Yesterday, 375 members of the National Academy of Sciences, including 30 Nobel Prize winners, posted an open letter reviewing the basics of established climate science, decrying claims of hoax and hype spouted by Republicans during the presidential campaign and warning against the United States pulling out of the Paris Agreement on climate change.

Although it did not name him, the letter was aimed squarely at Donald J. Trump. Trump has said he would “cancel” the climate deal if elected and starkly flip-flopped in his campaign from a past stance calling for such action.

Trump’s call for pulling out of the agreement is pretty weird for such a supposed master of the deal, given that nothing in the pact legally binds the United States to take steps on emissions or climate aid. But of course that kind of detail doesn’t matter in tribal politics.

Notably, at the United Nations this morning, 31 countries “deposited instruments” acceding to the agreement, bringing the total to 60 since its approval with a gavel stroke in Paris in December. United Nations officials tallied sufficient oral commitments today to bring the agreement into effect before the end of the year:

Latest #ParisAgreement tally. @UN officials say oral commitments today guarantee it goes into force this year.… https://t.co/VckDlCcvPA — Andy Revkin (@Revkin) 21 Sep 16

The two biggest emitters of greenhouse gases, China and the United States, joined officially on September 3 as President Obama and China’s President Xi Jinping signed documents during Obama’s most recent China visit.

As I’ve stressed before, this is both a remarkable achievement, gauged through the lens of diplomacy, and a largely inconsequential one, gauged from the standpoint of the atmosphere. There remains a huge “ reality gap” between the wishful greenhouse-gas emissions projections used to determine whether the agreement can avoid dangerous warming and the global capacity to cut emissions even as human energy needs continue to surge in coming decades.

I’ll be writing more on next steps under the Paris Agreement soon. In the meantime, read “The Paris Agreement and the inherent inconsistency of climate policymaking,” an invaluable analysis by Oliver Geden for Wiley Interdisciplinary Reviews – Climate Change. (The publisher is providing free access for a few weeks.) Geden heads a research division at the German Institute for International and Security Affairs.

I encourage you to read the scientists’ climate letter in full. (The authors stress it was not organized or endorsed by the National Academy.)

This isn’t the first time there’s been such an effort. Six years ago, after hundreds of climate researchers’ email exchanges were posted online, fueling conservative lawmakers’ attempts to challenge climate science, 255 members of the National Academy of Sciences signed a letter defending the integrity of research pointing to dangerous global warming.

But this is the first such letter in the heat of a presidential campaign. The drafting of the new letter was led by two climate researchers, Benjamin Santer of Lawrence Livermore National Laboratory and Kerry Emanuel of the Massachusetts Institute of Technology, and two astrophysicists, George Field of Harvard and Ray Weymann, who is retired from the Carnegie Institution and devotes much of his time these days to climate change education.

Here’s their prime point about the Paris agreement:

[I]t is of great concern that the Republican nominee for President has advocated U.S. withdrawal from the Paris Accord. A “Parexit” would send a clear signal to the rest of the world: “The United States does not care about the global problem of human-caused climate change. You are on your own.” Such a decision would make it far more difficult to develop effective global strategies for mitigating and adapting to climate change. The consequences of opting out of the global community would be severe and long-lasting – for our planet’s climate and for the international credibility of the United States. The United States can and must be a major player in developing innovative solutions to the problem of reducing emissions of greenhouse gases. Nations that find innovative ways of decarbonizing energy systems and sequestering CO2 will be the economic leaders of the 21st century. Walking away from Paris makes it less likely that the U.S. will have a global leadership role, politically, economically, or morally. We cannot afford to cross that tipping point.

Will it make a difference to voters who are so disengaged that they have not already locked in on a candidate?

I doubt it. But it never hurts to try. And, as I’ve written before, scientists have every right to express their views as citizens.

Is there any chance Trump might shape shift to some stance on climate science and policy remotely connected to reality?

Searching for hints, I clicked to the welcome effort by the organization Science Debate to engage the four presidential candidates’ campaign teams on 20 science questions, if not an actual science debate. The questions, on everything from climate and nuclear energy to vaccines and science education, are great and answers range from vexing to exciting.

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Here’s the Science Debate climate question:

The Earth’s climate is changing and political discussion has become divided over both the science and the best response. What are your views on climate change, and how would your administration act on those views?

Think of Trump’s stump rhetoric, full of definitive superlatives, as you read this bizarrely wishy-washy response:

There is still much that needs to be investigated in the field of “climate change.” Perhaps the best use of our limited financial resources should be in dealing with making sure that every person in the world has clean water. Perhaps we should focus on eliminating lingering diseases around the world like malaria. Perhaps we should focus on efforts to increase food production to keep pace with an ever-growing world population. Perhaps we should be focused on developing energy sources and power production that alleviates the need for dependence on fossil fuels. We must decide on how best to proceed so that we can make lives better, safer and more prosperous.

So is there a chance he’d shift?

Perhaps.