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60˚N60˚N WMO STATEMENT ON THE STATUS OF

THE GLOBAL CLIMATE IN 2004

World Meteorological OrganizationWeather • Climate • Water

WMO-No. 983

For information about WMO, please contact:

Communications and Public Affairs OfficeWorld Meteorological Organization7bis, avenue de la PaixP.O. Box 2300CH-1211 Geneva 2, SWITZERLANDTel: (+41-22) 730 83 14 / 730 83 15Fax: (+41-22) 730 80 27E-mail: cpa@wmo.intWeb: http://www.wmo.int

For more information about the contents of this brochure, please contact:

World Climate Programme DepartmentWorld Meteorological Organization7bis, avenue de la PaixP.O. Box 2300CH-1211 Geneva 2, SWITZERLANDTel: (+41-22) 730 83 77Fax: (+41-22) 730 80 42E-mail: wcdmp@wmo.intWeb: http://www.wmo.ch/web/wcp/wcp_prog.htm

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WorldMeteorologicalOrganization

Weather • Climate • Water

Geneva - Switzerland

WMO-No. 983© 2005, World Meteorological OrganizationISBN 92-63-10983-4

Front cover: Annual precipitation anomalies (departures in millimetres from a 1979–1995 base period) in 2004.Green and yellow indicate areas that received above normal precipitation for the calendar year 2004 as awhole. The different shades of burgundy depict those regions of the world that were drier than normal.Areas in white show regions where departures are within +/-50 mm of the average annual value.Precipitation values are obtained by merging raingauge observations and satellite-derived precipitationestimates (Source: Climate Prediction Centre, NOAA, United States).

Back cover: Right: Tracks of the typhoons which affected Japan during the 2004 cyclone season (Source: JapanMeteorological Agency).

Left: Maximum temperature anomalies (departures in degree Celsius from the 1961–1990 base period)over Australia for the fortnight ending 22 February 2004 (Source: Bureau of Meteorology, Australia).

NOTEThe designations employed and the presentation of material in this publication do not imply the expression of

any opinion whatsoever on the part of the Secretariat of the World Meteorological Organization concerning

the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its

frontiers or boundaries.

This statement is a summary of the information provided by the Hadley Centre of the Met Office, United Kingdom;the Climatic Research Unit, University of East Anglia, United Kingdom; and the National Climatic Data Centerand the Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA), UnitedStates. Other contributors were from the following WMO Member countries: Argentina, Australia, Canada, China,France, Germany, Iceland, India, Japan, Mauritius, New Zealand, Norway, Russia, Sweden, Switzerland, as well asfrom the International Research Institute for Climate Prediction in New York, the IGAD Climate Prediction andApplications Centre in Nairobi, and the AGRHYMET Centre in Niamey.

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FOREWORD

Since 1993, the World Meteorological Organization (WMO),through the Commission for Climatology and in coopera-tion with its Members, has issued annual statements on thestatus of the global climate to provide credible scientificinformation on climate and its variability. This year’s state-ment describes the climatic conditions, including extremeweather events, for the year 2004 and provides a historicalperspective on some of the variability and trends that haveoccurred since the nineteenth century. The statementscomplement the periodic assessments of the WMO/UnitedNations Environment Programme (UNEP) Intergovern-mental Panel on Climate Change (IPCC), which is now inthe process of preparing its fourth Assessment Report.

The information contained in this statementenhances our scientific understanding of the climate vari-ability and the associated impacts that have occurred inthe past. Through continuing research and the collectionof consistent and high quality observations by WMO andits Members, it is possible to progress towards betterunderstanding of the Earth’s climate system and toimprove on our projections for the future.

The 2004 cyclone season saw some of the mostdestructive hurricanes and typhoons on record, whichclaimed more than 6 000 lives and caused heavy damagesto property. Disastrous floods and landslides due to heavyprecipitation events were also reported worldwide.Prolonged drought conditions continued to affect parts ofAfrica, Australia, South Asia and the western UnitedStates. Conversely, in 2004, the natural climate variabilityalso produced benefits to society. An example is thesignificant boost in grain harvests in Europe due tofavourable climate conditions and Middle East wintergrain crops benefiting from early-season precipitation.

A significant threat to sustainable development is theincreased impact of extreme weather and climate events

such as tropical cyclones, floods, drought and heat waves.According to the IPCC Assessment Report the duration,location and frequency of extreme weather and climateevents are likely to change, and would result in mostlyadverse impacts on biophysical systems. In the longerterm, sustainable development also therefore requiresthat the climate system be better understood with thepossibility to project future climate changes and theirpotential impacts. A major challenge for the meteorolog-ical and hydrological communities is to work towards amajor reduction of the fatality rate associated with naturaldisasters of hydrometeorological origin. For countriesthat are at high risk of extreme weather and climateevents, increased awareness and preparedness of peopleand societies are required to face such events. Adequatepreparation and response to these events require animprovement of existing weather- climate- and water-related monitoring services and applications, and thedevelopment of new ones.

WMO remains committed to assisting the NationalMeteorological and Hydrological Services (NMHSs) toachieve these goals through the development of a moreintegrated approach to global observing comprising itssurface- and space-based networks. The timely provisionof authoritative climate statements, climate assessments,and climate reviews and their historical perspective willalso contribute to the important role of WMO in ensuringsustainable development in the twenty-first century.

(M. Jarraud)Secretary-General

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GLOBAL TEMPERATURESDURING 2004

The global mean surface temperature in 2004was 0.44°C above the 1961–1990 annual aver-age (14°C). This value places 2004 as the fourthwarmest year in the temperature record since1861 just behind 2003 (+0.49°C). However, 1998remains the warmest year, when surfacetemperatures averaged +0.54°C above the same30-year mean. The last 10 years (1995–2004),with the exception of 1996, are among thewarmest on record. The five warmest years indecreasing order are: 1998, 2002, 2003, 2004and 2001.

Over the twentieth century, the increase inglobal surface temperature has been between 0.6and 0.7°C. The rate of change since 1976 isroughly three times that for the past 100 years asa whole. In the northern hemisphere, the 1990swas the warmest decade with an average of0.38°C. The surface temperatures averaged overthe recent five years (2000–2004) were, however,much higher (0.58°C). Surface air temperaturesat a worldwide network of land stations haveshown that trends of night-time minimumtemperature on still nights have been the sameas on windy nights.

Calculated separately for both hemi-spheres, surface temperatures in 2004 for thenorthern hemisphere (+0.62°C) were the fourthwarmest and, for the southern hemisphere(+0.25°C), the sixth warmest in the instrumen-tal record from 1861 to the present. Globally,the land-surface air temperature anomalies forOctober and November 2004 were the warmeston record for these months. The blended landand sea-surface temperature (SST) value forthe Arctic (north of 70°N) in July and the

Figure 1 — Combinedannual land (near surface)and sea-surface temperatureanomalies from 1861–2004(departures in degreesCelsius from the average inthe 1961–1990 base period)for (a) the globe; (b) thenorthern hemisphere north of30°N; (c) the Tropics(30°N–30°S); and (d) thesouthern hemisphere south of30°S. The solid red curveshave had subdecadaltimescale variationssmoothed with a binomialfilter. Anomalies (in degreesCelsius) for 2004 are:+0.44 (a); +0.75 (b);+0.38 (c); and +0.22 (d)(Sources: Hadley Centre,The Met Office, and ClimaticResearch Unit, University ofEast Anglia, UK).

NOTE: There are somedifferences in annualanomalies between this andthe earlier WMOstatements. In this newanalysis, more quality-improved, land station datahave been used.

land-surface air temperature values for Africasouth of the Equator in July and Novemberwere the warmest on record for these months.Significant positive annual regional tempera-ture anomalies, notably across much of theland masses of central Asia, China, Alaska andwestern parts of the United States, as well asacross major portions of the North AtlanticOcean contributed to the high global meansurface temperature ranking.

REGIONAL TEMPERATUREANOMALIES

Large portions of the northern hemisphere hadwarm conditions in 2004 that exceeded 90 percent of the annual temperatures recorded in the1961–1990 period (the 90th percentile).Northern China, parts of central Asia and theeastern North Atlantic had warm temperaturesexceeding the 98th percentile. Only a few smallareas experienced temperatures below the 10thpercentile.

During June and July, heatwaves withnear-record temperatures affected southernSpain, Portugal and Romania, with maximumtemperatures reaching 40°C. In the second

week of August, an unusual heatwave affectedparts of Iceland, making the month of Augustthe second warmest on record.

An exceptional heatwave affected much ofeastern Australia during February, as maximumtemperatures soared to 45°C in many areaswith temperature anomalies exceeding 8°C (seeback cover). The spatial and temporal extent ofthe heatwave was greater than that of any otherFebruary heatwave on record and rankedamong the top five Australian heatwaves in anymonth.

A prolonged severe heatwave acrossnorthern parts of India during the last week ofMarch and the beginning of April caused morethan 100 deaths. During this period, maximumtemperatures generally exceeded the long-term averages by 5 to 7°C. In Japan, extremehot conditions persisted during the summerwith record-breaking maximum temperatures.Tokyo experienced a maximum temperature of 39.5°C on 20 July, which set a record since1923.

