Climate models have been correct for literally 40 years

Deniers say the models are unreliable. New research proves them hilariously wrong.

Welcome to HEATED, a newsletter for people who are pissed off about the climate crisis—written by me, Emily Atkin.

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Today’s issue is about new research published in Geophysical Research Letters evaluating the reliability of climate models dating back to the 1970s. Perhaps that sentence sounds boring to you. Well guess what—YOU’RE WRONG!

This research is interesting and validating and infuriating, because it helps debunk one of the oldest and yet still-persistent climate denier tricks in the books: questioning the reliability of climate models. The paper won’t be officially published until 9am PST this morning, but you can find the full thing HERE after that. Enjoy!

Hate to say they told us so

Thirty-one years ago, in 1988, Dr. James Hansen told Congress that climate change had arrived.

“It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here," said Hansen, then the director of the NASA Goddard Institute for Space Studies. As the Washington Post would later report, that statement and his full testimony made Hansen “one of the first climatologists to speak out about the potential dangers of man-made global warming.”

As evidence for his concern, Hansen attached to his testimony the results of something called a climate model—that is, a tool used to predict what the world might look like under different emissions scenarios. If we emit THIS much carbon dioxide, a climate model says, the world will warm THIS much by THIS year.

Here are the results of Hansen’s model:

Of course, Congress didn’t really listen to Hansen. Not that it was personal—they didn’t really listen to any of the climate scientists warning that, unless we stopped emitting huge quantities of greenhouse gases, global temperatures would rise with potentially catastrophic consequences.

But they didn’t listen to Hansen in part because his model was criticized heavily by climate deniers. In fact, Hansen’s model continues to be criticized today, because the highest point on the chart says the world will warm 1.5 degrees Celsius by the year 2019. To deniers, this means climate models “run hot” and can’t be trusted. (The world has only warmed about 1 degree Celsius since the Industrial Revolution).

But Hansen’s model didn’t “run hot,” as new research out this morning shows. That particular point on the graph just predicted humans would emit more carbon dioxide than we actually did. The only reason it didn’t warm that much is because we didn’t pollute that much. If we had polluted that much, the world would have warmed 1.5 degrees.

So Hansen’s 1988 model was correct. But that’s not all the new paper published in Geophysical Research Letters shows.

According to the research published today, almost every peer-reviewed climate model of human-caused global temperature rise dating back to 1970 lines up with the warming we see today.

“In scientific terms, we'd say there's no bias,” the paper’s co-author Henri Drake, a PhD candidate at MIT, told me over the phone. “Once we accounted for the differences in CO2 emissions, 14 of the 17 models we analyzed were consistent with current observations.”

“Taken together,” he added, “these climate models have always been quantitatively accurate.”

A “screw you” to climate deniers

I asked Drake whether the results of his research—published with Zeke Hausfather, Tristan Abbott, and Gavin Schmidt—represented a sort of “screw you” to climate deniers.

“I wouldn’t put that in my own words,” he said. “But sure.”

The group decided to do an assessment of past climate models because it simply hadn’t been done in a comprehensive way before. Some climate bloggers had attempted to verify singular models from the past, but as Drake explained, “There was little no talk of uncertainties, no talk of natural variabilities. They were no different than skeptic blogs that plot two curves together and make some wild conclusions. We wanted to do it the proper way.”

The “proper way,” he said, is accounting for all scientific literature. In this case, the paper’s authors looked at every past climate model that met three criteria:

  1. The model had a start date and an end date. That is, it started at the then-present or the past, and ended at a specific year in the future.

  2. The model included carbon dioxide concentrations in the atmosphere for both dates. In other words, it included the current concentration of CO2 at the time, and estimated a CO2 concentration for the future.

  3. The model noted what the global average temperature was at the time, and predicted what the global average temperature would be in the future.

The paper’s authors found and analyzed 17 examples of past climate models that fit these criteria. There would be a lot more, except for the fact that in 1990, the United Nations started essentially compiling all climate models into one, so the paper’s authors used those compiled models instead of assessing each one individually. However, “From 1970 to 1990, we have every single published paper we know of that meet those criteria,” Drake said.

