Introduction to the Community Earth System Model Jean-François Lamarque CESM Chief Scientist Atmospheric Chemistry Observations and Modeling and Climate and Global Dynamics Laboratories NCAR
What is a model? Graphical, mathematical (symbolic), physical, or verbal representation or simplified version of a concept, phenomenon, relationship, structure, system, or an aspect of the real world. The objectives of a model include (1) to facilitate understanding by eliminating unnecessary components, (2) to aid in decision making by simulating 'what if' scenarios, (3) to explain, control, and predict events on the basis of past observations.
Range of atmospheric models
Model development Goose et al., 2010
FROM CLIMATE TO EARTH SYSTEM MODELS
Earth System Model Holy Grail
Building an Earth System Model (NOAA) Systems of differential equations that describe fluid motion, radiative transfer, etc. Planet divided into 3- dimensional grid to solve the equations Atmosphere and land traditionally on same horizontal grid Similarly for ocean/ice Sub-gridscale processes must be parameterized
Earth System Model Evolution IPCC AR4
Horizontal resolution
Approaching cloud resolved scales Fully coupled CESM1-CAM5-SE simulations with a 25km atmosphere and 0.1o ocean 60 years in length Atmospheric Moisture content Yellowstone-NWSC Accelerated Science Discovery Run Project support from DOE-BER and NSF Courtesy of Justin Small, Tim Scheitlin Jean- François Lamarque
Community Earth System Model Forcings: Greenhouse gases Manmade aerosols Volcanic eruptions Solar variability Land (CLM) Atmosphere (CAM) Coupler (CPL) Chemistry (CAM-CHEM) High-Top Atm (WACCM) Sea Ice (CICE) Biogeochemistry (Carbon-Nitrogen Cycle) Ocean (POP) Biogeochemistry (Marine Ecosystem) Land Ice (CISM)
CESM Project CESM Advisory Board CESM Scientific Steering Committee Based on 20+ Years of Model development and application BioGeo- Chemistry Polar Climate Land Ice Chemistry- Climate Software Engineering Societal Dimensions CESM is primarily sponsored by the National Science Foundation and the Department of Energy Most working groups have winter/spring meetings. Annual meeting in June. Atmosphere Model Ocean Model Paleo- Climate CESM Whole Atmosphere Climate Variability and Change Land Model http://www.cesm.ucar.edu/management
Worldwide use Downloads over last 5 years
Community involvement Code access ~5100 registered users 2010-2015 418 registered developers (SVN developers access)!!! Revised developer s policy!!! DiscussCESM forums 53,688 sessions 2014-2015 25,971 returning user session 27,717 new user sessions Run database (https://csegweb.cgd.ucar.edu/expdb/): 1753 experiments entered into the database 2006-2015
Science Highlights Mechanisms of Climate Variations on Decadal to Century timescale Figure courtesy of Steve Ghan and DOE Graphics team BAMS Article: The Community Earth System Model: A Framework for Collaborative Research J.W. Hurrell, M.M. Holland, P.R. Gent, S. Ghan, J.E. Kay, P.J. Kushner, J.-F. Lamarque, W.G. Large, D. Lawrence, K. Lindsay, W.H. Lipscomb, M.C. Long, N. Mahowald, D.R. Marsh, R.B. Neale, P. Rasch, S. Vavrus, M. Vertenstein, D. Bader, W. D. Collins, J.J. Hack, J. Kiehl, S. Marshall, available online 15
Community Earth System Model OBS DART Atmosphere (CAM) Chemistry (CAM-CHEM) High-Top Atm (WACCM) Land (CLM) Coupler (CPL) Sea Ice (CICE) ( 1 o ) Biogeochemistry (Carbon-Nitrogen Cycle) Ocean (POP) Biogeochemistry ( 1 o ) (Marine Ecosystem) DART Land Ice (CISM) OBS
CESM supports these diverse climate science goals through a Single Model Code Base Desktop Small cluster HPC Single column/ Coarse resolution: Physics development Lower resolution: Paleo/Large Ensemble University research Higher resolution: CMIP Breakthrough ASD Jean- François L17 amarque
UNDERSTANDING THE CLIMATE SYSTEM
Observations: 20 th Century Warming Model Solutions with Human Forcing
Surface temperature
Surface temperature
Internal modes of variability
Teleconnections: ENSO
Internal variability and ensemble Slide from C. Deser Jean- François Lamarque
Benefits of Reduced Anthropogenic Climate change (BRACE) Ø Focuses on differences in impacts resulting from climate change driven by a higher emissions and radiative forcing scenario (the RCP-8.5 scenario) versus a lower scenario (the RCP-4.5 scenario) Ø Employing CESM ensembles for RCP8.5 (40 members) and RCP4.5 (15 members) to investigate differences in impacts Ø Special issue of Climatic Change established and under way, 20+ papers involving NCAR and 8 other institutions RCP8.5 Lg. Ens. RCP4.5 Med. Ens. Sanderson et al., submitted. Clark et al. WRR 2015
COUPLINGS AND FEEDBACKS
Example of climate feedback: fires Friedlingstein et al.
Biogeochemistry feedbacks Arneth et al., 2010
Nitrogen cycle in soils and plants
Ozone pollution vs climate impacts on regional food production Tai et al., Nature Clim. Change, 2014 31
Earth System Model Holy Grail
Summary Earth System Models are a virtual laboratory to explore response and feedback to external and internal forcings Important to capture important processes Evaluation against observations is key to create a robust model Beware of internal variability!
Chain of Models Integrated Assessment Models Earth System Models and Uncertainties and People Downscaling Methods Impact Models Decision Context
Additional questions? Comments? Purple: precipitation Slide courtesy of R. Knutti and O. Stebler