Steven Sherwood believes that economists are too confident in humanity’s ability to adapt to the effects of global warming. Sherwood is a University of New South Wales, Australia, climate change researcher, and recently published research showing that a 12ºC rise would make most of the planet uninhabitable.
“I noticed that economists and policy experts were, in effect, assuming that we could adapt to any amount of warming, even 12ºC,” he explained. “I suspected that such warmings would be beyond human physical tolerance, and realised nobody had examined this.” Economists produce cost estimates for climate change that are strongly influenced by the probability and cost of the worst possible outcomes. The consequences that they assume for those worst case scenarios are mild compared to what Sherwood says “the laws of physics say will happen”. “That means their calculations are too low,” he added. “It may be that their costs are too low even for more modest warmings.”
Together with Matthew Huber of Purdue University, USA, Sherwood looked at “wet bulb temperatures”, a measure that combines the effect of both humidity and temperature, in Proceedings of the National Academy of Science. Wet bulb temperatures above 35ºC would be fatal to humans, but currently 31ºC is the highest figure recorded on the planet. The highest wet-bulb temperatures today occur in the Amazon region and parts of India, followed by most of the Tropics, China and southeast Asia, northern Australia, and the eastern US. “Summers in many of these regions should begin to be very unpleasant after a few degrees of warming,” Sherwood told Simple Climate. “If global temperatures rise by, say, 5ºC, why wouldn’t you expect wet-bulb temperatures to go up by a similar amount? We found that, in fact, you need about 7ºC of global-average warming to raise the peak wet-bulbs by 5ºC.”
While a 7ºC long-term global-average rise is much more likely than 12ºC, Sherwood notes both figures are possible and avoidable. “Fortunately there is a lot of room to avoid anything close to 7ºC of warming if we can gradually but firmly move away from fuels like coal, shale oil, and tar sands, and leave most of them in the ground,” he says. “Currently, however, we’re going in the opposite direction.”
Understanding how it’s possible that such temperature rises might happen is the purpose of my blog, so I asked Sherwood to explain it for me. He pointed me the frequently-asked-questions section of his own website, and to those of NASA and the US National Oceanic and Atmospheric Administration.
“Global warming is real, and you ain’t seen nothing yet,” Sherwood affirmed. To help tackle it, he advised collective action to change our energy habits. “The first step is to better realise what these habits are,” he said. “Most of the emissions we cause, we are hardly aware of.” However like previous Simple Climate interviewees, Sherwood thinks that global warming is just one of several environmental and resource problems faced by humanity. He believes that these will dominate politics and society the 21st century.
Sherwood also has sharp words for those who hold views on global warming in opposition to his own, especially non-specialists. He tells them to stop pretending that after a few hours research “they can see the truth better than thousands of scientists who have spent their careers understanding the climate system”. “If they really want to challenge the scientists, they need to spend years learning enough to sift fact from propaganda,” he said. “It’s not a question of smarts – just work. It’s what we get paid to do, and we have the same professional pride as anyone else.”