Community climate simulations to assess avoided impacts in 1.5 and 2 °C futures

• Published in: Earth System Dynamics
• Main Authors: Sanderson, Benjamin M., Xu, Yangyang, Tebaldi, Claudia, Wehner, Michael, O'Neill, Brian, Jahn, Alexandra, Pendergrass, Angeline G., Lehner, Flavio, Strand, Warren G., Lin, Lei, Knutti, Reto, Lamarque, Jean Francois
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic
• Online Access: http://www.osti.gov/servlets/purl/1416921; https://www.osti.gov/biblio/1416921; https://doi.org/10.5194/esd-8-827-2017

The Paris Agreement of December 2015 stated a goal to pursue efforts to keep global temperatures below 1.5 °C above preindustrial levels and well below 2 °C. The IPCC was charged with assessing climate impacts at these temperature levels, but fully coupled equilibrium climate simulations do not currently exist to inform such assessments. Here, we produce a set of scenarios using a simple model designed to achieve long-term 1.5 and 2 °C temperatures in a stable climate. These scenarios are then used to produce century-scale ensemble simulations using the Community Earth System Model, providing impact-relevant long-term climate data for stabilization pathways at 1.5 and 2 °C levels and an overshoot 1.5 °C case, which are realized (for the 21st century) in the coupled model and are freely available to the community. We also describe the design of the simulations and a brief overview of their impact-relevant climate response. Exceedance of historical record temperature occurs with 60 % greater frequency in the 2 °C climate than in a 1.5 °C climate aggregated globally, and with twice the frequency in equatorial and arid regions. Extreme precipitation intensity is statistically significantly higher in a 2.0 °C climate than a 1.5 °C climate in some specific regions (but not all). The model exhibits large differences in the Arctic, which is ice-free with a frequency of 1 in 3 years in the 2.0 °C scenario, and 1 in 40 years in the 1.5 °C scenario. Significance of impact differences with respect to multi-model variability is not assessed.