SECOND 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/Australia), Bolívar Cáceres (Ecuador), Stephan Gruber 7 (Canada/Germany), Yukiko Hirabayashi (Japan), Miriam Jackson (Norway), Andreas Kääb (Norway), 8 Shichang Kang (China), Stanislav Kutuzov (Russia), Alexander Milner (UK), Ulf Molau (Sweden), Samuel 9 Morin (France), Ben Orlove (USA), Heidi Steltzer (USA) 10 11 Contributing Authors: Simon Allen (Switzerland), Lukas Arenson (Canada), Soumyadeep Baneerjee 12 (India), Iestyn Barr (UK), Roxana Bórquez (Chile), Lee Brown (UK), Bin Cao (China), Mark Carey (USA), 13 Graham Cogley (Canada), Alex de Sherbinin (USA), Nicolas Eckert (France), Marten Geertsema (Canada), 14 Martin Honsberg (Germany), Eran Hood (USA), Matthias Huss (Switzerland), Elizabeth Jimenez Zamora 15 (Bolivia), Sven Kotlarski (Switzerland), Pierre-Marie Lefeuvre (Norway/France), Juan Ignacio López 16 Moreno (Spain), Jessica Lundquist (USA), Graham McDowell (Canada), Scott Mills (USA), Cuicui Mou 17 (China), Santosh Nepal (Nepal), Jeannette Noetzli (Switzerland), Elisa Palazzi (Italy), Nick Pepin (UK), 18 Christian Rixen (Switzerland), Maria Shahgedanova (UK), Pasang Yangjee Sherpa (Nepal/USA), S. 19 McKenzie Skiles (USA), Isabella Velicogna (USA), Christian Vincent (France), Daniel Viviroli 20 (Switzerland), Gesa Weyhenmeyer (Sweden), Pasang Yangjee Sherpa (USA), Teppei Yasunari (Japan), 21 Qinglong You (China), Yangjiang Zhang (China) 22 23 Review Editors: Aditi Mukherji (Nepal), Georg Kaser (Austria) 24 25 Chapter Scientists: Pierre-Marie Lefeuvre (Norway/France), Santosh Nepal (Nepal) 26 27 Date of Draft: 16 November 2018 28 29 Notes: TSU Compiled Version 30 31 32 Table of Contents 33 34 Executive Summary ......................................................................................................................................... 3 35 2.1 Introduction .............................................................................................................................................. 7 36 2.2 Changes in the Mountain Cryosphere ................................................................................................... 8 37 2.2.1 Atmospheric Drivers of Changes in the Mountain Cryosphere ..................................................... 8 38 Box 2.1: What is Elevation Dependent Warming? ....................................................................................... 9 39 2.2.2 Snow Cover .................................................................................................................................. 11 40 2.2.3 Glaciers ........................................................................................................................................ 14 41 2.2.4 Permafrost .................................................................................................................................... 17 42 2.2.5 Lake and River Ice ........................................................................................................................ 20 43 Box 2.2: Local, Regional and Global Climate Feedbacks Involving the Mountain Cryosphere ............ 20 44 2.3 Change in Mountain Ecosystems, their Services, Managed System and Human Responses ......... 21 45 2.3.1 Water ............................................................................................................................................ 21 46 FAQ2.1: How does glacier shrinkage affect water supplies further downhill? ....................................... 23 47 Box 2.3: Local Adaptation Responses to Cryosphere Shrinkages and Water Shortage in Northwest 48 India ........................................................................................................................................................ 27 49 2.3.2 Landslide, Avalanche and Flood Hazards ................................................................................... 30 50 Box 2.4: Challenges to Farmers and Local Population Related to Shrinkages in the Cryosphere: 51 Cordillera Blanca, Peru ......................................................................................................................... 36 52 2.3.3 Biodiversity ................................................................................................................................... 37 53 2.3.4 Tourism and Recreation ............................................................................................................... 41 54 2.3.5 Spiritual and Intrinsic Values, and Human Well-being ............................................................... 43 55 2.3.6 Impacts on Household Economics, Residence Patterns and Habitability, and National 56 Economies .................................................................................................................................... 