When Governor Arnold Schwarzenegger announced an agreement this summer to impose the nation’s most sweeping controls on carbon dioxide emissions, the Hewlett Foundation was among the many institutions that could take satisfaction in helping to enact this historic legislation.

A key factor in the governor’s and the California legislature’s decision to pass this bill was scientific evidence on the potential impacts of climate change on the state that the Union of Concerned Scientists developed in part with support from the Foundation’s Environment Program.

“This is a terrific victory,” said Hal Harvey, Environment Program Director. “In the years before the bill, we supported a number of objective and broadly distributed studies on greenhouse gas emissions in California. Thanks to the work of the Union of Concerned Scientists and a lot of other people we all can breathe a little easier.”

The agreement between the Republican governor and the Democratic-controlled legislature mandates a 25 percent reduction in carbon dioxide emissions by 2020. The California Air Resources Board, which regulates air pollution, will develop regulations to limit carbon dioxide emissions on the part of utilities, oil refineries and cement plants starting in 2012. The plans call for market-based mechanisms, like emission credits, to help meet the reduction goals.

The research coordinated by the Union of Concerned Scientists was published in the “Proceedings of the National Academy of Sciences,” as well as in a publication entitled “Climate Change in California: Choosing Our Future” that was intended for a lay audience.

In addition to publishing the results of the eighteen-month study, which the Foundation supported with $150,000, the Union of Concerned Scientists gave briefings on the findings to key decisionmakers in the months before the agreement was struck. The Foundation also hosted two daylong meetings of all the senate and assembly leadership and key members of the governor’s cabinet and staff to look at alternative approaches to greenhouse gas reduction.

Among the findings published in the “Proceedings of the National Academy of Sciences” was that, left uncontrolled, global warming could reduce the size of California’s snow pack from a third to a full 90 percent by the end of the century and double the number of heat waves. Overall, the research looked at the impact of climate change on key facets of life in the state, including water resources, agriculture, public health and other climate-sensitive areas.  A fact sheet summarizing the work can be found here.

The Environment Program helped in other ways, too. It supported the energy program at the Silicon Valley Leadership Group, which provided key business support for reductions, and sponsored polling at the Public Policy Institute of California that revealed broad bipartisan support in the state for the reduction of greenhouse gases.