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    The Statistical Probability That Climate Change Is Not Manmade Is 0.1 Percent

    Written by

    Jason Koebler

    Staff Writer

    Image: Shutterstock

    That climate science relies too heavily on models is one of the last arguments that climate change deniers cling to—many of them argue that proving climate change is manmade is impossible. But one researcher says he’s basically just done the opposite: he used statistics, actual observed data, and, most importantly, no computer models at all to prove that climate change has not been a natural phenomenon.

    “There’s a difference between trying to prove a theory is correct and trying to prove something incorrect,” said Shaun Lovejoy, a nonlinear physicist at McGill University. “If we can’t prove the theory, we can reject the hypothesis that all we have is natural variability. I’ve rejected that with a 99.9 percent level of confidence.”

    In a paper published in Climate Dynamics, Lovejoy eschews computer models in exchange for empirical data found in ice cores, lake sediment records, Greenland ice cap information, and other commonly used (and commonly published) paleodata dating back to the 16th century, before humans contributed greenhouse gases to the atmosphere

    Lovejoy says that the computer models used by the Intergovernmental Panel on Climate Change and others are extremely useful, but says that climate skeptics aren't totally off base to raise their doubts, when nearly every paper published on the subject relies on one model or another.

    “The main rational argument held by climate skeptics is that, the global warming hypothesis depends on these giant models—they say, if the evidence is so strong, we shouldn’t need supercomputers to demonstrate it,” he said. “Well, it turns out, we don’t. Without supercomputers, I got quite similar results, and I can use this paleodata to suggest the probabilities [that climate change falls within established natural variation].”

    To do that, Lovejoy used surface air temperature measures from NASA, NOAA, and and the Climate Research Unit, and the paleodata proxies (at 100-year time intervals, where they are believed to be most accurate) to complete a statistical analysis of whether what we saw happen prior to human pollution matches up at all with what we’ve seen since humans began putting greenhouse gases into the atmosphere. It doesn’t. 

    “Even if you allow for very, very extreme natural fluctuations, the worst you can do is reject the hypothesis [of natural variation] with 99.8 percent certainty,” Lovejoy said. “This study will be a blow to any remaining climate change-deniers … their two most convincing arguments—that the warming is natural in origin, and that the computer models are wrong—are either directly contradicted by this analysis, or simply do not apply to it.”

    Of course, scientists haven't been split on that fact in a long, long time—just .01 percent of climate scientists reject global warming. Given the level of willful ignorance we’ve seen at places like Fox News and on Capitol Hill, I’m not so sure any climate deniers will concede so easily—but here’s one more piece of evidence, with a completely different methodology, that proves far beyond a reasonable doubt that what’s happening is not natural. Still want to gamble humanity's future on it?

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