Trump Twisted a Climate Debate Beyond Recognition

​Researchers concluded that one future climate scenario is unlikely to happen. Right-wingers went wild.

Over the last few weeks, the United States right loudly claimed victory in a battle that few people on earth knew was happening. The National Review’s Editorial Board gloated, “Science Has Spoken Against Climate Alarmism.” Several papers owned by Rupert Murdoch ran similarly hyperventilating headlines that scientists had reversed “doomsday predictions” and “quietly scrapped the apocalyptic forecasts that have terrified policymakers and the public.” Donald Trump wrote on social media that the United Nations’ “TOP Climate change committee,” the Intergovernmental Panel on Climate Change, or IPCC, “admitted that its own projections (RCP8.5) were WRONG WRONG WRONG!”

That isn’t what happened. And it’s hard to overstate the gulf between the scale of the right’s triumphalism and the size of the thing they are ostensibly talking about. The alleged victory in question is in reality an academic paper published last month by a team of Earth system modeling experts convened by the Coupled Model Intercomparison Project, or CMIP, an initiative of the UN’s World Climate Research Program. The paper describes several new forward-looking climate scenarios created to help researchers understand how and why the earth warms, and what might happen as it does. Such scenarios have been a mainstay of climate science since the 1980s, and are updated frequently to account for new research and observations. “These scenarios are not prediction machines,” said Detlef van Vuuren of the University of Utrecht, a veteran of emissions scenario development and the lead author on the CMIP paper. “They are simply ways to explore possible futures.” As the present changes, so too do researchers’ models of possible futures.

So what exactly was Trump celebrating? The CMIP paper—which was published in April—notes that its researchers now consider one older scenario “implausible.” First created in the early 2010s, RCP8.5 outlines a world that is between 4.2 and 5.4 degrees Celsius warmer by 2100, thanks to extremely high levels of coal burning. Somewhat confusingly, the “8.5” in RCP8.5 doesn’t refer to temperature degrees but to specific levels of radiative forcing—a measure of change in the earth’s energy balance caused by human-caused greenhouse gas emissions. It was also developed at a time of rapidly rising fossil fuel use and relatively expensive renewables. “RCP” itself stands for “representative concentration pathway,” meaning that it was chosen to represent a range of similarly dire preexisting scenarios.

Importantly, RCP8.5 was always intended as a “low-probability, high-risk” scenario among several others that show much lower........

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