The first study to specifically forecast the impact of global warming on a U.S. state also shows the snowpack melting in the Sierra Nevada mountains, more frequent heat waves hitting Los Angles and disruptions to crop irrigation.
Researchers from the Carnegie Institution\'s Department of Global Ecology in Stanford, the Union of Concerned Scientists, the National Center for Atmospheric Research and elsewhere ran scenarios through new computer models of global warming.
All predicted California\'s weather would be hotter and drier, but this would be worse if only weak action is taken to reduce emissions of carbon dioxide and other greenhouse gases contributing to warming the planet.
\"We are already in a situation where we have seen some warming and we have seen some impacts,\" said Carnegie\'s Christopher Field, who led the study.
\"If we stay on higher emissions trajectory, there will be consequences over the coming decades that are truly, truly serious and something I think reasonable people would be doing whatever they could to avoid,\" he said in a telephone interview.
Writing in the Proceedings of the National Academy of Sciences, Field and colleagues described the impact based on scenarios devised by the Intergovernmental Panel on Climate Change.
One forecast, the so-called high emissions trajectory, is what Field described as business as usual. \"High economic growth, high globalization and a strong emphasis on fossil fuels,\" he said.
The low-emissions trajectory has slightly lower economic growth with industries shifted from factories toward service industries and information technology.
Under the highest-emissions forecast, carbon emissions by the end of the century will be 28 billion tons of carbon per year - about four times the current rate of 6 billion to 7 billion tons a year. The low-emission scenario forecasts the emissions would stay at the current level.
\"By the end of the century under the (best) scenario, heat waves and extreme heat in Los Angeles quadruple in frequency while heat-related mortality increases two to three times; alpine/subalpine forests are reduced by 50 percent to 75 percent and Sierra snowpack is reduced 30 percent to 70 percent,\" Field and his colleagues wrote.
Under the worst scenario, heat waves in Los Angeles are six to eight times more frequent, with up to seven times as many heat-related deaths as now. The Sierra snowpack falls by 90 percent.
This could \"fundamentally disrupt California\'s water rights system,\" the researchers wrote.
They estimated that the $3.8 billion a year dairy industry and the $3.2 billion dollar grape industry would be especially vulnerable.
California, which has taken stronger action than other states to reduce emissions, for example with strict requirements for vehicles, cannot save itself, Field said.
\"California has something like 2 percent of the world\'s total global greenhouse emissions,\" he noted.
\"Even if California were to aggressively adopt emissions controls, global climate wouldn\'t respond to that directly. But if California is proactive, that could inspire the rest of the U.S. to be proactive, which could inspire the rest of the world, and you would see a domino effect.\"