Projected (2070-2099) Percentage Change in Mean Total Annual Precipitation for California under the HadCM3 A1Fi future climate scenario

Sep 9, 2010 (Last modified Sep 13, 2010)
Recommended by Dominique Bachelet

This product is one of a set of mapped model simulation results generated for a project called “Global Climate Change and California: Potential

Implications for Ecosystems, Health, and the Economy”. The project was conducted by the Electrical Power Research Institute (EPRI) and funded by the California Energy Commission’s Public Interest Energy Research (PIER) Program. The project was the most detailed study ever undertaken on the potential effect of climate change on California. The work examined a broad array of potentially affected sectors as well as the interactions between climate change and increased population, economic growth, and technological change. It considered a wide range of climate change scenarios, ranging from warmer and much wetter to warmer and much drier (

Lenihan et al. used a dynamic general vegetation model (MC1), which estimated both the distribution and the productivity of terrestrial ecosystems such as forests, grasslands, and deserts at a scale of 100 km2 (39 square miles), the highest resolution at which a dynamic model had been applied in California. They estimated that under all climate change scenarios, forests and other types of vegetation will migrate to higher elevations as warmer temperatures make those areas more suitable for survival. For example, with higher temperatures, the area of alpine and subalpine forests will be reduced as evergreen forests and shrublands migrate to higher altitudes. They estimated that if it gets wetter, forests would expand in northern California and grasslands would expand in southern California. If it gets drier, areas of grasslands would increase across the state. Both wetter and drier scenarios resulted in increases in carbon storage (biomass) in California vegetation of between 3% and 6%. Wetter conditions generally allow for more biomass. Under drier conditions, grasslands, which store a relatively high amount of carbon below ground, expand. Lenihan et al. found that the frequency and the size of fires would increase under most scenarios; however, the change is not significant until the latter part of the century. The drier scenarios result in more frequent fires and more area consumed by fires. The wetter scenarios result in fires of greater intensity than those in the dry scenarios because more fuel (vegetation) would grow when it is wet to be consumed by fire during occasional dry periods.

This map shows the projected percentage change in mean total annual precipitation for the future 2070-2099 period relative to the historical 1971-2000 period.  The climate scenario was generated by Hadley Climate Centre’s HADCM3 General Circulation Model forced with the A1Fi emission scenario (i.e., CO2 atmospheric concentration at 970 ppm by 2100).

Data Provided By:
Hayhoe, K., D. Cayan, C. Field, P. Frumhoff, E. Maurer, N. Miller, S. Moser, S. Schneider, K. Cahill, E. Cleland, L. Dale, R. Drapek, R. Hanemann, L. Kalkstein, J. Lenihan, C. Lunch, R. Neilson, S. Sheridan, and J. Verville. 2005. Emission pathways, climate change, and impacts on California. Proceedings of the National Academy of Sciences: 101: 12422-12427.
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