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Line 4: − ==Position of the EPA== − The Environmental Protection Agency of the United States asserts that<ref>http://www.epa.gov/climatechange/science/stateofknowledge.html</ref> − Scientists know with virtual certainty that: − − * Human activities are changing the composition of Earth's atmosphere. Increasing levels of greenhouse gases like carbon dioxide (CO2) in the atmosphere since pre-industrial times are well-documented and understood. − * The atmospheric buildup of CO2 and other greenhouse gases is largely the result of human activities such as the burning of fossil fuels. − * An “unequivocal” warming trend of about 1.0 to 1.7°F occurred from 1906-2005. Warming occurred in both the Northern and Southern Hemispheres, and over the oceans (IPCC, 2007). − * The major greenhouse gases emitted by human activities remain in the atmosphere for periods ranging from decades to centuries. It is therefore virtually certain that atmospheric concentrations of greenhouse gases will continue to rise over the next few decades. − * Increasing greenhouse gas concentrations tend to warm the planet. − − What's Very Likely? − The Intergovernmental Panel on Climate Change (IPCC) has stated "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations" (IPCC, 2007). In short, a growing number of scientific analyses indicate, but cannot prove, that rising levels of greenhouse gases in the atmosphere are contributing to climate change (as theory predicts). In the coming decades, scientists anticipate that as atmospheric concentrations of greenhouse gases continue to rise, average global temperatures and sea levels will continue to rise as a result and precipitation patterns will change.
→Position of the EPA: DELETE, because correlation is not causation
As far back as temperature records can be reconstructed, periods of global warming and global cooling have alternated; see [[ice age]]s and [[interglacial warming]].
As far back as temperature records can be reconstructed, periods of global warming and global cooling have alternated; see [[ice age]]s and [[interglacial warming]].
==Controversy==
==Controversy==