Climate scientist Michael E. Mann compared the scientific consensus on climate change to that of the theory of gravity during a House Science Committee hearing on Wednesday in which supporters and opponents of government action on greenhouse gases accused the other of politicizing the debate over the Earth’s temperatures.
“[It’s] just like the theory of gravity,” said Mann, an atmospheric science professor at Penn State University. “We haven’t proved it, but we don’t jump off a cliff. We understand it’s real. And the same thing is true with climate change. In fact, by some measures, there is as deep a consensus about human-caused climate change as there is about gravity. It literally goes back two centuries to Joseph Fourier in the 1800s.”
Fourier was a French mathematician who heavily influenced the science behind mathematical physics and heat conduction.
Mann was the lone defender of the certainty of mainstream climate science at the hearing. Georgia Institute of Technology Professor Emeritus Judith Curry, Alabama State Climatologist John Christy, and University of Colorado Environmental Studies Professor Roger Pielke also testified.
Curry, Christy and Pielke cast doubt on scientists’ ability to attribute the effects of climate change to emissions from human activities and to predict global temperature changes, though the witnesses had fewer disagreements about what the government should do.
The committee has held politicized debates over climate science and Environmental Protection Agency regulations. Wednesday’s discussion got tense when Mann quoted an article in Science magazine, which said Chairman Lamar Smith (R-Texas) uses the committee as “a tool to advance his political agenda rather than a forum to examine important issues facing the U.S. research community.” Smith interrupted, saying, “That is not known as an objective writer or magazine.”
The article referred to comments Smith made last week at a conference for critics of mainstream climate science, where Smith said Wednesday’s hearing would be “on the scientific method, which has been repeatedly ignored by the so-called self-professed climate scientists.”
Rep. Don Beyer (D-Va.) called the hearing “a food fight among scientists.”
Both sides said they had been victims of political attacks. Pielke mentioned an investigation prompted by Rep. Raul Grijalva (D-Ariz.) into who funded Pielke’s research on climate science. Pielke had published a controversial article in 2014 for FiveThirtyEight downplaying climate change’s role in the cost of natural disasters.
Republicans on the committee focused on uncertainty about predictions of future temperature increases and their effects. Christy said climate models were too sensitive to greenhouse gas emissions, underestimating mitigating factors such as cloud cover.
Mann said sea ice has melted faster than expected and when it comes to projected sea-level rise, “the uncertainties are breaking against us.”
Despite the personal jabs, the scientists did not express many differences in opinion on policies that could address climate change. Pielke said there would likely be scientific uncertainty about climate change long into the future, but still recommended a carbon tax to fund research into clean-energy technologies. Mann, meanwhile, sidestepped the question on policy solutions.
“There’s a worthy debate to be had about the solutions to this problem,” Mann said. “There is no longer a worthy debate to be had about whether the problem exists.”