John Reilly is co-director of MIT’s Joint Program on the Science and Policy of Global Change.
Fact Checkers Glenn Kessler and Michelle Lee examine several of President Trump's claims from his speech announcing the U.S. withdrawal from the Paris climate accord on Thursday. (Meg Kelly/The Washington Post)

As scientists concerned with the very real impact of human activity on climate, my colleagues and I certainly hope our research reaches policymakers at the highest levels of government — which, apparently, it did, when White House officials cited our work to justify President Trump’s decision to pull the United States out of the Paris climate accord.

Unfortunately, they got it wrong.

In talking points released along with the president’s withdrawal, the administration referenced an MIT study from the Joint Program on the Science and Policy of Global Change, which I co-direct with Ronald Prinn, to bolster the proposition that even if all signatories to the Paris agreement met their obligations, “the impact on the climate would be negligible.” But that runs counter to the view, held by my colleagues and I, that the Paris agreement’s unprecedented global framework is necessary to address climate change.

According to prior analyses, adding up all the commitments to reduce greenhouse gas emissions made by the 190-plus countries that signed the Paris agreement would reduce the increase in global temperatures expected in this century by about 1 degree Celsius. It’s a conclusion based on a comparison of what would happen under the agreement to what would happen if nations had made no commitments under this or previous agreements negotiated through the United Nations Framework Convention on Climate Change (UNFCCC).

Here’s the key: 1 degree Celsius (or 1.8 degrees Fahrenheit) might not sound like a lot — after all, would most of us really notice the difference if it were 72 degrees outside today, or 73.8 degrees? But that’s about how much warming the planet has experienced in roughly the past century and a half, and in that time we’ve observed retreating mountain glaciers, rising sea levels and other significant impacts.

One degree, though, wasn’t the figure the administration chose to pluck from our analysis. Instead, the White House said the Paris agreement would reduce the increase in average temperatures by just 0.2 degrees Celsius by 2100. That figure comes from our 2015 study; however, as we made clear in the text, it reflects only the incremental effect of Paris when built upon all the previous commitments made through the UNFCCC, not the cumulative effect — 1 degree — when compared with a business-as-usual policy. In addition, our analysis assumed no further strengthening of national commitments in years after 2030. These are critically important distinctions.

Yes, even supporters of the Paris accord, like me, believe that it is inadequate — even if the U.S. stays in, the average global temperature would rise in the range of 3.1 to 5.2 degrees above preindustrial levels by 2100 — increases that pose unacceptable risks. But in no way is that an argument to pull out.

Paris was a watershed as much for cementing a change worldwide, in process and responsibility, as for what it achieved numerically. Nearly every country in the world made a commitment of some kind and thereby acknowledged some degree of responsibility. This alone was a huge advance from the days of the Berlin Mandate and Kyoto Protocol, when the world was divided into two groups: wealthier countries bearing responsibility for everything, and the rest of the world that assumed no responsibility. Paris has an ongoing process for revisiting, revising and strengthening national climate commitments, with the ultimate goal of keeping the rise in average global temperature below 2 degrees Celsius.

The nature of the climate problem is one of gradual accumulation of greenhouse gases in the atmosphere that remain there for decades to centuries to thousands and tens of thousands of years. Achieving deep reductions in greenhouse gas emissions will be like turning around a large tanker in the ocean — it will take a long time. But pulling out of Paris is like criticizing the captain for starting to make the turn. The agreement is a recognition that, to address climate change, we have to start somewhere. A 1-degree drop isn’t enough, but that’s the relevant number, not 0.2 degrees.

Because carbon dioxide is a global, not local, air pollutant, climate change is a problem that demands a global solution. I want to make clear to anyone who may have been misled by the White House’s talking points that MIT does not favor withdrawal, and that my program’s research does not support that action.

This wasn’t the first time our program’s work has been mischaracterized by those who simply deny that climate change is real, human-caused or a significant threat. Finding a way to cite our study as a source for their decision seems to be an attempt to usurp the credibility and integrity for which MIT is known, to lend credibility to, in this case, a policy decision that my colleagues and I find misguided.

Bottom line, we think the Paris accord accomplishes something significant for the climate and that the U.S. should stay in it. The administration shouldn’t suggest that our research concludes otherwise.