Preprints
https://doi.org/10.5194/esd-2024-26
https://doi.org/10.5194/esd-2024-26
13 Aug 2024
 | 13 Aug 2024
Status: a revised version of this preprint was accepted for the journal ESD and is expected to appear here in due course.

Regional non-reversibility of mean and extreme climate conditions in CMIP6 overshoot scenarios linked to large-scale temperature asymmetries

Pedro José Roldán-Gómez, Paolo De Luca, Raffaele Bernardello, and Markus Donat

Abstract. Overshoot scenarios, in which the forcing reaches a peak before starting to decline, show non-symmetric changes during the CO2 increasing and decreasing phases, producing persistent changes on climate. Non-reversibility mechanisms, associated among others with lagged responses of climate components, changes in ocean circulation and heat transport and changes in the ice cover, bring hysteresis to the climate system. These mechanisms generally have an impact in global scales, potentially generating hemispheric temperature changes and alterations of the Intertropical Convergence Zone (ITCZ). This work analyzes simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to explore the relevance of these mechanisms in overshoot scenarios with different forcing conditions (SSP5-3.4OS and SSP1-1.9) and the impact of these large-scale mechanisms on regional climates, with a particular focus on the degree to which changes in regional extremes are reversible. Results show that non-reversibility of temperature and precipitation extremes mostly occurs during the transition period around the global temperature maximum, when a decoupling between regional extremes and global temperature generates persistent changes at regional level. These changes mainly impact temperature extremes in extratropical regions and precipitation extremes in tropical regions around the ITCZ. In scenarios with strong forcing changes like SSP5-3.4OS, regional non-reversibility can be mostly linked to a temperature asymmetry between Northern and Southern Hemisphere, associated with ITCZ shifts. This asymmetry may be associated with persistent changes in the heat transport and with a different thermal inertia depending on the region, leading regionally to a different timing of the temperature maximum. In scenarios with lower forcing changes like SSP1-1.9, the contribution of this mechanism is more limited and other factors like ice melting may also have a relevant role.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Pedro José Roldán-Gómez, Paolo De Luca, Raffaele Bernardello, and Markus Donat

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2024-26', Peter Pfleiderer, 27 Aug 2024
    • AC1: 'Reply on RC1', Pedro Roldán, 12 Oct 2024
  • RC2: 'Comment on esd-2024-26', Anonymous Referee #2, 14 Sep 2024
    • AC1: 'Reply on RC1', Pedro Roldán, 12 Oct 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2024-26', Peter Pfleiderer, 27 Aug 2024
    • AC1: 'Reply on RC1', Pedro Roldán, 12 Oct 2024
  • RC2: 'Comment on esd-2024-26', Anonymous Referee #2, 14 Sep 2024
    • AC1: 'Reply on RC1', Pedro Roldán, 12 Oct 2024
Pedro José Roldán-Gómez, Paolo De Luca, Raffaele Bernardello, and Markus Donat
Pedro José Roldán-Gómez, Paolo De Luca, Raffaele Bernardello, and Markus Donat

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Short summary
Current trends on CO2 emissions increase the probability of an overshoot scenario, in which temperatures exceed the targets of the Paris Agreement and are brought back afterwards with a net-negative emission strategy. This work analyses how the climate after the overshoot would differ from the climate before, linking large scale non-reversibility mechanisms to changes in regional climates, and identifying those regions more impacted by changes on temperature and precipitation extremes.
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