June 2008

WMO statement on the status of the global climate in 2007

This article has been reproduced from the WMO statement on the status of the global climate in 2007 (WMO-No. 1031).

Global temperatures during 2007

The analyses made by leading climate centres rank the year 2007 amongst the 10 warmest years on record. The Met Office Hadley Centre analyses showed that the global mean surface temperature in 2007 was 0.40°C above the 1961–1990 annual average (14°C) and hence marks the seventh warmest year on record. According to the National Climatic Data Center of the US National Oceanic and Atmospheric Administration, the global mean surface temperature anomaly was 0.55°C above the 20th century average (1901–2000) of 13.9°C, which ranks 2007 the fifth warmest year in its record.

figure Annual global and hemispheric combined land surface air temperature and sea surface temperature (SST) anomalies, 1850–2007, with respect to the 1961–1990 mean. The source data are blended land surface air temperature and SST from the HadCRUT3 series (Brohan et al., 2006). Values are simple area-weighted averages.
(Source: Met Office Hadley Centre, UK, and Climatic Research Unit, University of East Anglia, UK)

January 2007 was the warmest January since global surface records were instituted.

Based on the Met Office Hadley Centre analyses, 2007 surface temperatures averaged separately for each hemisphere were 0.62°C above the 30-year mean of 14.6°C for the northern hemisphere (second warmest year on record) and 0.18°C above the 30-year mean of 13.4°C for the southern hemisphere (10th warmest year on record). The global average temperature for January was 12.7°C compared with the 1961–1990 January long-term average of 12.1°C.

All temperature values have uncertainties, which arise mainly from gaps in data coverage. The size of the uncertainties is such that the global average temperature for 2007 is statistically indistinguishable from each of the nine warmest years on record.

Since the beginning of the 20th century, the global average surface temperature has risen by 0.74°C, but this increase has not been continuous. The linear warming trend over the past 50 years (0.13°C per decade) is nearly twice that for the past 100 years.

Note: Following established practice, WMO global temperature analyses are based on two different datasets. One is the combined dataset maintained by the Met Office Hadley Centre, UK, and the Climatic Research Unit, University of East Anglia, United Kingdom. The other is maintained by the US National Oceanic and Atmospheric Administration. Both centres use improved temperature analyses, but different methodologies. These differing methodologies result in small differences in global rankings.

Regional temperature anomalies

Warmer-than-average annual temperatures affected most land areas of the world, with the exception of cooler-than-average anomalies in the southern parts of South America. The largest warmer-than-average annual anomalies affected high latitude regions of the northern hemisphere including much of North America, Europe and Asia. Annual temperature anomalies in these regions reached 2–4°C above the 1961–1990 average. In the Russian Federation, 2007 was the warmest in 150 years of hydrometeorological measurements.

Much of the North Atlantic was significantly warm, a pattern that reflects the continuing warm phase of the Atlantic multi-decadal oscillation, which began in the mid-1990s. Sea surface temperatures in large areas of the Southern Ocean were below average.

The year 2007 started with record-breaking temperature anomalies throughout the world. In parts of Europe, winter and spring ranked among the warmest ever recorded, with anomalies of more than 4°C above the long-term monthly averages for January and April.

figure Global field of temperature anomalies (°C, relative to 1961–1990) for 2007. Crosses indicate that the anomaly in a pixel is the warmest in the 158-year record.
(Source: Met Office Hadley Centre, UK, and Climatic Research Unit, University of East Anglia, UK)

Extreme high temperatures occurred in much of Western Australia from early January to early March, with February temperatures more than 5°C above average.

Two extreme heat waves affected south-eastern Europe in June and July, breaking previous records with daily maximum temperatures exceeding 40°C in some locations, including up to 45°C in Bulgaria. Dozens of people died and firefighters battled blazes that devastated thousands of hectares of land. A severe heat wave occurred across the southern USA during much of August with numerous new all-time high temperature records established and more than 50 deaths attributed to the excessive heat. The months of August and September were extremely warm in parts of Japan, setting a new national record of absolute maximum temperature of 40.9°C on 16 August.

The Western Australian capital city of Perth recorded 44.2°C on 26 December, its hottest December day since records began in 1897, exceeding the previous record of 42.3°C on 31 December 1968 by almost 2°C.

