대기중 CO2 농도 증가에 따른 ENSO 크기 변화

Abstract

Simulations from six climate system models are analyzed to investigate ENSO amplitude changes in response to transient CO2 increases. The Meteorological Research Institute (MRI) model simulation shows that ENSO amplitude increases with increasing CO2 concentration. The amplitude of ENSO then weakens once the CO2 concentration stabilizes at the time of doubling. The other five models show no significant sensitivity to a CO2 increase, however. By comparing the MRI and Geophysical Fluid Dynamical Laboratory (GFDL) models, both of which simulate ENSO reasonably well for the unperturbed climate, we investigate the origin of the sensitivity or lack of sensitivity. It is found that in the MRI model the oceanic sensitivity to the equatorial zonal wind stress is significantly decreased at the time of doubling compared to the transient CO2 period. Moreover, the vertical stratification at upper levels is weaker at the time of doubling compared to the transient CO2 period. However, in the GFDL model there are little changes in the strength of coupled feedbacks between equatorial SST and zonal wind stress or in the vertical stratification between the two periods.