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The global climate in 2007
Remarkable global climatic events recorded so far in 2007 include record-low Arctic sea-ice extent, which led to first recorded opening of the Canadian North-west Passage; the relatively small Antarctic ozone hole; development of La Niña in the central and eastern equatorial Pacific; and devastating floods, drought and storms in many places around the world.
The preliminary information for 2007 is based on climate data up to the end of November from networks of land-based weather stations, ships and buoys, as well as satellites. The data are continually collected and disseminated by the National Meteorological and Hydrological Services (NMHS) of WMO’s 188 Members and several collaborating research institutions.
WMO’s global temperature analyses are based on two different sources. One is the combined dataset maintained by both the Hadley Centre of the UK Meteorological Office and the Climatic Research Unit, University of East Anglia, UK, which, at this stage, ranked 2007 as the seventh warmest on record. The other dataset is maintained by the US Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA), which indicated that 2007 is likely to be the fifth warmest on record.
Since the start of the 20th century, the global average surface temperature has risen by 0.74°C. But this rise has not been continuous. The linear warming trend over the last 50 years (0.13°C per decade) is nearly twice that for the last 100 years.
According to the Intergovernmental Panel on Climate Change’s Fourth Assessment (Synthesis) Report, 2007, “warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”
2007 global temperatures have been averaged separately for both hemispheres. Surface temperatures for the northern hemisphere are likely to be the second warmest on record, at 0.63°C above the 30-year mean (1961-90) of
January 2007 was the warmest January in the global average temperature record at 12.70°C/54.90°F, compared to the 1961-1990 January long-term average of 12.10°C/53.80°F.
Regional temperature anomalies
2007 started with record-breaking temperature anomalies throughout the world. In parts of Europe, winter and spring ranked amongst the warmest ever recorded, with anomalies of more than 4°C above the long-term monthly averages for January and April.
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/104°F in some locations, including up to 45°C/113°F in Bulgaria. Dozens of people died and fire-fighters battled blazes devastating thousands of hectares of land. A severe heat wave occurred across southern USA during much of August with more than 50 deaths attributed to excessive heat. August to September 2007 was extremely warm in parts of Japan, setting a new national record of absolute maximum temperature of 40.90°/105.60°F on 16 August.
In contrast, Australia recorded its coldest ever June with the mean temperature dropping to 1.5°C below normal. South America experienced an unusually cold winter (June-August), bringing winds, blizzards and rare snowfall to various provinces with temperatures falling to -22.00°C/-7.60°F in Argentina and -18.00°C/-0.40°F in Chile in early July.
Across North America, severe to extreme drought was present across large parts of the western USA and upper mid-west, including southern Ontario/Canada, for much of 2007. More than three-quarters of south-eastern USA was in drought from mid-summer into December, but heavy rainfall led to an end of drought in the southern Plains.
China experienced its worst drought in a decade, affecting nearly 40 million hectares of farmland. Tens of millions of people suffered from water restrictions.
Flooding and intense storms
Flooding affected many African countries in 2007. In February, Mozambique experienced its worst flooding in six years, killing dozens, destroying thousands of homes and flooding 80 000 hectares of crops in the Zambezi valley.
In Sudan, torrential rains caused flash floods in many areas in June/July, affecting over 410 000 people, including 200 000 who were left homeless. The strong south-westerly monsoon resulted in one of the heaviest July-September rainfall periods, triggering widespread flash floods affecting 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 homes destroyed.
In Bolivia, flooding in January and February affected nearly 200 000 people and 70 000 hectares 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 and covered half of the city of Jakarta by up to 3.7 m of water. Heavy rains in June ravaged areas across southern China, with flooding and landslides affecting over 13.5 million people and killing more than 120. 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 Bangladesh, India, Nepal and Pakistan. Thousands lost their lives. However, rainfall during the Indian 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.
A powerful storm system, Kyrill, affected much of northern Europe during 17-18 January 2007 with torrential rains and winds gusting up to 170 km/h. There were at least 47 deaths across the region, with disruptions in electricity supplies affecting tens of thousands.
England and Wales recorded their wettest May-July period since records began in 1766, receiving 415 mm of rain compared to the previous record of 349 mm in 1789. Extensive flooding in the region killed nine and caused more than US$ 6 billion in damage.
Development of La Niña
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 addition to 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. These are believed to have modified the usual La Niña impacts in certain regions around the world.
The current La Niña is expected to continue at least into the first quarter of 2008.
Devastating tropical cyclones
Twenty-four named tropical storms developed in the North-West Pacific during 2007, below the annual average of 27. Fourteen storms were classified as typhoons, equalling the annual average. Tropical cyclones affected millions in South-East Asia, with typhoons Pabuk, Krosa, Lekima and tropical storm Peipah among the most severe.
During the 2007 Atlantic hurricane season, 15 named storms occurred (annual average: 12), with six being classified as hurricanes, equalling the average. For the first time since 1886, two Category 5 hurricanes (Dean and Felix) made landfall in the same season. Tropical storm Olga developed in December after the official end of the Atlantic hurricane season. It was only the 10th named storm to develop in the month of December since record-keeping began in 1851.
In February, tropical cyclone Gamède occasioned a new worldwide rainfall record in French La Réunion with 3929 mm of rain measured in 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. There is no record of a tropical cyclone hitting Iran since 1945.
On 15 November, tropical cyclone Sidr made landfall in Bangladesh, generating winds of up to 240 km/h and torrential rains. More than 8.5 million people were affected and more than 3000 died. Nearly 1.5 million houses were damaged or destroyed. Often hit by cyclones, Bangladesh has developed a network of cyclone shelters and a storm early warning system, which significantly reduced casualties.
Australia’s 2006/2007 tropical season was unusually quiet, with only five tropical cyclones recorded, equalling the lowest number observed since at least 1943-1944.
Relatively small Antarctic ozone hole
The 2007 Antarctic ozone hole was relatively small due 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 to 29 million square kilometres in the record years of 2000 and 2006. The ozone mass deficit reached 28 megatonnes on 23 September, compared to more than 40 megatonnes in the record year of 2006.
Record low Arctic sea-ice extent opened the North-west Passage
Following the Arctic sea-ice melt season, which ends annually in September at the end of the northern summer, the average “sea-ice extent” was 4.28 million square kilometres, the lowest on record. The sea-ice extent in September 2007 was 39 per cent below the long-term 1979-2000 average, and 23 per cent below the previous record set two years ago in September 2005.
For the first time in recorded history, 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.
Sea-level rise continues
Sea-level continued to rise at rates substantially above the average for the 20th century of about 1.7 mm per year. Measurements show that the 2007 global averaged sea-level is about 20 cm higher than the 1870 estimate. Modern satellite measurements show that, since 1993, global averaged sea-level has been rising at about 3 mm per year.
Hadley Centre of the UK Meteorological Office, the Climatic Research Unit, University of East Anglia, UK, and in the USA: NOAA’s National Climatic Data Centre, National Environmental Satellite and Data Information Service, National Snow and Ice Data Centre and NOAA’s National Weather Service. Other contributors are WMO Member states: 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 Centro Internacional para la Investigación del Fenõmeno El Niño (CIIFEN, Guayaquil), the IGAD Climate Prediction and Applications Centre (ICPAC, Nairobi), the SADC Drought Monitoring Centre (SADC DMC, Gabarone) and the World Climate Research Programme (WCRP) also contributed.
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