During the northern hemisphere winter,very cold weather episodes were observed inparts of South Asia (northern parts of India andBangladesh), which were blamed for as manyas 600 deaths. Maximum and minimum

5

Figure 2 — Trends of night-time minimum air

temperature anomalies(departures in degreesCelsius relative to the

1961–1990 base period),averaged over a worldwide set

of land stations for1951–2000. The red line

shows the observationsrecorded on windy nights

and the blue line shows theobservations recorded on still

nights (Source: HadleyCentre, The Met Office,

UK).

Figure 3 — Global annualtemperature anomaly

percentiles for 2004 basedon a gamma distribution forthe 1961–1990 base period,calculated in five-degree grid

boxes. Orange and brownindicate regions where the

temperature anomalies wereestimated to be within thehighest (warm) 10 and 2

per cent, respectively, of theclimatological occurrences.

Blue and purple indicate thelowest (cold) 10 and 2 per

cent of occurrences,respectively. Note that grid

areas without sufficient datafor analysis are left blank(Source: Hadley Centre,

The Met Office, UK).

7

temperatures were below normal by 6–10°C.During the austral winter, abnormally coldconditions in the high-altitude areas of theAndes in southern Peru reportedly killed 92people and more than 100 000 farm animals.

PROLONGED DROUGHT INSOME REGIONS

In early 2004, drought conditions continued toaffect parts of eastern South Africa,Mozambique, Lesotho and Swaziland. However,enhanced precipitation in the last half of therainy season (November to March) providedsome benefit to crops in southern Africa.Rainfall during both the long (March to June)and short (October to November) rainy seasonsof 2004 was well below normal across parts ofthe Greater Horn of Africa, resulting in a contin-uation of multi-season drought in this region.Isolated regions in the southern sector andportions of Uganda experienced driest condi-tions on record since 1961. In Kenya, apremature end to the 2004 long rains exacer-bated the drought conditions resulting fromseveral years of poor rainfall in many areas.Food production in Kenya was projected atapproximately 40 per cent below normal. Inspite of abundant rainfall in 2004, multi-yeardrought conditions also continued in Somalia,threatening agriculture and food security in theregion. In Eritrea, which was struggling fromnearly four years of drought, poor rains duringthe March–May rains exacerbated drinking-water shortages.

In India, the 2004 seasonal rainfall duringthe south-west monsoon season (June–September) over the country as a whole was 13per cent below normal with 18 per cent of the

6

country experiencing moderate drought condi-tions. Rainfall deficiency was the highest overnorth-west India, where only 78 per cent ofnormal rainfall was received. In neighbouringPakistan, poor rains in July and August aggra-vated the long-term drought conditions, whichhad prevailed since the boreal spring. The rain-fall deficiency was the largest over theBalochistan and Sindh provinces, causing watercrisis over these regions. In Sri Lanka, droughtconditions prevailing since the end of 2003aggravated due to deficient rainfall during the2004 summer monsoon season. In Afghanistan,drought conditions that had plagued the coun-try for the past four years continued in 2004 dueto below normal precipitation in March–April.In the spring season, parts of north-east Chinaexperienced the worst drought conditions since1951, due to deficient spring rainfall and abovenormal temperatures. Later during the fallseason, the southern provinces of Chinareceived the lowest rainfall since 1951, result-ing in the worst drought in the region, affectingagriculture and drinking water.

Long-term hydrological drought continuedto affect much of southern and easternAustralia, as a result of rainfall deficits experi-enced since the major drought event of2002/2003. The weak El Niño conditions in thePacific, hindered any significant recovery fromlong-term rainfall deficiencies. This hasresulted in significant crop losses in manyareas of eastern Australia. Moderate to severedrought conditions continued in some areas ofthe western United States for the fifth year in arow. By the beginning of 2004, moderate toextreme drought conditions covered about one-third of the contiguous United States. Somerelief was experienced during September and

Southern and Eastern USWetter than average.9 landfalling tropicalsystems.

EuropeWidespreadabove averageannual temperatures (+1°C).

Hurricane FrancesCategory 2 at landfall.Extensive flooding in southern AppalachianMountains.

Hurricane JeanneCategory 3 at landfall.Over 3 000 liveslost in Haiti.

Atlantic hurricane season Above-average activity15 named storms; 9 hurricanes;6 ‘major’. 8 tropical storms inAugust—most named stormsfor any August on record.

Alaska/Yukon wildfiresRecord area burned (2.6 million hectares) in Alaska.

Neutral ENSO transitions into weak El Niño in late boreal summer and autumn.

AlaskaRecord warm May, June, July, August.

