Broad range of 2050 warming from an observationally constrained large climate model ensemble

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  2. Dr Kuniko Yamazaki
  3. Dr Hiro Yamazaki
Author(s)Rowlands DJ, Frame DJ, Ackerley D, Aina T, Booth BBB, Christensen C, Collins M, Faull N, Forest CE, Grandey BS, Gryspeerdt E, Highwood EJ, Ingram WJ, Knight S, Lopez A, Massey N, McNamara F, Meinshausen N, Piani C, Rosier SM, Sanderson BM, Smith LA, Stone DA, Thurston M, Yamazaki K, Yamazaki YH, Allen MR
Publication type Letter
JournalNature Geoscience
ISSN (print)1752-0894
ISSN (electronic)1752-0908
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Incomplete understanding of three aspects of the climate system—equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing—and the physical processes underlying them lead to uncertainties in our assessment of the global-mean temperature evolution in the twenty-first century1,2. Explorations of these uncertainties have so far relied on scaling approaches3,4, large ensembles of simplified climate models1,2, or small ensembles of complex coupled atmosphere–ocean general circulation models5,6 which under-represent uncertainties in key climate system properties derived from independent sources7–9. Here we present results from a multi-thousand-member perturbed-physics ensemble of transient coupled atmosphere–ocean general circulation model simulations. We find that model versions that reproduce observed surface temperature changes over the past 50 years show global-mean temperature increases of 1.4–3 K by 2050, relative to 1961–1990, under a mid-range forcing scenario. This range of warming is broadly consistent with the expert assessment provided by the Intergovernmental Panel on Climate Change Fourth Assessment Report10, but extends towards larger warming than observed in ensemblesof- opportunity5 typically used for climate impact assessments. From our simulations, we conclude that warming by the middle of the twenty-first century that is stronger than earlier estimates is consistent with recent observed temperature changes and a mid-range 'no mitigation' scenario for greenhouse-gas emissions.
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