Uncertainty of Future Precipitation Change Due to Global Warming Associated with Sea Surface Temperature Change in the Tropical Pacific

The effects of future tropical Pacific sea surface temperature (SST) changes on regional precipitation projections are statistically studied for December-January-February (DJF) and June-July-August (JJA) in the Coupled Model Inter-comparison Project phase 3 (CMIP3) experiments. The present climate precipitation responses to Nino3 SST variability appear as an uncertainty with regards to future regional precipitation changes among the CMIP3 model projections. Compared with the CMIP3 models projecting La Nina-like Pacific SST changes, the models projecting El Nino-like Pacific SST changes tend to simulate more precipitation in future DJF over the tropical central Pacific, southeastern North America and the tropical western Indian Ocean, and less over the tropical northwestern Pacific, the tropical South Pacific and tropical South America. For JJA, the models projecting El Nino-like Pacific SST changes tend to simulate greater future precipitation in the tropical central Pacific and less over the Maritime Continent and around Central America. Interestingly, the present climate features of the delayed JJA precipitation response to previous DJF Nino3 SST variability also appear as differences in future JJA precipitation changes between the models projecting future El Nino-like and La Nina-like Pacific SST changes in DJF. Compared to the later models, the former models have a tendency to show more precipitation south of Japan and south of the equator in the central to eastern Pacific, and less in the subtropical northwestern Pacific. CMIP3 model analysis indicates that the projected El Nino-like SST changes are related to the present precipitation climatology of the models in the near-equatorial eastern Pacific for each DIE and HA season, suggesting the importance of realistically simulating present precipitation climatology in the tropical Pacific for future projections.