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4 - The Earth system feedbacks that matter for contemporary climate
- Edited by Sarah E. Cornell, I. Colin Prentice, Macquarie University, Sydney, Joanna I. House, University of Bristol, Catherine J. Downy, European Space Agency
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- Book:
- Understanding the Earth System
- Published online:
- 05 November 2012
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- 09 August 2012, pp 102-128
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Summary for Policymakers
- from Section II
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- By Simon K. Allen, Vicente Barros, Ian Burton, Diarmid Campbell-Lendrum, Omar-Dario Cardona, Susan L. Cutter, O. Pauline Dube, Kristie L. Ebi, Christopher B. Field, John W. Handmer, Padma N. Lal, Allan Lavell, Katharine J. Mach, Michael D. Mastrandrea, Gordon A. McBean, Reinhard Mechler, Tom Mitchell, Neville Nicholls, Karen L. O'Brien, Taikan Oki, Michael Oppenheimer, Mark Pelling, Gian-Kasper Plattner, Roger S. Pulwarty, Sonia I. Seneviratne, Thomas F. Stocker, Maarten K. van Aalst, Carolina S. Vera, Thomas J. Wilbanks
- Edited by Christopher B. Field, Vicente Barros, Thomas F. Stocker, Qin Dahe
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- Book:
- Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation
- Published online:
- 05 August 2012
- Print publication:
- 28 May 2012, pp 3-22
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Summary
Context
This Summary for Policymakers presents key findings from the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). The SREX approaches the topic by assessing the scientific literature on issues that range from the relationship between climate change and extreme weather and climate events (‘climate extremes’) to the implications of these events for society and sustainable development. The assessment concerns the interaction of climatic, environmental, and human factors that can lead to impacts and disasters, options for managing the risks posed by impacts and disasters, and the important role that non-climatic factors play in determining impacts. Box SPM.1 defines concepts central to the SREX.
The character and severity of impacts from climate extremes depend not only on the extremes themselves but also on exposure and vulnerability. In this report, adverse impacts are considered disasters when they produce widespread damage and cause severe alterations in the normal functioning of communities or societies. Climate extremes, exposure, and vulnerability are influenced by a wide range of factors, including anthropogenic climate change, natural climate variability, and socioeconomic development (Figure SPM.1). Disaster risk management and adaptation to climate change focus on reducing exposure and vulnerability and increasing resilience to the potential adverse impacts of climate extremes, even though risks cannot fully be eliminated (Figure SPM.2). Although mitigation of climate change is not the focus of this report, adaptation and mitigation can complement each other and together can significantly reduce the risks of climate change. [SYR AR4, 5.3]
Chapter 3 - Changes in Climate Extremes and their Impacts on the Natural Physical Environment
- from Section III
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- By Sonia I. Seneviratne, Neville Nicholls, David Easterling, Clare M. Goodess, Shinjiro Kanae, James Kossin, Yali Luo, Jose Marengo, Kathleen McInnes, Mohammad Rahimi, Markus Reichstein, Asgeir Sorteberg, Carolina Vera, Xuebin Zhang, Matilde Rusticucci, Vladimir Semenov, Lisa V. Alexander, Simon Allen, Gerardo Benito, Tereza Cavazos, John Clague, Declan Conway, Paul M. Della-Marta, Markus Gerber, Sunling Gong, B. N. Goswami, Mark Hemer, Christian Huggel, Bart van den Hurk, Viatcheslav V. Kharin, Akio Kitoh, Albert M.G. Klein Tank, Guilong Li, Simon Mason, William McGuire, Geert Jan van Oldenborgh, Boris Orlowsky, Sharon Smith, Wassila Thiaw, Adonis Velegrakis, Pascal Yiou, Tingjun Zhang, Tianjun Zhou, Francis W. Zwiers
- Edited by Christopher B. Field, Vicente Barros, Thomas F. Stocker, Qin Dahe
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- Book:
- Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation
- Published online:
- 05 August 2012
- Print publication:
- 28 May 2012, pp 109-230
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Summary
Executive Summary
This chapter addresses changes in weather and climate events relevant to extreme impacts and disasters. An extreme (weather or climate) event is generally defined as the occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends (‘tails’) of the range of observed values of the variable. Some climate extremes (e.g., droughts, floods) may be the result of an accumulation of weather or climate events that are, individually, not extreme themselves (though their accumulation is extreme). As well, weather or climate events, even if not extreme in a statistical sense, can still lead to extreme conditions or impacts, either by crossing a critical threshold in a social, ecological, or physical system, or by occurring simultaneously with other events. A weather system such as a tropical cyclone can have an extreme impact, depending on where and when it approaches landfall, even if the specific cyclone is not extreme relative to other tropical cyclones. Conversely, not all extremes necessarily lead to serious impacts. [3.1]
Many weather and climate extremes are the result of natural climate variability (including phenomena such as El Niño), and natural decadal or multi-decadal variations in the climate provide the backdrop for anthropogenic climate changes. Even if there were no anthropogenic changes in climate, a wide variety of natural weather and climate extremes would still occur. [3.1]
A changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of weather and climate extremes, and can result in unprecedented extremes. Changes in extremes can also be directly related to changes in mean climate, because mean future conditions in some variables are projected to lie within the tails of present-day conditions. Nevertheless, changes in extremes of a climate or weather variable are not always related in a simple way to changes in the mean of the same variable, and in some cases can be of opposite sign to a change in the mean of the variable. Changes in phenomena such as the El Nino-Southern Oscillation or monsoons could affect the frequency and intensity of extremes in several regions simultaneously. [3.1]