Outline
• Background– Human energy balance– Strategies to temperature changes
• Morbidity– Heat Waves– Flooding– Famine
• Disease– Malaria
IPCC (2007) Working Group 2 Report
How climate change affects health
Heat Waves
• Associated with short-term increases in mortality
• Have been increasing in frequency
• Mortality displacement is a factor– People close to death will die sooner in a heat
wave– Drop off in deaths after the heat wave
Human Adaptability to Heat
• Humans maintain near constant core temperature through various adaptive strategies:– Physiological (sweating)– Acclimatization (adjustment to new conditions
over time)– Alteration of food intake– Changing when you do things– Migration– Clothing– Use energy for A/C or heating
Human Energy Balance
• Storage change = 0 over time to maintain temperature balance
SECRQM )(
Metabolic Rate
Incoming shortwave
Longwave Radiation
Convection
Evaporation
Storage
Clothing Impact
• The “private climate”• Quantified by estimating the resistance to
thermal transfer:
T
DT
T
ASCL hM
AqQM
M
TTI
/
Body Temp.Air Temp. Body Area
Incoming shortwave
Metabolic Rate Dry Heat Flux = 6.6+8.7(wind speed)0.5
Simplified Clothing Index
Acclimatization
• Evidence that some populations have become less sensitive to temperature extremes– USA (1964-1988)– South Carolina (since 1970s)
• Physiological responses include:– More efficient heat loss through sweat– Readjustment of temperature preference toward the
extreme values
• Leads to less discomfort, better work performance, sense of better well being
Flooding and Health Effects
• Large numbers of fatalities from the events themselves– Bangladesh
• Post-event impacts– Digestive diseases– Chemical contamination
(e.g. Katrina)– Mental disorders
(anxiety, depression)• Higher impacts on poor
– More live in flood prone areas
Drought
• Diminishes diversity in diet and reduces overall food consumption
• Malnutrition– Increases risk of acquiring and dying from
infectious disease
• May cause mass migration (rural to urban)– Increase in communicable disease
Climate Model Projections
Food Safety
• Studies have shown a linear increase in food poisoning with increase in temperature
• Higher temperatures increase contact between food and pests (flies, cockroaches, rodents)
• More ocean toxins (Harmful Algal Blooms) contaminate shellfish
Water Supply
• Water access already a global concern– 2 billion + do not
have access to clean water
– Leads to disease, malnutrition, infant mortality
Water Supply
• Climate extremes (projected to increase) stress water supply systems
• Lower river flows increases pathogen proportion
• Extreme rain/runoff events may increase water borne disease– Curriero et al. 2001
Vector Borne Diseases
• Transmitted through bites– Mosquitoes, ticks, bugs,
some flies
• Tick populations have shifted north (Sweden, Canada) and up (Czech Republic)
• Evidence of earlier arrival of mosquitoes
Malaria
• 515 million cases each year in tropics and subtropics– 1-3 million deaths
• Conflicting results on malaria trends and how they relate to climate– Some evidence that high minimum temperatures in
preceding months mean more malaria (Ethiopia)
Future Vulnerability to Climate Change
• Factors– Existing burden of disease and disability– Aging of the population– Population explosion
• From 6.4 bil to 9 bil by mid-21st century• Highest in poor countries
– Urbanization• Heat island effect, more efficient disease transfer
– Socio-economic• Rich get richer, poor get poorer