The Science Behind Climate Change

Climate change refers to change in the Earth’s weather patterns including the rise in the Earth’s temperature due to an increase in heat-trapping or "greenhouse" gases in the atmosphere. Unlike emissions of criteria and toxic air pollutants, which have local or regional impacts, emissions of greenhouse gases (GHGs) that contribute to global warming or global climate change have a broader, global impact.  Global warming is a process whereby GHGs accumulating in the atmosphere contribute to an increase in the temperature of the earth’s atmosphere.  The principal GHGs contributing to global warming are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2OO and fluorinated compounds.  These gases allow visible and ultraviolet light from the sun to pass through the atmosphere, but they prevent heat from escaping back out into space.  Among the potential implications of global warming are rising sea levels, and adverse impacts to water supply, water quality, agriculture, forestry and habitats.  In addition, global warming may increase electricity demand for cooling, decrease the availability of hydroelectric power, and affect regional air quality and public health.  Like most criteria and toxic air contaminants, much of the GHG production comes from motor vehicles.  GHG emissions can be reduced to some degree by improved coordination of land use and transportation planning on the city, county and subregional level, and other measures to reduce automobile use.  Energy conservation measures also can contribute to reductions in GHG emissions.

Climate change affects public health because the higher temperatures result in more air pollutant emissions, increased smog, and associated respiratory disease and heart-related illnesses. (In one instance, 21 to 38% of the deaths occurring during a heat wave were attributed to elevated ozone and PM10 levels.) Increasing temperatures threaten to erode the dramatic improvements in Bay Area air quality achieved over the past 50 years.

For more background information on climate change see:

• Intergovernmental Panel on Climate Change 
• U.S. Environmental Protection Agency
• Pew Center on Global Climate Change
• Union of Concerned Scientists Global Warming Web site
• Climatologic Stephen Schneider’s Climate Change Overview
• National Academy of Science Global Change Web site 

Additional Bay Area Climate Protection Resources

• Climate Change in the Bay Area 
• City of Berkeley Climate Wise Action Plan (196 k PDF, 79 pgs)
• Kyoto USA
• California Climate Action Registry