Temperature Effect on Hawaii's Climate
The temperature projections from the Hadley HADCM2 model show that the surface temperature in Hawaii will increase for both short and long-term simulations. Over the short-term (years 2025-2034), sea surface temperatures (Figure 17) will increase between 0.5 to 1.3o C for December, January, and February and 2.0 to 3.0o C for the long-term (years 2090-2099). For the months of June, July, and August, the short-term temperature increase is between 1.0 to 1.6o C and the long-term increase is from 2.3 to 3.3o C (Figure 17).
As a comparison, we'll look at future projections of temperature from two other global climate models (Figure 29). These two models (labeled A2 and B2; Figure 29) project increases in mean surface temperature of 2.3 to 2.6o C and 1.6 to 2.0o C, respectively, for years 2071-2100. The differences between these two models and their projections primarily stem from the fact that model A2 generally has greater increases of greenhouse gases and thus more positive radiative forcing (warming). However, all three models (Hadley HADCM2, A2, and B2) are in general agreement that the tropical Pacific will warm in the next century and that the warming will likely occur over the entire year and not just during the summer months.
Figure 17. Projected changes in skin temperature (sea surface temperature over ocean and surface–air temperature over land) difference for the short-term results (the model’s 2025-2034 average minus the 1961-1990 base period average) and the long-term results (2090-2099 average minus the 1961-1990 base period) for the seasons December-January-February and June-July-August, in o C.
Figure 29. Mean surface air temperature change from the IPCC SRES A2 scenario, 2071-2100 minus 1961-1990, and mean surface air temperature change for SRES B2 scenario; units in o C.
Overall, the model projections suggest that Hawaii will have elevated temperatures (at least in the summer months of June, July, and August) in the near- (2025-2034) and long- (2090-2099) term. These projections are counter to some historic evidence that warmer periods in Hawaii may not have had elevated precipitation, but instead experienced lower rainfall and increased evaporation which would lead to a decrease in the amount of available water. On the basis of soil distribution, researchers have concluded that higher rainfall was associated with colder, and not warmer, past climates. Additionally, studies of sediments and their distribution in Hawaii suggest that higher trade wind velocities – therefore elevated orographic processes and rainfall – accompanied colder temperatures in the past.