Tuesday, June 13, 2000 | Print this story

Harsh Change Predicted for State Climate
Weather: Global warming over the next 100 years could increase drought, fires and floods, a federal report says. Critics call the findings flawed.

By KENNETH R. WEISS, Times Staff Writer

     Global warming over the next 100 years will probably cause drastic changes in California's climate--increasing the state's bouts with fires, floods and drought, a new federal report says.
     For the nation as a whole, "direct economic impacts are likely to be modest," concludes the report--a three-year study commissioned by Congress in 1990 and prepared by a team of prominent federal and university experts on global climate.
     But some areas are likely to be harder hit.
     In California, "rising sea levels are likely to threaten many coastal wetlands, such as those in the San Francisco Bay Area, and the diversity of species they support," the report says.
     Moreover, rising temperatures could magnify California's periodic water shortages--although they may actually increase overall precipitation.
     The problem is that a warming trend could cut into California's natural way of storing the precipitation it does get--the Sierra snowpack.
     Instead of falling as snow, being stored in the mountains and slowly released in the spring and summer when the state needs it, precipitation would be more likely to fall as rain and be lost as runoff into the ocean.
     There is a growing scientific consensus that the world's climate is warming. During the 20th century scientists have witnessed an increase in average temperatures of 2 to 5 degrees in the Western United States.
     Scientists continue, however, to disagree about how much of the change is caused by natural temperature fluctuations and how much by human activities. The chief potential human culprit is the release of so-called "greenhouse gases"--primarily carbon dioxide that comes from burning fossil fuels in automobiles, power plants and industry.
     Although the time scale is long--the report projects that the full increase of 8 to 11 degrees will not be reached until the 2090s--measures to cope with climate changes, such as increased water storage and conservation efforts or moving people out of flood-prone areas, would require a long lead time. Decisions about whether to take such steps are made more difficult because of the uncertainty of climate forecasting.
     The report "paints quite a sobering picture of the future," President Clinton said Monday. "I have tried for several years to get the United States to respond, to do our part. We are the largest emitter of greenhouse gases in the world."
     At the same time, Richard Berk, a UCLA statistics professor who advised the study's authors, said there is "enormous uncertainty" in predicting the future.
     "We don't know how fast things are warming, or what dramatic changes they will bring," Berk said. "From a policy point of view, what we know about California is pretty skimpy. It makes a lot of sense to use our fossil fuels more sensibly. Beyond that, it's a lot of guessing."
     Because of the uncertainties, the authors of "Climate Change Impacts on the United States," who pulled together research by scores of experts at federal agencies and universities, said they didn't want to make specific predictions as much as provide reasonable scenarios on how things might play out.
     "Our hope is that it will help inform the American public about the potential consequences of climate variability and change," wrote D. James Baker, administrator of the National Oceanic and Atmospheric Administration.
     Even so, the report's more dire forecasts were attacked by a conservative think tank as alarmist. "The report," the Competitive Enterprise Institute said, "attempts to make specific predictions about future weather conditions that are simply not scientifically possible with current technology."
     The report examines the potential impacts of a rise in average temperatures by 5 to 10 degrees.
     Already, the report says, "the length of the snow season decreased by 16 days from 1951 to 1996 in California and Nevada." At the same time, heavy rainstorms have been on the upswing.
     Looking ahead, the report suggests further temperature increases will accelerate the deterioration of alpine meadows in the Rocky Mountains, coral reefs off Florida and coastal wetlands throughout the country. These fragile ecosystems may disappear. In addition, low-lying barrier islands could be eroded away as melting polar ice causes sea levels to rise anywhere from six inches to three feet.
     The climate change could present new hazards to human health--more heat-related deaths in Midwestern summers, more mosquito-borne illnesses as insect populations move north.
     Yet the report also sees some benefits from global warming, including milder winters and a surge in agricultural production because of the buildup of greenhouse gases.
     Ski resorts, the report says, might need to diversify their activities because "higher temperatures are likely to mean longer seasons for summer activities such as backpacking, but a shorter season for winter activities such as skiing."
     The climate models used in preparing the report project "increased rainfall during winter, especially over California, where runoff is projected to double by the 2090s," the report said. The Rockies would get drier. But both areas would see more extreme wet and dry years.
     As a result, the report predicts the fast-growing West will come under increasing environmental stress:
     * The risk of wildfires will soar with wider swings in rainfall totals. Wet years will build up vegetation and then dry years will desiccate the brush into tinder-dry fuel.
     * The potential for flooding will increase as less precipitation joins the snowpack and more of it is unleashed in heavy downpours. That could benefit hydroelectric plants, but is likely to increase "non-point" pollution washed from city streets into the ocean.
     But the semiarid region's biggest challenge will be hanging onto its precious water, the report said.
     "In some places, it is likely that the current reservoir systems will be inadequate to control earlier spring runoff and maintain supplies for the summer," the report said.
     It suggests building more flood control and water storage facilities, planting less water-demanding crops, pushing water conservation measures and pricing water to cover its true costs.
     The report can be viewed through the U.S. Global Change Research Information Office's Web site, http://www.gcrio.org.