Somalia, KenyaDespite good “long rains” in Somalia, long-term drought remains. Only 50% of normal rainfall for south-eastern Kenya over last 2 years.

Tropical Cyclone Elita Affected Madagascar making two separate landfalls. 29 people killed, tens of thousands homeless.

Tropical Cyclone Gafilo Strongest cyclone to hit Madagascar in 10 years. Winds at 260 km/hr at landfall.

Northern hemisphere snow cover extent largest since 1985 for January; 5th lowest in 38 years for March.

Antarctic ozone hole less extensive than the 10-year mean. Less than 20 million km2 in size.

Hurricane IvanReached category 5 in theCaribbean. 210 km/hr at landfall. Massive destructionin Grenada as it passedover the island.

East Pacific hurricane seasonBelow average activity.12 named storms; 6 hurricanes. Indian monsoon rainfall

87% of normal overall. Maximum regional deficit in north-west India with 22% less than average.

Peru, Chile, ArgentinaSevere cold and snow during June and July.

Typhoon TokageDeadliest typhoon to strike Japan since 1979; 94 deaths. 10th cyclone to make landfall in Japan during 2004 season; produced a record 24-meter high wave.

Typhoons:

ChinaFlooding inSichuan Provincein September.196 people killed.

South-east ChinaDrought is one ofthe worst in 50 years.Drinking water supplies threatened.

AfghanistanLong-term droughtcontinued. DryMarch–April season.

IndiaSevere heatwavein March. More than100 deaths.

Western USContinuation ofmulti-year droughtconditions, somerelief in autumn.

IndiaMonsoon-related floodiongJune–October. Millions of residentsdisplaced in Assam, Bihar andBangladesh. Worstflooding in 15 years.

TonadoesRecord year fortornadoes. Mostlya result of tropicalsystems.

Central andNorth-east USMuch colder-than-average summer.

CanadaRecord cold summer ineastern Prairies, record summerheat on west coast.

North America8th largest snow coverextent in 38 years for October.

Africa ITCZAverage annual ITCZclose to long-termmean position.

Western Asia, MongoliaAnnual warmth, anomalies 2–3°C.

Spain, PortugalHeatwave in Juneand July withmaximum temperaturesreaching 40°C.

Above-average activity in the West Pacific;29 named storms and 19 typhoons.

Record number of tropical cyclones (10, previous record 6) made landfall in Japan.

AustraliaIntense and widespread heatwave during February. Many city records broken. Long-term drought remains in southern and eastern Australia.

BrazilWet December–February. Major floodingin January in Brazil’snorth-eastern states.

Hurricane CharleyStrongest hurricane toimpact the U.S. sinceHurricane Andrew in 1992.

Tasmania2nd wettest January since 1900.

Tropical Cyclone HetaFirst cyclone to impact Samoa in a decade.

Strong winter storms in January for Pacific north-west.

Jordan, Syria, Greece, TurkeyWidespread winter storm in February. Approximately 60 cm of snow in Jordan.

South Atlantic hurricaneRare hurricane inthe South Atlanticin March. Made landfall in the state of SantaCatarina, Brazil.Maximum sustainedwinds of 120–130 km/hr.

Mexico/USSevere flooding inApril along theEscondido River.

Angola, ZambiaSevere flooding in April.In Zambia, also in May.

Desertlocust invasionMay–October 2004.

Super Typhoon NidaCame ashore in the Philippines in May with sustained winds of 260 km/hr.

Typhoon RananimStrongest typhoon to affect Zhejiang Province in China since 1956. Over US$ 2 billion in damage and 169 deaths.

Super Typhoon ChabaSuper-typhoon (category 4) in the Pacific, category 1 at landfall inJapan in August; 13 deaths.

JapanWetter-than-average yearfor much of the country. Partly due to landfallingtropicalsystems.

AustraliaNorthern Territory, much wetter than average rainy season.

New ZealandHeavy rainfall and damaging floods in February.

Sea-iceBelow long-term average.September 13% below10-year mean.

PhilippinesTwo typhoons and one tropicalstorm claimed over 1 000 lives inthe Philippines in November.

denotes point of landfall.

Typhoon Ma-onStrongest typhoon to strike the greater Tokyo areain 10 years in October. Wettest October since 1876 for the city.

Figure 4 — Global surfacetemperature anomalies(departures in degreesCelsius from the average inthe 1961–1990 base period)for the three-month periods(a) December2003–February 2004;(b) March–May 2004;(c) June–August 2004;(d) September– November2004 (Sources: HadleyCentre, The Met Office, andClimatic Research Unit,University of East Anglia,UK).

