Accuracy of National Climate Assessment Questioned by Trump Administration

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Accuracy of National Climate Assessment Questioned by Trump Administration

On November 23, 2018, a White House spokesperson questioned the accuracy of the Fourth National Climate Assessment (NCA). The NCA, which was prepared by thirteen federal government agencies, finds that climate change presents “growing challenges to human health and safety, quality of life, and the rate of economic growth” and indicates that “[w]ithout substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses” in the U.S.

Following release of the NCA, White House spokesperson Lindsay Walters suggested that it overstates the risks associated with climate change, saying:

“the report is largely based on the most extreme scenario, which contradicts long-established trends by assuming that . . . there would be limited technology and innovation, and a rapidly expanding population.”

That statement was challenged by climate scientists, including Katherine Hayhoe, a professor at Texas Tech University who co-authored the NCA. Professor Hayhoe wrote on twitter:

“I wrote the climate scenarios chapter [of the NCA] myself so I can confirm it considers ALL scenarios, from those where we go carbon negative before end of century to those where carbon emissions continue to rise. What [White House] says is demonstrably false.”

UpdateOn November 26, 2018, President Trump dismissed the findings of the NCA, telling reporters “I don’t believe it.” President Trump made similar remarks in an interview with the Washington Post on November 27, 2018. The President told reporters: “One of the problems that a lot of people like myself, we have very high levels of intelligence but we’re not necessarily such believers” in climate change. He then continued: “There is moving in the atmosphere. There’s no question. As to whether or not it’s man-made and whether or not the effects that you’re talking about are there, I don’t see it.”

Also on November 27, 2018, Secretary of the Interior Ryan Zinke asserted that the NCA only considered “the worst-case scenarios.” During a television interview, Secretary Zinke said: “it appears they took the worst-case scenarios and they built predictions upon that. It should be more probability — but we’re looking at it.”

Similar claims were made by White House Press Secretary Sarah Huckabee Sanders on November 27. Ms. Huckabee Sanders told reporters that the NCA reflects “the most extreme version and [is] not based on facts.” She continued: “It’s not data-driven. We’d like to see something that is more data-driven, that’s based on modeling, which is extremely hard to do when you’re talking about the climate.”

These claims have been disputed by the NCA’s authors, including Professor Hayhoe, who tweeted:

“Sarah Saunders says, ‘this report is based on the most extreme model scenario, which contradicts long-established trends.’ That’s two false statements because: 1, we considered many scenarios including vv low ones; and 2, the chapter I wrote concludes this, based on actual data . . . ‘[t]he observed increase in global carbon emissions over the past 15-20 years has been consistent with higher scenarios.'”

On November 28, 2018, the Acting Administrator of the Environmental Protection Agency, Andrew Wheeler, suggested that the Obama Administration had interfered in the preparation of the NCA. He told reporters: “this report was drafted at the direction of the Obama administration . . .  I wouldn’t be surprised if the Obama administration told the report’s authors to take a look at the worst case scenario for this report.” EPA later reiterated this claim in a press release. The claim was strongly denied by President Obama’s science adviser, John Holdren, who described it as “absolutely false.”

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