Climate change straight talk
Government draft report says factors driving global warming are clear
The conclusions contained in a draft federal report on climate change are unequivocal: Human-induced global warming is real, and left unchecked, the consequences could be dire.
Although not new, the findings are at odds with claims by President Trump and members of his administration, who continue to assert that the extent of the human contribution to climate change is not clear.
In June, Trump announced that the U.S. would withdraw from the agreement reached in Paris in 2015, in which nearly 200 countries pledged to reduce emissions of heat-trapping greenhouse gases, saying the deal was bad for the country.
The report’s authors, however, say the factors driving climate change are quite clear.
“Many lines of evidence demonstrate that human activities, especially emissions of greenhouse gases, are primarily responsible for the observed climate changes over the last 15 decades,” the authors wrote. “There are no alternative explanations.”
The report, a synthesis of the available science prepared by 13 government agencies, is part of the National Climate Assessment, which is mandated by Congress and is supposed to be published every four years.
The latest draft has been extensively reviewed, and the authors are waiting for permission from the Trump administration to release the report to the public — which probably explains why it was leaked to the New York Times.
“We have not received any indication yet that it is not on schedule for publication,” said Katharine Hayhoe, a professor of political science at Texas Tech University and one of the lead authors of the report. “But understandably there are fears that it won’t be approved, or that it could be returned to the authors with substantial changes that we might not be comfortable with because they aren’t consistent with the science.”
The draft report concludes that average temperatures over much of the world in recent decades have been much higher and have risen faster than at any time in the last 1,700 years. It is “extremely likely” that more than half of the rise in global temperatures since the mid-20th century was the result of human activity, it says.
Even small temperature increases can have major effects, such as more frequent droughts and extreme storms, melting polar ice sheets and rising seas.
Scientists have generally hesitated to attribute specific weather events to climate change. But the authors say there is now relatively strong evidence for a human contribution to events such as the heat waves in Europe in 2003 and in Australia in 2013.
Here are more of the findings contained in the draft report: