CalClim: California Climate Data Archive

CALIFORNIA CLIMATE WATCH
CURRENT ISSUE: July 2005

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The Air You Breathe and the Climate You Experience

By Laura Edwards
Western Regional Climate Center

California has been a leader in efforts to improve air quality in the United States. The state legislature has taken many measures over the last several decades to reduce the amount harmful emissions from vehicles, homes and businesses. Since 1988, California has studied the implications of a changing climate on the state's environment, economy and water supply, directed by California Energy Commission (CEC) as mandated by AB4420 [1]. A landmark bill was signed by Governor Gray Davis in 2002, AB 1493, to require the CARB to develop and adopt measures to reduce GHGs emitted by passenger vehicles and light duty trucks. In September 2004, regulations were approved for new motor vehicles beginning with the 2009 model year. The emissions included in these regulations are: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and hydrofluorocarbons (HFCs). (See the CARB website for more details, http://www.arb.ca.gov/cc/cc.htm.) On June 1, 2005, Governor Arnold Schwarzenegger announced an Executive Order

that set emission targets for the next half century and designated coordination to be led by the California Environmental Protection Agency. The Order calls for greenhouse gas emissions reduced to 2000 levels by 2010, 1990 levels by 2020 and a reduction to 80% of 1990 levels by 2050.

Figure 1. Smog over Los Angeles, 2004. http://www.usatoday.com/news/nation/2004-09-26-calsmog-usat_x.htm

The science behind the Order includes some important concepts. Greenhouse gas (GHG) reduction is important to improving air quality, but this action also has impacts on climate. GHGs absorb infrared energy that is radiated or reflected from the surface. As these gases absorb this energy, it heats the air around it, which occurs on a global scale with increased GHGs worldwide. There is some natural amount of GHGs in the atmosphere which makes the planet habitable, but human activities have increased the abundance of these gases, including carbon dioxide and methane beyond the natural level.

Other pollutants such as nitrous oxide, ozone (O3) and particulate matter or aerosols, also impact air quality, human health, agriculture, and climate. Ozone is healthy at the highest levels of our atmosphere, providing a beneficial block to some ultraviolet radiation, but is harmful at low levels, in the troposphere where we live. Tropospheric ozone is estimated to be the third largest forcing globally for radiation, in addition to influencing the lifetime of other GHGs such as methane [2].

Particulate matter, or aerosols, impact climate through radiative effects. This can be either a warming or cooling effect, depending on the aerosol characteristics and chemical composition. Regardless of aerosol type, however, "all major aerosol types are thought to have effects on the hydrological cycle at the regional level" [2]. Aerosols also have significant impacts on human health, including development of asthma and other respiratory problems.

Some modeling studies have taken into account various future emissions scenarios. These investigations can help decision-makers learn how policy changes can affect future climate. A recent paper by Hayhoe et al. [3] describes some of the anticipated impacts from two scenarios, the first being "business-as-usual" with no policies to reduce emissions, and the second being a fairly aggressive reduction of emissions (See figure 2 for a graphic explaining these scenarios, and http://www.grida.no/climate/ipcc/emission/012.htm). Using two climate models with each of these scenarios, they projected the impacts of these emission levels to the year 2099 for California. Elements included in their study were: temperature; precipitation; extreme heat and heat-related mortality; snowpack, runoff and water supply; and agriculture and vegetation distribution. In all simulations, annual average temperatures increased over the period, including extreme heat and heat waves. The most severe impacts were results of the higher "business-as-usual" emissions scenario. A significant conclusion of this paper is they support that "climate change and many of its impacts scale with the quantity and timing of greenhouse gas emissions" as reported in Climate Change 2001: The Scientific Basis [4].

Figure 2. Special Report on Emission Scenarios (SRES) tree of future emissions. Hayhoe et al. used A1fi and B1 in their study.

There are changes that individuals can make to reduce the harmful emission of GHGs in California, and legislation has helped accelerate that process. Air quality across the state and in areas like Los Angeles have benefited from such measures as improvements in vehicle manufacturing and technology, and Californians are leading the nationwide effort to create a better environment for living and reduce the impact of humans on the natural climate.

References:
1. The California Almanac of Emissions and Air Quality, 2005 edition. California Environmental Protection Agency and Air Resources Board.

2. Swart, R., M. Amann, F. Raes, W. Tuinstra, 2004. A good climate for clean air: linkages between climate change and air pollution, an editorial essay. Clim. Change 66: 263-269.

3. Hayhoe, K. et al., 2004. Emissions pathways, climate change, and impacts on California. PNAS, 101, 34, pp. 12422-12427. www.pnas.org/cgi/doi/10.1073/pnas.0404500101

4. Houghton, J. T., Y. Ding, D. J. Griggs, M. Boguer, P. J. van der Linden and D. Xiaosu, eds., 2001. Climate Change 2001: The Scientific Basis, Cambridge Univ. Press, Cambridge, U.K.

Page last updated 8/11/05.

