WMO Statement on the Status of the Global Climate in 2007

WMO statement on the status of the global climate in 2007

WMO-No. 1031 WMO-No. 1031

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Chairperson, Publications Board World Meteorological Organization (WMO) 7 bis, avenue de la Paix Tel.: +41 (0) 22 730 84 03 P.O. Box No. 2300 Fax: +41 (0) 22 730 80 40 CH-1211 Geneva 2, Switzerland E-mail: [email protected]

ISBN 92-63-11031-1

Cover: Dancing with the clouds. Illustration by Ka-Woon Ng, 12 years old, Hong Kong, China

This Statement is a summary of information provided by the Met Office Hadley Centre and the Climatic Research Unit, University of East Anglia, United Kingdom, and, in the United States, by the National Climatic Data Centre of the National Oceanic and Atmospheric Administration (NOAA), the National Snow and Ice Data Center, the National Interagency Fire Center and NOAA’s National Weather Service. Other contributors are WMO Member countries: Argentina, Australia, Brazil, Canada, China, Fiji, France, Germany, Iceland, India, Japan, the Netherlands, New Zealand, Sweden and Tunisia. The African Centre of Meteorological Applications for Development (ACMAD, Niamey), the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), the International Research Centre on El Niño (CIIFEN, Guayaquil), the Global Precipitation Climatology Centre (GPCC, Offenbach), the IGAD Climate Prediction and Applications Centre (ICPAC, Nairobi), the SADC Drought Monitoring Centre (SADC DMC, Gaborone) and the World Climate Research Programme (WCRP) also contributed.

NOTE

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Through its predecessor, the International It is relevant to recall that 2007 was a special Meteorological Organization (IMO), and year in many respects, for it was during 2007 since 1950 on its own account, the World that the IPCC issued the different compo- Meteorological Organization (WMO) has nents of its Fourth Assessment Report, which been very active in the field of climate ever then served as a fundamental contribution since the First International Meteorological to the thirteenth Conference of the Parties to Congress was convened in Vienna in 1873. the United Nations Framework Convention The IMO Commission for Climatology was on Climate Change (COP-13), held in Bali, established in 1929 and fifty years later, Indonesia, from 3 to 14 December 2007. In Bali, in 1979, WMO organized the First World WMO actively contributed to the session and Climate Conference, in collaboration with organized a successful side event, Improved such partners as the International Council for decision-making for climate adaptation: Science, the Intergovernmental Oceanographic providing a science basis. Furthermore, the Commission of the United Nations Educational, International Polar Year 2007–2008, launched Scientific and Cultural Organization, the United in 2007 as a WMO co-sponsored scientific Nations Environment Programme (UNEP) and venture, is also making a key contribution to the Food and Agriculture Organization of the our increasing understanding of the global United Nations. This historic conference would climate system. In following suite, in May 2007 soon lead to the establishment of WMO’s own the Fifteenth World Meteorological Congress World Climate Programme and, in 1980, that decided that in 2009 WMO would organize of the World Climate Research Programme with partners a World Climate Conference-3, with the International Council for Science and under the overall theme of climate prediction later the Intergovernmental Oceanographic for decision-making. Commission. Furthermore, the conference would also pave the way for the establishment, I would like to stress, once more, the impor- in 1988, of the WMO/UNEP co-sponsored tance of receiving feedback from Members on Intergovernmental Panel on Climate Change the relevance and content of these statements. (IPCC), which recently received the 2007 Nobel A questionnaire circulated by WMO among Peace Prize for its efforts “to build up and dis- recipients of the 2006 Statement revealed seminate greater knowledge about man-made important messages that were used proac- climate change, and to lay the foundations for tively in preparing the present issue. WMO the measures that are needed to counteract therefore looks forward to your comments such change”. on the WMO Statement on the Status of the Global Climate in 2007, or to your suggestions The Second World Climate Conference, for further improvement. organized by WMO and its partners in 1990, provided decisive momentum to the international efforts that resulted in the development of the United Nations Framework Convention on Climate Change in 1992 and the Global Climate Observing System. In the midst of these significant contributions, in 1993 WMO began to issue an annual statement on the status of the global climate, which has by now become an established source of information eagerly sought after, each year, by the scientific community and the media. The WMO Statement on the Status of the Global Climate in 2007 is the latest in this successful (M. Jarraud) series. Secretary-General

