FACTBOX-Excerpts from EPA's greenhouse gas document

April 17 - The U.S. Environmental Protection Agency said on Friday six emissions of greenhouse gases, including carbon dioxide, are a danger to public health and welfare. Here are excerpts from the EPA's so-called endangerment finding, which opens the way for possible regulation of climate-warming pollution.

* "The scientific evidence clearly indicates that atmospheric levels of the six greenhouse gases are at unprecedented elevated levels due to human activities, and that most of the observed global and continental warming can be attributed to this anthropogenic rise in greenhouse gases."

* "It is clear that current and projected levels of greenhouse gases and resultant climate change are already adversely affecting, and will continue to adversely affect, public welfare within the meaning of the (Clean Air) Act."

* "These six gases, once emitted, remain in the atmosphere for decades to centuries." The gases are: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

* "The heating effect caused by the human-induced buildup of greenhouse gases in the atmosphere is very likely the cause of most of the observed global warming over the last 50 years."

* "Transportation sources subject to regulation ... are the second largest greenhouse gas-emitting sector in the U.S., after electricity generation, and accounted for 24 percent of total U.S. greenhouse gas emissions ... Total U.S. greenhouse gas emissions make up about 18 percent of the world's greenhouse gas emissions."

* "The impacts of climate change are increased drought, more heavy downpours and flooding, more frequent and intense heat waves and wildfires, greater sea level rise, more intense storms, and harm to water resources, agriculture, wildlife and ecosystems ... Over the 21st century, changes in climate will cause some species to shift north and to higher elevations and fundamentally rearrange U.S. ecosystems."