Below that text were 55 names. They included squishily liberal executives and various other famous people, like the CEOs of Patagonia, Timberland, Blue Man Group, and Chipotle; and Deepak Chopra, Martha Stewart, Kenneth Cole, and Ben and Jerry.

Someone else was on that list, too: Donald J. Trump, and his three children. That’s right: The Republican nominee for president supported urgent climate action before he opposed it.

The full-page ad was forgotten until it was discovered this week by Ben Adler and Rebecca Leber, two journalists at the environmental-news site Grist.

The Copenhagen talks ultimately came to very little. Not until last year did the UN managed to produce a successful document to halt climate change at its Paris conference. Ironically, Trump promised to pull the United States out of the Paris Agreement last month during his sole speech on energy policy. The speech didn’t say much else about climate change.

As Adler and Leber write, Trump flipped on climate change long before his presidential run. Less than two months after that letter ran in the Times, he had implied to a crowd that global warming couldn’t exist if snowfall was setting records. In 2012, he tweeted that climate change was a hoax invented by the Chinese. And though he later said that tweet was a joke, Trump has regularly maintained that climate change doesn’t exist or is a fraud.

The Trump campaign didn’t respond to a request for comment about the open letter or the candidate’s views on climate change.

So first, let’s state unequivocally: 97 percent of actively publishing climate scientists understand global warming to be a real phenomenon, caused by human activity. And every major American scientific organization, including the American Medical Association, has unambiguously stated that climate change is real, caused by the burning of fossil fuels, and a threat to public health.

Indeed, 2009-Trump might have said it best: Climate change is “scientifically irrefutable.”

Now he seems to find it quite refutable. But climate change wouldn’t be the first issue that Trump has flipped on or seemed to lie about. Trump endorsed invading Iraq on a national radio show in 2002; now he claims he opposed the invasion long before the war began. He has lied about his relationship with former Libyan dictator Muammar Qaddafi, a supporter of terrorism. And he has repeated multiple inaccuracies about the Trump University case.

What exactly does Trump believe about the climate? To an outside observer, it almost—almost—seems like Trump takes the position that makes him look best to a certain audience at a certain time. It almost seems like he can’t stand to take a stand on anything: Trump endorsed urgent climate action when the liberal CEOs came calling; now he rejects the overwhelming scientific consensus on climate change because, you know, he’s running as a Republican, and on climate change, Republican politicians long ago stopped having to correspond to reality.