Global temperatures during 2007 years on record. The Met Office Hadley Centre analyses showed that the global mean surface The analyses made by leading climate centres temperature in 2007 was 0.40°C (0.72°F) above rank the year 2007 amongst the ten warmest the 1961–1990 annual average (14°C/57.2°F) and hence marks the seventh warmest year

(a) Globe on record. According to the National Climatic

Figure 1 – Annual 0.6 Data Center of the National Oceanic and global and hemispheric 0.4 Atmospheric Administration, the global mean 0.2 combined land surface 0.0 surface temperature anomaly was 0.55°C air temperature and sea −0.2 (0.99°F) above the twentieth century average surface temperature −0.4 (1901–2000) of 13.9°C (56.9°F), which ranks (SST) anomalies, −0.6 2007 the fifth warmest year in its record. −0.8

1850–2007, with respect Difference (°C) from 1961−1990 1860 1880 1900 1920 1940 1960 1980 2000 to the 1961–1990 mean. January 2007 was the warmest January since (b) Northern hemisphere The source data are global surface records were instituted. 1.2 blended land surface air 1.0 0.8 0.6 temperature and SST 0.4 Based on the Met Office Hadley Centre analy- 0.2 from the HadCRUT3 0.0 ses, 2007 surface temperatures averaged −0.2 series (Brohan et al., −0.4 separately for each hemisphere were 0.62°C −0.6 2006). Values are simple −0.8 (1.12°F) above the 30-year mean of 14.6°C −1.0 area-weighted averages. −1.2 (58.28°F) for the northern hemisphere (second

Difference (°C) from 1961−1990 1860 1880 1900 1920 1940 1960 1980 2000 (Source: Met Office Hadley warmest year on record) and 0.18°C (0.32°F)

Centre, UK, and Climatic (c) Southern hemisphere above the 30-year mean of 13.4°C (56.12°F) for

Research Unit, University of 0.6 the southern hemisphere (tenth warmest year 0.4

East Anglia, UK) 0.2 on record). The global average temperature for 0.0 January was 12.7°C (54.9°F), compared with −0.2 −0.4 the 1961–1990 January long-term average of −0.6

−0.8 12.1°C (53.8°F).

−1.0

−1.2

Difference (°C) from 1961−1990 1860 1880 1900 1920 1940 1960 1980 2000

Figure 2 – Global ranked surface temperatures for 0.5 the warmest 50 years. 1998 2005

Inset shows global 2003 0.6 2002 0.0 2004 2007 ranked surface 2006 2001 temperatures from 1850.

1997 −0.5 The size of the bars indicates the 95 per 1995 0.4 1999 0 50 100 150 cent confidence limits 1990 2000 Rank associated with each 1991 1983 1994 1987 year. The source data 1988 1996 are blended land surface 1981 1944 1993 1980 1989 1941 1878

air temperature and 1877 1992 1973 1977

0.2 1979 1939 SST from the HadCRUT3 1940 1986 1938 1982 1945 1969 1937 1984 series (Brohan et al., 1943 1985 1958 1962 1942 1961 1963 1953 1978 2006). Values are simple 1990−2007 1972 area-weighted averages 1970−1989 0.0 for the whole year. 1950−1969 (Source: Met Office Hadley Anomaly (°C) with respect to 1961−1990 1930−1949 Centre, UK, and Climatic Research Unit, University of 1910−1929 East Anglia, UK) 1890−1909 −0.2 1850−1889

