A large ozone-circulation feedback and its implications for global warming assessments.
State-of-the-art climate models now include more climate processes which are simulated at higher spatial resolution than ever1. Nevertheless, some processes, such as atmospheric chemical feedbacks, are still computationally expensive and are often ignored in climate simulations1,2. Here we present evidence that how stratospheric ozone is represented in climate models can have a first order impact on estimates of effective climate sensitivity. Using a comprehensive atmosphere-ocean chemistry-climate model, we find an increase in global mean surface warming of around 1°C (~20%) after 75 years when ozone is prescribed at pre-industrial levels compared with when it is allowed to evolve self-consistently in response to an abrupt 4×CO2forcing. The difference is primarily attributed to changes in longwave radiative feedbacks associated with circulation-driven decreases in tropical lower stratospheric ozone and related stratospheric water vapour and cirrus cloud changes. This has important implications for global model intercomparison studies1,2in which participating models often use simplified treatments of atmospheric composition changes that are neither consistent with the specified greenhouse gas forcing scenario nor with the associated atmospheric circulation feedbacks3-5.
Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
Peer J
PJ
Nowack
National Centre for Atmospheric Science, United Kingdom ; Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
N Luke
NL
Abraham
Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom ; National Centre for Atmospheric Science, United Kingdom.
Amanda C
AC
Maycock
National Centre for Atmospheric Science, United Kingdom ; Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
Peter
P
Braesicke
National Centre for Atmospheric Science, United Kingdom ; Department of Meteorology, University of Reading, Reading, United Kingdom ; Met Office Hadley Centre, Met Office, Exeter, United Kingdom.
Jonathan M
JM
Gregory
National Centre for Atmospheric Science, United Kingdom ; Department of Meteorology, University of Reading, Reading, United Kingdom.
Manoj M
MM
Joshi
National Centre for Atmospheric Science, United Kingdom ; Department of Meteorology, University of Reading, Reading, United Kingdom.
Annette
A
Osprey
Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom ; National Centre for Atmospheric Science, United Kingdom.
John A
JA
Pyle