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| A draft report by government scientists concludes that Americans are feeling the effects of climate change right now. Credit Branden Camp/Associated Press |
WASHINGTON
— The average temperature in the United States has risen rapidly and
drastically 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 the Trump 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 by President
Trump and members of his cabinet who say 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 a special science section of the
National Climate Assessment, which is congressionally mandated every
four years. The National Academy of Sciences has signed off on the draft report, and the authors are awaiting permission from the Trump administration to release it.
One government scientist who worked on the report, Katharine Hayhoe,
a professor of political science at Texas Tech University, called the
conclusions among “the most comprehensive climate science reports” to be
published. Another scientist involved in the process, who spoke to The
New York Times on the condition of anonymity, said he and others were
concerned that it would be suppressed.
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| Read the Draft of the Climate Change Report
A draft report by scientists from 13 federal agencies, which has not yet been made public but was obtained by The New York Times, concludes that Americans are feeling the effects of climate change right now.
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The White House and the Environmental Protection Agency did not immediately return calls or respond to emails requesting comment on 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 0.50 degrees Fahrenheit (0.30 degrees Celsius) of
warming over this century compared with today. The projected actual
rise, scientists say, will be as much as 2 degrees Celsius.
A
small difference in global temperatures can make a big difference in
the climate: The difference between a rise in global temperatures of 1.5
degrees Celsius and one of 2 degrees Celsius, for example, could mean
longer heat waves, more intense rainstorms and the faster disintegration
of coral reefs.
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
E.P.A. is one of 13 agencies that must approve the report by Aug. 18.
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.”
Scientists
say they fear that the Trump administration could change or suppress
the report. But 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.
The report says significant advances have been made linking human influence to individual extreme weather events since the last 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 where “relatively strong evidence” showed
that a man-made factor contributed to the extreme weather.
In
the United States, the authors write, the heat wave that broiled Texas
in 2011 was more complicated. That year was Texas’ driest on record, and
one study cited in the report said local weather variability and La
Niña were the primary causes, with a “relatively small” warming
contribution. Another study had concluded that climate change made
extreme events 20 times more likely in Texas.
Based
on those and other conflicting studies, the federal draft concludes
that there was a medium likelihood that climate change played a role in
the Texas heat wave. But it avoids assessing other individual weather
events for their link to climate change. Generally, the report described
linking recent major droughts in the United States to human activity as
“complicated,” saying that while many droughts have been long and
severe, they have not been unprecedented in the earth’s hydrologic
natural variation.
Worldwide,
the draft report finds it “extremely likely” that more than half of the
global mean temperature increase since 1951 can be linked to human
influence.
In
the United States, the report concludes with “very high” confidence
that the number and severity of cool nights have decreased since the
1960s, while the frequency and severity of warm days have increased.
Extreme cold waves, it says, are less common since the 1980s, while
extreme heat waves are more common.
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It
says the average annual rainfall across the country has increased by
about 4 percent since the beginning of the 20th century. Parts of the
West, Southwest and Southeast are drying up, while the Southern Plains
and the Midwest are getting wetter.
With
a medium degree of confidence, the authors linked the contribution of
human-caused warming to rising temperatures over the Western and
Northern United States. It found no direct link in the Southeast.
Additionally,
the government scientists wrote that surface, air and ground
temperatures in Alaska and the Arctic are rising at a frighteningly fast
rate — twice as fast as the global average.
“It
is very likely that the accelerated rate of Arctic warming will have a
significant consequence for the United States due to accelerating land
and sea ice melting that is driving changes in the ocean including sea
level rise threatening our coastal communities,” the report says.
Human activity, the report goes on to say, is a primary culprit.
The
study does not make policy recommendations, but it notes that
stabilizing the global mean temperature increase to 2 degrees Celsius —
what scientists have referred to as the guardrail beyond which changes
become catastrophic — will require significant reductions in global
levels of carbon dioxide.
Nearly
200 nations agreed as part of the Paris accords to limit or cut fossil
fuel emissions. If countries make good on those promises, the federal
report says, that will be a key step toward keeping global warming at
manageable levels.
Mr. Trump announced this year that the United States would withdraw from the Paris agreement, saying the deal was bad for America.
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