By contrast, Australia also recorded its coldest ever June with the mean temperature dropping to 1.5°C below normal. South America had an unusual cold winter (June–August), which brought strong winds, severe blizzards and rare snowfall to various provinces that experienced temperatures of –22°C in Argentina and –18°C in Chile in early July. Severe winter storms and freezing rain hit the mid-western states of the USA in the second week of December, covering huge areas in a layer of thick ice and leaving hundreds of thousands of homes without power.


Across North America, severe-to-extreme drought was present across large parts of the western USA and the upper mid-west, as well as southern Ontario, Canada, for much of 2007. More than three-quarters of the south-eastern USA was in drought from mid-summer into December, but heavy rainfall led to an end of drought in the southern plains. Ongoing drought and strong Santa Ana winds brought devastating fires to parts of southern California in October, destroying more than 1 500 homes and affecting hundreds of thousands of people. Based on preliminary estimates, over 85 000 wildfires and more than 37 000 square kilometres had burned across the USA, ranking 2007 the second worst fire season on record.

In Australia, while conditions were not as severely dry as in 2006, water resources remained extremely low in many areas owing to long-term drought. Below-average rainfall —especially from July to October—over the densely populated and agricultural regions resulted in significant crop and stock losses and a continuing need for water restrictions in most major cities. Extensive fires that started in early December 2006 in the mountains of north-eastern Victoria continued to burn into early February; the longest-lived fire in Victoria’s history burned over 11 000 square kilometres.

Southern China experienced severe drought conditions from late September to mid-December. The provinces of Hunan, Jiangxi, Guangdong, Guangxi, Guizhou and Fujian received only 40 per cent of normal rainfall. Millions of people suffered from water restrictions and crop losses.

map   Figure 4 – Significant climate anomalies and events in 2007
(Source: National Climatic Data Center, NOAA, United States)


Flooding and intense storms

Global precipitation over land in 2007 was above the 1961–1990 average. However, regionally drier-than-average conditions were recorded across the south-eastern and western contiguous USA, northern India, the eastern coast of Brazil, the southern and eastern parts of Australia and parts of eastern Asia. Meanwhile, central USAand parts of Europe and Asia experienced wetter-than-average conditions.

Flooding affected many African countries in 2007. In February, Mozambique experienced its worst flooding in six years, killing dozens of people, destroying thousands of homes and flooding 800 square kilometres of crops in the Zambezi valley. In Sudan, torrential rains caused flash floods in many areas in June/July, affecting over 410 000 people, of which 200 000 were left homeless. The strong south-westerly monsoon resulted in one of the heaviest July–September rainfall periods, triggering widespread flash floods that affected several countries in West Africa, Central Africa and parts of the Greater Horn of Africa. Some 1.5 million people were affected and hundreds of thousands of homes were destroyed.

In Bolivia, flooding in January/February affected nearly 200 000 people and 700 square kilometres of cropland. Strong storms brought heavy rain that caused extreme flooding in the littoral region of Argentina in late March/early April. In early May, Uruguay was hit by its worst flooding since 1959, with heavy rain producing floods that affected more than 110 000 people and severely damaged crops and buildings. Triggered by storms, massive flooding in Mexico in early November destroyed the homes of half a million people and seriously affected the country’s oil industry.

In Indonesia, massive flooding on Java in early February killed dozens of people and covered half of the city of Jakarta by up to 3.7 metres of water. Persistent heavy rains in China ravaged the Huai He valley in late June and July, affecting more than 29 million people. This flood is believed to be the worst in the region since 1954. Monsoon-related extreme rainfall events caused the worst flooding in years in parts of South Asia. About 25 million people were affected in the region, especially in India, Pakistan, Bangladesh and Nepal, and thousands lost their lives. However, in India, rainfall during the summer monsoon season (June–September) was, generally, near normal (105 per cent of the long-term average), but with marked differences in the distribution of rainfall in space and time.

Heavy rains in the second half of December resulted in massive flooding in Sri Lanka and Indonesia. In Sri Lanka, more than one-quarter of a million people were affected, whilst widespread floods triggering devastating landslides on the island of Java in Indonesia affected tens of thousands with more than 100 casualties.

