Reduced Complexity Model Intercomparison Project Phase 2: Synthesizing Earth System Knowledge for Probabilistic Climate Projections

• Published in: Earth's future Vol. 9; no. 6; pp. e2020EF001900 - n/a
• Main Authors: Nicholls, Z, Meinshausen, M, Lewis, J, Corradi, M Rojas, Dorheim, K, Gasser, T, Gieseke, R, Hope, A P, Leach, N J, McBride, L A, Quilcaille, Y, Rogelj, J, Salawitch, R J, Samset, B H, Sandstad, M, Shiklomanov, A, Skeie, R B, Smith, C J, Smith, S J, Su, X, Tsutsui, J, Vega-Westhoff, B, Woodard, D L
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center Wiley Open Access 01.06.2021; John Wiley & Sons, Inc; American Geophysical Union (AGU); John Wiley and Sons Inc; Wiley
• Subjects: Abrupt/Rapid Climate Change; Aerosols; Air/Sea Constituent Fluxes; Air/Sea Interactions; Atmospheric; Atmospheric Composition and Structure; Atmospheric Effects; Atmospheric Processes; Avalanches; Benchmarks; Benefit‐cost Analysis; Biogeosciences; Carbon; Carbon cycle; climate; Climate and Interannual Variability; Climate change; Climate Change and Variability; Climate Dynamics; Climate Impact; Climate Impacts; Climate science; Climate Variability; Climatology; Complexity; Computational Geophysics; Computer applications; Coupled Models of the Climate System; Cryosphere; Decadal Ocean Variability; Disaster Risk Analysis and Assessment; Domains; Earth System Modeling; Earthquake Ground Motions and Engineering Seismology; Effusive Volcanism; Emissions; ENVIRONMENTAL SCIENCES; Experiments; Explosive Volcanism; General Circulation; General or Miscellaneous; Geodesy and Gravity; Geological; Global Change; Global Change from Geodesy; Global Climate Models; Gravity and Isostasy; Heat; Hydrological Cycles and Budgets; Hydrology; Impacts of Global Change; Informatics; Land/Atmosphere Interactions; Marine Geology and Geophysics; Markov analysis; Mass Balance; Meteorology And Climatology; Model Calibration; model intercomparison; Modeling; Modelling; Mud Volcanism; Natural Hazards; Numerical Modeling; Numerical Solutions; Ocean influence of Earth rotation; Ocean Monitoring with Geodetic Techniques; Ocean/Atmosphere Interactions; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Oceanic; Oceanography: General; Oceanography: Physical; Oceans; Paleoceanography; Physical Modeling; Physical sciences; Policy Sciences; probabilistic projections; Radio Oceanography; Radio Science; RCMIP; reduced complexity climate model; Regional Climate Change; Regional Modeling; Rigidity; Risk; Sea Level Change; Sea Level: Variations and Mean; Seismology; Solid Earth; Surface Waves and Tides; Theoretical Modeling; Tsunamis and Storm Surges; Uncertainty; Volcanic Effects; Volcanic Hazards and Risks; Volcano Monitoring; Volcano Seismology; Volcano/Climate Interactions; Volcanology; Water Cycles; Working groups; Rcmip; Climate; Model Intercomparison; Reduced Complexity Climate Model; Probabilistic Projections; RCMIP; reduced complexity climate model; climate; probabilistic projections; model intercomparison
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1029/2020EF001900

Over the last decades, climate science has evolved rapidly across multiple expert domains. Our best tools to capture state-of-the-art knowledge in an internally self-consistent modelling framework are the increasingly complex fully coupled Earth System Models (ESMs). However, computational limitations and the structural rigidity of ESMs mean that the full range of uncertainties across multiple domains are difficult to capture with ESMs alone. The tools of choice are instead more computationally efficient reduced complexity models (RCMs), which are structurally flexible and can span the response dynamics across a range of domain-specific models and ESM experiments. Here we present Phase 2 of the Reduced Complexity Model Intercomparison Project (RCMIP Phase 2), the first comprehensive intercomparison of RCMs that are probabilistically calibrated with key benchmark ranges from specialized research communities. Unsurprisingly, but crucially, we find that models which have been constrained to reflect the key benchmarks better reflect the key benchmarks. Under the low-emissions SSP1-1.9 scenario, across the RCMs, median peak warming projections range from 1.3 to 1.7°C (relative to 1850-1900, using an observationally-based historical warming estimate of 0.8°C between 1850-1900 and 1995-2014). Further developing methodologies to constrain these projection uncertainties seems paramount given the international community's goal to contain warming to below 1.5°C above pre-industrial in the long-term. Our findings suggest that users of RCMs should carefully evaluate their RCM, specifically its skill against key benchmarks and consider the need to include projections benchmarks either from ESM results or other assessments to reduce divergence in future projections.