Probability of committed warming exceeding 1.5 ^∘ C and 2.0 ^∘ C Paris targets

Journal Article · 25 May 2022 · Environmental Research Letters

DOI: https://doi.org/10.1088/1748-9326/ac6ff6 · OSTI ID:1869738

Sherwood, Steven C. ; Sen Gupta, Alex ; Schwartz, Stephen E.

Abstract The feasibility of achieving the Paris 1.5 ^∘ C target continues to be a complex and hotly debated question. To help resolve this question we calculate probability distributions of the committed warming that would ensue if all anthropogenic emissions were stopped immediately, or at successive future times. We use a simple Earth system model together with a Bayesian approach that incorporates multiple lines of evidence and accounts for known model biases. This analysis reveals a wide range of possible outcomes, including no further warming, but also a 15% chance of overshooting the 1.5 ^∘ C target, and 1%–2% chance for 2 ^∘ C, even if all emissions had stopped in 2020. If emissions merely stabilize in 2020 and stop in 2040, these probabilities increase to 90% and 17%. The uncertainty arises mainly from that of present forcing by aerosols. Rather than there being a fixed date by which emissions must stop, the probability of reaching either target—which is already below 100%—gradually diminishes with delays in eliminating emissions, by 3%–4% per year for 1.5 ^∘ C.

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0012704
• OSTI ID: 1869738
• Journal Information: Environmental Research Letters, Journal Name: Environmental Research Letters Journal Issue: 6 Vol. 17; ISSN 1748-9326
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United Kingdom
• Language: English