2 High Mountain Areas
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SPM2 High Mountain Areas Coordinating Lead Authors: Regine Hock (USA), Golam Rasul (Nepal) Lead Authors: Carolina Adler (Switzerland/Australia), Bolívar Cáceres (Ecuador), Stephan Gruber (Canada/ Germany), Yukiko Hirabayashi (Japan), Miriam Jackson (Norway), Andreas Kääb (Norway), Shichang Kang (China), Stanislav Kutuzov (Russian Federation), Alexander Milner (UK), Ulf Molau (Sweden), Samuel Morin (France), Ben Orlove (USA), Heidi Steltzer (USA) Contributing Authors: Simon Allen (Switzerland), Lukas Arenson (Canada), Soumyadeep Banerjee (India), Iestyn Barr (UK), Roxana Bórquez (Chile), Lee Brown (UK), Bin Cao (China), Mark Carey (USA), Graham Cogley (Canada), Andreas Fischlin (Switzerland), Alex de Sherbinin (USA), Nicolas Eckert (France), Marten Geertsema (Canada), Marca Hagenstad (USA), Martin Honsberg (Germany), Eran Hood (USA), Matthias Huss (Switzerland), Elizabeth Jimenez Zamora (Bolivia), Sven Kotlarski (Switzerland), Pierre-Marie Lefeuvre (Norway/France), Juan Ignacio López Moreno (Spain), Jessica Lundquist (USA), Graham McDowell (Canada), Scott Mills (USA), Cuicui Mou (China), Santosh Nepal (Nepal), Jeannette Noetzli (Switzerland), Elisa Palazzi (Italy), Nick Pepin (UK), Christian Rixen (Switzerland), Maria Shahgedanova (UK), S. McKenzie Skiles (USA), Christian Vincent (France), Daniel Viviroli (Switzerland), Gesa Weyhenmeyer (Sweden), Pasang Yangjee Sherpa (Nepal/USA), Nora M. Weyer (Germany), Bert Wouters (Netherlands), Teppei J. Yasunari (Japan), Qinglong You (China), Yangjiang Zhang (China) Review Editors: Georg Kaser (Austria), Aditi Mukherji (Nepal/India) Chapter Scientist: Pierre-Marie Lefeuvre (Norway/France), Santosh Nepal (Nepal) This chapter should be cited as: Hock, R., G. Rasul, C. Adler, B. Cáceres, S. Gruber, Y. Hirabayashi, M. Jackson, A. Kääb, S. Kang, S. Kutuzov, A. Milner, U. Molau, S. Morin, B. Orlove, and H. Steltzer, 2019: High Mountain Areas. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press. 131 Chapter 2 High Mountain Areas Table of contents Executive Summary ..................................................................................... 133 2.4 International Policy Frameworks and Pathways to Sustainable Development .............. 173 2.1 Introduction ........................................................................................... 136 2.5 Key Gaps in Knowledge and Prospects .......................... 174 2.2 Changes in the Mountain Cryosphere ............................. 137 References .............................................................................................................. 176 2.2.1 Atmospheric Drivers of Changes in the Mountain Cryosphere ............................................. 137 Appendix 2.A: Additional Information 2 Box 2.1: Does Atmospheric Warming on Global and Regional Glacier Mass Change in the Mountains Depend on Elevation? ........................... 138 Estimates for 2006–2015 ....................................................................... 199 2.2.2 Snow Cover .............................................................................. 140 2.2.3 Glaciers ....................................................................................... 141 Frequently Asked Questions .................................................................... 151 Cross-Chapter Box 6: Glacier Projections FAQ 2.1 How does glacier shrinkage affect in Polar and High Mountain Regions ............................................... 143 river runoff further downhill? ............................ 151 2.2.4 Permafrost ................................................................................ 145 2.2.5 Lake and River Ice ................................................................ 147 Box 2.2: Local, Regional and Global Climate Feedbacks Involving the Mountain Cryosphere.......... 148 2.3 Mountain Social-Ecological Systems: Impacts, Risks and Human Responses ............................. 148 2.3.1 Water Resources ....................................................................... 148 Box 2.3: Local Responses to Water Shortage in northwest India ................................................................................ 156 2.3.2 Landslide, Avalanche and Flood Hazards .............. 158 Box 2.4: Challenges to Farmers and Local Population Related to Shrinkages in the Cryosphere: Cordillera Blanca, Peru ...................................... 164 2.3.3 Ecosystems ............................................................................... 165 2.3.4 Infrastructure and Mining ............................................... 