Multisectoral climate impact hotspots in a warming world
- aPotsdam Institute for Climate Impact Studies, Potsdam 14473 Germany;
- bInstitute of Meteorology and Climate Research, Atmospheric and Environmental Research, Karlsruhe Institute of Technology, 82467 Garmisch-Partenkirchen, Germany;
- cCentre for Ecology and Hydrology, Wallingford OX1 08BB, United Kingdom;
- dSchool of Environmental Sciences, Tyndall Centre, University of East Anglia, Norwich NR4 7TJ, United Kingdom;
- eUniversity of Chicago Computation Institute, Chicago, IL 60637;
- fAbdus Salam International Centre for Theoretical Physics, 34151 Trieste, Italy;
- gCenter for Environmental Systems Research, University of Kassel, 34109 Kassel, Germany,
- hSwiss Federal Institute of Aquatic Science and Technology (EAWAG), 8600 Dübendorf, Switzerland;
- iEarth System Science, Wageningen University, 6708PB, Wageningen, The Netherlands;
- jDepartment of Geography, University of Cambridge, Cambridge CB2 1TN, United Kingdom;
- kSchool of Geography, University of Nottingham, Nottingham NG7 2RD, United Kingdom;
- lMet Office Hadley Centre, Exeter EX1 3PB, United Kingdom;
- mInternational Institute for Applied Systems Analysis, 2361 Laxenburg, Austria;
- nInstitute of Industrial Science,University of Tokyo, Tokyo 153-8505, Japan;
- oDepartment of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom;
- pCenter for Global Environmental Research, National Institute for Environmental Studies, Tsukuba 305-8506, Japan;
- qSchool of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, United Kingdom;
- rPBL Netherlands Environmental Assessment Agency, 3720 AH Bilthoven, The Netherlands;
- sRural Development Sociology, Wageningen University, 6706 KN Wageningen, The Netherlands;
- tMax Planck Institute for Biogeochemistry, 07745 Jena, Germany,
- uNational Aeronautics and Space Administration Goddard Institute for Space Studies, New York, NY 10025;
- vDepartment for Economic and Social Sciences, University of Natural Resources and Life Sciences, 1180 Vienna, Austria,
- wMax Planck Institute for Meteorology, 20146 Hamburg, Germany,
- xInstitute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China,
- yCity University of New York Environmental Cross-Roads Initiative, City College of New York, New York, NY 10031;
- zDepartment of Physical Geography, Utrecht University, 3508 TC Utrecht, The Netherlands; and
- aaSanta Fe Institute, Santa Fe, NM 87501
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Edited by Robert W. Kates, Independent Scholar, Trenton, ME, and approved June 4, 2013 (received for review January 31, 2013)

Abstract
The impacts of global climate change on different aspects of humanity’s diverse life-support systems are complex and often difficult to predict. To facilitate policy decisions on mitigation and adaptation strategies, it is necessary to understand, quantify, and synthesize these climate-change impacts, taking into account their uncertainties. Crucial to these decisions is an understanding of how impacts in different sectors overlap, as overlapping impacts increase exposure, lead to interactions of impacts, and are likely to raise adaptation pressure. As a first step we develop herein a framework to study coinciding impacts and identify regional exposure hotspots. This framework can then be used as a starting point for regional case studies on vulnerability and multifaceted adaptation strategies. We consider impacts related to water, agriculture, ecosystems, and malaria at different levels of global warming. Multisectoral overlap starts to be seen robustly at a mean global warming of 3 °C above the 1980–2010 mean, with 11% of the world population subject to severe impacts in at least two of the four impact sectors at 4 °C. Despite these general conclusions, we find that uncertainty arising from the impact models is considerable, and larger than that from the climate models. In a low probability-high impact worst-case assessment, almost the whole inhabited world is at risk for multisectoral pressures. Hence, there is a pressing need for an increased research effort to develop a more comprehensive understanding of impacts, as well as for the development of policy measures under existing uncertainty.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: piontek{at}pik-potsdam.de.
Author contributions: F.P., K.F., J.S., L.W., and H.J.S. designed research; F.P. performed research; F.P., C.M., T.A.M.P., D.B.C., D.D., J.E., F.d.J.C.G., M.F., C.F., W.F., A.D.F., S.N.G., D.H., N.K., H.K., M.R.L., Y.M., M.M., A.M., K. Neumann, K. Nishina, S.O., R.P., A.C.R., E.S., T.S., Q.T., Z.D.T., A.M.T., and D.W. analyzed data; and F.P., C.M., and T.A.M.P. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1222471110/-/DCSupplemental.
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