Federal report blames humans for global warming and its effects

An extensive report published by the federal government Friday asserts that humans are the primary driver of climate change, causing higher temperatures, sea level rise, agriculture problems and more.

The report, the first volume of the Fourth National Climate Assessment, is years in the making, and involved contributions from more than a dozen federal agencies.

It is meant to be an authoritative assessment of the current state of climate change science.

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Many of the report’s conclusions directly contradict the Trump administration’s positions on climate change.

For example, Trump officials like Environmental Protection Agency chief Scott PruittEdward (Scott) Scott PruittGovernment watchdog probing EPA’s handling of Hurricane Harvey response Wheeler won’t stop America’s addiction to fossil fuels Overnight Energy: Trump rolls back methane pollution rule | EPA watchdog to step down | China puts tariffs on US gas MORE and Energy Secretary Rick PerryJames (Rick) Richard PerryPartisan politics at independent agency draws bipartisan rebuke Overnight Energy: House panel approves park funding, offshore drilling bills | Green group putting M into races | Perry applauds Russia boosting oil production Perry welcomes efforts by Russia, OPEC to boost oil production MORE say they can’t be sure whether human-caused greenhouse gases like carbon dioxide are the primary cause of climate change.

But the Climate Assessment plainly states that is the case.

“This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century,” it says. “For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”

"Globally averaged, annually averaged surface air temperature has increased by about 1.8 degrees Fahrenheit, or 1 degree Centigrade, over the last 115 years," David Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration (NOAA) and one of the leading authors of the report, told reporters. "This period is now the warmest in the history of modern civilization."

The report cites “thousands of studies conducted by researchers around the world” that show evidence of a warming globe, including “changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.”

It includes dire warnings about the impact of climate change on human activities.

Heavy rainfall, which causes flooding, is expected to increase over the rest of the century, and heat waves will become more frequent.

Severe weather events like forest fires and drought will grow more prevalent, and sea levels will rise “by at least several inches in the next 15 years and by 1–to-4 feet by 2100.”

This underlines warnings from scientists around the globe who say the only way to get climate change under control will be to reduce the amount of greenhouse gas emissions, especially carbon dioxide.

Emission growth has slowed in recent years, but the report concludes it’s not enough to keep temperatures from rising more than 2 degrees Celsius, the limit at which scientists expect the worst effects of climate change to be irreversible.

The study is the fourth time this century that federal scientists have put together a report on the impacts of climate change around the globe and in the United States.

The report is mandated by Congress, with three federal agencies — NOAA, NASA and the Department of Energy — coordinating its publication. It uses research from thousands of scientists around the world.

This year’s assessment comes amid concerns that the White House would work to undermine the study’s conclusions. Scientists shared a draft version of the study with The New York Times in August, seeking extra publicity for its findings in the hope of rebuffing any attempt to water it down.

The topline conclusions of the final study, though, appear to be in line with those of the draft, and the accepted scientific consensus on the role humans play in warming the globe.

Fahey told reporters that there was no political interference in the assessment released Friday, though he conceded that some on the team had feared it would happen.

"Of course there are perhaps fears. We’re all citizens and scientists at the same time. But I think whatever fears we had weren’t realized," Fahey said.

"The word ‘interference’ might have been a threat, but it never materialized. This report says what the scientists wanted it to say."

In a statement, White House Principal Deputy Press Secretary Raj Shah said that “the climate has changed and is always changing” and pointed to a line in the report that concluded the future of climate change depends primarily on “remaining uncertainty in the sensitivity of Earth's climate to [greenhouse gas] emissions.”

The report said, with “very high confidence,” that the magnitude of climate change will also depend on the “amount of greenhouse gases emitted globally” over the next few decades.

“The administration supports rigorous scientific analysis and debate and encourages public comment on the draft documents being released today,” Shah said.

“To address climate change as well as other risks, the U.S. will continue to promote access to the affordable and reliable energy needed to grow economically, and to support technology, innovation and the development of modern and efficient infrastructure that will reduce emissions and enable us to address future risks, including climate related risks."

—Updated at 3:36 p.m.