There has been a subtle shift recently in the rhetoric of many conservative pundits and politicians around climate change. For decades, the common refrain has been flat-out denial—either that climate change is not happening, or that any change is not caused by human activity. Which is why viewers might have been surprised to see Tucker Carlson of Fox News nodding along thoughtfully on January 6 as climate scientist Judith Curry, a controversial figure in climate science, explained, “Yes it’s warming and yes humans contribute to it. Everybody agrees with that, and I’m in the 98 percent [of scientists who agree]. It’s when you get down to the details that there’s genuine disagreement.” Carlson immediately turns to the camera and moots a multi-part series: “What do we know? What don’t we know?”

This rhetorical stance—yes, climate change is real, and yes, human activity is implicated, but we don’t know how much human activity is to blame—is fast becoming the go-to position for conservatives. In confirmation hearings last week, Senator Ed Markey asked Scott Pruitt, Trump’s pick to head the Environmental Protection Agency, if he agrees with Trump that global warming is a “hoax.” Pruitt replied that he does not. But later, under questioning by Senator Bernie Sanders, Pruitt refused to say how much change is caused by human activity. He would say only that the “climate is changing, and human activity contributes to that in some manner.” When pressed by Sanders on whether he agreed with 97 percent of scientists who have published in peer-reviewed journals that human activity is “the fundamental reason we are seeing climate change,” Pruitt equivocated. “I believe the ability to measure with precision the degree of human activity’s impact on the climate is subject to more debate.”

The key phrases in Pruitt’s testimony are “in some manner” and “with precision.” These allow Pruitt to acknowledge climate change is happening while moving uncertainty downstream, into the “details.”

This rhetoric is out of step with the latest science. The most recent IPCC report expresses 95 percent confidence that humans are the main cause of most global warming observed since the 1950s. According to one paper summarized on NASA’s Global Climate Change website, “97 percent or more of actively publishing climate scientists agree: Climate-warming trends over the past century are extremely likely due to human activities.” The list of scientists and agencies in agreement goes on and on.

Some conservatives have introduced uncertainty by suggesting climate change might be driven by “natural” global cycles. But according to Maureen Raymo of Columbia University’s Lamont-Doherty Earth Observatory, we know why climate changes naturally, and non-human activity can’t explain the rapid changes observed in the past century. “The Ice Ages happen due to subtle changes in the sun-earth distance that unfold over thousands of years, and which can lead to sometimes rapid climate change, when thresholds are crossed.” These cycles are still happening, but “the same factors that cause these huge Ice Age swings could not possibly be invoked to explain the warming we now see.” In fact, Raymo said, “left to its own devices, right now Mother Nature would be making the climate colder.”

The planet has warmed by about 2 degrees Fahrenheit since the 19th century. “You can quibble about tiny bits,” said Raymo, “but the vast majority of what we observe is that it’s because we’ve been combusting fossil fuels.”

As Gavin Schmidt, Director of the Goddard Institute for Space Studies and Principal Investigator for the GISS ModelE Earth System Model, put it, “In science, nothing is ever known perfectly. Is there remaining uncertainty in the exact value of gravity? Yes. But to something like the fourth decimal place. It doesn’t matter. So the question is: Is the remaining uncertainty relevant to any policy decision anyone would want to make? And the answer is: no.

Uncertainty has proved a reliable tool to manipulate public perception of climate change and stall political action. In 2015, the Union of Concerned Scientists released The Climate Deception Dossiers, which describes a 1998 memo from the American Petroleum Institute that, according to the dossiers, “mapped out a multifaceted deception strategy for the fossil-fuel industry that continues to this day—outlining plans to reach the media, the public, and policy makers with a message emphasizing ‘uncertainties’ in climate science.” The UCS authors write that the memo (included in the report) states “victory” would be achieved “when ‘average citizens’ and the media were convinced of uncertainties in climate science despite overwhelming evidence of the impact of human-caused global warming and nearly unanimous agreement about it in the scientific community.”

Another “victory” listed on the API memo’s bullet-point list would be when, “those promoting the Kyoto treaty on the basis of extant science appear to be out of touch with reality.”

The new climate-denial rhetoric dovetails with longstanding tactics used by conservatives and fossil fuel companies to sow doubt about climate change, even as they publicly recognize its reality. In a 2006 Letter from ExxonMobil Vice President of Public Affairs Ken Cohen to the Royal Society, the corporation acknowledged that “the use of fossil fuels is a ‘major source’ of carbon dioxide emissions” and tied emissions to climate change: “Given the important role fossil fuels play in providing energy for the global economy, the issues of global economic development, future energy supply, and climate change are closely linked.” This past November, ExxonMobil even endorsed the Paris Agreement in a carefully-worded statement that balanced the need to reduce global emissions with the statement that, “access to affordable and reliable energy is critical to economic growth and improved standards of living worldwide.” Despite this acknowledgement, ExxonMobil has, since November, launched a suite of massive extraction projects in Nigeria, Mozambique, Liberia and Texas.