10 20 30 40 50

Rank All temperature values have uncertainties, which in the southern parts of South America. The arise mainly from gaps in data coverage. The largest warmer-than-average annual anomalies size of the uncertainties is such that the global affected high latitude regions of the northern average temperature for 2007 is statistically hemisphere including much of North America, indistinguishable from each of the nine warm- Europe and Asia. Annual temperature anoma- est years on record. lies in these regions reached 2–4°C (3.6–7.2°F) above the 1961–1990 average. In the Russian Since the beginning of the twentieth century, Federation, 2007 was the warmest in 150 years the global average surface temperature has of hydrometeorological measurements. risen by 0.74°C, but this increase has not been continuous. The linear warming trend over Much of the North Atlantic was significantly the past 50 years (0.13°C per decade) is nearly warm, a pattern that reflects the continuing twice that for the past 100 years. warm phase of the Atlantic multi-decadal oscillation, which began in the mid-1990s. Note: Following established practice, WMO global tempera- Sea surface temperatures in large areas of the ture analyses are based on two different data sets. One is the combined data set maintained by the Met Office Hadley Southern Ocean were below average. Centre, UK, and the Climatic Research Unit, University of East Anglia, UK. The other is maintained by the United The year 2007 started with record-break- States Department of Commerce’s National Oceanic and ing temperature anomalies throughout the Atmospheric Administration. Both centres use improved temperature analyses, but different methodologies. These world. In parts of Europe, winter and spring differing methodologies result in small differences in ranked among the warmest ever recorded, global rankings. with anomalies of more than 4°C (7°F) above the long-term monthly averages for January and April. Regional temperature anomalies Extreme high temperatures occurred in much Warmer-than-average annual temperatures of Western Australia from early January to affected most land areas of the world, with the early March, with February temperatures exception of cooler-than-average anomalies more than 5°C above average.

90N ++ − + Figure 3 – Global field of + + ++ ++ + + + ++ + temperature anomalies + + ++ + ++ + +++ (°C, relative to 1961–1990) 60N + + + ++ + ++ +++++ + + + ++++ for 2007. Crosses indicate + + + +++ + ++++++ + + + +−+++ + + that the anomaly in a + + + + + − ++ ++ pixel is the warmest in 30N ++ + + + + the 158-year record. ++ + + ++ (Source: Met Office Hadley + ++ 0 + + ++ Centre, UK, and Climatic + + + ++ + +++ Research Unit, University of + + + East Anglia, UK) 30S + + + + − + −−− − − − − −− −−−++ − −− ++ − − − 60S − − −++ + ++ − − −−+ − +− +−−− +++ ++ −− −−− −++++ −−− − + − − + − + 90S 180 120W 60W 0 60E 120E 180

