Info notes

Info Note No. 44

For use of the information media. Not an official record

Temporary La Niña’s cooling effect does not stall global warming

GENEVA, 4 April 2008 (WMO) - The long-term upward trend of global warming, mostly driven by greenhouse gas emissions, is continuing.  Global temperatures in 2008 are expected to be above the long-term average. The decade from 1998 to 2007 has been the warmest on record, and the global average surface temperature has risen by 0.74C since the beginning of the 20th Century.

The current La Niña event, characterized by a cooling of the sea surface in the central and eastern Equatorial Pacific, is a “climate anomaly” part of natural climate variability. This La Niña started in the third quarter of 2007 and is likely to persist through to the middle of 2008. It has influenced climate patterns during the last six months across many parts of the globe, including in the Equatorial Pacific, across the Indian Ocean, Asia, Africa and the Americas.

 “For detecting climate change you should not look at any particular year, but instead examine the trends over a sufficiently long period of time. The current trend of temperature globally is very much indicative of warming,” World Meteorological Organization Secretary-General, Mr Michel Jarraud said in response to media inquiries on current temperature “anomalies”.

"La Niña modulates climate variability. There has always been and there will always be cooler and warmer years, but what is important for climate change in the present context is that the trend is still upwards; the global climate on an average is warming despite the temporary cooling brought about by La Niña."

Between December 2007 and February 2008, global temperature anomalies are still on the warmer side relative to long-term averages. High positive temperature anomalies were recorded in much of Europe and Northern Russia. Anomalies of +2°C to + 5 °C with respect to the 1961-1990 reference period dominated much of the Scandinavian region and the Russian Federation. Also temperature anomalies of +1 to +2 °C were recorded over the western United States, Mexico, North East Brazil and South of South America. Atlantic and Indian Oceans and much of the Western Pacific also experienced positive temperature anomalies.

Australia had its warmest January on record at the same time - with temperatures 3-4°C (5-7°F) above average across large areas in Western and Central Australia. According to the Bureau of  Meteorology, the January 2008 average temperature for the country  was 1.23°C (2.21°F) above the 1961-1990 mean, which exceeded the  previous record of +1.16°C (+2.09°F) set in January 1999.

However, cooling was recorded over the Middle East, Turkey, Central Asia and China.  Also, largely in connection with La Niña, significant parts of the central and eastern Pacific, including the domain off shore of the entire Northern American West Coast, have been dominated by sea-surface temperature cooling.

WMO reported in February that in the preceding three months, La Niña conditions had become slightly stronger, with sea surface temperatures about 1.5 to 2 degrees Celsius colder than average over large parts of the central and eastern Equatorial Pacific.

This La Niña is in the mid range of past historically recorded events, but the slight further cooling in recent months will likely place it on the stronger side of the middle range. Despite this cooling, global temperatures remain on average high in comparison to historical records.

It is rare for a La Niña event to persist for two years or more, such as occurred from early 1998 to early 2000. The likelihood of the current La Niña continuing for such a period will remain unclear for some months, but will be closely monitored.

WMO is to release its next El Niño/La Niña Update in early May.

WMO is the United Nations’ authoritative voice on weather, climate and water
For more information please contact:
Ms Carine Richard-Van Maele, Chief, Communications and Public Affairs, WMO.
Tel: +41 (0)22 730 83 15.
Mr. Paul Garwood, Press officer, Tel: +41 (0)22 730 84 17.

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