California will become hotter and
drier by the end of the century, menacing the valuable wine and
dairy industries, even if dramatic steps are taken to curb
global warming, researchers said on Monday.
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
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
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
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
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."
© Copyright 2004 Associated Press