Intermodel relationships between Southern Ocean surface temperature and global climate — Australian Meteorological and Oceanographic Society
  1. Schedule
  2. Afternoon Tea + Poster Session 1
  3. Intermodel relationships between Southern Ocean surface temperature and global climate

Intermodel relationships between Southern Ocean surface temperature and global climate (#1026)

Jules B Kajtar 1 2 3 , Agus Santoso 2 4 , Matthew Collins 3 , Matthew H England 2 4 , Leela M Frankcombe 2 4 , Andréa S Taschetto 2 4
  1. University of Tasmania, Battery Point, Tasmania
  2. ARC Centre for Climate Extremes, Sydney, Australia
  3. University of Exeter, Exeter, UK
  4. University of New South Wales, Sydney

CMIP models tend to overestimate the absorbed solar radiation over the Southern Ocean1,2, with implications for the representation of the Southern Hemisphere climate system and beyond. Specifically, a strong anti-correlation between equilibrium climate sensitivity (the global mean temperature response to doubled atmospheric CO2) and net top-of-atmosphere radiation in the Southern Hemisphere was found in CMIP31. That anti-correlation does not manifest to the same extent in CMIP5, and it has been argued that it is not a robust physical relationship, but a symptom of unrealistic processes in a subset of models2. Here we revisit the issue by examining intermodel relationships between surface temperature and various climate variables such as top-of-atmosphere radiation, cloud fraction, sea-ice extent, and atmospheric circulation, with compelling connections among them. Our analysis highlights the dominance of Southern Ocean processes on global mean temperature change, in that models that exhibit cooler sea surface over Southern Ocean tend to project stronger global warming. Our findings suggest that while a physical constraint on equilibrium climate sensitivity may yet be plausible, understanding model biases over the Southern Ocean is of primary importance. Forthcoming CMIP6 analysis could provide further evidence.

1. Trenberth KE, Fasullo JT. Simulation of present-day and twenty-first-century energy budgets of the southern oceans. J Clim 23, 440–454 (2010)

2. Grise KM, Polvani LM, Fasullo JT. Reexamining the relationship between climate sensitivity and the Southern Hemisphere radiation budget in CMIP models. J Clim 28, 9298–9312 (2015)

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