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California Climate Watch Archive All data in the Climate Watch is provisional and subject to change. Please contact us for updated and quality-checked data. For 2004 stories, click here For 2005 stories, click here Monthly Weather Summaries 2005 2004	CALIFORNIA CLIMATE WATCH CURRENT ISSUE: July 2005 Read the full newsletter here: PDF format The Air You Breathe and the Climate You Experience By Laura Edwards Western Regional Climate Center California has been a leader in efforts to improve air quality in the United States. The state legislature has taken many measures over the last several decades to reduce the amount harmful emissions from vehicles, homes and businesses. Since 1988, California has studied the implications of a changing climate on the state's environment, economy and water supply, directed by California Energy Commission (CEC) as mandated by AB4420 [1]. A landmark bill was signed by Governor Gray Davis in 2002, AB 1493, to require the CARB to develop and adopt measures to reduce GHGs emitted by passenger vehicles and light duty trucks. In September 2004, regulations were approved for new motor vehicles beginning with the 2009 model year. The emissions included in these regulations are: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and hydrofluorocarbons (HFCs). (See the CARB website for more details, http://www.arb.ca.gov/cc/cc.htm.) On June 1, 2005, Governor Arnold Schwarzenegger announced an Executive Order that set emission targets for the next half century and designated coordination to be led by the California Environmental Protection Agency. The Order calls for greenhouse gas emissions reduced to 2000 levels by 2010, 1990 levels by 2020 and a reduction to 80% of 1990 levels by 2050. Figure 1. Smog over Los Angeles, 2004. http://www.usatoday.com/news/nation/2004-09-26-calsmog-usat_x.htm The science behind the Order includes some important concepts. Greenhouse gas (GHG) reduction is important to improving air quality, but this action also has impacts on climate. GHGs absorb infrared energy that is radiated or reflected from the surface. As these gases absorb this energy, it heats the air around it, which occurs on a global scale with increased GHGs worldwide. There is some natural amount of GHGs in the atmosphere which makes the planet habitable, but human activities have increased the abundance of these gases, including carbon dioxide and methane beyond the natural level. Other pollutants such as nitrous oxide, ozone (O3) and particulate matter or aerosols, also impact air quality, human health, agriculture, and climate. Ozone is healthy at the highest levels of our atmosphere, providing a beneficial block to some ultraviolet radiation, but is harmful at low levels, in the troposphere where we live. Tropospheric ozone is estimated to be the third largest forcing globally for radiation, in addition to influencing the lifetime of other GHGs such as methane [2]. Particulate matter, or aerosols, impact climate through radiative effects. This can be either a warming or cooling effect, depending on the aerosol characteristics and chemical composition. Regardless of aerosol type, however, "all major aerosol types are thought to have effects on the hydrological cycle at the regional level" [2]. Aerosols also have significant impacts on human health, including development of asthma and other respiratory problems. Some modeling studies have taken into account various future emissions scenarios. These investigations can help decision-makers learn how policy changes can affect future climate. A recent paper by Hayhoe et al. [3] describes some of the anticipated impacts from two scenarios, the first being "business-as-usual" with no policies to reduce emissions, and the second being a fairly aggressive reduction of emissions (See figure 2 for a graphic explaining these scenarios, and http://www.grida.no/climate/ipcc/emission/012.htm). Using two climate models with each of these scenarios, they projected the impacts of these emission levels to the year 2099 for California. Elements included in their study were: temperature; precipitation; extreme heat and heat-related mortality; snowpack, runoff and water supply; and agriculture and vegetation distribution. In all simulations, annual average temperatures increased over the period, including extreme heat and heat waves. The most severe impacts were results of the higher "business-as-usual" emissions scenario. A significant conclusion of this paper is they support that "climate change and many of its impacts scale with the quantity and timing of greenhouse gas emissions" as reported in Climate Change 2001: The Scientific Basis [4]. Figure 2. Special Report on Emission Scenarios (SRES) tree of future emissions. Hayhoe et al. used A1fi and B1 in their study. There are changes that individuals can make to reduce the harmful emission of GHGs in California, and legislation has helped accelerate that process. Air quality across the state and in areas like Los Angeles have benefited from such measures as improvements in vehicle manufacturing and technology, and Californians are leading the nationwide effort to create a better environment for living and reduce the impact of humans on the natural climate. References: 1. The California Almanac of Emissions and Air Quality, 2005 edition. California Environmental Protection Agency and Air Resources Board. 2. Swart, R., M. Amann, F. Raes, W. Tuinstra, 2004. A good climate for clean air: linkages between climate change and air pollution, an editorial essay. Clim. Change 66: 263-269. 3. Hayhoe, K. et al., 2004. Emissions pathways, climate change, and impacts on California. PNAS, 101, 34, pp. 12422-12427. www.pnas.org/cgi/doi/10.1073/pnas.0404500101 4. Houghton, J. T., Y. Ding, D. J. Griggs, M. Boguer, P. J. van der Linden and D. Xiaosu, eds., 2001. Climate Change 2001: The Scientific Basis, Cambridge Univ. Press, Cambridge, U.K. Page last updated 8/11/05.