Editing IPCC:AR6/WGII/Chapter-14 (section)

==== 14.5.9.3 Adaptation ====

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Climate hazards undermine adaptation by damaging livelihoods ( ''high confidence'' ). Many actions that enhance and promote resilient livelihoods can have substantial benefit for adaptation to climate hazards ( ''medium confidence'' ). Livelihoods in the context of climate change are characterised by adjustments that then feed back into the assets that comprise a livelihood. Social capital–in the form of household and community cohesion–facilitates the development of adaptation strategies to the impacts of climate change in rural and urban communities at the household level and for small groups ( [[#Barbier--2014|Barbier, 2014]] ; [[#Nawrotzki--2015b|Nawrotzki et al., 2015b]] ; [[#Nawrotzki--2015c|Nawrotzki et al., 2015c]] ). Cultural capital, especially in the form of Indigenous knowledge and local knowledge, can guide adaptation practices in North America ( [[#Akpinar%20Ferrand--2014|Akpinar Ferrand and Cecunjanin, 2014]] ), preserving Indigenous cultures and enhancing future adaptation and resilience (see Box 14.1; [[#Pearce--2012|Pearce et al., 2012]] ; [[#Audefroy--2017|Audefroy and Cabrera Sánchez, 2017]] ). In Mexico, rainwater harvesting (practised by some Mayan communities) and the use of local–traditional varieties of maize have assisted in the adaptation to climate impacts and promoted food security ( [[#Akpinar%20Ferrand--2014|Akpinar Ferrand and Cecunjanin, 2014]] ; [[#Hellin--2014|Hellin et al., 2014]] ). Funding and support for these social adaptation strategies have been uneven ( [[#Barbier--2014|Barbier, 2014]] ; [[#Romeo-Lankao--2014|Romeo-Lankao et al., 2014]] ). The legacy of colonialism and historical patterns of development will continue to shape the adaptation responses and resiliency of Indigenous Peoples ( [[#Todd--2015|Todd, 2015]] ; [[#Davis--2017|Davis and Todd, 2017]] ; [[#Whyte--2017|Whyte, 2017]] ; [[#Cameron--2019|Cameron et al., 2019]] ).

Migration is a common adaptation strategy to maintain and diversify people’s livelihoods and will continue to play an important role when households manage climate and social risks ( ''high confidence'' ) ( [[IPCC:Wg2:Chapter:Chapter-7#7.4.3|Section 7.4.3]] ). In the near term, actions that enhance ''in situ'' adaptive capacities as well as foster safe and orderly migration can result in synergies for both adaptation and development (Cross-Chapter Box MIGRATE in Chapter 7). Populations that experience less mobility or cannot engage in voluntary migration as an adaptation may need additional support to adapt to climate hazards, for example, northern communities that are at risk of climatic events ( [[#Hamilton--2016|Hamilton et al., 2016]] ). Policies associated with the transition from high-GHG intensive extractive industries, sometimes referred to as ‘just transitions’, may also support ''in situ'' livelihoods if they also aim to address and redress existing inequalities to reduce vulnerabilities (McCauley, 2018); however, these policies could result in maladaptation if they create new inequalities or generate other environmental damages.

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'''Box 14.6 | The Costs and Economic Consequences of Climate Change in North America'''
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'''Observed Impacts'''
Extreme weather events, including hurricanes, droughts and flooding, and wildfires, have been partly attributed to anthropogenic climate change ( ''high confidence'' ) (Table SM 16.21; e.g., [[#Rupp--2015|Rupp et al., 2015]] ; [[#Emanuel--2017|Emanuel, 2017]] ). Direct, indirect and non-market economic damages from extreme events have increased in some parts of North America ( ''high confidence'' ). The number of extreme events with inflation-adjusted damages totalling more than 1 billion USD has risen in the USA over the past decades (NOAA, 2020; [[#Smith--2020|Smith, 2020]] ), and similar increases have been observed in Canada ( [[#Boyd--2021|Boyd and Markandya, 2021]] ). Factors other than climate change, including increases in exposure and the value of the assets at risk, also explain increasing damage amounts (Freeman and Ashley, 2017; [[#Vano--2018|Vano et al., 2018]] ). Climate change explains a portion of long-term increases in economic damages of hurricanes ( ''limited evidence, low agreement'' ). Studies of US hurricanes since 1900 have found increasing economic losses that are consistent with an influence from climate change ( [[#Estrada--2015|Estrada et al., 2015]] ; [[#Grinsted--2019|Grinsted et al., 2019]] ), although another study found no increase ( [[#Weinkle--2018|Weinkle et al., 2018]] ).

Formal attribution of economic damages from individual extreme events to anthropogenic climate change has been limited, but climate change could account for a substantial fraction of the damages ( ''limited evidence, medium agreement'' ). Two recent studies have shown approaches for how damages may be attributed for individual events in the USA. Assuming a direct proportionality between attributable risk of the event to the attributable economic damages, one study suggested that 30–75% of the direct damages from Hurricane Harvey was caused by climate change, with a best estimate of 67 billion USD out of an estimated 90 billion USD total of attributable damages ( [[#Frame--2020|Frame et al., 2020]] ). Another study modelled the component of the flooding from Hurricane Sandy due to rising SLR and mapped that to coastal damages. That study estimated that 8.1 billion USD (13% of the total) was attributable to the climate influence on SLR ( [[#Strauss--2021|Strauss et al., 2021]] ).

