Articles | Volume 8, issue 3
Earth Syst. Dynam., 8, 827–847, 2017

Special issue: The Earth system at a global warming of 1.5°C and 2.0°C

Earth Syst. Dynam., 8, 827–847, 2017

Research article 19 Sep 2017

Research article | 19 Sep 2017

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

Benjamin M. Sanderson1, Yangyang Xu2, Claudia Tebaldi1, Michael Wehner3, Brian O'Neill1, Alexandra Jahn4, Angeline G. Pendergrass1, Flavio Lehner1, Warren G. Strand1, Lei Lin5, Reto Knutti6,1, and Jean Francois Lamarque1 Benjamin M. Sanderson et al.
  • 1National Center for Atmospheric Research, Boulder, CO, USA
  • 2Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA
  • 3Lawrence Berkeley National Lab, CA, USA
  • 4Department of Atmospheric and Oceanic Sciences and Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
  • 5School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China
  • 6Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland

Abstract. 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. In this study, 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. Here we 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.

Short summary
We present the results of a set of climate simulations designed to simulate futures in which the Earth's temperature is stabilized at the levels referred to in the 2015 Paris Agreement. We consider the necessary future emissions reductions and the aspects of extreme weather which differ significantly between the 2 and 1.5 °C climate in the simulations.
Final-revised paper