Figure 5 — Significant climatic anomalies and events in 2004. Theaverage global temperature was the fourth warmest on record. Therehas been a rise in global temperature greater than 0.6°C since 1900(Source: National Climatic Data Center, NOAA, United States).

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October causing a decrease in the nationaldrought area to about 5 per cent by the end ofOctober. In 2004, due to deficient annual rain-fall, the eastern provinces of Cuba experiencedthe effects of the worst drought, eroding 40 percent of farmlands. A prolonged drought alsoaffected and severely threatened the food secu-rity and health in the south-eastern El Chacoregion of Bolivia.

RAINFALL AND FLOODING

Precipitation in 2004 was above average for theglobe and 2004 was the wettest year since 2000.Wetter-than-average conditions prevailed in thesouthern and eastern United States, Russia,parts of western Asia, Bangladesh, Japan,coastal Brazil, Argentina and north-westAustralia.

The Asian summer monsoon during June-September brought heavy rain and flooding toparts of northern India, Nepal and Bangladesh,leaving millions stranded. Throughout India,Nepal and Bangladesh, some 1 800 deathsresulted from flooding brought by heavymonsoon rains. Flooding in north-east India(the states of Assam and Bihar, in particular)and Bangladesh was the worst in over a decade.In eastern and southern China, heavy rainsduring the summer produced severe floodingand landslides that affected more than 100million people and caused more than 1 000deaths nationwide. Heavy monsoon rainfallduring July and August produced floodingalong several rivers in north-eastern and centralThailand. A significant low-pressure systembrought record-breaking snowfalls in theRepublic of Korea on 5 March, resulting indamage to agriculture worth more than

US$ 500 million. In October, two typhoons andactive frontal systems brought record-breakingheavy rainfall to Japan. Tokyo received a totalamount of 780 mm precipitation in October,which is the largest monthly amount on recordsince 1876. In the second half of November andthe beginning of December, two typhoons andone tropical storm passed over southern andcentral parts of the Philippines, drenching theislands with several days of torrential rainfalland triggering catastrophic flash floods andlandslides, which killed, according to reports,more than 1 800 people.

Mudslides and floods due to heavy rainsacross areas of Brazil during January and earlyFebruary left tens of thousands of peoplehomeless and resulted in 161 deaths. The rainyseason in the Peruvian and Bolivian highlandsbrought heavy seasonal rainfall, hailstorms andlandslides, which caused heavy damage to agri-cultural crops and lands and killed at least 50people. In Haiti, torrential rainfall due to thepassage of Hurricane Jeanne produced disas-trous flooding that claimed some 3 000 lives.This disaster came in the wake of flooding andlandslides that affected Haiti and theDominican Republic in late May 2004, in whichmore than 2 000 people were killed and severalthousand others were affected. A series ofwinter storms during late June and into earlyJuly 2004 brought heavy rains and producedmudslides over the Patagonia region of Chileand Argentina.

In April, a storm brought heavy rain to thesouth-western United States and adjoiningMexico, causing the worst flash floods in theregion. In February, a winter storm broughtrecord-breaking snowfalls and blizzard condi-tions in Canada. The city of Halifax recorded

8

Disastrous cyclone seasonThe 2004 tropical cyclone season over the North Atlantic and the north-west Pacific saw some of the most deadlyhurricanes and typhoons responsible for more than 6 000 deaths and heavy damages to infrastructure. The 2004 cycloneseason was the second costliest cyclone season after 1992 and the number of deaths due to tropical cyclones was thehighest since 2000.

During the Atlantic hurricane season, 15 named tropical storms developed; the average is around 10. During August,eight tropical storms formed, which is a record for the most named storms for any month of August. Since 1995, there hasbeen a marked increase in the annual number of tropical storms in the Atlantic Basin, which is coincident with the activephase of the Atlantic multi-decadal signal. Nine of the named storms were classified as hurricanes. Six of those were“major” hurricanes (category three or higher on the Saffir-Simpson scale). Hurricane Ivan was the most powerful storm toaffect the Caribbean in 10 years. Hurricane Charley was the strongest and most destructive hurricane to strike the UnitedStates since Andrew in 1992. In all, nine named storms impacted the United States, causing extensive damage estimatedat more than US$ 43 billion and making 2004 the costliest hurricane season in the United States on record. Atlantictropical cyclones were directly responsible for more than 3 000 deaths in 2004; the vast majority were in Haiti due tofloods from Hurricane Jeanne.

Conversely, in the eastern North Pacific, tropical cyclone activity was below average. Only 12 named stormsdeveloped during the year, compared to an average of 16. Out of those 12 storms, six reached hurricane strength andthree reached “major” status. None of the cyclones made landfall as a tropical storm or hurricane.

In the South Atlantic Ocean, sea-surface and atmospheric conditions do not favour the formation of hurricanes.During March 2004, however, the first documented hurricane since geostationary satellite records began in 1966developed. Unofficially named Catarina, it made landfall along the southern coast of Brazil (in the state of Santa Catarina)on 28 March 2004, causing great damage to property and some loss of life.

In the north-west Pacific, 29 named storms developed; the average is around 27. Nineteen of them reached typhoonintensity, which was slightly more than the long-term average. On an average, three tropical cyclones make landfall inJapan. However, in 2004, 10 tropical cyclones made landfall, breaking the previous record of six, established in 1990.Typhoon Tokage was the deadliest typhoon to affect Japan since 1979. Two hundred and nine people were killed in Japanby floods, landslides, strong wind and storm surge caused by the tropical cyclones. They also caused damages toinfrastructures worth around US$ 10 billion. Typhoon Rananim, which was the most severe typhoon affecting Zhejiang,China since 1956, claimed 169 fatalities and caused damages worth over US$ 2 billion.

The South-west Indian Ocean cyclone season was also active with an above normal number of tropical storms.Tropical Cyclone Gafilo, which is responsible for 237 deaths, was the strongest to affect Madagascar in 10 years. Thetropical storm 02B made landfall on the coast of Myanmar on 19 May, which caused 200 fatalities. However, tropicalcyclone activity over the South Pacific/Australian region was suppressed.

Figure 6 — Accumulatedprecipitation anomalies(departures in millimetresfrom a 1979–1995 baseperiod) in 2004 for Africa.Green indicates areas thatreceived above normalprecipitation for the calendaryear 2004 as a whole whilepurple depicts those regionsthat were drier than normal.Areas in white show regionswhere departures are within+/-50 mm of the averageannual value. Precipitationvalues are obtained bymerging raingaugeobservations and satellite-derived precipitationestimates (Source: ClimatePrediction Center, NOAA,United States).

October causing a decrease in the nationaldrought area to about 5 per cent by the end ofOctober. In 2004, due to deficient annual rain-fall, the eastern provinces of Cuba experiencedthe effects of the worst drought, eroding 40 percent of farmlands. A prolonged drought alsoaffected and severely threatened the food secu-rity and health in the south-eastern El Chacoregion of Bolivia.

RAINFALL AND FLOODING

Precipitation in 2004 was above average for theglobe and 2004 was the wettest year since 2000.Wetter-than-average conditions prevailed in thesouthern and eastern United States, Russia,parts of western Asia, Bangladesh, Japan,coastal Brazil, Argentina and north-westAustralia.

The Asian summer monsoon during June-September brought heavy rain and flooding toparts of northern India, Nepal andBangladesh, leaving millions stranded.Throughout India, Nepal and Bangladesh,some 1 800 deaths resulted from floodingbrought by heavy monsoon rains. Flooding innorth-east India (the states of Assam andBihar, in particular) and Bangladesh was theworst in over a decade. In eastern and south-ern China, heavy rains during the summerproduced severe flooding and landslides thataffected more than 100 million people andcaused more than 1 000 deaths nationwide.Heavy monsoon rainfall during July andAugust produced flooding along several riversin north-eastern and central Thailand. Asignificant low-pressure system broughtrecord-breaking snowfalls in the Republic ofKorea on 5 March, resulting in damage to

agriculture worth more than US$ 500 million.In October, two typhoons and active frontalsystems brought record-breaking heavy rain-fall to Japan. Tokyo received a total amount of780 mm precipitation in October, which is thelargest monthly amount on record since 1876.In the second half of November and thebeginning of December, two typhoons andone tropical storm passed over southern andcentral parts of the Philippines, drenching theislands with several days of torrential rainfalland triggering catastrophic flash floods andlandslides, which killed, according to reports,more than 1 800 people.

Mudslides and floods due to heavy rainsacross areas of Brazil during January and earlyFebruary left tens of thousands of peoplehomeless and resulted in 161 deaths. Therainy season in the Peruvian and Bolivianhighlands brought heavy seasonal rainfall,hailstorms and landslides, which causedheavy damage to agricultural crops and landsand killed at least 50 people. In Haiti, torren-tial rainfall due to the passage of HurricaneJeanne produced disastrous flooding thatclaimed some 3 000 lives. This disaster camein the wake of flooding and landslides thataffected Haiti and the Dominican Republic inlate May 2004, in which more than 2 000people were killed and several thousandothers were affected. A series of winter stormsduring late June and into early July 2004brought heavy rains and produced mudslidesover the Patagonia region of Chile andArgentina.

