ENSO response to greenhouse warming

The response of the tropical Pacific climate system and its interannual variability to enhanced greenhouse warming was investigated by means of integrations with a global climate model. The climate model is the first one applied to transient greenhouse warming simulations which simulates the El Ni no/southern oscillation (ENSO) phenomenon, the leading mode of interannual variability, realistically. The long-term changes in the mean state of the tropical Pacific climate system are similar to those observed during present-day El Ni nos. Furthermore, the changes in the mean state lead to changes in the statistics of the interannual variability. An ENSO mode exists under enhanced greenhouse conditions also, but it becomes more energetic relative to present, so that variations from year to year become more extreme. In particular, the cold phases of the ENSO cycle amplify considerably, while the statistics of the warm phases do not change significantly. It is shown that changes in the ocean dynamics associated with a sharper thermocline lead to the enhanced interannual variability. Our results have strong implications not only for the global climate system but also for the ecology of the tropical Pacific and the societies and economies of many countries. (orig.)20 refs.Available from TIB Hannover: RR 1347(251) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman