Preprints
https://doi.org/10.5194/egusphere-2023-2307
https://doi.org/10.5194/egusphere-2023-2307
24 Oct 2023
 | 24 Oct 2023

Climate feedbacks with latitude derived from climatological data and theory

Philip Goodwin, Richard Williams, Paulo Ceppi, and B. B. Cael

Abstract. Most current methods for evaluating climate feedbacks utilise variation with time in Earth’s energy balance and surface temperatures, either from observations or Earth system model perturbation experiments. This study presents a new semi-empirical evaluation of Earth’s climate feedbacks at equilibrium, constrained instead by variation with latitude in recent mean climatology. Latitudinally binned surface temperature and outgoing radiation climatology provides a first order net climate feedback estimate  λ= -1.3±0.1 Wm-2 K-1, but this does not isolate the temperature influence on outgoing radiation from other factors. To isolate the surface temperature influence: First, we derive approximated functional relations for outgoing shortwave and longwave radiation in terms of surface temperature, surface relative humidity, fractional cloud amount, tropopause height and incident solar radiation. Second, we use observations of current zonal-mean climatology to constrain the relations and apply calculus to evaluate non-cloud climate feedbacks with latitude, including the Planck, water vapour-lapse rate and surface albedo. Our novel climatology-based evaluations of climate feedbacks weighted by the recent warming pattern, when combined with a recent estimate of cloud feedback from multiple lines of evidence, implies a global mean total net climate feedback λ= -1.1 (-0.8 to -1.4 at 66 % range) Wm-2 K-1 consistent with recent assessments of the literature. Our latitudinal method to constrain non-cloud climate feedback is independent of previous temporal approaches, using different observational lines of evidence, and so our method complements existing methods to help constrain climate feedback and climate sensitivity.

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Philip Goodwin, Richard Williams, Paulo Ceppi, and B. B. Cael

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2307', Anonymous Referee #1, 07 Dec 2023
    • AC3: 'Reply on RC1', P. Goodwin, 26 Apr 2024
  • CC1: 'Comment on egusphere-2023-2307', Timothy Merlis, 16 Dec 2023
    • AC1: 'Reply on CC1', P. Goodwin, 26 Apr 2024
  • RC2: 'Comment on egusphere-2023-2307', Anonymous Referee #2, 01 Apr 2024
    • AC2: 'Reply on RC2', P. Goodwin, 26 Apr 2024
Philip Goodwin, Richard Williams, Paulo Ceppi, and B. B. Cael

Model code and software

Energy_Balance_Climate_Feedback P. Goodwin, R. G. Williams, P. Ceppi, and B. B. Cael https://doi.org/10.5281/zenodo.8421164

Philip Goodwin, Richard Williams, Paulo Ceppi, and B. B. Cael

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Short summary
Climate feedbacks are normally evaluated by considering the change over time for Earth's energy balance and surface temperatures in the climate system. However, we only have around 1 degree Celsius of temperature change to utilise. Here, climate feedbacks are instead evaluated from the change in latitude of Earth's energy balance and surface temperatures, where we have around 70 degrees Celsius of temperature change to utilise.