Title: Baseline evaluation of the impact of updates to the MIT Earth System Model on its model parameter estimates

Abstract

For over 20 years, the Massachusetts Institute of Technology Earth System Model (MESM) has been used extensively for climate change research. The model is under continuous development with components being added and updated. To provide transparency in the model development, we perform a baseline evaluation by comparing model behavior and properties in the newest version to the previous model version. In particular, changes resulting from updates to the land surface model component and the input forcings used in historical simulations of climate change are investigated. We run an 1800-member ensemble of MESM historical climate simulations where the model parameters that set climate sensitivity, the rate of ocean heat uptake, and the net anthropogenic aerosol forcing are systematically varied. By comparing model output to observed patterns of surface temperature changes and the linear trend in the increase in ocean heat content, we derive probability distributions for the three model parameters. Moreover, we run a 372-member ensemble of transient climate simulations where all model forcings are fixed and carbon dioxide concentrations are increased at the rate of 1%year^-1. From these runs, we derive response surfaces for transient climate response and thermosteric sea level rise as a function o fclimate sensitivity and ocean heatmore » uptake. We show that the probability distributions shift towards higher climate sensitivities and weaker aerosol forcing when using the new model and that the climate response surfaces are relatively unchanged between model versions. Because the response surfaces are independent of the changes to the model forcings and similar between model versions with different land surface models, we suggest that the change in land surface model has limited impact on the temperature evolution in the model. Thus, we attribute the shifts in parameter estimates to the updated model forcings.« less

Authors:

Libardoni, Alex G.; Forest, Chris E. ;

• Search DOE PAGES for author "Forest, Chris E."
• Search DOE PAGES for ORCID "0000-0002-2643-0186"

Sokolov, Andrei P.; Monier, Erwan

• Search DOE PAGES for author "Monier, Erwan"
• Search DOE PAGES for ORCID "0000-0001-5533-6570"

Publication Date:

Tue Aug 21 00:00:00 EDT 2018

Research Org.:

Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1465599

Alternate Identifier(s):

OSTI ID: 1511026

Grant/Contract Number:  

FG02-94ER61937

Resource Type:

Published Article

Journal Name:

Geoscientific Model Development (Online)

Additional Journal Information:

Journal Name: Geoscientific Model Development (Online) Journal Volume: 11 Journal Issue: 8; Journal ID: ISSN 1991-9603

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

58 GEOSCIENCES