Editing IPCC:AR6/WGII/Cross-Chapter-Paper-5 (section)

== CCP5.1 Point of Departure ==

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Mountains are an extensive and significant ''typological region'' ( [[IPCC:Wg2:Chapter:Chapter-1#1.3.3|Section 1.3.3]] and Annex II: Glossary) in the context of climate change and sustainable development, with large populations directly or indirectly depending on them. Further, mountains are areas of high biological and cultural diversity that provide vital goods and services—such as water, food, energy, minerals, medicinal plants, tourism and recreation and aesthetic and spiritual values—to people living in and around these mountain regions and in downstream areas. Mountain regions are hotspots of climate-related losses in, for example, ecosystems, landscapes, culture and habitability, and while mountain people are adaptive, resourceful and independent, they live in highly fragile environments and in some regions under challenging socioeconomic circumstances that increase their vulnerability to climate change ( [[#Alfthan--2018|Alfthan et al., 2018]] ).

Chapter 2, ‘High Mountain Areas’, ( [[#Hock--2019|Hock et al., 2019]] ) of the IPCC’s SROCC, presented an assessment of observed changes in the high mountain cryosphere, their impacts in situ and further downstream and the state of adaptation responses to these impacts. Before SROCC, the last time climate change in mountain regions had been systematically assessed in IPCC reports was in [[IPCC:Wg2:Chapter:Chapter-5|Chapter 5]] of the Second Assessment Report (SAR) ( [[#Beniston--1996|Beniston et al., 1996]] ). Projections made at the time for climate-related changes in mountain regions were expected towards the middle and the second half of the 21st century, rather than as early as recent decades ( [[#Haeberli--2021|Haeberli and Beniston, 2021]] ), underscoring the striking pace of change already observed in mountain regions.

Whereas SROCC focused on impacts from a changing climate on the high mountain cryosphere, this CCP on mountains synthesises key relevant content from across the AR6 WGII report with a broader scope on the impacts of and adaptation to climate change in mountain regions as defined for this assessment (Figure CCP5.1, SMCCP5.1). It provides a wider assessment of the solution space and consequences for sustainable development due to climate change in mountain regions and downstream areas.

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'''Figure CCP5.1 |''' '''Delineation of mountain regions in CCP Mountains, population numbers and densities in 2015 and their projections to 2100.'''

'''(a)''' Population in mountain regions in 2015 aggregated per IPCC WGII Continental Regions, considering population densities, mountain areas and total population in mountain regions.

'''(b)''' Population projections in mountain regions by 2100 for different Shared Socioeconomic Pathways (SSP) scenarios.

'''(c)''' Projected changes in population in mountain regions from 2015 to 2100 across five different SSP scenarios, per IPCC WGII Continental Region (SMCCP5.1 and Tables SMCCP5.1–5.4).

To define the geographical scope of the assessment in this CCP and to quantify the human population residing within these regions, the mountain characterisation given by [[#Kapos--2000|Kapos et al. (2000)]] (Figure CCP5.1 a and SMCCP5.1), minus Antarctica, Svalbard and Greenland (which fall under the assessment scope of CCP6 Polar Regions), was employed. This characterisation is consistent with the mountain region extents used in the AR6 WGI report (see AR6 WGI Atlas ( [[#Gutiérrez--2021|Gutiérrez et al., 2021]] )) and yields a global mountainous area of 31.74 million km 2 , which corresponds to approximately 23.5% of the global land surface. In 2015, a total of 1.28 billion people resided in mountain regions as delineated for this CCP (SMCCP5.1).

The scope of the assessment presented in this CCP covers observed and projected climate change impacts in mountains, present, emerging and future key risks and observed adaptation responses, leading to an exploration of the adaptation solution space and climate resilient development (pathways) in mountains. [[IPCC:Wg2:Chapter:Chapter-5#5.2|Section 5.2]] presents observed impacts and adaptation responses by synthesising information on mountains in the sectoral and regional chapters of WGII AR6, additional supporting evidence found in the literature, a detection and attribution assessment (SMCCP5.2) and a reanalysis of the mountain literature collected and synthesised in the Global Adaptation Mapping Initiative (GAMI) (SMCCP5.3). [[IPCC:Wg2:Chapter:Chapter-5#5.3|Section 5.3]] presents an assessment of future key risks in mountains drawing from the regional and sectorial chapters and a key risks assessment carried out for this CCP (SMCCP5.4). [[IPCC:Wg2:Chapter:Chapter-5#5.4|Section 5.4]] explores the solution space for future adaptation opportunities and constraints as well as climate resilient development in mountains. This CCP concludes with key assessment limitations and knowledge gaps and prospects for addressing these gaps in [[IPCC:Wg2:Chapter:Chapter-5#5.5|Section 5.5]] .

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