title: Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.
abstract: Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.
authors.affiliation: Research and Development, Weather and Climate Modeling, Royal Netherlands Meteorological Institute, 3730AE De Bilt, The Netherlands; National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom; S.S.Drijfhout@soton.ac.uk.
authors.forename: Sybren
authors.initials: S
authors.lastname: Drijfhout
authors.affiliation: Department of Environmental Sciences, Wageningen University, 6708PB Wageningen, The Netherlands; The Land in the Earth System, Max Planck Institute for Meteorology, 20146 Hamburg, Germany;
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bathiany
authors.affiliation: National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom;
authors.forename: Claudie
authors.initials: C
authors.lastname: Beaulieu
authors.affiliation: The Land in the Earth System, Max Planck Institute for Meteorology, 20146 Hamburg, Germany;
authors.forename: Victor
authors.initials: V
authors.lastname: Brovkin
authors.affiliation: The Land in the Earth System, Max Planck Institute for Meteorology, 20146 Hamburg, Germany; Center for Earth System Research and Sustainability, Universität Hamburg, 20146 Hamburg, Germany;
authors.forename: Martin
authors.initials: M
authors.lastname: Claussen
authors.affiliation: Climate System Group, Centre for Ecology and Hydrology, Wallingford OX10 8BB, United Kingdom;
authors.forename: Chris
authors.initials: C
authors.lastname: Huntingford
authors.affiliation: Department of Environmental Sciences, Wageningen University, 6708PB Wageningen, The Netherlands;
authors.forename: Marten
authors.initials: M
authors.lastname: Scheffer
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnnement, Institut Pierre Simon Laplace, 91191 Gif-sur-Yvette, Paris, France;
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sgubin
authors.affiliation: Environnements et Paleoenvironnements Oceaniques et Continentaux, University of Bordeaux, 33615 Pessac, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Swingedouw
keywords: CMIP5; IPCC; abrupt climate change; climate change; critical transitions