High Mountain Areas

Abstract

The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high mountain regions, which are home to roughly 10% of the global population.Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean.Building on the IPCC's 5th Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems.Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter.Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland and Scandinavia, which are included in this chapter. Observations of cryospheric changes, impacts, and adaptation in high mountain areasObservations show general decline in low-elevation snow cover (high confidence 1 ), glaciers (very high confidence) and permafrost (high confidence) due to climate change in recent decades.Snow cover duration has declined in nearly all regions, especially at lower elevations, on average by 5 days per decade, with a likely 2 range from 0-10 days per decade.Low elevation snow depth and extent have declined, although year-to-year variation is high.Mass change of glaciers in all mountain regions (excluding the Canadian and Russian Arctic, Svalbard, Greenland and Antarctica) was very likely -490 100 kg m -2 yr -1 (-123 24 Gt yr -1 ) in 2006-2015.Regionally averaged mass budgets were likely most negative (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 (-150 110 kg m -2 yr -1 ) but variations within regions are strong.Between 3.6-5.2 million km 2 are underlain by permafrost in the eleven high mountain regions covered in this chapter corresponding to 27-29% of the global permafrost area (medium confidence).Sparse and unevenly distributed measurements show an increase in permafrost temperature (high confidence), for example, by 0.19C 0.05C on average for about 28 locations in the European Alps, Scandinavia, Canada and Asia during the past decade.Other observations reveal decreasing permafrost thickness and loss of ice in the ground.{2.2.2, 2.2.3, 2.2.4}Glacier, snow and permafrost decline has altered the frequency, magnitude and location of most related natural hazards (high confidence).Exposure of people and infrastructure to natural hazards has increased due to growing population, tourism and 1 In this report, the following summary terms are used to describe the available evidence: limited, medium, or robust; and for the degree of agreement: low, medium or high.A level of confidence is expressed using five qualifiers: very low, low, medium, high and very high, and typeset in italics, for example, medium confidence.For a given evidence and agreement statement, different confidence levels can be assigned, but increasing levels of evidence and degrees of agreement are correlated with increasing confidence (see Section 1.9.2 and Figure 1.4 for more details). 2In this report, the following terms have been used to indicate the assessed likelihood of an outcome or

Topics & Concepts