In April, a storm brought heavy rain to thesouth-western United States and adjoiningMexico, causing the worst flash floods in theregion. In February, a winter storm brought

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Disastrous cyclone seasonThe 2004 tropical cyclone season over the North Atlantic and the north-west Pacific saw some of the most deadlyhurricanes and typhoons responsible for more than 6 000 deaths and heavy damages to infrastructure. The 2004 cycloneseason was the second costliest cyclone season after 1992 and the number of deaths due to tropical cyclones was thehighest since 2000.

During the Atlantic hurricane season, 15 named tropical storms developed; the average is around 10. During August,eight tropical storms formed, which is a record for the most named storms for any month of August. Since 1995, there hasbeen a marked increase in the annual number of tropical storms in the Atlantic Basin, which is coincident with the activephase of the Atlantic multi-decadal signal. Nine of the named storms were classified as hurricanes. Six of those were“major” hurricanes (category three or higher on the Saffir-Simpson scale). Hurricane Ivan was the most powerful storm toaffect the Caribbean in 10 years. Hurricane Charley was the strongest and most destructive hurricane to strike the UnitedStates since Andrew in 1992. In all, nine named storms impacted the United States, causing extensive damage estimatedat more than US$ 43 billion and making 2004 the costliest hurricane season in the United States on record. Atlantictropical cyclones were directly responsible for more than 3 000 deaths in 2004; the vast majority were in Haiti due tofloods from Hurricane Jeanne.

Conversely, in the eastern North Pacific, tropical cyclone activity was below average. Only 12 named stormsdeveloped during the year, compared to an average of 16. Out of those 12 storms, six reached hurricane strength andthree reached “major” status. None of the cyclones made landfall as a tropical storm or hurricane.

In the South Atlantic Ocean, sea-surface and atmospheric conditions do not favour the formation of hurricanes.During March 2004, however, the first documented hurricane since geostationary satellite records began in 1966developed. Unofficially named Catarina, it made landfall along the southern coast of Brazil (in the state of Santa Catarina)on 28 March 2004, causing great damage to property and some loss of life.

In the north-west Pacific, 29 named storms developed; the average is around 27. Nineteen of them reached typhoonintensity, which was slightly more than the long-term average. On an average, three tropical cyclones make landfall inJapan. However, in 2004, 10 tropical cyclones made landfall, breaking the previous record of six, established in 1990.Typhoon Tokage was the deadliest typhoon to affect Japan since 1979. Two hundred and nine people were killed in Japanby floods, landslides, strong wind and storm surge caused by the tropical cyclones. They also caused damages toinfrastructures worth around US$ 10 billion. Typhoon Rananim, which was the most severe typhoon affecting Zhejiang,China since 1956, claimed 169 fatalities and caused damages worth over US$ 2 billion.

The South-west Indian Ocean cyclone season was also active with an above normal number of tropical storms.Tropical Cyclone Gafilo, which is responsible for 237 deaths, was the strongest to affect Madagascar in 10 years. Thetropical storm 02B made landfall on the coast of Myanmar on 19 May, which caused 200 fatalities. However, tropicalcyclone activity over the South Pacific/Australian region was suppressed.

record-breaking snowfalls and blizzard condi-tions in Canada. The city of Halifax recorded88.5 cm of snow on 19 February, which doubledthe previous record for a single day. In July,torrential rain and hail deluge due to a stormresulted in horrendous flash floods inEdmonton and Peterborough, which are esti-mated to be the worst in 200 years.

Severe winter weather also affected muchof western and northern Europe during the lastweek of January with heavy accumulations ofsnow reported in parts of the United Kingdom,France, Germany and Denmark. In April, heavylong rains caused flooding in some parts ofwestern Siberia. In northern Caucasus,hundreds of buildings, bridges and motorwayswere heavily damaged; crop production hasalso been affected. In November, an earlyseason winter storm brought record-breakingheavy snowfall and strong winds across muchof the Scandinavian region and central Europecausing heavy damages.

Heavy rains from mid-January to March inareas of Angola produced flooding along theriver system, which flows into neighbouringZambia, Botswana and Namibia. Extensiveflooding along the Zambezi River, the worstflooding since 1958, threatened more than20 000 people in north-eastern Namibia andcaused extensive damage to crops.

Rainfall was above normal over most ofthe western and central Australian tropicsduring the 2003–2004 tropical wet season(October–April). In some parts of the NorthernTerritory, it was the wettest rainy season onrecord. A series of strong storms duringFebruary produced heavy rainfall and damagingfloods in southern parts of New Zealand’sNorth Island.

