An Analysis of Extreme Heat and Energy Demand

Summer temperatures in the southwest U.S. are projected to increase more rapidly than previously expected, accompanied by longer, more frequent, and more severe extreme heat conditions. A heat and energy impacts analysis was performed using three Atmosphere-Ocean General Circulation Models, the HadCM3, GFDL, and the PCM, forced with the A1fi, A2, and B1 greenhouse gas emissions detailed in the IPCC Special Report on Emission Scenarios, and statistically downscaled to specific urban locations in California. Results show summer average temperature increases of 2-5oC under the lower B1 scenario and 4-8oC under the higher A1fi scenario. Results indicate that heat waves become longer and more frequent, with projections for California heat wave onset occurring by as much as 30 days earlier than present by 2050 and 70 days earlier by 2099. In addition, the number of heat wave days for six metropolitan areas in California (Los Angeles, Riverside/San Bernardino, San Francisco, Sacramento, Fresno and El Centro) show an increase by 15 to 40 more heat wave days in the 2050s than during the 1990s, and by the 2090s, the increase in heat wave days rises by 30 to 50 days under B1 and 70 to 100 days under A1fi. Heat waves are also projected to become more intense, with higher temperatures sustained over longer periods. Increases in mean and extreme heat events during the summer months have significant implications for energy demand in the heavily air-conditioned Southwest summers. Electricity load in these areas have a strong correlation with high temperature and increases proportionally, primarily due to increased air conditioning use. California's state-wide electricity demand at present increases by approximately 400 MW/oC for temperatures above 28oC, and the power grid is strained as temperatures increase, as this recent summer has seen energy alerts for Southern California. The projected temperature increases discussed here will likely further strain the California power grid requiring a combination of increased energy efficiency practices, conservation, and alternative energy sources.