A group of Senate Republicans notorious for denying climate science sent a letter to the Environmental Protection Agency on Wednesday, demanding that the agency explain the science it used to justify proposed regulations on carbon dioxide emissions. Much of the letter asks for the EPA to compare climate projections with data about what has actually happened, suggesting that if the projections have been wrong, they shouldn’t be used to make inferences about climate change in the future.
Written by Sen. Jeff Sessions (R-AL), the letter follows a March hearing where Sessions claimed that EPA administrator Gina McCarthy failed to directly answer questions about whether the models the agency uses have correctly predicted climate change. During that hearing, Sessions asked McCarthy whether soil worldwide was “more or less moist,” or whether there have been more tropical cyclones. McCarthy said she did not immediately know the answer to the soil question, and said that hurricane intensity has increased, though the question of land-falling hurricanes was “complicated.”
Sessions was not happy with her response.
“Although questions regarding the impacts of climate change were clear and straightforward, none of the questions received direct answers, and many responses contained caveats and conditions,” his letter states. Also signed by Sens. James Inhofe (R-OK), Roger Wicker (R-MS), and John Barrasso (R-WY), it asks for EPA models on drought, hurricanes, temperature rise, and climate impact monitoring.
But even if the EPA does supply all that is asked for, it seems unlikely that it would sway the group, which is made up of some of the most vocal fossil fuel advocates and climate deniers in the Senate. Inhofe, who is chairman of the Senate Environment committee, in February brought a snowball onto the floor of the Senate as a prop in an attempt to disprove global warming. He also has a long track record of using the Bible to refute climate change, citing Genesis in his book The Greatest Hoax as proof that humans are incapable of altering the climate.
Wicker has been called “the next Jim Inhofe,” and was the only member of the Senate to vote against a resolution calling climate change “real and not a hoax” (a resolution that even Inhofe voted for). Barrasso, while admitting that climate change is real, contends that humanity’s impact on the problem is “unknown.” And Sessions has vocally disagreed with the idea that there’s a scientific consensus about climate change, calling it “a danger that is not as real as it appears.”
So it seems strange that these senators would be so interested in diving into the science of climate modeling, a task so complex that a single atmospheric model can contain more than a million lines of code. Indeed, it makes sense that McCarthy’s answers would contain “caveats and conditions,” considering how complicated the task truly is.
“Climate models are fundamentally based on scientific principles, the physical laws that we know about in nature,” Michael Winton, a scientist with NOAA’s Geophysical Fluid Dynamics Laboratory, told ThinkProgress.
These basic scientific principles — like conservation of mass or conservation of energy — are universally accepted and hard to argue with, but they only get scientists so far in predicting what will happen to the climate years down the road. There are other things — like cloud cover or the tiny ridges of snowflakes — that are too poorly understood or too small to be solely understood using those scientific principles. To include these in models, scientists have to use methods that are more subjective, which can lead to disagreement between climate models. This is why climate models are so good at predicting big-picture trends, but less solid at answering small, regional questions.
Still, as the supercomputers used to create climate models have become more advanced, scientists have been increasingly able to create more nuanced models.
“Climate models, largely because of the availability of supercomputers these days, have gotten very effective, especially being able to predict climate from the past 100 years,” said Jack Fellows, director of the Climate Change Science Institute at the Oak Ridge National Laboratory. “This gives us a lot of confidence that these climate models are useful in looking into the future.”
The Republicans who submitted the letter, however, do not share Fellow’s confidence in climate models. The letter’s first request is “worldwide data about whether or not we are having fewer or less droughts,” compared to what drought models suggested we might see in a warming world. Droughts are a particularly difficult phenomenon to model, especially in specific areas, where projecting how precipitation will change means relying on regional predictions, which tend to vary more widely. And looking at the United States as a whole is difficult because precipitation might become heavier in some places (the Northeast) and more scarce in others (the Southwest), creating a trends that, when looked at together, can appear to cancel each other out.
Where climate models do a good job of predicting precipitation change, however, is on a large, more global scale.
“Certain aspects of drought are not that hard. The general global pattern of wetting and drying we understand physically and it makes sense to us,” Winton said. “Wet places are going to get wetter and dry places are going to get drier.”
That’s a conclusion supported by the most recent National Climate Assessment, whose models have a high confidence for suggesting what regional climates are going to look like in the future, according to Fellows. Even the U.S. Climate Change Science Program’s 2008 report, cited in the letter as concluding that droughts “have, for the most part, become shorter, less frequent, and cover a smaller portion of the U. S. over the last century” makes an exception for the dry U.S. Southwest, noting that “the main exception is the Southwest and parts of the interior of the West, where increased temperature has led to rising drought trends.” Recently, several studies have suggested, with increasing certainty, that megadroughts will become more common if carbon emissions aren’t reduced.
The letter also requests information about “global tropical cyclone frequency and trends in annual tropical storms, hurricanes, and major hurricanes in the North Atlantic basin.” Predicting events like these with current climate models, according to Fellows, is relatively easy. According to NOAA, climate models increasingly suggest that global warming will cause hurricanes, globally, to become more intense and contain more precipitation. In the North Atlantic specifically, Fellows says, models suggest that hurricanes may become less frequent, but will most likely be more intense when they do occur.
When it comes to the letter’s last question — modeling the rate of temperature rise — Fellows says that models have been very consistent over the long-term — as long as you take into account human activity. “You can only match the observed warming by including both the natural and human forcing,” Fellows said, which makes scientists very confident that the warming over the past 100 years is because of human activity.
The letter asks for the EPA to provide data and explanations of their modeling no later than April 21, and the EPA has said that while it plans on responding to the specific questions, it remains confident in its scientific grounding.
“We stand by science and the models that inform assessment reports such as the IPCC reports and the National Climate Assessment,” Liz Purchia, an EPA spokesperson, said in an emailed statement. “The scientific record and numerous lines of evidence all point to the reality of climate change.”