Report finds strong link between climate change, human activity

By Steven Mufson / The Washington Post

A climate report based on work conducted by scientists in 13 federal agencies is under active review at the White House, and its conclusions about the far-reaching damage already occurring from global warming are at odds with the Trump administration’s views.

The report, known as the Climate Science Special Report, finds it is “extremely likely” that more than half of the rise in temperatures over the past four decades has been caused by human activity — in contrast to Trump cabinet members’ views, who consider the magnitude of that contribution to be uncertain.

The draft report estimates that human impact is responsible for a Fahrenheit increase in global temperatures of 1.1 to 1.3 degrees from 1951 to 2010.

“Many lines of evidence demonstrate that human activities, especially emissions of greenhouse (heat trapping) gases, are primarily responsible for recent observed climate changes,” the report notes. “There are no alternative explanations, and no natural cycles are found in the observational record that can explain the observed changes in climate.”

That counters what both Environmental Protection Agency Administrator Scott Pruitt and Energy Secretary Rick Perry have recently said.

It remains unclear how the White House — which announced in June it would pull out of the Paris climate accord — will handle the report. Many scientists are looking at it as a test case of the administration’s attitude toward science in general.

The Climate Science Special Report is a key element of the National Climate Assessment, which according to the 1990 Global Change Research Act, is supposed to be issued every four years. However, the assessment has only come out three times. The 2000 assessment, finalized under President Bill Clinton, came under attack once George W. Bush took office. Bush officials declined to cite it in subsequent federal reports, arguing that aspects of the data analysis were flawed.

Trump administration officials received a copy of the most recent version of this report — which has undergone extensive review — several weeks ago, according to senior administration officials.

The New York Times reported on the latest draft late Monday. The Washington Post subsequently obtained a third draft of the report. The version at the White House is the fifth draft, but people familiar with both versions say there is no substantive difference.

The report also ventures into “attribution science,” drawing links between climate change and specific weather events. For example, it says that rainfall across the United States has decreased by about 4 percent since the beginning of the 20th century.