* Originally published on September 27, 2019.

By now, you've hopefully read the headlines — climate change is a real threat, and it is happening now. But you may have also heard claims that it's an overblown issue generated by the scientific community.

Naomi Oreskes, a Harvard science historian, argues right-wing conservative movements have historically been the source of climate change skepticism or outright denial.

While news outlets now report on climate change every day, "we've known about [climate change] for more than half a century," she said at a 2017 Vancouver talk.

According to a 2018 Pew Research Center survey, 39 per cent of American respondents see climate change as either a minor threat or not a threat at all. The number sits similarly with Canadian respondents at 34 per cent.

Trust in scientists is also eroding; a recent poll by Ipsos for 3M company found that 44 per cent of Canadian respondents see scientists as "elitist."

Naomi Oreskes during a conference in Berlin. (Bloomsbury Publishing, Adrian Grycuk/Wikimedia Commons)

In her book Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming, co-authored with historian Erik M. Conway, Oreskes takes a look at the origins of climate change doubt.

Ideas invites you to walk through the decades of climate change doubt.

1960s

In 1965, the President's Science Advisory Committee presented a report to U.S. President Lyndon B. Johnson, predicting that by the year 2000 there will be 25 per cent more carbon dioxide in the atmosphere, causing marked changes in global climate.

"The climatic changes that may be produced by the increased CO2 content could be deleterious from the point of view of human beings," the committee wrote.

Johnson permitted the report to be shared publicly. However, according to Oreskes, "there wasn't a lot of serious interest generated in policy circles right away."

Resident Stephanie Bolduc takes a picture of her flooded street on April 29, 2019 in Ste.Marthe-sur-la-Lac, Que. (Ryan Remiorz/Canadian Press)

1970s

Climate change became a growing topic of discussion and studies within the government and among scientific circles.

The Global 2000 Report, presented by Gus Speth to U.S. President Jimmy Carter in 1977, warned that population growth will deplete resources.

"If present trends continue, the world in 2000 will be more crowded, more polluted, less stable ecologically, and more vulnerable to disruption than the world we live in now," Speth wrote.

By 1979 it was clear that climate change was going to occur — but it was uncertain when we would begin to notice the effects.

"Most scientists working on the issue at that time thought the changes would probably not really be detectable until the early part of the 21st century," said Oreskes.

1980s and 1990s

Former NASA climate scientist James Hansen testifying in front of a congressional committee in 1988. (James Hansen/CPAC)

In 1988, NASA climate scientist James Hansen and his team published a report stating that climate change was already underway.

He testified in front of the U.S. Senate, and the news hit major media outlets, including the New York Times with the headline "Global warming has begun, expert tells Senate."

As the scientific debate over climate change heated up, a propagated campaign to discredit the consensus was also in the works.

Oreskes points to three Cold War-era influencers — American physicists Frederick Seitz, Bill Nierenberg and Robert Jasper — who were leading climate change skeptics with ties to institutes that published claims debunking climate change science.

"The campaign focused on the claim that the science was uncertain and unsettled, that we didn't really know what was causing climate change or if there even was climate change … and therefore, it would be premature to act," said Oreskes.

The campaign, she said, was a major factor in why the U.S. National Energy Policy Act of 1988 to reduce greenhouse gas emissions died in Congress.

They found a new enemy, and that new enemy was they considered in what they called environmental extremism. - Naomi Oreskes

With the fall of the Berlin Wall in 1989 and the dissolution of the Soviet Union in 1991, the perceived threat of communism was no longer apparent.To the physicists, said Oreskes, environmentalism became the new threat to capitalism, because regulations needed to counter it could stifle unfettered economic growth.

"They found a new enemy, and that new enemy was they considered in what they called environmental extremism, a kind of new 'reds under the bed,' what they believed was an exaggeration of environmental threats by people with a left wing agenda," said Oreskes.

2000s and 2010s

More recently, a growing number of world leaders have recognized the existence of climate change, which for a time was more commonly referred to as global warming. However, efforts to dismiss it as a non-issue persist.

Oreskes points to American billionaires David and Charles Koch, who for many years funded groups and think-tanks denying a climate change crisis — up to $120 million, according to Oreskes. This includes the Cato Institute, founded by the Koch family in 1974, and the Heartland Institute, which mailed books questioning the current scientific consensus to tens of thousands of science teachers.

Investigative journalist Jane Mayer explains how the Koch brothers have used their billions to shift American policies to the far right. 8:40

Following the 2016 U.S. election, President Donald Trump rolled back legislation introduced by his predecessor Barack Obama aimed at fighting climate change, and removed the U.S. from the 2015 Paris Agreement.

In February, the U.S. administration started exploring the idea of forming a committee to investigate "climate security," coordinated by physicist William Happer, who once stated that carbon dioxide has been demonized like "the poor Jews under Hitler."

Former U.S. Navy Rear Adm. David Titley, now a meteorology professor, said "Happer would be a fringe figure even for climate skeptics."

Swedish environmental activist Greta Thunberg watches as U.S. President Donald Trump enters the United Nations to speak with reporters in a still image from video taken in New York City on Sept. 23, 2019. (Andrew Hofstetter/Reuters)

This week, young activist Greta Thunberg grabbed the world's attention when she demanded action from world leaders at the United Nations Climate Action Summit. Trump briefly attended the summit, and did not mention environmental issues in his speech to the Assembly the next day.

Climate change apathy continues to be the position of many Republican politicians, Oreskes told Ideas in an email.

"Not much has changed except that the fossil fuel majors have become a bit more nuanced, saying that they accept that climate change is real," she said.

"Yet their business models remain unchanged and they continue to lobby in the U.S. congress against any climate action … Climate change is a bad news story, so it's easier for all of us to just look the other way."

Written by Chelsey Gould. Episode produced by Mary O'Connell.