EGU2020-8433
https://doi.org/10.5194/egusphere-egu2020-8433
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Controls of the Transient Climate Response to Emissions: effects of physical feedbacks, heat uptake and saturation of radiative forcing

Ric Williams1, Paulo Ceppi2, and Anna Katavouta1,3
Ric Williams et al.
  • 1Liverpool University, School of Environmental Sciences, Earth, Ocean & Ecological Sciences, Liverpool, United Kingdom of Great Britain and Northern Ireland (ric@liv.ac.uk)
  • 2Grantham Institute, Imperial College London, London, UK
  • 3National Oceanography Centre, Liverpool, UK

The surface warming response to carbon emissions, defines a climate metric, the Transient Climate Response to cumulative carbon Emissions (TCRE), which is important in estimating how much carbon may be emitted to avoid dangerous climate. The TCRE is diagnosed from a suite of 9 CMIP6 Earth system models following an annual 1% rise in atmospheric CO2 over 140 years.   The TCRE   is nearly constant in time during emissions for these climate models, but its value   differs between individual models. The near constancy of this climate metric is due to a strengthening in the surface warming per unit radiative forcing, involving a weakening in both the climate feedback parameter and   fraction of radiative forcing warming the ocean interior, which are compensated by a weakening in the radiative forcing per unit carbon emission from the radiative forcing saturating with increasing atmospheric CO2. Inter-model differences in the TCRE are mainly controlled by the   surface warming response to radiative forcing with large inter-model differences in physical climate feedbacks dominating over smaller, partly compensating differences in ocean heat uptake. Inter-model differences in the radiative forcing per unit carbon emission   provide smaller inter-model differences in the TCRE, which are mainly due to differences in the ratio of the radiative forcing and change in atmospheric CO2 rather than from differences in the airborne fraction.     Hence, providing tighter constraints in the climate projections for the TCRE during emissions requires improving estimates of the physical climate feedbacks,   the rate of ocean   heat uptake, and how the radiative forcing saturates with atmospheric CO2.

How to cite: Williams, R., Ceppi, P., and Katavouta, A.: Controls of the Transient Climate Response to Emissions: effects of physical feedbacks, heat uptake and saturation of radiative forcing , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8433, https://doi.org/10.5194/egusphere-egu2020-8433, 2020

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