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

==== CCP5.2.7.1 Observed Impacts and Attribution to Anthropogenic Climate Change ====

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The assessment of observed impacts identified a large number of impacts across all major mountain regions of the world and for a large variety of systems, based on more than 300 references (SMCCP5.2). The literature was assessed and the results classified on a per-region and per-system basis. Confidence statements on detection and attribution are based on expert judgement following IPCC guidelines ( [[IPCC:Wg2:Chapter:Chapter-1#1.3.4|Section 1.3.4]] ), building on evidence from multiple sources in the literature ( [[#Mach--2017|Mach et al., 2017]] ) (SMCCP5.2). Figure CCP5.4 provides an overview of the assessment results.

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'''Figure CCP5.4 |''' '''Synthesis of detection and attribution of impacts of anthropogenic climate change on different natural and human systems in mountain regions.''' For each system and region assessed, the level of confidence for detection and for attribution to anthropogenic climate change is indicated. Also indicated is how strong the contribution of climate change is to the observed changes, considering climatic and non-climatic causal factors. Observed impacts were analysed in terms of negative impacts (e.g., economic or non-economic damages, losses, contribution to increasing risks for society), where the numbers refer to the percentage of references indicating negative impacts for a given impact. The percentage of local community perception indicates the percentage of all literature references for a given system and region that account for local knowledge. The number of references refers to the total number of literature references considered for an impact on a specific system and region. ‘Not assessed’ refers to ''limited evidence'' in the literature (SMCCP5.2 and Table SMCCP5.5–5.14).

Climate change impacts have been documented in mountains on all continents. A wide range of human and natural systems have been affected by climate change to date, including the cryosphere, water resources, terrestrial and aquatic ecosystems, agriculture, tourism, energy production, infrastructure, health and life, migration, disasters and community and cultural values. The confidence levels for the detection of impacts are generally in the range of medium to high. The contribution of climate change to detected impacts varies depending on the affected system and on climatic and non-climatic drivers. The highest levels of confidence for the attribution of detected impacts to anthropogenic climate change are related to the cryosphere. More generally, those impacts are more strongly driven by increasing temperatures and show higher confidence for attribution than those impacts driven mainly by precipitation changes. The level of contribution of climate change to observed impacts is predominantly medium or high, indicating the high sensitivity of natural and human systems in mountains to climate change. Furthermore, the vast majority of detected impacts imply negative impacts on natural and human systems ( ''high confidence'' ).

Local knowledge plays an important role in documenting impacts of climate change in mountain regions. Since IPCC AR5, the evidence for meaningful climate change impacts being reported using local knowledge sources has increased substantially ( ''high confidence'' ). Similarly, important regional gaps present in the IPCC AR5 are addressed here (e.g., Africa), resulting in a much more comprehensive and regionally balanced assessment and perspective.

Furthermore, the science of attributing negative impacts of climate change to anthropogenic emissions or even individual polluters is becoming increasingly important for climate litigation ( [[#Marjanac--2017|Marjanac et al., 2017]] ; [[#McCormick--2017|McCormick et al., 2017]] ; [[#Otto--2017|Otto et al., 2017]] ; [[#Setzer--2019|Setzer and Vanhala, 2019]] ), and there is emerging evidence that mountains are becoming sites of litigation cases, with cases, for instance, in Peru, Colombia and India ( [[#UNEP--2017|UNEP, 2017]] ). Recent studies put litigation cases such as the Lliuya vs RWE (the German multi-national energy company) case, on the risk of glacier lake floods in Peru, in a broader context of differentiated responsibilities and justice ( [[#Huggel--2020b|Huggel et al., 2020b]] ).

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