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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 11, NUMBER 8, AUGUST 1998

NEWS...
Recent El Niños Unlikely Caused by Global Warming

Item #d98aug34

The global temperature increases this century are unlikely to be the cause of the spate of El Niño events during the 1990s, according to Rob Allan, as quoted in a Mar. 9, 1998, press release from the Commonwealth Scientific and Industrial Research Organisation (CSIRO). To reach his conclusion, Allan analyzed global atmospheric pressure and sea-surface temperature data collected during the past 125 years from almost 700 land locations and from numerous ship measurements. Allan and his colleagues compiled much of this information and published it in an atlas featuring global historical atmospheric-pressure and sea-surface-temperature maps detailing every El Niño event since 1871. CSIRO is now running climate models to assess likely future changes to El Niño caused by increasing levels of greenhouse gases. Results to date indicate that El Niño events are features of climate that can be expected to continue in the future, even under greenhouse conditions.

This work marks a major advance in understanding the nature and structure of El Niño and is an important step toward resolving the physical mechanisms that give rise to the El Niño cycle. The research will also help establish what influence the greenhouse effect might have on El Niño. “We know that El Niño tends to occur every two to seven years,” says Allan. “I have found two additional longer climatic fluctuations linked with El Niño: one occurs every 11 to 13 years; the other, every 15 to 20 years. These climatic fluctuations have probably occurred for thousands of years. This makes me think that the gradual warming we’ve seen around the globe this century is unlikely to be the cause of the recent series of El Niño events. The dominant influences governing the strength and occurrence of El Niño are the three climatic fluctuations and other natural climatic variations.”

Contact information: Rob Allan, CSIRO, 107-121 Station Street, PB 1, Aspendale, Victoria 3195, Australia; tel: 0418 123 914 (mobile), (03) 9239 4540 (W); rob.allan@dar.csiro.au.