California’s Climate Policies Reduce Particulate Air Pollution Too, UC Davis Research Finds

A pair of studies led by UC Davis researcher Mike Kleeman examines the local air-quality impacts of California’s current climate-change laws and long-term climate goals, and calculates the health and monetary benefits of the projected reduction in tiny airborne particles known as PM2.5.

The findings of one study indicate California’s climate and goods-movement policies can deliver pollution benefits that save lives and money — more than $5 billion annually in the relatively short term — by 2030. Looking farther out, to the state’s 2050 goal to reduce greenhouse gases 80 percent below 1990 levels, the other study finds that combinations of transportation strategies will be more effective than single approaches.

The companion studies funded by the U.S. Environmental Protection Agency are published in the March 2013 print issue of the journal Climatic Change.

California’s Global Warming Solutions Act, AB 32, calls for strategies to reduce greenhouse-gas emissions across all sectors of the state’s economy by 2020. As Kleeman explains, his research examines the co-benefits of AB 32.

“My research focuses on the gases and airborne particles that contribute to air pollution where people live and work,” Kleeman says. “I’m especially interested in the relationship between different air pollutants, and how a policy designed to reduce one group of pollutants — in this case, greenhouse gases — also cuts PM2.5 as a co-benefit,” Kleeman explains.

The first report is “PM2.5 Co-benefits of Climate Change Legislation Part 1: California’s AB 32.” It compares air quality in 2030 under a business-as-usual scenario (without AB 32) to a scenario with AB 32 across each sector. It also assumes that policies under the Emission Reduction Plan for Ports and Goods Movement in California, which regulates goods transported by ships and trucks, are in effect. Kleeman’s co-authors are UC Davis student Christina Zapata and Middlebury College professor Nicholas Muller.

When the researchers simulated the effects of these climate-change and goods-movement policies on the general California population, they found that the reduced exposure to PM2.5 could save roughly 880 lives per year in 2030. The monetary benefit from these avoided premature deaths translates to roughly $5.4 billion per year.

The second paper is “PM2.5 Co-benefits of Climate Change Legislation Part 2: California Governor’s Executive Order S-3-05 Applied to the Transportation Sector.” Kleeman’s co-authors are Zapata and UC Davis students John Stilley and Mark Hixson.

In this paper, the researchers examine the particulate-emissions benefits of seven transportation scenarios that could be adopted in efforts to reach the state’s 2050 climate goal. Each scenario considers technological or behavioral changes, or a combination of the two.

Five of the scenarios that take a single technology or behavioral approach don’t meet the 2050 greenhouse-gases target due to various practical limitations, such as market adoption for new technologies. The final two combined-approach scenarios achieve greater reductions of GHG emissions. They also result in larger reductions of PM2.5 emissions.

“The findings in this study support the point we’ve heard from many researchers and policymakers: We need combined approaches to achieve our long-term goals,” Kleeman says.

Further reading:

2012 C. Zapata, N. Muller, and M.J. Kleeman.  PM2.5 Co-benefits of Climate Change Legislation Part 1: California’s AB32.  Climatic Change, 117:1, pp377-397.


2012 M. Kleeman, C. Zapata, J. Stilley, and M. Hixson.  PM2.5 Co-benefits of Climate Change Legislation Part 2: California Governor’s Executive Order S-3-05 Applied to the Transportation Sector.  Climatic Change, 117:1, pp399-414.


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