Global Warming Report: More Big Storms in State's Future By John D. Cox Bee Staff Writer (Published Nov. 4, 1999) A future of more frequent major storms and less reliable water supplies emerges from the first comprehensive study of the effects of global warming on California. A report of the two-year investigation by a team of seven scientists is being released today in San Francisco and Los Angeles by the Union of Concerned Scientists and the Ecological Society of America. "The likelihood of extreme weather events is clearly going to increase," said Norman L. Miller, research meteorologist at the Regional Climate Center at Lawrence Berkeley National Laboratory and an author of the study. While the picture is not "gloom and doom," he said, changes that might appear gradual and benign in many areas can be especially troublesome to a metropolitan area such as Sacramento that lives on the edge of a flood threat many winters. The report points to a variety of environmental impacts, including more landslides in the mountains and along the coast and a greater threat of wildfires. Patterns of crop and natural plant growth could change, and warming ocean temperatures could accelerate the shift away from commercial northern fish species such as rockfish to noncommercial southern species. But it's the weather that will be noticed by most Californians. Daytime and nighttime average temperatures may be noticeably warmer over time, the report noted, but the more dramatic changes will be the increased frequency of major storms that punctuate the long-term trend. Although the idea of global warming remains the subject of debate in political circles, the mainstream of climate scientists regard it as established fact. The average temperature of the lower atmosphere has increased nearly 1 degree in the past century and the pace of the rise is increasing along with the buildup of industrial greenhouse gases. "The dissenters are those with some special interest at this point in time," said Miller. The argument now is about the pace of warming and its effects. "The timing of stream-flow is going to be earlier in the season than what we know now," said Miller. This means that in the Sierra Nevada the earlier onset of melting snow could eventually intersect with the time of heavy rainfall. Such a trend already is evident on the American River, he said, where measurements show that in the past 30 years the Sierra snowmelt is beginning earlier in the season. "Now if that is significantly earlier, and there's a number of storms coming through, then the likelihood of flooding through the city will increase," Miller said. Extreme storms provoked by more frequent and intense El Nino winters are likely, the report says, and a projected one-foot sea level rise will open the Sacramento-San Joaquin Delta -- linchpin of the state's water system -- to the threat of levee failures and flooding. Among the environmental effects of warming, the scientists cited some that already are under way. Offshore, recent warming of the California Current has led to population declines of tiny zooplankton and seabirds known as sooty shearwaters. Since the 1970s, Southern California's kelp forests have seen a 50 percent drop in cold-water fish such as greenspottedrockfish and a similar boost in warm-water species. Both California winters and summers will become warmer, the report said, although the winter warming is more pronounced and its implications are more profound. It cites one key climate model that projects warming of 4 degrees in the western United States by 2030-2050, which corresponds to 5 degrees in winter, 2 degrees in summer. "Most of California's precipitation falls in winter, and in the future more of it is likely to fall as rain, less as snow, a change that is likely to lead to increased winter runoff and decreased summer stream flow," the report said. Such shifts in seasonal precipitation patterns would be especially difficult in a state so reliant on large-scale water storage and transportation. The warming-climate scenario of more rainfall in winter but less snowfall suggests the worst of both worlds -- a greater threat of winter flooding, yet less stored water to supply the state through the long dry months of summer. At present, the season of Sierra Nevada snowmelt begins in May, replenishing the major reservoirs after they have done double duty protecting downstream populations from winter flooding. Losing the big snowpack sooner is like losing the storage benefits of a major reservoir in the system. "We're a very water-dependant state," said Miller. "And we're highly vulnerable to any change in what we know is our current amount." In addition to Miller, the researchers included Stanford University environmental scientists Christopher B. Field, Gretchen C. Daily and Pamela A. Matson, and from the University of California, Santa Barbara, biologists Steven Gaines and John Melack and environmental specialist Frank W. Davis. The scientists noted that "although the driving forces behind greenhouse warming are global in scale," the state was not powerless to deal with its effects. "Limiting the footprint of development on the landscape, particularly in vulnerable habitats such as wetlands and areas subject to fires, floods, and landslides, is probably the most important action Californians can take," they said.