On Friday, thirteen agencies within the United States government jointly issued the Climate Science Special Report, declaring that roughly 90% of climate change is caused by human activity, most notably the production of carbon dioxide by the burning of fossil fuels.  This directly contradicts assertions made by politicians within the administration of the current president, Donald Trump.
The report notes, "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century[...] For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence."
Officially, the report was submitted through the Trump Administration's Office of Science and Technology Policy, to which President Trump has not appointed a head. The official response from the rest of the White House, given to the press by White House spokesperson Raj Shah, reads as follows: "The climate has changed and is always changing. As the Climate Science Special Report states, the magnitude of future climate change depends significantly on 'remaining uncertainty in the sensitivity of Earth's climate to [greenhouse gas] emissions[...] In the United States, energy related carbon dioxide emissions have been declining, are expected to remain flat through 2040, and will also continue to decline as a share of world emissions."
The report clocks in at roughly 500 pages and places the human contribution to the increase in the Earth's temperature at 92–123% since 1950.  As explained by co-author Katherine Hayhoe, the space over 100% indicates counteraction of forces that have a cooling effect, like sun-blocking dust kicked into the upper atmosphere by volcanoes.  Overall, the report calls the past 115 years "the warmest in the history of modern civilization."
The study cites several factors, called "tipping points," that might make global climate change more intense, such as changes in El Niño and other major patterns in ocean currents, the loss of arctic and antarctic ice sheets, and the release of methane, a greenhouse gas, from rotting material as previously permafrozen ground begins to thaw and cites both the wildfires in California and Superstorm Sandy for effects due to global climate change.  It predicts one scenario in which ocean levels rise as much as 8 feet (2.4 m) by the year 2100.
Unlike with previous studies on climate change released by U.S. government agencies, said one lead author, David Fahey of the National Oceanic and Atmospheric Administration, the Trump Administration does not appear to have made an effort to block publication of the report or alter the wording describing its scientific findings, though there were some alterations to the description of U.S. policy with respect to the Paris Climate Accords. Fahey remarked, "I'm quite confident to say there has been no political interference in the scientific messages from this report...] Whatever fears we had weren't realized."
Head of the Environmental Protection Agency Scott Pruitt and Secretary of Energy Rick Perry have both said publicly that carbon dioxide does not cause much global warming.
Phil Duffy of the Woods Hole Research Center noted, "This is a federal government report whose contents completely undercut [the Trump Administration's] policies, completely undercut the statements made by senior members of the administration." President Trump has announced plans to withdraw the United States form the Paris Climate Accords, in which participating countries pledge to reduce carbon emissions, and to loosen federal laws regulating fossil fuels.
The Climate Science Special Report is part of the fourth National Climate Assessment, the last of which was in 2014. The National Climate Assessments are required by a law passed by the United States Congress in 1990.

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U.S. government report says climate change is human-made