Ensembles of Global Climate Model Variants Designed for the Quantification and Constraint of Uncertainty in Aerosols and Their Radiative Forcing

M. Yoshioka*, L. A. Regayre, K. J. Pringle, J. S. Johnson, G. W. Mann, D. G. Partridge, D. M.H. Sexton, G. M.S. Lister, N. Schutgens, P. Stier, Z. Kipling, N. Bellouin, J. Browse, B. B.B. Booth, C. E. Johnson, B. Johnson, J. D.P. Mollard, L. Lee, K. S. Carslaw

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Tropospheric aerosol radiative forcing has persisted for many years as one of the major causes of uncertainty in global climate model simulations. To sample the range of plausible aerosol and atmospheric states and perform robust statistical analyses of the radiative forcing, it is important to account for the combined effects of many sources of model uncertainty, which is rarely done due to the high computational cost. This paper describes the designs of two ensembles of the Met Office Hadley Centre Global Environment Model-U.K. Chemistry and Aerosol global climate model and provides the first analyses of the uncertainties in aerosol radiative forcing and their causes. The first ensemble was designed to comprehensively sample uncertainty in the aerosol state, while the other samples additional uncertainties in the physical model related to clouds, humidity, and radiation, thereby allowing an analysis of uncertainty in the aerosol effective radiative forcing. Each ensemble consists of around 200 simulations of the preindustrial and present-day atmospheres. The uncertainty in aerosol radiative forcing in our ensembles is comparable to the range of estimates from multimodel intercomparison projects. The mean aerosol effective radiative forcing is −1.45 W/m2 (credible interval of −2.07 to −0.81 W/m2), which encompasses but is more negative than the −1.17 W/m2 in the 2013 Atmospheric Chemistry and Climate Model Intercomparison Project and −0.90 W/m2 in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The ensembles can be used to reduce aerosol radiative forcing uncertainty by challenging them with multiple measurements as well as to isolate potential causes of multimodel differences.

Original languageEnglish
Pages (from-to)3728-3754
Number of pages27
JournalJournal of Advances in Modeling Earth Systems
Volume11
Issue number11
DOIs
Publication statusPublished - 1 Nov 2019

Keywords

  • aerosols
  • emulators
  • ERF
  • perturbed parameter ensemble
  • radiative forcing
  • uncertainty

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