for Infectious Disease Epidemiology, University College London, UK; D. H.Campbell-Lendrum, London School of Hygiene and Tropical Medicine, London, United Kingdom; U.Confalonieri, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil; C. F. Corvalán, World Health Organization,Geneva, Switzerland; K. L. Ebi, World Health Organization, Regional Office for Europe, European Centre forEnvironment and Health, Rome, Italy; S. J. Edwards, London School of Hygiene and Tropical Medicine,London, UK; J. Furlow, US Environmental Protection Agency, Washington DC, USA; A. Githeko, KenyaMedical Research Institute, Kisumu, Kenya; H. N.B. Gopalan, United Nations Environment Programme,Nairobi, Kenya; A. Grambsch, US Environmental Protection Agency, Washington DC, USA; S. Hales,Wellington School of Medicine, University of Otago, Wellington, New Zealand; S. Hussein, Johns HopkinsUniversity, Baltimore, Maryland, USA; R. S. Kovats, London School of Hygiene and Tropical Medicine,London, UK; K Kuhn, London School of Hygiene and Tropical Medicine, London, UK; P. Llansó, WorldMeteorological Organization, Geneva, Switzerland; R. Lucas, National Centre for Epidemiology and PopulationHealth, The Australian National University, Canberra, Australia; J. P. McCarty, University of Nebraska atOmaha, Nebraska, USA; A. J. McMichael, National Centre for Epidemiology and Population Health, TheAustralian National University, Canberra, Australia; L. O. Mearns, National Center for Atmospheric Research,Boulder, Colorado, USA; B. Menne, World Health Organization, Regional Office for Europe, European Centrefor Environment and Health, Rome, Italy; A. R. Moreno, The United States-Mexico Foundation for Science,Col. Del Valle, Mexico; B.S. Nyenzi, World Meteorological Organization, Geneva, Switzerland; J. A. Patz, JohnsHopkins University, Baltimore, Maryland, USA; A-L Ponsonby, National Centre for Epidemiology andPopulation Health, The Australian National University, Canberra, Australia; A. Prüss – Ustün, World HealthOrganization, Geneva, Switzerland; J. D. Scheraga, US Environmental Protection Agency, Washington DC,USA; N. de Wet, The International Global Change Institute, University of Waikato, New Zealand; P.Wilkinson, London School of Hygiene and Tropical Medicine, London, UK; A. Woodward, University ofOtago, Wellington, New Zealand.

Design and layout: James Elrington. Graphics: Sue Hobbs.

Front cover illustration: Paintings from the UNFCCC global multicultural multimedia communications project2002 (conception and art direction by Helmut Langer, Germany). Paintings by Enesia Nyazorwe, Zimbabweand Agnes Mwidadi Mpata, Tanzania. Graph of global average temperature rise 1900-2000 and projected for2000-2100 from an emission scenario which stabilizes CO2 concentrations at 750ppm (Hadley Centre, UK).Temperature increase shown is approximately 3º C between 1900-2100. Graph courtesy of the UK Met Office,originally published in "Climate change and its impacts; stabilization of CO2 in the atmosphere", 1999.

Acknowledgements

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SUMMARY