44 57 2.4 Key Knowledge Gaps, Global Policy Frameworks and Pathways to Sustainable Development ... 47 Do Not Cite, Quote or Distribute 2-1 Total pages: 106 SECOND ORDER DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 1 2.4.1 Key Gaps in Knowledge and Evidence ........................................................................................ 47 2 2.4.2. High Mountains, Global Policy Frameworks, and Climate-resilient Development Pathways ... 48 3 References ....................................................................................................................................................... 50 4 Appendix 2.A: Supplementary Material...................................................................................................... 74 5 6 Do Not Cite, Quote or Distribute 2-2 Total pages: 106 SECOND ORDER DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 1 Executive Summary 2 3 The cryosphere, which includes glaciers, snow cover, permafrost, and river/lake ice, is a prominent feature in 4 high mountain environments influencing down valley lowlands far beyond the mountains themselves. Recent 5 and projected changes in the mountain cryosphere and associated risks and impacts on a multitude of societal 6 needs, including adaptation responses, are synthesized in this chapter. 7 8 How has the High Mountain Cryosphere changed? Why and what have been the Impacts and 9 Responses? 10 11 High mountain regions, as part of the global climate system, have experienced significant warming 12 since the beginning of the 20th century and decrease in snowfall below the mean snowline elevation 1 13 (very high confidence ). Temperature trends often increased with increasing elevations or were more 14 pronounced around the mean 0°C elevation (medium confidence). Total precipitation often showed 15 insignificant trends, and experienced large variability (high confidence). {2.2.1.1, 2.2.1.2, Box 2.1} 16 17 The snow cover amount and duration has declined in many high mountain regions since the beginning 18 of the 20th century, especially at or below the mean snowline elevation (very high confidence) although 19 subject to high variability. The decline is mostly due to atmospheric warming and associated decrease in 20 snowfall and increase in snow melt (very high confidence). {2.2.2} 21 22 The vast majority of glaciers in all high mountain regions have been retreating and losing mass during 23 the last two decades (very high confidence). Mass losses from the glaciers in 11 glacierized mountain -2 -1 2 -1 24 regions increased from 470 ± 80 kg m yr in the period 1986-2005 to 610 ± 90 kg m yr between 2006- 2 -1 25 2015. Regional-scale average mass losses in units of kg m yr in the latter period were largest in the 2 -1 26 southern Andes, the low latitudes and central Europe (>900 kg m yr ), and smallest in High Mountain Asia 2 -1 27 (190 kg m yr ), where mass budgets have been balanced or slightly positive in some regions due to local 28 meteorological conditions partially counteracting the effects of increasing air temperatures. {2.2.3.1} 29 30 In situ measurements in the European Alps, Scandinavia, and the Tibet Plateau show that permafrost 31 has undergone warming, degradation and ground-ice loss in the past two decades (high confidence). 32 The observed rates of change in the 21st century are higher than in the late 20th century (medium 33 confidence). Other mountain regions lack in-situ observations to assess trends. {2.2.4} 34 35 Glacier shrinkage and snow cover changes have led to changes in the amount and timing of river 36 runoff in many mountain regions during the last two decades (high confidence). In some regions with 37 predominantly small glaciers (e.g., western USA and Canada), runoff from glaciers has decreased due to 38 glacier shrinkage while in other regions typically with larger glaciers (e.g., Alaska) runoff from glaciers has 39 increased (medium confidence) {2.3.1}. Runoff changes have caused significant shifts in downstream 40 nutrients (dissolved organic carbon, nitrogen, phosphorus) and influenced water quality through increases in 41 heavy metals, particularly mercury, and other legacy contaminants. {2.3.1.2} 42 43 The decline of the cryosphere in recent decades has affected the frequency and magnitude of some 44 natural hazards. Retreat of mountain glaciers and thaw of mountain permafrost has decreased the stability 45 of mountain slopes (high confidence). Glacier retreat has led to an increasing number and area of glacier 46 lakes (high confidence, medium agreement) {2.3.2.1}. Over the past decades, there has been