Examining the Tropical Pacific's Response to Global Warming

The response of the tropical Pacific to increasing greenhouse gases represents an exciting intersection of theory, modeling, and observations. In this article, we contrast competing theories for the response of the tropical Pacific to global warming, illustrate the utility of models for understanding and reconciling these theories, and highlight the need for improved instrumental and paleoclimatic reconstructions to better evaluate the fidelity of current model projections. There is a long‐standing debate in the climate community as to how the tropical Pacific will respond to increased greenhouse gases: Will the structure of changes in the ocean surface temperature more closely resemble an El Niño or a La Niña [e.g., Knutson and Manabe , 1995; Clement et al. , 1996; Meehl and Washington , 1996; Cane et al. , 1997; Cobb et al. , 2003; Collins et al. , 2005; Vecchi et al. , 2006; Zhang and Song , 2006]? This distinction is of profound significance because conditions in the tropical Pacific affect a range of weather phenomena including tropical cyclone activity, global patterns of drought and flood, agricultural productivity, and oceanic biological activity. The debate extends beyond global warming, with El Niño‐ and La Niña‐like responses being invoked as frameworks for interpreting past climate changes on timescales of centuries to millions of years [e.g., Koutavas et al. , 2002; Stott et al. , 2002; Mann et al. , 2005; Wara et al. , 2005].