Arctic sea ice Western and Central Russian Federation All-time lowest extent May heatwave; Moscow recorded its highest temperature in May since 1891 United Kingdom on record in September; Eurasian snow cover extent surpassed previous Second lowest extent on record for January Worst flooding in 60 years Alaska North Hemisphere snow cover extent record set in 2005 (behind 1981) and April (behind 1990); third lowest extent (July); wettest May–July Nome was frost-free during Third lowest extent on record by 23 per cent for 2006–2007 winter since records began in 1766 Central Europe June–September, its second for April and spring China longest frost-free season in its North-east United States/South-east Canada Warmest winter and spring ever recorded in parts of Europe Heaviest snowfall in 100+ period of record; Major winter storm (February); about 56 years (March) North-west Pacific typhoon season September 2007, the North 300 000 people affected Tropical Cyclone Sidr (November) Below-average activity Slope had its largest fire on record Winter storm Kyrill (January) Maximum winds at landfall 240 km/h; the worst 24 storms, 14 typhoons United States Subtropical storm Andrea (May) Powerful extratropical storm with storm to hit Bangladesh since 1991; more than Second worst fire season, 8.7 million people affected and over 3 000 fatalities Typhoon Fitow (September) United States Maximum winds 65 km/h; wind gusts up to 170 km/h affected behind 2006 Northern Europe; nearly 50 lives lost. Maximum winds 157 km/h; August heatwave; over first storm in May since 1981 China the strongest typhoon to hit 50 deaths attributed to South-east United States Hurricane Noel (October) Switzerland South-eastern Europe and Persistent heavy rains in late-June and July Tokyo since October 2002 affected more than 29 million people. the heat; prompted numerous Persistent severe to Maximum winds 135 km/h; Zurich received its largest daily Mediterranean area This flood is believed to be the worst all-time record high and exceptional drought; tropical storm at landfall in the Caribbean; rainfall amount in 100 years June and July heatwaves South Asia Typhoon Man-Yi (July) prompted record levels of in the region since 1954. low temperatures driest spring on record became the deadliest storm in the 2007 season (August); had its heaviest Monsoon-related rainfall Maximum winds at landfall 160 km/h; electricity demand; about Hurricane Humberto (September) snowfall since caused the worst flooding the most powerful cyclone to hit Japan 40 deaths and over 130 fires Maximum winds at landfall 137 km/h; Hurricane Dean (August) 1955 (November) in years. Nearly 25 million in July since records began in 1951 blamed on the heat Southern China first storm on record to intensify Maximum winds 270 km/h people were affected. Sudan Severe drought conditions from tropical storm to a category 1 First major hurricane in the 2007 season and first Typhoon Krosa (October) Heavy rain and flooding from late September to hurricane within 16 hours and first category 5 to make landfall in the Atlantic basin Maximum winds at landfall 162 km/h; (June); described as the mid-December; millions of United States landfalling hurricane since Andrew in 1992; third strongest Atlantic the strongest typhoon in this area worst flooding in decades people suffered since 2005 hurricane ever at landfall Tropical Cyclone Gonu (June) during the 2007 season Mexico from water restrictions Atlantic hurricane season Uganda Maximum winds 260 km/h; East Pacific hurricane season Heavy rain and flooding and crop losses Near average activity Heaviest maximum winds at landfall 148 km/h; Below-average activity (November); worst flooding Bangladesh 15 storms, 6 hurricanes; first time rainfall in strongest cyclone on record in the Typhoon Lekima (September) 11 storms, 4 hurricanes in 5 decades; the worst January coldwave; since 1886, two category 5 hurricanes 35 years Arabian Sea and second strongest Maximum winds at landfall 116 km/h; natural disaster in coldest temperatures made landfall in the same season (August) cyclone in the North Indian Ocean brought heavy rain to Viet Nam causing Mexico’s history in nearly 40 years Burkina Faso its worst flooding in 45 years Hurricane Felix (September) Malaysia ENSO Heavy rain and flooding Maximum winds 270 km/h (July); characterized as the Heavy rain and flooding Neutral ENSO transitions into a weak La Niña Second major hurricane in the 2007 season worst flooding in 16 years North Indian Ocean cyclone season (January), continued from in late August; moderate La Niña developed late year Above-average activity December 2006; about 110 000 Tropical Cyclone George (March) Global tropical cyclone activity 6 storms, 3 cyclones people affected; described as the Maximum winds at second landfall 205 km/h; Below-average activity worst flooding in decades the most destructive cyclone to affect Port Costa Rica 79 storms Hedland since Joan in 1975 Heavy rain and flooding prompted Tropical Cyclone Gamède (February) 44 hurricanes/typhoons/cyclones a deadly mudslide in October. This is Brought a new worldwide rainfall 18 “major” hurricanes/typhoons/cyclones record to French La Réunion with the worst weather disaster for Costa Bolivia Australia Rica in years. nearly 4 000 mm within 3 days Heavy rain and Second hottest February Australia Brazil in the 1950–2007 period Sixth consecutive year of drought in Murray–Darling flooding affected South Africa South Indian Ocean cyclone season nearly 200 000 people Heavy rain and of record Basin, characterized as the worst in the nation’s Cold front led to 54 weather Mozambique Above-average activity and 70 000 hectares flooding in January history; New South Wales worst flooding in records in May. In June, Flooding in February; 10 storms, 8 cyclones of cropland 3 decades (June) Uruguay Johannesburg received its described as the worst (January–February) Worst flooding since first significant snowfall since 1981. flooding in 6 years 1959 (May); more than Australian cyclone season 110 000 people affected Below-average activity 5 storms, 5 cyclones Argentina Several nights below freezing temperatures led to electricity and South Pacific tropical cyclone season natural gas shortages (May). Below-average activity Buenos Aires experienced its first major 8 storms, 4 cyclones snowfall since 1918 (July). Antarctic ozone hole — 25 million km² at its peak in mid-September

