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Chapter 3: Changes in Climate Extremes and Their Impacts On SECOND ORDER DRAFT IPCC SREX Chapter 3 1 2 Chapter 3: Changes in Climate Extremes and their Impacts on the 3 Natural Physical Environment 4 5 Coordinating Lead Authors: 6 Neville Nicholls (Australia), Sonia Seneviratne (Switzerland) 7 8 Lead Authors: 9 David Easterling (USA), Clare Goodess (United Kingdom), Shinjiro Kanae (Japan), James Kossin (USA), Yali Luo 10 (China), Jose Marengo (Brazil), Kathleen McInnes (Australia), Mohamad Rahimi (Iran), Markus Reichstein 11 (Germany), Asgeir Sorteberg (Norway), Carolina Vera (Argentina), Xuebin Zhang (Canada) 12 13 Contributing Authors: 14 Lisa Alexander (Australia), Gerardo Benito (Spain), Tereza Cavazos (Mexico), John Clague (Canada), Declan Conway 15 (UK), Paul Della-Marta (Switzerland), Sunling Gong (Canada), B. N. Goswami (India), Mark Hemer (Australia), Bart 16 van den Hurk (Netherlands), Christian Huggel (Switzerland), Viatcheslav Kharin (Canada), Akio Kitoh (Japan), Albert 17 Klein Tank (Netherlands), Simon Mason (USA), William McGuire (UK), Boris Orlowksy (Switzerland), Wassila 18 Thiaw (USA), Adonis Velegrakis (Greece), Pascal Yiou (France), Tingjun Zhang (USA), Tianjun Zhou (China), 19 Francis Zwiers (Canada) 20 21 22 Table of Contents 23 24 Executive Summary .......................................................................................................................................................... 2 25 3.1. Weather and Climate Events Related to Disasters ............................................................................................... 5 26 3.1.1. Categories of Weather and Climate Events Discussed in this Chapter ......................................................... 5 27 3.1.2. Characteristics of Weather and Climate Events Relevant to Disasters ....................................................... 5 28 3.1.3. Compound (Multiple) Events ....................................................................................................................... 7 29 3.1.4. Feedbacks ..................................................................................................................................................... 8 30 3.1.5. Confidence and Likelihood of Assessed Changes in Extremes ...................................................................... 9 31 3.1.6. Changes in Extremes and Their Relationship to Changes in (Regional and Global) Mean Climate ............ 9 32 3.1.7. Surprises ..................................................................................................................................................... 10 33 3.2. Requirements and Methods for Analysing Changes in Extremes ..................................................................... 11 34 3.2.1. Observed Changes ..................................................................................................................................... 11 35 3.2.2. The Causes Behind the Changes ................................................................................................................. 12 36 3.2.3. Projected Long-Term Changes and Uncertainties ...................................................................................... 15 37 Box 3.1: Variations in Confidence in Projections of Climate Change: Mean vs. Extremes, Variables, Scale ........ 19 38 3.3. Observed and Projected Changes of Weather and Climate Extremes .............................................................. 20 39 3.3.1. Temperature ................................................................................................................................................ 20 40 3.3.2. Precipitation ................................................................................................................................................ 25 41 3.3.3. Wind ............................................................................................................................................................ 31 42 3.4. Observed and Projected Changes in Phenomena Related to Weather and Climate Extremes ...................... 34 43 3.4.1. Monsoons .................................................................................................................................................... 34 44 3.4.2. El Niño – Southern Oscillation ................................................................................................................... 37 45 3.4.3. Other Modes of Variability ......................................................................................................................... 39 46 3.4.4. Tropical Cyclones ....................................................................................................................................... 40 47 3.4.5. Extratropical Cyclones ................................................................................................................................ 45 48 3.5. Observed and Projected Impacts on the Natural Physical Environment ......................................................... 49 49 3.5.1. Droughts ..................................................................................................................................................... 49 50 Box 3.2: The Definition of Drought ............................................................................................................................... 49 51 3.5.2. Floods ......................................................................................................................................................... 55 52 3.5.3. Extreme Sea Levels ..................................................................................................................................... 58 53 3.5.4. Waves .......................................................................................................................................................... 60 54 3.5.5. Coastal Impacts ........................................................................................................................................... 62 55 Box 3.3: Small Islands .................................................................................................................................................... 63 56 3.5.6. Glacier, geomorphological and geological impacts ................................................................................... 66 57 3.5.7. High-Latitude Changes including Permafrost ........................................................................................... 69 58 3.5.8. Sand and Dust Storms ................................................................................................................................. 70 59 FAQ 3.1: Is the Climate Becoming More Extreme? .................................................................................................... 71 60 FAQ 3.2: Can we Determine Whether Climate Change has Affected Individual Extreme Events? ...................... 72 61 References ....................................................................................................................................................................... 74 62 Tables and Figures ....................................................................................................................................................... 111 63 DO NOT CITE, QUOTE OR DISTRIBUTE 1 7 February 2011 SECOND ORDER DRAFT IPCC SREX Chapter 3 1 Executive Summary 2 3 A changing climate can lead to changes in the frequency, intensity or duration of an extreme event, or result in an 4 unprecedented, previously unobserved, extreme. As well, a weather or climate event, although not necessarily extreme 5 in a statistical sense, still may have an extreme impact, either by crossing a critical threshold in a social, ecological or 6 physical system, or because it occurs simultaneously with another event combined with which it leads to extreme 7 conditions or impact. Conversely, not all extremes necessarily lead to serious impacts. Meteorological phenomena such 8 as a tropical cyclone can have an extreme impact, depending on where and when it makes landfall, even if the specific 9 cyclone is not extreme relative to other tropical cyclones. Changes in phenomena such as El Niño – Southern 10 Oscillation or monsoons may affect the frequency and intensity of extremes in several regions simultaneously. [3.1] 11 12 Many weather and climate extremes are the result of natural climate variability (including phenomena such as El Niño), 13 and natural decadal or multi-decadal variations in the climate provide the backdrop for possible anthropogenic changes. 14 Even if there were no anthropogenic changes in climate over the next century, we can still anticipate a wide variety of 15 natural weather and climate extremes to occur. Changes in extremes of a climate or weather variable are not always 16 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 17 change in the mean of the variable (e.g., precipitation intensity may increase in some areas and seasons even if the total 18 precipitation decreases). [3.1] 19 20 There is evidence of some changes in extremes occurring over recent decades (i.e., since 1950). It is very likely that 21 there has been an overall decrease in the number of unusually cold days and nights, and an overall increase in the 22 number of unusually warm days and nights, on the global scale, i.e., for land areas with data It is likely that this 23 statement also applies at the continental scale in North America and Europe,
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