We consider the possibility that variations in solar irradiance have a significant impact on tropical Pacific sea surface temperatures (SSTs), which influence drought in much of the US, including Gene's home state of Kansas. Very recent work (Schubert et al. 2004; Seager et al. 2004) has shown that a prime cause of the Dust Bowl droughts of the 1930s is a La Niņa-like pattern of decadal mean SST anomalies in the Pacific. These anomalies were very small amplitude (<0.5°C everywhere). Similar SST anomalies are associated with other persistent droughts in the 19th and 20th centuries, and a pattern of opposite sign prevailed during the relatively wet period, 1976-1998.

Other recent work (Mann et al. 2005; Emile-Geay et al 2006) has shown that coupled ocean-atmosphere interactions in the tropical Pacific generate a significant response to solar and volcanic radiative forcing over the past 1000 years. While these variations rarely have much effect on individual ENSO events, they may influence longer period changes. Such shifts in the background state of the tropical Pacific could help explain the persistent droughts in North America evident in the climate record of the last 1000 years.