WASHINGTON -- Californians should brace for hotter temperatures, reduced water supplies, longer droughts and more wildfires in the future, a new federal climate-change report warned Tuesday.
Coastal residents should expect the sea level to rise and anticipate more flooding, according to the 1,100-page National Climate Assessment, the largest report of its kind done in the U.S.
California farmers, who grow much of the nation's fruits and vegetables, should be prepared for crop losses, yield declines and overstressed livestock due to prolonged drought conditions punctuated by sudden swings between blazing and frigid weather, the report said.
The report also predicted a 74 percent increase in wildfires throughout California by the end of this century and said northern California could see a 100 percent jump unless humans reduce the use of coal, oil and gas.
California Democratic Sen. Barbara Boxer, chairwoman of the Senate Environment and Public Works Committee, said in a statement that the report "confirms with the greatest level of detail yet that climate change in the United States is all around us and we are already feeling the impacts."
"We must act in a comprehensive way to reduce carbon pollution for the sake of public health, our nation's economy, and the well-being of future generations," said Boxer, who has pushed for taxing carbon emissions to discourage the use of fossil fuels.
Sen. Dianne Feinstein, D-Calif., said in a statement that inaction on climate change is not an option.
"We have to reduce our carbon footprint by limiting greenhouse gas pollution, adopting energy efficient technologies and developing renewable energy resources," said Feinstein, who authored a bill to help drought-affected farmers in California and Oregon.
The Obama administration's climate-change assessment agreed with a recent report by the United Nations Intergovernmental Panel on Climate Change that showed the planet is warming mostly due to human activity, particularly the emission of heat-trapping gases such as carbon dioxide and methane resulting from burning fossil fuels.
The White House assessment was written by 300 experts from academia, all levels of government, the private sector and nonprofit groups and was endorsed by environmental groups like the Nature Conservancy and oil companies such as ConocoPhillips and Chevron.
"If people took the time to read the report, they would see that it is not necessarily about polar bears, whales or butterflies," said meteorologist Marshall Shepherd of the University of Georgia. "I care about all of those, but the NCA is about our kids, dinner table issues, and our well-being."
The White House said state and local officials throughout California are combating climate change. One big step: California's decision to ask power companies to generate 33 percent of the electricity from some renewable sources like the sun and the wind by 2020. According to the California Energy Commission, 22 percent of the electricity generated in 2012 came from wind, solar, geothermal, biomass and small hydroelectric power plants that produce less than 30 megawatts.
The inexact science of climate prediction shows two scenarios for California.
In one, which some computer models show, the state will be drier in the future than it is now. But some other computer models show the exact opposite scenario, said F. Martin Ralph, director of the Center for Western Weather and Water Extremes at the University of California-San Diego.
This inconsistency stems from the models' inability to account for extreme weather occurrences like torrential rains that quench long-parched regions in a matter of days.
Scientists are learning more about these weather shifts and working to refine the models to increase the accuracy of the forecasts, said Ralph, one of three water experts from the University of California system who briefed Capitol Hill lawmakers and staff Tuesday about their research.
Climate change will undoubtedly continue to exacerbate water woes in California, where the groundwater is already being depleted rapidly, said Jay Famiglietti, director of the U.C. Center for Hydrologic Modeling at the Irvine campus. Though computer models may disagree on small points, they generally point to a global trend of less and less snow and rain as the 21st century wears on, he added.
Water conservation is a critical first step, he said.
"Learn how to do more with less. That's the message," Famiglietti said. "After we . . . improve on our efficiency then we can worry about other, more grandiose things."
USA Today contributed to this story.
Contact Raju Chebium at email@example.com; Twitter: @rchebium