Thursday, 13 February 2003: 4:00 PM
Linkages between El Niņo and Recent Tropical Warming
The El Niņo-Southern Oscillation phenomenon (ENSO) is the most important source for interannual climate variability. It originates from tropical coupled air-sea interactions in the Pacific but encompasses weather patterns globally with severe impacts1-2 for both societies and ecological systems. Recently the possibility has been dicussed3-8 that an anticipated anthropogenic greenhouse warming might have an influence not only on the climate mean state of the tropical Pacific, but also on its variability. In particular the fact that the two strongest El Niņo events (1982/83 and 1997/98) occurred within the last three decades spun up the debate on possible linkages between ENSO and global warming9-10. Here we present evidences to reveal that strong El Niņo events have an influence on long term tropical warming as well as vice versa. The nonlinear dynamic heating in the tropical Pacific ocean heat budget is essential in linking the enhanced El Niņo activity and the recent tropical Pacific warming trend. In addition, the analysis of the nonlinear dynamic heating provides a mechanism for intense El Niņo events and a natural explanation for the observed asymmetry between El Niņo (warm) and La Niņa (cold) events.