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Edison International's commitment to operating with sensitivity and intelligence toward the environment is reflected in its Global Climate Change Policy. But what exactly is global climate change? In brief, it is the change in global temperatures. Many leading scientist believe that this phenomenon has accelerated within the last 100 years. Most of the scientific evidence indicates that this has been a result of greater emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) gases.
Global Climate Basics
The earth's average temperature is around 60°F. That temperature has resulted through the exchange of energy between the earth and the sun: the sun heats the earth's surface while energy is radiated back into space. With atmospheric greenhouse gases (such as water vapor, carbon dioxide, and other gases) some of the outgoing energy is trapped. The heat is thus retained, somewhat like what occurs within the glass panels of a greenhouse. (see illustration)
 The increased concentration of greenhouse gases may lead to problems for our atmosphere. Where do greenhouse gases come from? Most of the carbon dioxide in our atmosphere comes from plants and the decomposition of organic matter. These release more than 10 times the carbon dioxide as that released by human activities. But these releases have generally been in balance during the centuries leading up to the industrial revolution, with carbon dioxide absorbed by earth's vegetation and the oceans.
Gas emissions have taken on a new pattern since the beginning of the industrial revolution, when atmospheric concentrations of carbon dioxide increased nearly 30 percent, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15 percent. These increases have enhanced the heat-trapping capability of the earth's atmosphere.
The Source of Additional Greenhouse Gases
Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide. Energy burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 80 percent of society's carbon dioxide emissions, about 25 percent of U.S. methane emissions, and about 20 percent of global nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions.
Estimating future emissions is difficult because demographic, economic, technological, institutional and policy developments all play a role in estimation forecasts. Several emissions scenarios have been developed based on differing projections of these underlying factors.
For more information on the causes and consequences of climate change, you can go to the U.S. Global Change Research Program website.
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