Preprints
https://doi.org/10.5194/egusphere-2024-429
https://doi.org/10.5194/egusphere-2024-429
20 Feb 2024
 | 20 Feb 2024

Why does stratospheric aerosol forcing strongly cool the warm pool?

Moritz Günther, Hauke Schmidt, Claudia Timmreck, and Matthew Toohey

Abstract. Previous research has shown that stratospheric aerosols cause only a small temperature change per unit forcing because they produce stronger cooling in the tropical Indian and Western Pacific Ocean than in the global mean. The enhanced temperature change in this so-called “warm pool” region activates strongly negative local and remote feedbacks, which dampen the global mean temperature response. This paper addresses the question why stratospheric aerosol forcing affects warm pool temperatures more strongly than CO2 forcing, using idealized MPI-ESM simulations. We show that the aerosol’s enhanced effective forcing at the top of the atmosphere (TOA) over the warm pool contributes to the warm pool-intensified temperature change, but is not sufficient to explain the effect. Instead, the pattern of surface effective forcing, which is substantially different from the effective forcing at the TOA, is more closely linked to the temperature pattern. Independent of surface temperature changes, the aerosol heats the tropical stratosphere, which leads to an acceleration of the Brewer-Dobson circulation. The intensified Brewer-Dobson circulation exports additional energy from the tropics to the extratropics, which leads to a particularly strong negative forcing at the tropical surface. These results show how forced circulation changes can affect the climate response by altering the surface forcing pattern. Furthermore, they indicate that the established approach of diagnosing effective forcing at the TOA is useful for global means, but a surface perspective on the forcing must be adopted to understand the evolution of temperature patterns.

Moritz Günther, Hauke Schmidt, Claudia Timmreck, and Matthew Toohey

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-2024-429', Chen Zhou, 12 Mar 2024
    • AC1: 'Reply on RC1', Moritz Günther, 27 Mar 2024
  • RC2: 'Comment on egusphere-2024-429', Anonymous Referee #2, 13 Mar 2024
    • AC2: 'Reply on RC2', Moritz Günther, 27 Mar 2024
  • RC3: 'Comment on egusphere-2024-429', Daniele Visioni, 13 Mar 2024
    • AC3: 'Reply on RC3', Moritz Günther, 27 Mar 2024
Moritz Günther, Hauke Schmidt, Claudia Timmreck, and Matthew Toohey
Moritz Günther, Hauke Schmidt, Claudia Timmreck, and Matthew Toohey

Viewed

Total article views: 375 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
267 87 21 375 9 8
  • HTML: 267
  • PDF: 87
  • XML: 21
  • Total: 375
  • BibTeX: 9
  • EndNote: 8
Views and downloads (calculated since 20 Feb 2024)
Cumulative views and downloads (calculated since 20 Feb 2024)

Viewed (geographical distribution)

Total article views: 409 (including HTML, PDF, and XML) Thereof 409 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 19 Apr 2024
Download
Short summary
Stratospheric aerosol affects temperatures differently across the globe, with pronounced cooling in the tropical Indian and Western Pacific ocean. The aerosol also heats the stratosphere. Using a climate model, we show that the resulting circulation changes cause enhanced heat fluxes out of the tropical oceans, resulting in the pronounced local surface cooling. This highlights the importance of circulation adjustments and surface perspectives on forcing for understanding temperature responses.