168 2.3.5 Tourism and Recreation ................................................... 168 2.3.6 Cultural Values and Human Well-being ................. 171 2.3.7 Migration, Habitability and Livelihoods ................. 172 132 High Mountain Areas Chapter 2 Executive Summary socioeconomic development (high confidence). Glacier retreat and permafrost thaw have decreased the stability of mountain slopes The cryosphere (including, snow, glaciers, permafrost, lake and and the integrity of infrastructure (high confidence). The number river ice) is an integral element of high mountain regions, which and area of glacier lakes has increased in most regions in recent are home to roughly 10% of the global population. Widespread decades (high confidence), but there is only limited evidence that cryosphere changes affect physical, biological and human systems in the frequency of glacier lake outburst floods (GLOF) has changed. In the mountains and surrounding lowlands, with impacts evident even some regions, snow avalanches involving wet snow have increased in the ocean. Building on the IPCC’s 5th Assessment Report (AR5), (medium confidence), and rain-on-snow floods have decreased at this chapter assesses new evidence on observed recent and projected low elevations in spring and increased at high elevations in winter changes in the mountain cryosphere as well as associated impacts, (medium confidence). The number and extent of wildfires have risks and adaptation measures related to natural and human systems. increased in the Western USA partly due to early snowmelt (medium Impacts in response to climate changes independently of changes in confidence). {2.3.2, 2.3.3} the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Changes in snow and glaciers have changed the amount and Iceland and Scandinavia, which are included in this chapter. seasonality of runoff in snow-dominated and glacier-fed river 2 basins (very high confidence) with local impacts on water resources and agriculture (medium confidence). Winter runoff Observations of cryospheric changes, impacts, has increased in recent decades due to more precipitation falling as and adaptation in high mountain areas rain (high confidence). In some glacier-fed rivers, summer and annual runoff have increased due to intensified glacier melt, but decreased Observations show general decline in low-elevation snow where glacier melt water has lessened as glacier area shrinks. cover (high confidence1), glaciers (very high confidence) and Decreases were observed especially in regions dominated by small permafrost (high confidence) due to climate change in recent glaciers, such as the European Alps (medium confidence). Glacier decades. Snow cover duration has declined in nearly all regions, retreat and snow cover changes have contributed to localized declines especially at lower elevations, on average by 5 days per decade, in agricultural yields in some high mountain regions, including the with a likely2 range from 0–10 days per decade. Low elevation snow Hindu Kush Himalaya and the tropical Andes (medium confidence). depth and extent have declined, although year-to-year variation is There is limited evidence of impacts on operation and productivity high. Mass change of glaciers in all mountain regions (excluding the of hydropower facilities resulting from changes in seasonality and Canadian and Russian Arctic, Svalbard, Greenland and Antarctica) both increases and decreases in water input, for example, in the was very likely -490 ± 100 kg m–2 yr–1 (-123 ± 24 Gt yr–1) in 2006– European Alps, Iceland, Western Canada and USA, and the tropical 2015. Regionally averaged mass budgets were likely most negative Andes. {2.3.1} (less than -850 kg m–2 yr–1) in the southern Andes, Caucasus and the European Alps/Pyrenees, and least negative in High Mountain Asia Species composition and abundance have markedly changed (-150 ± 110 kg m–2 yr–1) but variations within regions are strong. in high mountain ecosystems in recent decades (very high Between 3.6–5.2 million km2 are underlain by permafrost in the confidence), partly due to changes in the cryosphere (high eleven high mountain regions covered in this chapter corresponding confidence). Habitats for establishment by formerly absent species to 27–29% of the global permafrost area (medium confidence). have opened up or been altered by reduced snow cover (high Sparse and unevenly distributed measurements show an increase confidence), retreating glaciers (very high confidence), and thawing in permafrost temperature (high confidence), for example, by of permafrost (medium confidence). Reductions in glacier and 0.19ºC ± 0.05ºC on average for about 28 locations in the European