Greenhouse gases include carbon dioxide (CO₂), methane (CH4), chlorofluorocarbons (CFC), both nitrous oxides (N2O) and nitrogen oxides (NO_x), ozone (O₃), carbon tetrachloride (CCl₄), and water vapor (H₂O). The burning of any carbon-based fuel (including coal, natural gas, oil, propane, gasoline, etc.) produces carbon dioxide, but coal-fired power plants are the primary culprit.

The electricity industry is the nation’s leading source of carbon dioxide emissions (although vehicles are a close second) and the largest source of greenhouse gases generally. While carbon dioxide is not the most potent greenhouse gas, its sheer volume makes it the most significant. An average coal-fired power plant releases more than 2 pounds of carbon dioxide for each kilowatt-hour of energy it produces (by comparison, oil-fired plants produce 16% less carbon and natural gas plants 44% less). For a typical Montana household using 9000 kilowatt-hours of energy each year, this would mean nearly ten tons of carbon dioxide (about what an average sport utility vehicle produces).

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In addition to potentially severe economic, social, and political dislocations, global warming poses numerous environmental and public health concerns including increases in insect populations and the spread of infectious tropical diseases, a greater frequency of El Niño and extreme weather events (such as floods, droughts, and fires), the melting of glaciers and polar ice caps, rising sea levels, desertification, and general ecosystem disruption and extinctions caused by the rapid rate of change.

Some of these effects, such as massive cracking of polar ice shelves and the disappearance of glaciers in our own Glacier National Park (which may be left “glacierless” by the year 2030 and which is already down to only 26 of the 150 glaciers that were present in 1850), are already dramatically evident.

Further evidence of anthropogenic global warming includes atmospheric CO₂ concentrations 35% higher than at the beginning of the industrial revolution, the twenty hottest years on record all having occurred since 1980, and a rate of temperature change greater than any seen in the last 10,000 years. Currently there are no federal limits on carbon dioxide production, although steps are beginning to be taken at the state and local level.

It is important to note that beyond direct CO₂ emissions, the mining of coal releases significant amounts of methane, a gas which, molecule for molecule, has 20 to 60 times the heat-trapping potential of CO₂.