Extreme Weather Events Might Increase
PRESS RELEASE n.695 / WMO 2jul03
Geneva—Record extremes in weather and climate events continue to occur around the world. Recent scientific assessments indicate that, as the global temperatures continue to warm due to climate change, the number and intensity of extreme events might increase, the World Meteorological Organization (WMO) states in a press release issued today.
In June, record high temperatures were recorded across southern France, with maximum temperatures exceeding 40°C in parts of southwest France. This resulted in June average temperatures of 5 to 7°C above the long-term average. In Switzerland, the month of June was the hottest in at least the past 250 years, according to environmental historians. In Geneva, since 29 May, maximum daytime temperatures did not drop below 25°C, making June the hottest June on record for the city.
In the United States, there were 562 tornados during May, which resulted in 41 deaths. This established a record for the number of tornados in any month. The previous monthly record was 399 tornados in June 1992. In the eastern and southeastern part of the US, wet and cold conditions prevailed for well over a month. Weekly negative temperature anomalies of –2°C to –6°C were experienced in May while precipitation excesses, ranging from 50 mm to 350 mm over a period of more than 12 weeks starting in March 2003, have been recorded.
In India, this year’s pre-monsoon heat wave brought peak temperatures of between 45°C and 49°C which correspond to weekly temperature departures from the normal of +2 to +5°C. At least 1400 people died in India due to the hot weather. In Sri Lanka, heavy rainfalls from Tropical Cyclone 01B exacerbated already wet conditions, resulting in flooding and landslides and killing at least 300 people. The infrastructure and economy of southwestern Sri Lanka was heavily damaged. A reduction of 20-30% is expected for the output of low-grown tea in the next three months.
These record extreme events (high temperatures, low temperatures and high rainfall amounts and droughts) all go into calculating the monthly and annual averages which, for temperatures, have been gradually increasing over the past 100 years. New record extreme events occur every year somewhere in the globe, but in recent years the number of such extremes have been increasing. According to recent climate change scientific assessment reports of the joint WMO/UNEP Intergovernmental Panel on Climate Change (IPCC), the global average surface temperature has increased since 1861. Over the 20th century the increase has been around 0.6°C. This value is about 0.15°C larger than that estimated by the previous reports. New analyses of proxy data for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest in any century during the past 1000 years. It is also likely that, in the Northern Hemisphere, the 1990s were the warmest decade and 1998 the warmest year. While the trend towards warmer globally averaged surface temperatures has been uneven over the course of the last century, the trend for the period since 1976 is roughly three times that for the past 100 years as a whole. Global average land and sea surface temperatures in May 2003 were the second highest since records began in 1880. Considering land temperatures only, last May was the warmest on record.
The influence of El Niño and La Niña on these extreme events is in general undefined. The World Meteorological Organization (WMO) and its Members, the National Meteorological and Hydrological Services along with various research institutes, will continue to organize research and document the influence of El Niño and other large scale climate phenomena on climate extreme events.
For more information please contact:
Ms Carine Richard-Van Maele
Chief, Information and Public Affairs
World Meteorological Organization
Tel: +41 (0) 22 730 83 14/5
Fax:+41 (0) 22 730 80 27
Internet website: http://www.wmo.ch
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