Out of these 17 models, Drake said, 14 correctly predicted how much the earth would warm based on how much CO2 was in the atmosphere. The ones that predicted more warming than there is now only did so because they predicted more CO2 emissions, not because the models were "running hot.” The ones that predicted too little warming only did so because they predicted less CO2 emissions. If they had predicted the right amount of CO2 emissions, they would have predicted the correct amount of warming.

In fact, of the three models that incorrectly predicted warming trends, two “ran cold”—that is, they predicted that CO2 would cause less warming than it actually did. Only one climate model from the last 40 years “ran hot.”

One reason this is so impressive is because the climate models scientists use today are far better than the ones Drake’s group analyzed.

“These models we surveyed are operationally obsolete,” he said. “They're written in old programming languages. Virtually no one is using them. But there's value in understanding how good they were back then, because it tells us whether or not we made the right choices back then.”

Spoiler alert: We didn’t!

Fossil fuel companies deny the reliability of climate models, and Republicans follow suit

Climate models are our best evidence to justify rapid, radical climate action. That’s why Republicans and fossil fuel industry executives are doing everything they can to discredit or erase them.

Falsely denying the reliability of climate models is tried and true tactic of the fossil fuel industry. Some of the first evidence of the tactic being used comes from ExxonMobil in 1989, the year after Hansen’s testimony.

As reported by InsideClimate News in 2015, emphasis mine:

Through much of the 1980s, Exxon researchers worked alongside university and government scientists to generate objective climate models that yielded papers published in peer-reviewed journals. Their work confirmed the emerging scientific consensus on global warming's risks.

Yet starting in 1989, Exxon leaders went down a different road. They repeatedly argued that the uncertainty inherent in computer models makes them useless for important policy decisions. Even as the models grew more powerful and reliable, Exxon publicly derided the type of work its own scientists had done. The company continued its involvement with climate research, but its reputation for objectivity began to erode as it campaigned internationally to cast doubt on the science.

In 1998, the tactic was picked up by the Competitive Enterprise Institute, an influential libertarian think tank. Since then, questioning and attacking climate models has since become a regular tactic of climate denier lawmakers in the Republican Party, and contrarian scientists who attack climate models have been featured regularly in House Science Committee hearings.

The Trump administration regularly attacks climate models, too. As the New York Times reported back in May:

In the most recent example, the White House-appointed director of the United States Geological Survey, James Reilly, a former astronaut and petroleum geologist, has ordered that scientific assessments produced by that office use only computer-generated climate models that project the impact of climate change through 2040, rather than through the end of the century, as had been done previously.

In that article, a spokesperson for the Trump administration Environmental Protection Agency decried the use of “inaccurate modeling” to justify climate action.

This, again, is the Environmental Protection Agency.

The lesson here? Trust climate scientists.

Most people in the United States trust scientists. In fact, public trust of scientists is on the rise, according to a Pew Research Center poll released this summer. Eighty-six percent of people now think scientists act in our best interest; up from 76 percent in 2016.

But the results differ when it comes to environmental scientists. A majority of Democrats and Democrat-leaning people—70 percent—have a positive view of environmental scientists. But only 40 percent of Republican and Republican-leaning people hold that view.

That is not a coincidence. It is by design. As the badass science historian Naomi Oreskes has said, “discrediting science is a political strategy.” And it’s been an effective strategy, too, helping to prevent action for the last 40 years.

If the climate is going to remain livable, that strategy must be destroyed. Climate science must be given respect and authority. That’s not to say “accept everything climate scientists say is true”—trust, but verify. But for God’s sake, if there were ever a time to do a little more trusting and defending, it’s now. After all, scientists have been giving us the tools we need to make effective decisions to save the climate for the last 40 years, and we haven’t listened. They deserve at least a little love now.

Plus, if we don’t listen, we’re screwed. So you know. There’s that.


Comment your own climate change lyrics to Photograph by @nickelback - winner(s) get(s) a shoutout 🎶🎶🎶🎶🎶
October 3, 2019

That was probably depressing too. SORRY AGAIN BYE!

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