It is “extremely likely” that human activities are the “dominant cause” of global warming, according to the the most comprehensive study ever of climate science by U.S. government researchers.
The climate report, obtained by NPR, notes that the past 115 years are “the warmest in the history of modern civilization.” The global average temperature has increased by about 1.8 degree Fahrenheit over that period. Greenhouse gases from industry and agriculture are by far the biggest contributor to warming.
The findings contradict statements by President Trump and many of his Cabinet members, who have openly questioned the role humans play in changing the climate.
“I believe that measuring with precision human activity on the climate is something very challenging to do,” EPA Administrator Scott Pruitt said in an interview earlier this year. “There’s tremendous disagreement about the degree of impact.”
That is not consistent with the conclusions of the 600-plus page Climate Science Special Report, which is part of an even larger scientific review known as the fourth National Climate Assessment. The NCA4, as it’s known, is the nation’s most authoritative assessment of climate science. The report’s authors include experts from leading scientific agencies, including the National Oceanic and Atmospheric Administration, NASA and the Department of Energy, as well as academic scientists.
The report states that the global climate will continue to warm. How much, it says, “will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally.” Without major reductions in emissions, it says, the increase in annual average global temperature could reach 9 degrees Fahrenheit relative to pre-industrial times. Efforts to reduce emissions, it says, would slow the rate of warming.
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