Climate effects in U. S. detailed

Report finds rapid warming

WASHINGTON — The average temperature in the United States has risen rapidly since 1980, and recent decades have been the warmest of the past 1,500 years, according to a sweeping federal climate change report awaiting approval by President Donald Trump’s administration.

The draft report by scientists from 13 federal agencies, which has not yet been made public, concludes that Americans are feeling the effects of climate change right now. It directly contradicts claims, made by Trump and members of his Cabinet, that the human contribution to climate change is uncertain and that the ability to predict the effects is limited.

“Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans,” a draft of the report states. A copy of it was obtained by The New York Times.

The authors note that thousands of studies, conducted by tens of thousands of scientists, have documented climate changes on land and in the air. “Many lines of evidence demonstrate that human activities, especially emissions of greenhouse ( heat- trapping) gases, are primarily responsible for recent observed climate change,” they wrote.

The report was completed this year and is part of the National Climate Assessment, which is congressionally mandated every four years. The National Academy of Sciences has signed off on the draft and is awaiting permission from the Trump administration to release it.

One government scientist who worked on the report, and who spoke to the Times on the condition of anonymity, said he and others were concerned that it would be suppressed.

The White House and the Environmental Protection Agency did not immediately return calls or respond to emails requesting comment Monday night.

The report concludes that even if humans immediately stopped emitting greenhouse gases into the atmosphere, the world would still feel at least an additional 0.3 degree Celsius, or 0.5 degree Fahrenheit, of warming over this century compared with today. The projected actual rise, scientists say, will be as much as 2 degrees Celsius.

Among the more significant of the study’s findings is that it is possible to attribute some extreme weather to climate change. The field known as “attribution science” has advanced rapidly in response to increasing risks from climate change.

The draft report finds it “extremely likely” that worldwide, more than half of the global mean temperature increase since 1951 can be linked to human influence.

The report says significant advances have been made linking human influence to individual extreme weather events since the previous National Climate Assessment was produced in 2014. Still, it notes, crucial uncertainties remain.

It cites the European heat wave of 2003 and the record heat in Australia in 2013 as specific episodes in which “relatively strong evidence” showed that a man- made factor contributed to the extreme weather.

The report finds with “very high” confidence that in the United States, the number and severity of cool nights has decreased, while the frequency and severity of warm days has increased since the 1960s. Extreme cold waves, it says, are less common since the 1980s, while extreme heat waves are more common.

The Environmental Protection Agency is one of 13 agencies that must approve the report by Sunday. The agency’s administrator, Scott Pruitt, has said he does not believe that carbon dioxide is a primary contributor to global warming.

“It’s a fraught situation,” said Michael Oppenheimer, a professor of geoscience and international affairs at Princeton University who was not involved in the study. “This is the first case in which an analysis of climate change of this scope has come up in the Trump administration, and scientists will be watching very carefully to see how they handle it.”

Those who challenge scientific data on human- caused climate change say they are equally worried that the draft report, as well as the larger National Climate Assessment, will be publicly released.

“The National Climate Assessment seems to be on autopilot because there’s no political that has taken control of it,” said Myron Ebell, a senior fellow at the Competitive Enterprise Institute. He was referring to a lack of political direction from the Trump administration.