Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Strong remote control of future equatorial warming by off-equatorial forcing

TitleStrong remote control of future equatorial warming by off-equatorial forcing
Publication TypeJournal Article
Year of Publication2020
JournalNature Climate Change
Volume10
Number2
Pages124-129
Abstract / Summary

The tropical climate response to GHG forcing is spatially non-uniform1,2,3. Even though enhanced equatorial and eastern Pacific warming is simulated by most climate models, the underlying mechanisms—including the relative roles of atmospheric and oceanic feedbacks—remain debated. Here, we use a climate model with idealized CO2-radiative forcing patterns to show that off-equatorial radiative forcing and corresponding coupled circulation/cloud adjustments are responsible for much of equatorial warming in response to global CO2 forcing. For equatorial forcing, the atmosphere responds by enhancing atmospheric heat export to the extra-tropics, an associated strengthening of the ascending Hadley circulation branch and strong negative equatorial cloud feedbacks. These processes together greatly dampen equatorial surface warming. Intensification of the oceanic subtropical cells and increased cold subsurface water upwelling in the eastern tropical Pacific provide an additional negative feedback for surface temperatures. In contrast, applying off-equatorial forcing, the atmosphere responds by exporting less heat from the tropics, Hadley circulation weakening and weaker negative equatorial cloud feedbacks, while the subtropical cells slow down in the ocean. Our results demonstrate a delicate balance in the coupled climate system between remote circulation adjustments and regional feedbacks that create the patterns of future climate change.

URLhttp://dx.doi.org/10.1038/s41558-019-0667-6
DOI10.1038/s41558-019-0667-6
Journal: Nature Climate Change
Year of Publication: 2020
Volume: 10
Number: 2
Pages: 124-129
Publication Date: 02/2020

The tropical climate response to GHG forcing is spatially non-uniform1,2,3. Even though enhanced equatorial and eastern Pacific warming is simulated by most climate models, the underlying mechanisms—including the relative roles of atmospheric and oceanic feedbacks—remain debated. Here, we use a climate model with idealized CO2-radiative forcing patterns to show that off-equatorial radiative forcing and corresponding coupled circulation/cloud adjustments are responsible for much of equatorial warming in response to global CO2 forcing. For equatorial forcing, the atmosphere responds by enhancing atmospheric heat export to the extra-tropics, an associated strengthening of the ascending Hadley circulation branch and strong negative equatorial cloud feedbacks. These processes together greatly dampen equatorial surface warming. Intensification of the oceanic subtropical cells and increased cold subsurface water upwelling in the eastern tropical Pacific provide an additional negative feedback for surface temperatures. In contrast, applying off-equatorial forcing, the atmosphere responds by exporting less heat from the tropics, Hadley circulation weakening and weaker negative equatorial cloud feedbacks, while the subtropical cells slow down in the ocean. Our results demonstrate a delicate balance in the coupled climate system between remote circulation adjustments and regional feedbacks that create the patterns of future climate change.

DOI: 10.1038/s41558-019-0667-6
Citation:
Stuecker, M, A Timmermann, F Jin, C Proistosescu, S Kang, D Kim, K Yun, et al.  2020.  "Strong remote control of future equatorial warming by off-equatorial forcing."  Nature Climate Change 10(2): 124-129.  https://doi.org/10.1038/s41558-019-0667-6.