Preprints
https://doi.org/10.5194/esd-2021-86
https://doi.org/10.5194/esd-2021-86

  26 Nov 2021

26 Nov 2021

Review status: this preprint is currently under review for the journal ESD.

Does feedback temperature dependence influence the slow mode of the climate response?

Tim Rohrschneider1,2, Jonah Bloch-Johnson3, and Maria Rugenstein4 Tim Rohrschneider et al.
  • 1Max Planck Institute for Meteorology, Hamburg, Germany
  • 2International Max Planck Research School on Earth System Modelling, Hamburg, Germany
  • 3University of Reading, Reading, UK
  • 4Colorado State University, Colorado, US

Abstract. Atmosphere-Ocean General Circulation models (AOGCMs) are a necessary tool to understand climate dynamics on centennial timescales for which observations are scarce. We explore to which degree the temperature dependence of the climate radiative feedback influences the slow mode of the surface temperature response. We question whether long-term climate change is described by a single e-folding mode with a constant timescale which is commonly assumed to be independent of temperature or forcing and the evolution of time. To do so, we analyze AOGCM simulations which have an integration time of 1000 years and are forced by atmospheric CO2 concentrations ranging from 2 times (2X) to 8 times (8X) the preindustrial level. Our findings suggest that feedback temperature dependence strongly influences the equilibrium temperature response and adjustment timescale of the slow mode. The magnitude and timescale of the slow mode is approximately reproduced by a zero-dimensional energy balance model that has a constant effective heat capacity and incorporates a background feedback parameter and a coefficient for feedback temperature dependence. However, the effective heat capacity of the slow mode increases over time, which makes the adjustment timescale also time-dependent. The time-varying adjustment timescale can be approximated by a multiple timescale structure of the slow temperature response, or vice versa, a multiple timescale structure of the slow temperature response is described by a time-dependent timescale. The state-dependence and time-dependence of the adjustment timescale of long-term climate change puts into question common eigenmode decomposition with a fast and a slow timescale in the sense that the slow mode is not well described by a single linear e-folding mode with a constant timescale. We find that such an eigenmode decomposition is valid at a certain forcing level only, and an additional mode or a multiple mode and timescale structure of the slow adjustment is necessary to reproduce the details of AOGCM simulated long-term climate change.

Tim Rohrschneider et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2021-86', Anonymous Referee #1, 10 Jan 2022
  • RC2: 'Comment on esd-2021-86', Anonymous Referee #2, 24 Jan 2022

Tim Rohrschneider et al.

Tim Rohrschneider et al.

Viewed

Total article views: 541 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
478 61 2 541 1 3
  • HTML: 478
  • PDF: 61
  • XML: 2
  • Total: 541
  • BibTeX: 1
  • EndNote: 3
Views and downloads (calculated since 26 Nov 2021)
Cumulative views and downloads (calculated since 26 Nov 2021)

Viewed (geographical distribution)

Total article views: 512 (including HTML, PDF, and XML) Thereof 512 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 25 Jan 2022
Download
Short summary
We question whether the timescale of long-term climate change is independent of temperature or forcing and the evolution of time. The timescale of long-term climate change depends on feedback temperature dependence and the evolution of time.
Altmetrics