New climate report actually understates threat, some researchers argue

By Scott Waldman, E&E NewsOct. 12, 2018

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The Intergovernmental Panel on Climate Change (IPCC) report states in plain language that averting a climate crisis will require a wholesale reinvention of the global economy. By 2040, the report predicts, there could be global food shortages, the inundation of coastal cities and a refugee crisis unlike the world has ever seen.

A number of scientists contend that the report wasn't strong enough and that it downplayed the full extent of the real threat. They say it doesn't account for all of the warming that has already occurred and that it downplays the economic costs of severe storms and displacement of people through drought and deadly heat waves.

The world has a smaller carbon budget—the amount of fossil fuels that can be consumed before a critical tipping point is reached—than the report states, said Michael Mann, a professor of atmospheric science and director of the Earth System Science Center at Pennsylvania State University in Philadelphia. He published two papers with other researchers in recent years to show that the "preindustrial" baseline used for the report should not be based on late 19th-century data. The Industrial Revolution was already underway by then, he said, and humans had warmed the world by several tenths of a degree.

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In other places, the report fails to highlight some major risks from climate change, said Bob Ward, policy and communications director of the Grantham Research Institute on Climate Change and the Environment at the London School of Economics in the United Kingdom. In the summary for policymakers, the section that receives the most attention, it does not mention population displacements or conflict, he said. It also does not describe any risks except for destabilization of the Greenland and West Antarctic ice sheets, he said.

"The danger of omitting these big risks is that policymakers underestimate the scale and urgency of the situation," Ward wrote in an email. "The authors may have left them out because they are uncertain. However, policymakers may misinterpret their omission as a sign that the authors examined the risks and decided either that the impacts would be unimportant or that the probabilities are zero. It is the difference between an academic literature review and a professional risk assessment."

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The report also ignores "wild cards" in the climate system, or self-reinforcing feedbacks, said Veerabhadran Ramanathan, a professor of climate sciences at the University of California, San Diego. That includes thinning Arctic sea ice, which allows the ocean to absorb more heat, causing even more ice loss and diminished reflectivity in the region, he said. Such feedback loops have a real possibility of pushing the planet into a period of chaos that humans cannot control, he said.

Ramanathan said the report also takes solid research, such as his finding that 1.5 degrees Celsius of warming could be reached by 2030 to 2035, and downplays it in favor of being overly cautious.

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