The new EPA leader takes aim at the heart of climate-change orthodoxy.

It’s hard to overstate the significance of the recent comment by EPA administrator Scott Pruitt that there is disagreement about whether carbon dioxide is the main cause of global warming. In an interview on CNBC on March 9, Pruitt said:

Measuring with precision human activity on the climate is something very challenging to do, and there is tremendous disagreement about the degree of impact. So, no, I would not agree that it [CO2] is a primary contributor to the global warming that we see. But we need to continue the review and the analysis.

This statement is truly extraordinary: A leading U.S. official is taking direct aim at the heart of the international climate-change crusade.. It represents a total reversal of the past eight years, when everyone from the president down to low-level bureaucrats warned that climate change was a bigger threat to mankind than terrorism — to the point where they forced us to endure costly, job-killing federal regulations to stop it. Now the head of our top environmental agency is questioning the whole thing. Of all the conservative pit bulls in Trump’s Cabinet, Pruitt might be the biggest badass of them all.

Right on cue, the climate tribe went ballistic, trotting out the usual platitudes about a 97 percent consensus, settled science, climate deniers, blah blah blah. Obama’s EPA chief Gina McCarthy slammed Pruitt without (of course) refuting his claim head-on: “When it comes to climate change, the evidence is robust and overwhelmingly clear that the cost of inaction is unacceptably high.” Senator Kamala Harris (D., Calif.) — who weirdly asked Mike Pompeo about his position on climate change during his Senate confirmation hearing for the post of CIA director — subtweeted Pruitt’s comments and said: “This is absurd. Denying causes of global warming will hurt our nation and our planet in the long-run.”

Pruitt is setting the stage for a long-overdue and critical debate about how much of an impact CO2 has on global warming. He is not the only one speaking out. In her recent report, “Climate Models for the Layman,” Judith Curry says that global climate models (GCM) are “running hot” and “predict too much warming from increased atmospheric carbon dioxide.” Curry, a climate scientist and co-founder of the Climate Forecast Applications Network, says scientists frequently make ad hoc adjustments to climate models that often overestimate carbon dioxide’s impact on warming.

By tying rising carbon dioxide levels to a projected rise in temperatures, the models predict that temperatures will be much higher than they really are. Curry says in her report that current models for this century projected warming at about twice the rate of observed temperatures: “The reason for the discrepancy between observations and model simulations in the early 21st century appears to be caused by a combination of inadequate simulations of natural internal variability and oversensitivity of the models to increasing carbon dioxide.”

As for Pruitt’s comments, Curry gave me this response in an e-mail:

If I am interpreting his statements correctly, I do not find anything to disagree with in what he said: We don’t know how much of recent warming can be attributed to humans. In my opinion, this is correct and is a healthy position for both the science and the policy debate.

The biggest concern about overestimating carbon dioxide’s role as the primary cause of global warming is that the estimates drive public policy. In the summary of her report, Curry says that climate models are useful from a scientific perspective but are “not fit for the purpose of justifying political policies to fundamentally alter world social, economic, and energy systems.” This is precisely what has occurred on a global scale for years and another reason that Pruitt’s comments — in addition to President Trump’s executive orders on climate policy — are so consequential.

Climate regulations hold a vise grip on government and industry. According to the American Action Forum, President Obama’s policies to limit greenhouse-gas emissions cost at least $437 billion. The Clean Power Plan, which Trump is expected to rescind this week via executive order, would have cost trillions of dollars over the next several years (just remember that the next time you cringe at a Trump tweet). Releasing climate’s grip on our economy could arguably have a bigger impact than either tax or health-care reform.

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