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High Mountain Areas FIRST-ORDER DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 1 2 Chapter 2: High Mountain Areas 3 4 Coordinating Lead Authors: Regine Hock (USA), Golam Rasul (Nepal) 5 6 Lead Authors: Carolina Adler (Switzerland), Bolívar Cáceres (Ecuador), Stephan Gruber (Canada), Yukiko 7 Hirabayashi (Japan), Miriam Jackson (Norway), Andreas Kääb (Norway), Shichang Kang (China), Stanislav 8 Kutuzov (Russia), Alexander Milner (UK), Ulf Molau (Sweden), Samuel Morin (France), Ben Orlove (USA) 9 10 Contributing Authors: Simon Allen (Switzerland), Lukas Arenson (Canada), Soumyadeep Baneerjee 11 (India), Lee Brown (UK), Bin Cao (China), Mark Carey (USA), Graham Cogley (Canada), Alex de 12 Sherbinin (USA), Kathrin Dicinson (New Zealand), Nicolas Eckert (France), Marten Geertsema (Canada), 13 Martin Honsberg (Germany), Eran Hood (USA), Matthias Huss (Switzerland), Elizabeth Jimenez Zamora 14 (Bolivia), Jessica Lundquist (USA), Juan Ignacio López Moreno (Spain), Cuicui Mou (China), Jeannette 15 Noetzli (Switzerland), Elisa Palazzi (Italy), Harald Pauli (Austria), Nick Pepin (UK), Christian Rixen 16 (Switzerland), Maria Shahgedanova (UK), Christian Vincent (France), Gesa Weyhenmeyer (Sweden), 17 Pasang Yangjee Sherpa (USA), Teppei Yasunari (Japan), Qinglong You (China), Yangjiang Zhang (China) 18 19 Review Editors: Aditi Mukherji (Nepal), Georg Kaser (Austria) 20 21 Chapter Scientists: Pierre-Marie Lefeuvre (Norway), Santosh Nepal (Nepal) 22 23 Date of Draft: 20 April 2018 24 25 Notes: TSU Compiled Version 26 27 28 Table of Contents 29 30 Executive Summary ......................................................................................................................................... 3 31 2.1 Introduction .............................................................................................................................................. 5 32 2.1.1 Characteristics and Relevance ....................................................................................................... 5 33 2.1.2 Services Provided by the Mountain Cryosphere ............................................................................ 6 34 Box 2.1: How Do We Observe the Cryosphere? ........................................................................................... 7 35 2.2 Changes in the Mountain Cryosphere ................................................................................................... 9 36 Box 2.2: Simulating Changing Climate and Cryosphere in Mountains ..................................................... 9 37 2.2.1 Atmospheric Drivers of Changes in the Mountain Cryosphere ................................................... 10 38 Box 2.3: What is Elevation Dependent Warming? ..................................................................................... 11 39 2.2.2 Snow ............................................................................................................................................. 15 40 2.2.3 Glaciers ........................................................................................................................................ 17 41 2.2.4 Permafrost .................................................................................................................................... 21 42 2.2.5 Lake and River Ice ........................................................................................................................ 23 43 2.2.6 Local, Regional and Global Climate Feedbacks Involving the Mountain Cryosphere ............... 24 44 2.3 Change in Mountain Ecosystems, their Services, Managed System and Human Responses ......... 25 45 2.3.1 Water Supply ................................................................................................................................ 25 46 Box 2.4: How Glaciers, Snow and Permafrost Affect Runoff? .................................................................. 25 47 Box 2.5: Local Adaptation Responses to Cryosphere Shrinkages and Water Shortage in Northwest 48 India ........................................................................................................................................................ 31 49 2.3.2 Other Provisioning Services ......................................................................................................... 34 50 2.3.3 Landslide, Avalanche and Flood Hazards ................................................................................... 34 51 Box 2.6: Challenges to Farmers and Local Population Related to Shrinkages in the Cryosphere: 52 Cordillera Blanca, Peru ......................................................................................................................... 42 53 2.3.4 Terrestrial and Aquatic Biodiversity ............................................................................................ 