Two extreme heatwaves affected south-eastern The Western Australian capital city of Perth Europe in June and July, breaking previous recorded 44.2°C (111.6°F) on 26 December, its records with daily maximum temperatures hottest December day since records began exceeding 40°C (104°F) in some locations, in 1897, exceeding the previous record of including up to 45°C (113°F) in Bulgaria. Dozens 42.3°C (108.1°F) on 31 December 1968 by of people died and firefighters battled blazes almost 2°C. that devastated thousands of hectares of land. A severe heatwave occurred across By contrast, Australia also recorded its coldest the southern United States of America dur- ever June with the mean temperature dropping ing much of August with numerous new all- to 1.5°C (2.7°F) below normal. South America time high temperature records established had an unusual cold winter (June–August), and more than 50 deaths attributed to the which brought strong winds, severe blizzards excessive heat. The months of August and and rare snowfall to various provinces that September were extremely warm in parts experienced temperatures of –22°C (–7.6°F) in of Japan, setting a new national record of Argentina and –18°C (–0.4°F) in Chile in early absolute maximum temperature of 40.9°C July. Severe winter storms and freezing rain (105.6°F) on 16 August. hit the Midwestern states of the United States

in the second week of December, covering Ana winds brought devastating fires to parts Figure 4 – Significant huge areas in a layer of thick ice and leaving of Southern California in October, destroy- climate anomalies and hundreds of thousands of homes without ing more than 1 500 homes and affecting events in 2007 power. hundreds of thousands of people. Based on (Source: National Climatic preliminary estimates, over 85 000 wildfires Data Center, NOAA, United and more than 37 000 square kilometres had States) Droughts burned across the United States, ranking 2007 the second worst fire season on record. Across North America, severe to extreme drought was present across large parts of In Australia, while conditions were not as the western United States and the Upper severely dry as in 2006, water resources Midwest, as well as southern Ontario, Canada, remained extremely low in many areas owing for much of 2007. More than three quarters of to long-term drought. Below-average rainfall the South-east United States was in drought —especially from July to October—over the from mid-summer into December, but heavy densely populated and agricultural regions rainfall led to an end of drought in the south- resulted in significant crop and stock losses ern Plains. Ongoing drought and strong Santa and a continuing need for water restrictions in

Figure 5 – Monthly air temperature anomalies showing departures in degrees Celsius, 1961–1990 base for April 2007 over Europe (Source: Deutscher Wetterdienst, Germany) Less than –4 –4 to –3 –3 to –2 –2 to –1 –1 to 0 0 to 1 1 to 2 2 to 3 3 to 4 More than 4

