1 Department of Geography, Planning & Environment, Concordia University, Montréal, QC Canada.
2 Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON Canada.
3 Dept. of Earth System Science, Stanford University, Stanford, CA USA.
4 Department of Communication, George Mason University, Fairfax, VA USA.
5 Grantham Institute Climate Change and Environment, Centre for Environmental Policy, Imperial College London, London, UK.
6 Energy Climate and Environment Programme, International Institute for Applied Systems Analysis, Laxenburg, Austria.
7 Department of Geography, Simon Fraser University, Burnaby, BC Canada.

The Intergovernmental Panel on Climate Change (IPCC) employs emission scenarios to explore a range of future climate outcomes but refrains from assigning probabilities to individual scenarios. However, IPCC authors have their own views on the likelihood of different climate outcomes, which are valuable to understand because authors possess both expert insight and considerable influence. Here we report the results of a survey of 211 IPCC authors about the likelihood of four key climate outcomes. We found that most authors are skeptical that warming will be limited to the Paris targets of well below 2 °C, but are more optimistic that net zero CO₂ emissions will be reached during the second half of this century. When asked about the beliefs of their peers, author responses showed strong correlations between personal and peer beliefs, suggesting that participants with extreme beliefs perceive their own estimates as closer to the community average than they actually are.