Among climate change deniers, there has long been this idea that scientists aren’t certain about what’s causing the rapidly escalating global warming occurring on this planet because they’re not 100 percent sure. But science is never 100 percent sure about anything. Even the theory of gravity is still called a theory, although you’d be hard-pressed to find anyone who doesn’t believe gravity is real.
That said, a Reuters story recently reported that evidence for man-made global warming has reached a “gold standard” level of certainty. A team of scientists led by Benjamin Santer of the Lawrence Livermore National Laboratory in California said that “confidence that human activities were raising the heat at the Earth’s surface had reached a ‘five-sigma’ level, a statistical gauge meaning there’s only a one-in-a-million chance that [rising temperatures and other climate signals] would appear if there was no warning.”
“The narrative out there that scientists don’t know the cause of climate change is wrong,” Santer said. “We do.” He added that he hoped the findings would win over skeptics and possibly spur serious action.
Scientists have repeatedly said that the burning of fossil fuels like oil, gas, and coal is causing more floods, heat waves, droughts, and rising sea levels. And despite U.S. president Donald Trump’s repeated expressions of doubt on global warming and his plan to pull out of the Paris Climate Agreement, agreement on climate change has increased among the general public.
According to the Yale Program on Climate Change Communication, 62 percent of Americans polled in 2018 believed that climate change is caused by people, up from 47 percent in 2013.
Obviously, there’s still a long way to go.
The scientists said that two of three sets of satellite data used by researchers to determine the extent of climate change reached five-sigma level by 2005; the third set showed five-sigma confidence in 2016. However, the 2016 data shows a slower pace of warming than the other two sets.
In 2013, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) concluded that it’s “extremely likely”—that is, at least 95 percent probable—that human activities have been the main cause of climate change.
Peter Stott of the British Met [Meteorological] Office, who was one of the IPCC scientists that made the 95 percent decision, said he would favor raising the probability of human-caused climate change to “virtually certain,” or 99 to 100 percent. “The alternative explanation of natural factors dominating has got even less likely,” Stott said.
Even with all this scientific proof, it’s not terribly likely that hardcore skeptics will be convinced that humans have caused most of the global warming we’re currently seeing.
The IPCC will publish its next formal assessment of the probabilities in 2021.
“I would be reluctant to raise to 99-100 percent, but there is no doubt there is more evidence of change in the global signals over a wider suite of ocean indices and atmospheric indices,” said University of Tasmania climate scientist Professor Nathan Bindoff.