most major cities. Extensive fires that started Flooding and intense storms in early December 2006 in the mountains of north-eastern Victoria continued to burn into Global precipitation over land in 2007 was early February; the most long-lived fire in above the 1961–1990 average. However, Victoria’s history burned over 11 000 square regionally drier-than-average conditions were kilometres. recorded across the south-eastern and western contiguous United States, northern India, Southern China experienced severe drought the eastern coast of Brazil, the southern and conditions from late September to mid- eastern parts of Australia, and parts of eastern December. The provinces of Hunan, Jiangxi, Asia. Meanwhile, the central United States Guangdong, Guangxi, Guizhou and Fujian and parts of Europe and Asia experienced received only 40 per cent of normal rainfall. wetter-than-average conditions. Millions of people suffered from water restrictions and crop losses. Flooding affected many African countries in 2007. In February, Mozambique experienced its worst flooding in six years, killing dozens 20S Figure 6 – Averaged of people, destroying thousands of homes winter air temperature and flooding 800 square kilometres of crops anomalies showing in the Zambezi valley. In Sudan, torrential 25S departures in degrees rains caused flash floods in many areas in Celsius, 1961–1990 base 5 June/July, affecting over 410 000 people, of for June/July/August 2007 30S 4 which 200 000 were left homeless. The strong over Argentina. south-westerly monsoon resulted in one of the 3 White dots indicate heaviest July–September rainfall periods, trig- 2 meteorological stations 35S gering widespread flash floods that affected where 2007 averaged 1 several countries in West Africa, Central Africa winter temperatures 0 and parts of the Greater Horn of Africa. Some were the coldest for the 40S 1.5 million people were affected and hundreds –1 period 1961–2007. of thousands of homes were destroyed. (Source: Servicio –2 Meteorológico Nacional, 45S –3 In Bolivia, flooding in January/February affected Argentina) –4 nearly 200 000 people and 700 square kilometres of cropland. Strong storms brought –5 50S heavy rain that caused extreme flooding in the littoral region of Argentina in late March/ www.smn.gov.ar early April. In early May, Uruguay was hit by 55S its worst flooding since 1959, with heavy rain 75W 70W 65W 60W 55W producing floods that affected more than

110 000 people and severely damaged crops on the island of Java in Indonesia affected tens and buildings. Triggered by storms, massive of thousands with more than 100 casualties. flooding in Mexico in early November destroyed the homes of half a million people and seriously A powerful storm system, Kyrill, affected much affected the country’s oil industry. of northern Europe on 17 and 18 January with torrential rains and winds gusting up to In Indonesia, massive flooding on Java in early 170 km/h. There were at least 47 deaths across February killed dozens of people and covered the region, and disruptions in electric supply half of the city of Jakarta by up to 3.7 metres that affected tens of thousands of people of water. Persistent heavy rains in China rav- during the storm. aged the Huai He river valley in late June and July, affecting more than 29 million people. England and Wales recorded the wettest This flood is believed to be the worst in the May–July period since records began in region since 1954. Monsoon-related extreme 1766, receiving 415 mm of rain compared rainfall events caused the worst flooding in with the previous record of 349 mm in 1789. years in parts of South Asia. About 25 million Extensive flooding in the region killed nine people were affected in the region, especially people and caused more than US$ 6 billion in India, Pakistan, Bangladesh and Nepal, and in damages. thousands lost their lives. However, in India, rainfall during the summer monsoon season (June–September) was, generally, near normal Tropical cyclones (105 per cent of the long-term average), but with marked differences in the distribution of In the North-West Pacific, 24 named tropical rainfall in space and time. storms developed during 2007, below the long- term annual average of 27. Of those, 14 storms Heavy rains in the second half of December were classified as typhoons, equalling the resulted in massive flooding in Sri Lanka and long-term annual average. Tropical cyclones Indonesia. In Sri Lanka, more than one quarter affected millions in South-East Asia, with of a million people were affected, whilst wide- typhoons Pabuk, Krosa, Lekima and tropical spread floods triggering devastating landslides storms such as Peipah among the severest.

Figure 7 – Australian rainfall deciles for the years 2002 to 2007. Deciles are calculated Rainfall decile ranges relative to the period 1900–2007, with Highest on distribution based on record gridded data from the Very much 10 above average National Climate Centre. For the agriculturally 8–9 Above average important Murray– 4–7 Average Darling Basin (outlined in bold) it was the sixth 2–3 Below average consecutive year of Very much 1 lower-than-average below record rainfall totals and the Lowest on record driest such six-year period on record. (Source: Commonwealth of Australia, Australian Bureau of Meteorology, Australia)

Figure 8 – Annual 90N precipitation anomalies for global land areas for

2007; gridded 1.0-degree 60N raingauge-based analysis as normalized departures in mm/month from 1961–1990 base period 30N (Source: Global Precipitation Climatology Centre, Deutscher Wetterdienst, 0 Germany)

