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Title: Midlatitude atmospheric circulation responses under 1.5 and 2.0 °C warming and implications for regional impacts

This study investigates the global response of the midlatitude atmospheric circulation to 1.5 and 2.0°C of warming using the HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) ensemble, with a focus on the winter season. Characterising and understanding this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to 1.5°C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks, and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5°C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equatorward intensification of the South Pacific jet. Signals that emerge under an additional 0.5°C of warming include a poleward shift of themore » North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, in western Europe, and on the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2°C warmer world, with exceptionally dry decades becoming 5 times more likely.« less
 [1] ;  [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [4] ;  [5] ;  [6] ; ORCiD logo [4] ;  [2] ;  [3] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ; ORCiD logo [12] ;  [13]
  1. Univ. of Bergen, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway)
  2. Norwegian Meteorological Institute, Oslo (Norway)
  3. Uni Climate, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway)
  4. Univ. of Reading, Reading (United Kingdom)
  5. British Antarctic Survey, Cambridge (United Kingdom)
  6. ETH Zurich, Zurich (Switzerland)
  7. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  8. German Climate Computing Center (DKRZ), Hamburg (Germany)
  9. Univ. of Bristol, Bristol (United Kingdom)
  10. Canadian Centre for Climate Modelling and Analysis, Victoria (Canada)
  11. National Institute for Environmental Studies, Tsukuba (Japan)
  12. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Global Climate Adaptation Partnership, Oxford (United Kingdom)
  13. Oregon State Univ., Corvallis, OR (United States); Univ. of Bergen, Bergen (Norway); Bjerknes Centre for Climate Research, Bergen (Norway)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Earth System Dynamics (Online)
Additional Journal Information:
Journal Name: Earth System Dynamics (Online); Journal Volume: 9; Journal Issue: 2; Related Information: © 2016 Copernicus GmbH. All rights reserved.; Journal ID: ISSN 2190-4987
European Geosciences Union
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
OSTI Identifier: