Updated estimates will enable evaluation of complex multi-sector, economy/natural resource interactions
Earth-system responses to radiative forcing are uncertain, leading to uncertainty in complex energy, water and land systems and their broader interaction with the economy. Methods to estimate the uncertainty in key Earth-system responses, including equilibrium climate sensitivity, effective ocean diffusivity, and the aerosol-forcing scaling factor, combine Earth-system models with data on ocean and atmosphere temperatures and climate forcers. As these models are updated, it becomes necessary to recalibrate estimated Earth-system responses (and their uncertainty ranges).
Quantification of uncertainty in Earth-system responses is necessary to assess risks to energy, water and land systems—and to better understand the range of possible changes in these systems. Recalibrated estimates are needed to develop ensembles of future scenarios of the Earth system consistent with recent observations and our understanding of the Earth system as represented in the current version of a given modeling system.
A study by researchers at the MIT Joint Program on the Science and Policy of Global Change and collaborators has provided an open, transparent means of testing changes in the response and parameters of the MIT Earth System Model (MESM). By providing a systematic accounting of how changes in the model result in changes in estimates of Earth-system response, the research provides a template for others in the research community to calibrate similar modeling frameworks. Among the changes in MESM were revisions to the radiative forcing code, new solar radiation data, and new data on ozone concentrations. The combined changes led to a net energy deficit in the Earth system, driving an upward shift in estimates of climate sensitivity (a 90% confidence interval of 1.3° to 5.7° C, up from 1.2° to 5.3° C), better constrained ocean diffusivity, and weaker aerosol forcing (from a 90% confidence interval of -0.83 to -0.19 Wm-2 to -0.53 to -0.03 Wm-2). The estimated responses were independent of the changes to the model forcings and similar between model versions with different land-surface models. This suggests that the change in land-surface model had limited impact on the temperature evolution in the model.
BER PM Contact
Andrei Sokolov (firstname.lastname@example.org)
MIT Joint Program on the Science and Policy of Global Change
The study was funded by the U.S. Department of Energy (DOE) Office of Science under the grant DE-FG02-94ER61937; co-authors Libardini and Forest received a sub-award from MIT to Penn State under the DOE grant.
Libardoni, A.G., C.E. Forest, A.P. Sokolov and E. Monier (2018): Baseline evaluation of the impact of updates to the MIT Earth System Model on its model parameter estimates. Geoscientific Model Development, 11(8): 3313-3325 (doi: 10.5194/gmd-11-3313-2018)
Image: Model response surfaces for (a) TCR and (b) thermosteric sea level rise. Contours for the MESM response surfaces are shown in black, and contours for the Integrated Global System Modeling (IGSM) framework surfaces are shown in red. Differences between the fits are also shown (c, d). The systematic approach developed provides a template for others in the research community to calibrate similar modeling frameworks. (Source: MIT Joint Program on the Science and Policy of Global Change)