ThinkProgress

Trump’s White House just declared that humans are responsible for all recent warming

Projected changes in annual average temperatures (2070–2099) with strong climate policies (left) and with current policies (right). CREDIT: National Climate Assessment

On Friday, the Trump administration released the congressionally mandated National Climate Assessment, the “authoritative assessment of the science of climate change, with a focus on the United States,” as the report states.

What’s so stunning about the 600-page report, the work of scientists from 13 federal agencies, is that the White House Office of Science and Technology Policy (OSTP) oversaw the final review and clearance process of the report — and yet the report details just how dangerous the Trump administration’s policy of climate science denial is to Americans.

The National Climate Assessment (NCA) projects a devastated America — widespread Dust-Bowlification, 18°F Arctic warming, sea levels rising a foot a decade — on our current path of unrestricted carbon pollution. The report makes clear just how grave a threat are Trump’s plans to abandon the Paris climate deal, undo Obama-era climate rules, and boost carbon pollution.

Indeed, the report explicitly states that if governments don’t meet their Paris targets, and then go beyond them, catastrophic impacts would be inevitable.

The report “indicates that a path of inaction will truly lead to disastrous climate change impacts,” as climatologist Michael Mann said in an email to ThinkProgress, confirming a point he made when the New York Times published the leaked final draft in August. “Sadly, the Trump presidency has steered the U.S. toward this path.”

“Based on extensive evidence… 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,” explains the NCA, the most comprehensive and detailed report ever done on climate change and its specific impact on America (emphasis in original).

“For the warming over the last century, there is no convincing alternative explanation supported by the extant of the observational evidence,” notes the report, which was peer-reviewed by the National Academy of Sciences. “This period is now the warmest in the history of modern civilization.”

Contrast these conclusions with the standard talking points from senior administration officials, which asserts we don’t know enough to act. “I believe that measuring with precision human activity on the climate is something very challenging to do,” Environmental Protection Agency Administrator Scott Pruitt told NPR earlier this year. “There’s tremendous disagreement about the degree of impact.”

These are the core lies routinely propagated by the Trump administration: We don’t know how much humans are affecting the climate so far, and we don’t know what the impact will be. The new National Climate Assessment dismantles both of those lies.

In fact, the report makes clear that measuring with precision the impact of human activity on the climate is very straightforward. “The likely range of the human contribution to the global mean temperature increase over the period 1951–2010 is 1.1° to 1.4°F.” But “the central estimate of the observed warming of 1.2°F” lies within this range (high confidence).” The scientists conclude “this translates to a likely human contribution of 93 percent –123 percent of the observed 1951–2010 change.

In other words, the best estimate is that humans are responsible for all of the warming since 1950 — which is the exact conclusion the world’s top scientists came to in 2014, a finding every government in the world signed off on.

How could humans contribute to more than 100 percent of the warming since 1950? Absent human activity, the  planet probably would have cooled slightly since 1950, since volcanoes have continued to emit dust that blocks the sun. So human activity would have caused all the observed warming since 1950, plus compensated for the slight cooling.

You may recall that when Sen. Al Franken (D-MN) confronted Energy Secretary Rick Perry with this core scientific reality, Perry lost his cool and said the whole notion is “I think on its face, is just indefensible.” Like so many in the current administration, Perry is not just unaware of the science; when presented with it, he’s sure it can’t be true. That’s why he’s a denier and not a skeptic.

The even more dangerous lie is that Trump’s moves to abandon the Paris climate deal, undo Obama-era climate rules, and boost carbon pollution are decisions that benefit Americans. In fact, they are a clear and present danger to us.

As ThinkProgress reported Thursday, Trump’s own EPA just released an analysis concluding Trump’s policies could kill 100,000 Americans by 2050 — simply from the increased air pollution.

The NCA makes clear just how ruinous the climate change impacts of Trump’s policies would also be to this country. The report’s “higher emissions” scenario projects a stunning 8°F to 10°F warming over the interior of this country — and, unimaginably, upwards of 18°F over in the Arctic — by 2071 to 2100.

In that case, global sea levels could rise as much as 8 feet, inundating every major coastal city in this country and around the world. And seas would keep rising by more than a foot a decade by century’s end, which makes adaptation all but impossible.

America’s top climate scientists also project that most of the country would see serious to devastating drops in soil moisture most of the year. Here are the key projections for change in soil moisture by 2100, again in the “higher emissions” (business as usual) case, the one the Trump administration’s policies would lead to.

PROJECTED CHANGES IN SOIL MOISTURE IN “HIGHER EMISSIONS” SCENARIO. DOTS INDICATE WHERE CHANGES WOULD BE LARGE COMPARED VARIATION. CREDIT: NCA.

This would be the “new normal” climate, a near permanent state of drought over large segments of our country, including much of the California and Great Plains breadbaskets. In such a world, we would routinely suffer mega-droughts as intense as the 1930s Dust Bowl, but lasting many decades.

Furthermore, the report warns that “climate models are more likely to underestimate than to overestimate the amount of long-term future change,” so there is a greater chance things will be worse than the report lays out than they will be better.

To get to the more manageable “lower emissions” scenario, the nation and the world must far exceed the emissions reduction goals agreed to in Paris in December 2015. Trump’s decision to withdraw the U.S. from the Paris accord and kill actions aimed at meeting our commitment puts the world on track for a “higher emissions” scenario that leads to unimaginable impacts.

We hold our future in our hands, as the report makes clear: “Choices made today will determine the magnitude of climate change risks beyond the next few decades.”