"In recent years, the federal government has allocated several billion dollars annually for projects to expand the understanding of climate change or to reduce carbon dioxide and other greenhouse-gas (GHG) emissions. Most of that spending is done by the Department of Energy (DOE) and by the National Aeronautics and Space Administration (NASA), although a dozen other federal agencies also participate. The work is coordinated by committees in the Executive Office of the President. Successive Administrations have tracked the funding of climate change programs and the cost of tax incentives related to climate change through what is sometimes called the 'climate change budget.'"
Congressional Budget Office: http://www.cbo.gov/