Climate scientists express their views on possible future climate scenarios in a new study

A new survey of climate experts reveals that a majority believes the Earth to be headed for a rise in global temperatures far higher than the 2015 Paris Agreement targets of 1.5 to well-below 2°C.

The study was published in the Nature journal Communications Earth & Environment. It also shows that two-thirds of respondents — all of them authors on the Intergovernmental Panel on Climate Change (IPCC) — believe we may succeed in achieving net zero CO₂ emissions during the second half of this century. This indicates some optimism that mitigation efforts may be starting to bend the emissions curve toward what would be needed to achieve the Paris temperature goal.

A majority also acknowledged the potential for atmospheric CO₂ removal, with a median response indicating a belief that the technology could remove up to five gigatons of carbon dioxide (GtCO₂) a year by 2050. That is at the lower end of the range believed to be necessary to meet the Paris targets.

“We wanted to survey some of the top climate experts in the world to get some insight into their perceptions of different future climate outcomes,” says the paper’s lead author, Seth Wynes, a former postdoctoral fellow at Concordia, now an assistant professor at the University of Waterloo.

“These scientists also engage in important climate change communication, so their optimism or pessimism can affect how decision-makers are receiving messages about climate change.”

More is needed to avert catastrophe

The 211 respondents to the survey were generally pessimistic about reaching the Paris targets given current policies, with 86 per cent estimating warming above 2˚C by 2100. The median estimate was 2.7˚C, which is expected to have catastrophic consequences for the planet.

Co-author Damon Matthews, a professor in the Department of Geography, Planning and Environment, notes that this does not mean that level of warming is inevitable.

“These responses are not a prediction of future warming, but rather a gauge of what the scientific community believes. The answers are surprisingly consistent with previous estimates of what would happen if our current climate policies continued without any increase in ambition, which range from about 2.5 to 3˚C.”

Along with questions about the likelihood of future climate outcomes, the respondents were also asked to estimate their peers’ responses to the same questions.

“There was a strong correlation between what people believe and what they sense their peers believe,” Wynes says. “They had a bias to see their beliefs as representative of the larger group. This can indicate an overconfidence in their own beliefs, so we think this is a good opportunity for them to reevaluate what their peers actually believe.”

Working with data, not policy

An IPCC author himself, Matthews admits that scientists’ views on possible climate scenarios are valuable, but other perspectives on the issues around climate change are necessary if we hope to slow it.

“Climate scientists certainly have expertise in climate systems and energy transitions, but it will be policy implementation and societal change that actually determine how quickly emissions drop,” he says.

“Ultimately, the decision as to what we do and how we respond to the climate challenge is up to policymakers and the public that they represent, and I think the full range of outcomes is still very much on the table.”

Contributing authors to this paper include Steven Davis of Stanford University, PhD candidate Mitchell Dickau and MSc student Susan Ly at Concordia University, Edward Maibach at George Mason University, Joeri Rogelj at Imperial College, London and Kirsten Zickfeld at Simon Fraser University.

Read the cited paper: “Perceptions of carbon dioxide emission reductions and future warming among climate experts.