30S

60S

90S 180 120W 60W 0 60E 120E 180

–70 –50 –30 –10 10 30 50 70

During the 2007 Atlantic hurricane season, In June, cyclone Gonu made landfall in 15 named storms occurred, compared with the Oman, affecting more than 20 000 people 1981–2000 annual average of 12, with 6 being and killing 50, before reaching the Islamic classified as hurricanes, equalling the average. Republic of Iran. Gonu was the strongest For the first time since records began in 1886, tropical cyclone to hit the region since records two Atlantic category 5 hurricanes, Dean and began in 1945. Felix, made landfall in the same season. On 15 November, tropical cyclone Sidr made In February, due to tropical cyclone Gamède, landfall in Bangladesh, generating winds of a new worldwide rainfall record was set in up to 240 km/h and torrential rains. More La Réunion with 3 929 mm measured within than 8.7 million people were affected by the three days. category 4 storm, 52 000 were injured and over 3 000 died. Nearly 1.5 million houses were damaged or destroyed. Figure 9 – Monthly precipitation totals in mm 30N In Australia, the 2006/2007 tropical season for Africa for was unusually quiet, with only five tropi- 20N January 2007 cal cyclones recorded, equalling the lowest (Source: The African 10N number observed since at least 1943–1944. Centre of Meteorological Rainfall in January 2007 Applications for 0 850 Development, Niamey) 750 El Niño/Southern Oscillation conditions 650 10S 550 450 300 200 The brief El Niño event of late 2006 quickly 20S 100 50 dissipated in January 2007, and La Niña con- 25 30S 10 ditions became well established across the 0.1 central and eastern Equatorial Pacific in the 20W 10W 0 10E 20E 30E 40E 50E latter half of 2007.

10 In the course of the year, with La Niña estab- Over the last three months of the year, how- lished, conditions in the western Equatorial ever, sea surface temperature patterns became Pacific were initially not typical of a La Niña. generally consistent with a La Niña event. Unusual sea surface temperature patterns, with cooler-than-normal values across the north of The evolution of La Niña has influenced cli- Australia to the Indian Ocean, and warmer-than- mate patterns across many parts of the globe, normal values in the Western Indian Ocean, including in the direct vicinity of the Equatorial were recorded. The sea surface temperature Pacific, and more widely, across the Indian patterns in the Indian Ocean were similar to Ocean, Africa, Asia and the Americas. those associated with a positive phase of the Indian Ocean Dipole, a recently documented mode of the climate system (see box). Ozone in the Antarctic

The 2007 Antarctic ozone hole was relatively small owing to mild stratosphere winter temperatures. Since 1998, only the 2002 and 2004 The Indian Ocean Dipole ozone holes were smaller. In 2007, the ozone hole reached a maximum of 25 million square A positive phase of the Indian Ocean kilometres in mid-September, compared with Dipole is characterized by the presence more than 29 million square kilometres in the of cooler-than-normal sea surface tem- record years of 2000 and 2006. The ozone mass peratures in the eastern equatorial Indian deficit reached 28 megatons on 23 September, Ocean near Indonesia and Australia compared with more than 40 megatons in the and warmer-than-normal sea surface record year of 2006. temperatures in the western equatorial Indian Ocean, near Madagascar. A nega- tive phase of the Indian Ocean Dipole Arctic sea ice extent has the opposite features. The average sea ice extent for the month of September was 4.28 million square kilometres,

Figure 10 – Arctic sea ice extent at the end of the 12 summer melt season (Source: National Snow and Ice Data Center, United States) 10

2007 2005 record low Extent (millions of square kilometres) square of (millions Extent 1979–2000 average 4

July August September October November

11 the lowest September value on record. At Passage for about five weeks starting the end of the melt season, the Arctic sea ice 11 August. Nearly 100 voyages in normally extent was 39 per cent below the long-term ice-blocked waters sailed without the threat average from 1979 to 2000 and 23 per cent of ice. below the previous record set in 2005. The September rate of sea ice decline since The disappearance of ice across parts of 1979 is now approximately 10 per cent per the Arctic opened the Canadian Northwest decade, or 72 000 square kilometres per year.

