Nation

US climate report warns of damaged environment and shrinking economy

WASHINGTON — A major scientific report issued by 13 federal agencies Friday presents the starkest warnings to date of the consequences of climate change for the United States, predicting that if significant steps are not taken to rein in global warming, the damage will knock as much as 10 percent off the size of the US economy by century’s end.

The report, which was mandated by Congress and made public by the White House, is notable not only for the precision of its calculations and bluntness of its conclusions, but also because its findings are directly at odds with President Trump’s agenda of environmental deregulation, which he asserts will spur economic growth.

Trump has taken aggressive steps to allow more planet-warming pollution from vehicle tailpipes and power plant smokestacks, and has vowed to pull the United States out of the Paris Agreement, under which nearly every country in the world pledged to cut carbon emissions. Just this week, he mocked the science of climate change because of a cold snap in the Northeast, tweeting, “Whatever happened to Global Warming?”

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But in direct language, the 1,656-page assessment lays out the devastating effects of a changing climate on the economy, health, and environment, including record wildfires in California, crop failures in the Midwest, and crumbling infrastructure in the South. Going forward, American exports and supply chains could be disrupted, agricultural yields could fall to 1980s levels by midcentury, and fire season could spread to the Southeast, the report finds.

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“There is a bizarre contrast between this report, which is being released by this administration, and this administration’s own policies,” said Philip B. Duffy, president of the Woods Hole Research Center.

All told, the report says, climate change could slash up to a 10th of gross domestic product by 2100, more than double the losses of the Great Recession a decade ago.

Scientists who worked on the report said it did not appear that administration officials had tried to alter or suppress its findings. However, several noted that the timing of its release, at 2 p.m. the day after Thanksgiving, appeared designed to minimize its public impact.

“This report will weaken the Trump administration’s legal case for undoing climate change regulations and it strengthens the hands of those who go to court to fight them,” said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton.

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The report says the Northeast “is projected to be more than 3.6-degrees warmer on average than during the preindustrial era. This would be the largest increase in the contiguous United States and would occur as much as two decades before global average temperatures reach a similar milestone.’’

“Projected increases in temperature are expected to lead to substantially more premature deaths, hospital admissions, and emergency department visits across the Northeast,’’ the report said.

The report finds that the continental United States already is 1.8 degrees Fahrenheit warmer than it was 100 years ago, surrounded by seas that are on average nine inches higher and being racked by far worse heat waves than the nation experienced only 50 years ago.

It also puts the most precise price tags to date on the cost to the US economy of projected climate impacts: $141 billion from heat-related deaths, $118 billion from sea level rise, and $32 billion from infrastructure damage by the end of the century, among others.

The report is the second volume of the National Climate Assessment, which the federal government is required by law to produce every four years.

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The results of the 2014 report helped inform the Obama administration as it wrote a set of landmark climate change regulations. The following year, the Environmental Protection Agency finalized president Barack Obama’s signature climate change policy, known as the Clean Power Plan, which aimed to slash planet-warming emissions from coal-fired power plants. At the end of 2015, Obama played a lead role in brokering the Paris Agreement.

‘There is a bizarre contrast between this report. . . and this administration’s own policies.’

But in 2016, Republicans in general and Trump in particular campaigned against those regulations. In rallies before cheering coal miners, Trump vowed to end what he called Obama’s “war on coal” and to withdraw from the Paris deal. Since winning the election, his administration has move decisively to roll back environmental regulations.

The authors put forth three main solutions: putting a price on greenhouse gas emissions, which usually means imposing taxes or fees on companies that release carbon dioxide into the atmosphere; establishing government regulations on how much greenhouse pollution can be emitted; and spending public money on clean-energy research.

A White House statement said the report, which was started under the Obama administration, was “largely based on the most extreme scenario” of global warming and that the next assessment would provide an opportunity for greater balance.

No area of the country will be untouched by climate disruption, from the Southwest, where droughts will curb hydropower and tax already limited water supplies, to Alaska, where the loss of sea ice will cause coastal flooding and erosion and force communities to relocate, to Puerto Rico and the Virgin Islands, where salt water will taint drinking water.

There is always some uncertainty in climate projections, but scientists’ estimates about the effects of global warming to date have largely been borne out. The variable going forward, the report says, is the amount of carbon emissions that humans produce.

Two areas of impact particularly stand out: trade and agriculture.

Trade disruptions

Trump has put trade issues at the center of his economic agenda, placing new tariffs on imports and renegotiating trade deals such as the North American Free Trade Agreement. But climate change is likely to be a disruptive force in trade and manufacturing, the report says.

Extreme weather events driven by global warming are “virtually certain to increasingly affect US trade and economy, including import and export prices and businesses with overseas operations and supply chains,” the report concludes.

Such disasters will temporarily shutter factories both in the United States and abroad, causing price spikes for products from apples to automotive parts, the scientists predicted.

Agricultural risks

The nation’s farm belt is likely to be among the hardest-hit regions, and farmers in particular will see their bottom lines threatened.

“Expect increases in challenges to livestock health, declines in crop yields and quality, and changes in extreme events in the United States and abroad,” the report says.

By 2050, the scientists forecast, changes in rainfall and hotter temperatures will reduce the agricultural productivity of the Midwest to levels last seen in the 1980s.

Material from The Washington Post was used in this report.