45 54 2.3.5 Aesthetic and Cultural Services ................................................................................................... 47 55 2.3.6 Livelihood, Habitability and Human Mobility ............................................................................. 51 56 2.4 Synthesis of Risks, Adaptation Experiences, and Pathways to Sustainable Development ............. 54 57 2.4.1 What do We Know Across Regions and Cases ............................................................................. 54 Do Not Cite, Quote or Distribute 2-1 Total pages: 83 FIRST-ORDER DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 1 2.4.2 Linking Adaptation Experiences with Response to Address Global Policy Frameworks ............ 54 2 2.4.3 Key Knowledge Gaps and Open Questions .................................................................................. 54 3 FAQ2.1: How do resilience, adaptation and mitigation of climate change contribute to sustainable 4 development in mountain regions? ...................................................................................................... 56 5 FAQ2.2: Why do not all glaciers retreat with global warming? ............................................................... 56 6 FAQ2.3: How does glacier retreat affect water supplies further downhill? ............................................ 56 7 FAQ2.4: How may climate change alter the tourism industry and livelihoods that depend on it? ....... 56 8 References ....................................................................................................................................................... 57 9 10 Do Not Cite, Quote or Distribute 2-2 Total pages: 83 FIRST-ORDER DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 1 Executive Summary 2 1 3 It is very likely that most high mountain regions are currently undergoing and will continue to 2 4 undergo significant warming along with global temperature trends (robust evidence, high agreement ). 5 In many cases, temperature trends depend on altitude and are likely to exceed global temperature 6 increases at intermediate altitude levels (roughly corresponding to the 0°C average isotherm) (medium 7 evidence, medium agreement) Precipitation trends are more difficult to detect, but regions and altitude levels 8 corresponding to the snow/rain transition line are very likely to exhibit significant decreases of solid 9 precipitation (robust evidence, high agreement). Other drivers such as the deposition and impact of light 10 absorbing impurities play a significant role in the response of snow and ice to climate change, often leading 11 to amplified responses. {2.2.1} 12 13 It is very likely that long-term seasonal snow conditions (characterized by snow depth, snow water 14 equivalent, season length) undergo and will continue to undergo significant decreases, especially for 15 locations corresponding to typical rain/snow transition altitude (corresponding in general to the mean 16 0°C altitude). In this altitude range, in mid-latitude mountain regions, it is very likely that seasonal snow 17 will undergo a significant reduction in the 21st century (high agreement, high confidence). At higher altitude 18 (i.e., significantly above the mean rain/snow transition altitude), trends are more difficult to detect for past 19 conditions (in part due to the paucity of reliable long-term records), and it is likely that snow conditions will 20 also be reduced in the 21st century, especially for higher global temperature scenarios (medium agreement, 21 medium confidence). {2.2.2} 22 23 Since AR5, mountain glaciers have continued to decline in all glacierized regions with only a few 24 exceptions, and are expected to continue to shrink throughout this century (high confidence). It is likely 25 that the average mountain glacier mass loss rates in the early 21st century are unprecedented during the >70 26 year observational record. Relative volume and area reductions are largest in regions with predominantly 27 smaller glaciers (high confidence). {2.2.3} 28 29 Mountain glacier shrinkage causes a temporary increase in glacier-derived runoff, followed by a 30 decrease (high confidence), the timing and duration of which is regionally highly variable. In some 31 regions with predominantly smaller glaciers, this turning point has already been reached or will be reached in 32 the next two decades. It will be reached in almost all regions by the end of the century (medium confidence). 33 {2.3.1} 34 35 Large permafrost areas, about XXX [PLACEHOLDER FOR SECOND ORDER DRAFT] million 2 36 km , exist in high-mountains (very high confidence) and are subject to warming and thaw that is 37 expected to persist and intensify. In the present-day period (~2005–2015),
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