WEAK EL NIÑO CONDITIONS

Sea-surface temperature and sea-levelatmospheric pressure patterns in the tropicalPacific at the beginning of 2004 reflected near-neutral El Niño conditions. However, theincrease and eastward expansion of anomalouswarmth in the central and east-centralequatorial Pacific during July–Decemberindicated weak El Niño conditions. Since thelast week of July, SSTs over the equatorialcentral Pacific region were approximately 0.8°Cabove average. However, the pattern of above-average SST anomalies was focused only nearthe dateline. The eastern Pacific, which isusually instrumental in the development of anEl Niño event, remained largely neutralthroughout 2004. The Tahiti-Darwin SouthernOscillation Index was negative since June 2004,but fluctuated considerably. The large-scaleatmospheric changes expected during anEl Niño event were however conspicuouslyabsent during this episode.

ANTARCTIC OZONE HOLE

Extensive ozone depletion was observedover Antarctica during the southernhemisphere winter/spring of 2004. This year,the Antarctic ozone hole area (defined asthe area covered by extremely low ozonevalues of less than 220 Dobson Units)reached maximum size of 19.6 million km2 inmid-September. Except for the year 2002,when the ozone hole split into two, theOctober ozone hole this year was thesmallest observed in more than a decade.The ozone hole in 2004 dissipated earlierthan usual, in mid-November.

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Variations in size, depth and persistence ofthe ozone hole are due to year-to-year changes inthe meteorological conditions in the lower strat-osphere, rather than to changes in the amount ofozone-depleting substances present in the ozonelayer. Measurements show that most of thesesubstances are decreasing in the lower atmos-phere. However, chemicals already in theatmosphere are expected to continue to impactthe ozone concentration for many decades tocome. Continued monitoring and measurementsare essential to achieve the understandingneeded to identify ozone recovery.

ARCTIC SEA-ICE

In 2004, sea-ice extent in the Arctic remainedwell below the long-term average. In September2004, it was about 13 per cent less than the1973–2003 average. Satellite informationsuggests a general decline in Arctic sea-iceextent of about 8 per cent over the last two-and-a-half a decades. This is the third year in arow with extreme sea-ice losses. The Septembersea-ice deficit was especially evident in extremenorthern Alaska and eastern Siberia. Sea-iceextent responds to a variety of climatic factors.While natural variability is responsible foryear-to-year variations in sea-ice extent, three

extreme minimum extent years along with theevidence of thinning of the ice pack suggestthat the sea-ice system is experiencing changesnot solely related to natural variability.

CONCLUDING REMARKS

According to the third IPCC Assessment Reportthe duration, location and frequency of extremeweather and climate events are likely to change,and would result in mostly adverse impacts onbiophysical systems. The IPCC also notes thatfor certain extreme phenomena there iscurrently insufficient information to assessrecent trends, and climate models currently lackthe spatial detail required to make confidentprojections. Therefore the linkages betweenclimate variability and climate change andpatterns of natural hazards remain a researchtopic that needs to be further investigated bythe scientific community.

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(a) Arctic

(b) Antarctic1 August 31 August 30 September 29 November30 October

Are

a of

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Figure 8 (Right) —Monthly sea-ice extent

anomalies for 1973–2004(departures in millions of

km2 from the average in the1973–2004 base period) for

(a) the Arctic and (b) theAntarctic. The values are

derived from satellite passivemicrowave sounder data

(Source: Hadley Centre,The Met Office, UK).

Figure 7 (Left) — Daily sizeof the Antarctic ozone hole

(in million square km) from1 August to 15 Decemberfor the period 2001–2004

using total ozoneobservations from NOAA’ssolar backscatter ultraviolet

(SBUV/2) instrument onboard NOAA’s polar-

orbiting satellites (Source:Climate Prediction Center/

NOAA, United States).

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60˚N60˚N WMO STATEMENT ON THE STATUS OF

THE GLOBAL CLIMATE IN 2004

World Meteorological OrganizationWeather • Climate • Water

WMO-No. 983

For information about WMO, please contact:

Communications and Public Affairs OfficeWorld Meteorological Organization7bis, avenue de la PaixP.O. Box 2300CH-1211 Geneva 2, SWITZERLANDTel: (+41-22) 730 83 14 / 730 83 15Fax: (+41-22) 730 80 27E-mail: cpa@wmo.intWeb: http://www.wmo.int

For more information about the contents of this brochure, please contact:

World Climate Programme DepartmentWorld Meteorological Organization7bis, avenue de la PaixP.O. Box 2300CH-1211 Geneva 2, SWITZERLANDTel: (+41-22) 730 83 77Fax: (+41-22) 730 80 42E-mail: wcdmp@wmo.intWeb: http://www.wmo.ch/web/wcp/wcp_prog.htm

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