In his recent confirmation hearings, Rex Tillerson, ex-CEO of ExxonMobil and newly-minted U.S. Secretary of State, carefully avoided making any of the links that ExxonMobil’s own scientists had made by the early 1980s between fossil fuels, rising greenhouse gases, and the ability of those gases to affect climate “in potentially destructive ways.” When asked to explain his “personal view” of climate change by Senator Tom Udall, Tillerson would say only that “after 20 years as an engineer and a scientist,” he had concluded “the risk of climate change does exist,” and “the consequences could be serious enough that action should be taken.” Senator Bob Corker, who chairs the Senate Foreign Relations Committee, then pointedly asked, “Do you believe that human activity, based on science, is contributing?” Tillerson dodged again, saying only, “The increase in greenhouse gas in the atmosphere is having an effect. Our ability to predict that effect is very limited.”  

Tillerson can make statements like these because climate research is ongoing, and climate models are inherently imprecise. According to Schmidt, “To say that science isn’t settled on things people are still researching is totally irrelevant. Does the earth orbit the sun? There’s no substantial ambiguity about the answer to that question, despite the fact that there are hundreds, perhaps thousands of scientists working on gravity. There are lots of interesting things about gravity, it’s just that that is not one of them. There are lots of interesting things about climate change, and adaptation, and interactions between air pollution and clouds, but they’re just not relevant to the question, which is: Is what’s going on related to humans? And the answer is: Yes, it is.”

When Tillerson was pushed by Senator Tim Kaine to admit ExxonMobil’s “history with the issue of climate change,” including the oil giant’s well-documented practice of funding work to discredit climate science and delay political action, he stonewalled until Kaine finally asked, “Are you not answering because you don’t know, or because you don’t want to?” To which Tillerson replied, “A little of both.”

There has been a flurry of recent Republican efforts to stall action on climate policy, including a pair of bills just introduced to the U.S. House of Representatives. Bill H.R. 861, introduced by Representative Matt Gaetz, proposes “to terminate the EPA.” This bill may not even get a vote, but as The New York Times reported earlier this week, Pruitt “has a blueprint to repeal climate change rules, cut staffing levels, close regional offices and permanently weaken the agency’s regulatory authority.”

Meanwhile, Bill H.R. 673, introduced by Representative Blaine Luetkmeyer, proposes to “prohibit United States contributions to the Intergovernmental Panel on Climate Change, the United Nations Framework Convention on Climate Change, and the Green Climate Fund.” It’s also no secret that many Republicans want to halt funding for the UN FCCC, the international treaty system of 195 nations that produced the Paris Agreement. As the Republican party platform stated in the run-up to the presidential election: “We reject the agendas of both the Kyoto Protocol and the Paris Agreement.”

On February 8, a cohort of old-guard Republicans came out in favor of a carbon tax, which they call a “conservative approach to climate change.” Rather than setting limits on emissions (as with cap-and-trade), a carbon tax would put a higher price on fossil fuel emissions and leave it to the market to curb emissions. This approach may be appealing to some voters, because as the tax slowly increases consumers receive increasing rebates. While this approach at least acknowledges that human use of fossil fuels is contributing to climate change, many experts argue this would not be a meaningful restriction, given the convulsive climate changes already under way.

In September 2016, carbon-dioxide levels in the air crossed the dreaded 400 ppm threshold, and we are not likely to dip back below that level in our lifetimes. Crossing this red line signals an irrevocable shift toward an increasingly unrecognizable planet (the last time the planet’s air was consistently above 400 ppm was 16 million years ago, and the planet looked a lot different). In just the past few months, we have seen record-breaking global temperatures and a stunning decline in sea ice. A slab of ice bigger than Long Island is poised to crack off the Antarctic’s Larsen C ice shelf and the climate-stabilizing flow of the Gulf Stream, which has decreased by 20 percent  in the last 50 years, may be accelerating toward full shut-down. According to the Pentagon’s 2014 Climate Change Adaptation Roadmap, climate change will cause catastrophic changes to Earth’s ecosystems and wreak havoc on human populations, including famine, mass migration, and war. A carbon tax may be too little, too late, but even it would be preferable to rhetoric that fails to acknowledge scientific consensus on climate change.

The recent shift in conservative rhetoric exploits legitimate scientific uncertainty that most scientists agree is irrelevant to crafting responsible climate policy. Despite overwhelming evidence, many conservatives are still willing to ignore scientific consensus and stall political action. But offering evidence that this rhetoric is out of step with science may not, in fact, matter when it comes to public perception. When the U.S. House of Representatives Committee on Science, Space, and Technology published a press release on February 5, alleging that the National Oceanic and Atmospheric Administration (NOAA) “manipulated climate records,” scientists and journalists rushed to correct the statement and demonstrate how it was based on faulty information. But the damage was already done; uncertainty about NOAA and their data are now a part of the public dialogue around climate change.