A powerful storm system, Kyrill, affected much of northern Europe on 17 and 18 January with torrential rains and winds gusting up to 170 km/h. There were at least 47 deaths across the region, and disruptions in electric supply that affected tens of thousands of people during the storm.

England and Wales recorded the wettest May-July period since records began in 1766, receiving 415 mm of rain compared with the previous record of 349 mm in 1789. Extensive flooding in the region killed nine people and caused more than US$ 6 billion of damage.

Tropical cyclones

In the North-West Pacific, 24 named tropical storms developed during 2007, below the long-term annual average of 27. Of those, 14 storms were classified as typhoons, equalling the long-term annual average. Tropical cyclones affected millions in South-East Asia, with typhoons Pabuk, Krosa, Lekima and tropical storms such as Peipah among the severest.

During the 2007 Atlantic hurricane season, 15 named storms occurred, compared with the 1981–2000 annual average of 12, with six being classified as hurricanes, equalling the average. For the first time since records began in 1886, two Atlantic Category 5 hurricanes, Dean and Felix, made landfall in the same season.

In February, due to tropical cyclone Gamède, a new worldwide rainfall record was set in La Réunion with 3 929 mm measured within three days.

In June, cyclone Gonu made landfall in Oman, affecting more than 20 000 people and killing 50, before reaching the Islamic Republic of Iran. Gonu was the strongest tropical cyclone to hit the region since records began in 1945.

On 15 November, tropical cyclone Sidr made landfall in Bangladesh, generating winds of up to 240 km/h and torrential rains. More than 8.7 million people were affected by the category 4 storm, 52 000 were injured and over 3 000 died. Nearly 1.5 million houses were damaged or destroyed.

In Australia, the 2006/2007 tropical season was unusually quiet, with only five tropical cyclones recorded, equalling the lowest number observed since at least 1943–1944.

El Niño/Southern Oscillation conditions

The brief El Niño event of late 2006 quickly dissipated in January 2007 and La Niña conditions became well established across the central and eastern Equatorial Pacific in the latter half of 2007.

In the course of the year, with La Niña established, conditions in the western Equatorial Pacific were initially not typical of a La Niña. Unusual sea-surface temperature patterns, with cooler-than-normal values across the north of Australia to the Indian Ocean, and warmer-than-normal values in the western Indian Ocean, were recorded. The sea-surface temperature patterns in the Indian Ocean were similar to those associated with a positive phase of the Indian Ocean Dipole, a recently documented mode of the climate system.

The Indian Ocean Dipole

A positive phase of the Indian Ocean Dipole is characterized by the presence of cooler-than-normal sea surface temperatures in the eastern equatorial Indian Ocean near Indonesia and Australia and warmer-than-normal sea surface temperatures in the western equatorial Indian Ocean, near Madagascar. A negative phase of the Indian Ocean Dipole has the opposite features.

Over the last three months of the year, however, sea-surface temperature patterns became generally consistent with a La Niña event.

The evolution of La Niña has influenced climate patterns across many parts of the globe, including in the direct vicinity of the Equatorial Pacific, and more widely, across the Indian Ocean, Africa, Asia and the Americas.

Antarctic ozone

The 2007 Antarctic ozone hole was relatively small owing to mild stratosphere winter temperatures. Since 1998, only the 2002 and 2004 ozone holes were smaller. In 2007, the ozone hole reached a maximum of 25 million square kilometres in mid-September, compared with more than 29 million square kilometres in the record years of 2000 and 2006. The ozone mass deficit reached 28 megatons on 23 September, compared with more than 40 megatons in the record year of 2006.

Arctic sea ice extent

The average sea ice extent for the month of September was 4.28 million square kilometres, the lowest September value on record. At the end of the melt season, the Arctic sea ice extent was 39 per cent below the long-term average from 1979 to 2000 and 23 per cent below the previous record set in 2005.

The disappearance of ice across parts of the Arctic opened the Canadian North-west Passage for about five weeks starting 11 August. Nearly 100 voyages in normally ice-blocked waters sailed without the threat of ice.

The September rate of sea ice decline since 1979 is now approximately 10 per cent per decade, or 72 000 square kilometres per year.

map   map
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)



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