Climate Feedback

AGU 2008: On the home front

I hadn’t anticipated quite so much rain during the AGU’s Fall conference in San Francisco, but apparently this exact week is, on average, the city’s wettest of the year. Or so I heard at today’s session on how the region is likely to be impacted by climate change.

California has been long recognized as a leader on climate policy, both on the home front and even internationally. It passed its first climate bill twenty years ago and just last week, the state adopted the nation’s most sweeping climate action plan to date, pledging to cut its greenhouse gas emissions by 15% by 2020.

A close look at how the region is expected to fare under various warming scenarios makes its leadership in this arena look a lot like common sense. While temperatures in California are expected to increase in line with global averages, more worrying for the state is the projected water shortages, according to Dan Cayan of the Scripps Institution of Oceanography in La Jolla, San Diego, who spoke at AGU today. California faces the possibility of a 10% decrease in precipitation over the course of the century and could concurrently lose half of its late spring snowmelt. That’s bad news for a region that is already heavily reliant on external water sources.

Sea-level rise will also be part of the equation, especially for the numerous coastal properties with little protection, said Peter Gleick, president of the Oakland, California –based Pacific Institute. Should those in the interior think they’re better off, though, climate models show that inland regions will warm more rapidly than the coast and will likely be more populated in the future owing to lack of available living space on the coast.

Climate extremes will be responsible for a large fraction of climate-related damages in California, according to Michael Mastrandrea of Stanford University. Based on new, yet-to-be-published temperature projections for the region, Mastrandrea and colleagues show that under high emissions scenarios, present-day 100-year events such as severe heatwaves could occur once every ten years or even annually in many areas within 50 to 100 years. For lower emissions scenarios, the picture is a bit better, but there is still a doubling of the frequency of extreme events during this century.

Also presented today at AGU, research by David Lobell of Stanford and Chris Fields of the Carnegie Institute shows that California, which is by far the leading agricultural producer in the US, could see some considerable changes in its yield of key crops such as cherries, almonds and grapes this century. Under warming scenarios, cherries show a considerable decrease in yield, table grapes show only a slight decrease and the yield of almonds potentially increases – good news for almond enthusiasts, considering California supplies 80% of the global demand. Lobell said that the impact on other crops remains uncertain.

But despite the gloomy predictions, California is getting prepared for the worst. The first California adaptation strategy is due out in draft form by February and will be released in April. For further information, check out California’s climate change portal.

Olive Heffernan


  1. Report this comment

    Sierra Summit said: blogs about climate change and California

    Nature magazine’s new online climate page has an interesting blog post about global warming and California. The Golden State has long been a climate policy leader, the blog points out. But such leadership, it adds, is also a matter of…

Comments are closed.