Figure 11 – Sea ice extent for September 2007 (left) and September 2005 (right); the magenta line indicates the long-term median from 1979 to 2000. September 2007 sea ice extent was 4.28 million square kilometres (1.65 million square miles), compared with 5.57 million square kilometres (2.14 million square miles) in September 2005. This image is from the NSIDC Sea Ice Index. (Source: National Snow and Ice Data Center, United States)

12 Sea-level rise and global climate change by John Church,1 Chair WCRP JSC2

Global averaged sea level continued to rise and that the twentieth century rate of rise is through 2006 and 2007. Modern satellite meas- anomalous relative to the recent Holocene. urements reveal that since 1993, sea level has been rising at an average rate of about 3 mm The main contributions to sea-level change in per year, substantially faster than the average the twentieth and twenty-first centuries are for the twentieth century of about 1.7 mm the following: per year, estimated from coastal sea-level measurements. These coastal measurements ß Thermal expansion of the oceans (water indicate that the 2006/2007 global averaged expands as it warms); sea level is about 200 mm higher than in 1870 and since then there has been a significant ß The addition of mass to the oceans from increase in the rate of the sea-level rise. Both the melting of glaciers and ice caps in data sets show interannual variability in the areas such as the Himalayas, Alaska rate of rise. The increase in the rate of rise and Patagonia; during the latter half of the nineteenth century and the early twentieth century is confirmed ß The exchange of mass with the ice by the few multi-century direct coastal sea- sheets of Antarctica and Greenland; level measurements as well as by sea-level estimates from sediment cores in various parts ß The exchange of mass with terrestrial of the world. This is consistent with estimates water storages (groundwater, aquifers, made from sea-level benchmarks carved in dams, lakes). rock in Tasmania in 1840 and other data such as the height of ancient Roman fish tanks. Since 1960, the thermal expansion of the oceans Together these results imply that there had and the melting of glaciers and ice caps are the been little net change in the sea level from the largest contributions to sea-level rise. There first century AD to the nineteenth century AD has also been an increasing contribution from

Figure 12 – Global averaged sea level determined from coastal 25 sea-level measurements (solid line with one and tide gauge data two standard deviation 20 error estimates, from satellite altimeter data 1870 to 2006) and from satellite altimeter data 15 (red line, from 1993 to 2007) (Source: CSIRO Marine and Atmospheric Research, 10 Australia, based on coastal tide-gauge data from the Permanent Service for Mean 5 Sea Level (PSMSL) and altimeter data from NASA, Global mean sea level (cm) United States, and CNES, 0 France.)

−5 1880 1900 1920 1940 1960 1980 2000 Year

13 surface melt from the Greenland ice sheet over and frequency, of low-lying areas, erosion of this period. These contributions are directly beaches, and damage to infrastructure and related to recent climate change. the environment, including wetlands, inter- tidal zones and mangroves, with significant Over the last decade, however, there are impacts on biodiversity and ecosystem func- indications of a larger contribution from tion. Millions of people in low-lying nations the movement of outlet glaciers of both the such as Bangladesh, the Mekong and other Greenland and West Antarctic ice sheets. If deltas, and Pacific islands such as Tuvalu, will this were a sign of an acceleration in response have to respond to rising sea levels during the to global warming, it would be a major con- twenty-first century and beyond. cern as the ice sheets contain enough water to raise sea level by 7 and 6 m, respectively, Improved sea-level rise projections will con- and any such dynamic response could raise tribute to more effective coastal planning and sea level significantly faster than surface management. Adaptation measures include, for melting alone. example, enhanced building codes, restrictions on where to build and developing infrastructure The impacts of sea level rise will be felt through better able to cope with flooding. an increase in both mean sea level and the frequency of extreme sea level events, for 1 CSIRO Marine and Atmospheric Research, Australia example storm surges, of a given level. Impacts 2 World Climate Research Programme Joint Scientific include increased flooding, both severity Committee

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