Air Pollution as a Climate Forcing: A Workshop

Day 3 Presentations

California Emission Control Case Study

Michael Scheible
California Air Resources Board, Sacramento, CA, U.S.A.

You may download a PDF version (1.0 MB) of this presentation.


Time chart (1870-2000) of greenhouse gas trends

Figure 1: California greenhouse gas emission trend (CO2 equivalents for Kyoto Protocol Gases)

California has realized significant non-CO2 greenhouse gas reductions. The California Air Resources Board (CARB) is responsible for emission controls on motor vehicles, and California is the only state in the U.S. allowed to establish more stringent standards than the U.S. Environmental Protection Agency, although other states are permitted to adopt California's standards. Emissions of CO and NMVOC (and to a lesser extent NOx) from new passenger vehicles are reduced by a factor of a hundred in comparison to pre-control vehicles in 1963, and the standards are now applicable for 100,000 miles. Major controls include passive crankcase exhaust gas recirculation adopted for the 1971 model year, oxidation-reduction ("three-way") catalytic converters first introduced in 1977, and the Low-Emission Vehicles and Clean Fuels (LEV/CF) and Zero-Emission Vehicle (ZEV) regulations currently in effect. Reformulated gasoline and diesel fuels have resulted in further reductions. Stationary source NOx emissions have been reduced by a factor of ten since 1980 using low-NOx burners, selective catalytic reduction, cleaner fuels (i.e., natural gas), vapor recovery, and low-NMVOC coatings and solvents. From 1980 to 2000, emissions from stationary source (NMVOC+NOx) decreased from 0.93 to 0.40 Tg/yr, electricity production (NOx) from 0.11 to 0.02 Tg/yr, passenger vehicle (NMVOC+NOx) from 1.8 to 0.8 Tg/yr and CO from 10.3 to 4.0 Tg/yr, and trucks (PM ~~ BC) from 0.013 to 0.007 Tg/yr. California has slowed the growth of CO2 emissions seen in the U.S. as a whole, primarily through improvements in power generation (see Figure 1) and increasing use of renewable energy. California's CO2 emissions per capita and per unit of gross national product are similar to many European countries.

These reductions were realized for reasons other than global climate change. The improvement in ambient air quality over the past twenty years is 50% in peak ozone levels, and 37% in annual-average PM10 and 46% in cancer risk from known air toxics over the past twelve years. This has been achieved despite a 50% growth increase in population and a doubling of vehicle miles traveled, and the growth of California into the 5th largest economy in the world. However, levels of particulate matter and ozone continue to exceed the ambient air quality standards, and air pollution in California contributes annually to as many as: 17,000 premature deaths; 55,000 hospital admissions; 1,300,000 asthma attacks; and 3,300,000 lost work days.

Regulatory efforts over this decade will focus on diesel engines and greenhouse gas emissions from passenger vehicles. California is targeting a 75% reduction by 2010 through the use of particle traps, low sulfur fuels, advanced engine technologies, and alternative fuels. The recently adopted Assembly Bill 1493 (Pavley, 2002) instructs CARB to set regulations that achieve the maximum feasible, cost-effective, and technologically achievable reductions of greenhouse gases emitted by passenger vehicles and light-duty trucks for the 2009 model year.

Further descriptions of many of these programs can be found on CARB's webpage.

Workshop Homepage * Background
Summaries: Overview, Gases, Aerosols, Tech., Health, Agri./Eco.
Abstracts: Day 1, Day 2, Day 3, Day 4, Day 5 * Participants