COLUMN 3

The Green Room 19th Street, Hermosa Beach Photo © Richard L. Koenig

Both coastal storms and flooding can be expected to change due to global warming. The changes in regional storms and precipitation trends are not yet well established. Several studies have found an increase in the intensity of significant storm wave events for much of the California coast over the past 50 years. This may be connected to the increase in sea level and atmospheric temperature that has been observed recently; or the sea level and temperature changes may be independent events. Some models predict that, on average, northern and central California will have more precipitation, and precipitation in southern California will remain the same as it is now; other models predict that much of California will experience a long-term drought. One recent study by Environment California concludes that most of California will experience extreme rainfall events interspersed by long periods of drought.

An increase in temperature will have the overall consequence that more of the precipitation will fall as rain and less as snow, the snow level (the lowest elevation at which snow is falling) would increase, less precipitation would be stored as snow, a larger percentage of precipitation would be released as winter stream run-off, spring snow melt would occur earlier in the year and there would be less spring run-off. Overall, coastal flooding may happen less often, but when floods do occur, they would likely be more intense.

Additional information on this topic can be found at the following sites:

• Environment California's Global Warming Report

• UC Santa Cruz's 2002 California climate study

• Tropical drying trends in global warming models and observations, 2006