evidence: Perceptions of carbon dioxide emission reductions and future warming among climate experts [...] IPCC authors play a critical role communicating climate science information to policy makers and the public, so it is important to understand the personal beliefs that inform their thinking and how those beliefs are formed. In this study we found that IPCC authors are skeptical, given current evidence, that warming will be limited to 1.5 °C or well below 2 °C rise in temperature compared to pre-industrial averages. This is an interesting finding in light of independent estimates that suggest a median end-of-century temperature rise of 2.7 °C under existing national climate policies, or 2.1 °C based on a scenario in which all nations achieve their current pledges and targets24. The large majority (86%) of our respondents believed that warming would exceed 2 °C this century, and 58% of our sample believed there was at least a 50% likelihood of exceeding 3 °C. This suggests that IPCC author responses are closely aligned with a projection of current emission trends in the absence of widespread increases in national climate ambition. [...] The median estimate for maximum warming by or before 2100 was 2.7 °C in our sample, and yet the median estimate for the year of net zero CO2 (2075) is consistent with 2 °C of warming by the end of this century. This inconsistency in IPCC author responses was puzzling, and could reflect a range of underlying causes, from low confidence in scenarios to low understanding of current model estimates of the climate response to future emissions scenarios.