By its final year, it was obvious that the 2000s were going to be the warmest decade in history. 2005, after all, set records as the hottest year ever recorded. And 2007 was the second-hottest year—until 2009 stole that record. 2002, 2003, 2004, and 2006 also all landed in the top-ten.

Climate change was real, its effects were felt planet-wide. But the United States, the world’s largest economy and its second-largest polluter, seemed to be doing little about it.

Or maybe something was changing. In the autumn of 2009, climate-concerned Americans held out hope that progress might be made at the United Nations’ annual climate conference, planned for December in Copenhagen. The new president, Barack Obama, and his Secretary of State Hillary Clinton would be attending. It was the first time in eight years that a U.S. administration had recognized the reality of climate change. 

It was in that environment that, in late November, a full-page ad appeared in The New York Times. The ad, an open letter, called on President Obama and Congress to finally pass legislation restricting greenhouse-gas emissions.

“We support your effort to ensure meaningful and effective measures to control climate change, an immediate challenge facing the United States and the world today,” it read. “If we fail to act now, it is scientifically irrefutable that there will be catastrophic and irreversible consequences for humanity and our planet.”

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 Timeshe 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.

During their presidencies, Ronald Reagan and George H. W. Bush both took climate change seriously as a crisis. An internal memo to Bush’s secretary of state called climate change “the most far reaching environmental issue of our time” and urged American leadership on the issue. 

The memo then quotes Secretary of State James A. Baker III’s words back to him. “As you yourself stated,” it said, “we cannot wait until all the uncertainties have been resolved before we act to limit greenhouse gas emissions and to prepare for whatever climate change we are already committed to.”

By the time Bush’s son was president, American climate leadership was in retreat. Bush pulled the United States out of the Kyoto Protocol, the first emissions-restricting climate treaty, under advisement from Exxon-Mobil. Republicans began to deny that climate change existed at all. And by the time this election rolled around, Senator Ted Cruz could cite Galileo as a role model for his evidence-free rejection of climate science.

“Today, the global warming alarmists are the equivalent of the flat-Earthers,” Cruz said. “It used to be [that] it is accepted scientific wisdom the Earth is flat, and this heretic named Galileo was branded a denier.”

It’s funny. Partisans regularly quibble with this economist or that intellectual, suggesting why one theory of welfare, immigration, or the market is more valid than another. And society is hard to study: It’s complex, culture-driven, and impossible to run experiments on. But the climate, a vast and impersonal system, is simply a different kind of subject. Scientists can come to conclusions about the climate’s operation in much clearer and difficult-to-dispute ways than economists can come to conclusions about their chosen field. Observation and commentary  do not alter the climate in the same way they alter the economy. And scientists are unified in their understanding that fossil fuel emissions are spurring the planet to get warmer, leading to consequences that could be catastrophic within our and our children’s lifetimes.

It’s almost boring to note that the Republican Party, as an organization, has simply rejected these findings. (Sixty-eight percent of Republican representatives and senators reject anthropogenic climate change outright.) But it is worth noting. It has made the party weak, subject to people like Trump, who know how to say the right thing to the right people. And it has put the party on the wrong side of business interests and the free market: The solar industry already employs more people in this country than either the oil and gas industry or the coal industry.

Catching Trump in a double-bind, as Grist did, would be enjoyable if it weren’t so serious. The United States really did postpone the Earth, as Trump and the progressive gang warned them not to in that Times ad seven years ago. Congress did not pass a market-based scheme to cap greenhouse-gas emissions during Obama’s first term, and only last year did the Obama administration introduce EPA regulations to reduce carbon emissions from the power sector.

Yet climate change ground on, unfeeling and uncaring about political gridlock or intransigence. And all those climate records set during the 2000s have passed away. The three warmest years ever recorded are now considered to be 2014, 2015, and the one we’re living in right now.