The effect of climate change has been identified in aggregate measures of economic performance, such as GDP, in North America and globally ( ''medium confidence'' ) '','' although the magnitude of these changes is difficult to constrain ( ''medium confidence'' ) ''.'' Climate change has been observed to affect national GDP level and economic growth ( ''low confidence'' ). The extent to which climate has affected GDP may be challenging to identify statistically (Cross-Working Group Box ECONOMIC in Chapter 16). Observed GDP effects are generally slightly negative in the USA, higher and negative for Mexico, and the directionality of the effects in Canada varies by study and modelling approach ( [[#Burke--2015|Burke et al., 2015]] ; [[#Colacito--2018|Colacito et al., 2018]] ; [[#Kahn--2019|Kahn et al., 2019]] ).

'''Projected Risks'''
Projections of market and non-market economic damages demonstrate the substantial economic risks of climate impacts associated with high-temperature pathways (RCP8.5) ( ''high confidence'' ). Since AR5, a wide range of estimates of the costs of climate change have been developed for the USA ( [[#EPA--2015a|EPA, 2015a]] ; [[#Houser--2015|Houser et al., 2015]] ; [[#EPA--2017|EPA, 2017]] ; [[#Hsiang--2017|Hsiang et al., 2017]] ; [[#Martinich--2019|Martinich and Crimmins, 2019]] ), with ongoing processes to update national estimates for Canada and Mexico ( [[#Semarnat--2009|Semarnat, 2009]] ; [[#NRTEE--2011|NRTEE, 2011]] ; [[#Estrada--2013|Estrada et al., 2013]] ; [[#Sawyer--2020|Sawyer et al., 2020]] ). While the magnitudes of the estimates depend on approach and assumptions in the methods and expectations of future socioeconomic conditions, these studies show substantial projected economic damages across North America by the end of the century, especially for warming greater than 4°C ( ''high evidence, high agreement'' ). Whether these damages translate into GDP effects is not clear for Canada. Some modelling approaches show modest GDP increases in 2050 and 2100, while others suggest modest decreases although it is anticipated that the economic effects for Canada will be large and negative ( [[#Boyd--2021|Boyd and Markandya, 2021]] ). Large costs and risks, such as those associated with extreme events such as wildfires ( [[#Hope--2016|Hope et al., 2016]] ) and the increased need for infrastructure replacement ( [[#Neumann--2015|Neumann et al., 2015]] ; [[#Maxwell--2018a|Maxwell et al., 2018a]] ), will have compounding effects in the markets by disrupting economic activities (see Box 14.5).

Market and non-market risks and costs will not be experienced equally across countries, sectors and regions in North America ( ''high confidence'' ). For the USA, energy expenditures and improvements in agricultural yields are projected to result in net gains in the north and Pacific Northwest whereas in the south, higher heat-related mortality, increases in energy expenditures, SLR and storm surge are projected to result in economic losses by the end of century ( [[#Hsiang--2017|Hsiang et al., 2017]] ). No region in the USA is expected to avoid some level of adverse effects ( ''medium evidence, high agreement'' ) ( [[#EPA--2017|EPA, 2017]] ; [[#Martinich--2019|Martinich and Crimmins, 2019]] ). Economic models generally show losses in the agricultural sector across North America, especially at higher GWL ( [[#Boyd--2021|Boyd and Markandya, 2021]] ; EPA 2017). Some models show large gains in parts of Canada, although these models do not capture the full range of climate hazards including change in precipitation or extreme events ( [[#Boyd--2021|Boyd and Markandya, 2021]] ).

'''Economics of Adaptation Opportunities'''
Economic analysis can help reveal where the avoided economic damages are greater than the costs of adaptation, improving decision making for adaptation planning and efforts in North America ( ''high confidence'' ). Detailed assessment of total needs and costs of climate adaptation are limited ( [[#Sussman--2014|Sussman et al., 2014]] ), but estimates suggest that the costs are large ( ''low evidence, high agreement'' ). Cost–benefit and other economic analyses that incorporate damage estimates are expanding for adaptation decision making ( [[#Li--2014|Li et al., 2014]] ), especially for technical options in areas with high exposure such as coastal areas in Mexico ( [[#Haer--2018|Haer et al., 2018]] ) and Alaskan infrastructure ( [[#Melvin--2017|Melvin et al., 2017]] ). Cost–benefit analysis has also been applied to coordinating planning across jurisdictions in North America for SLR and flood control ( [[#Adeel--2020|Adeel et al., 2020]] ). Adaptation costs in the USA are lower on RCP4.5 compared with RCP8.5 emission pathways ( [[#Martinich--2019|Martinich and Crimmins, 2019]] ). Adaptation, however, cannot be based solely on the cost–benefit analysis due to the high level of uncertainty related to climate risks (Cross-Chapter Box DEEP in Chapter 17).

Improving projections of future economic risk and damages facilitates the development of tools that can be used for economic analysis of climate policies ( ''high confidence'' ). Monetised estimates of the damages from climate change have been developed and refined since AR5, motivated in part by efforts to estimate the Social Cost of Carbon (SCC) ( [[#National%20Academies%20of%20Sciences--2017|National Academies of Sciences, 2017]] ). Support for these efforts and the use of SCC in regulatory analysis of mitigation and adaptation efforts have been pledged across the national and subnational governments of Canada, the USA and Mexico. Harmonising SCC and consistent use can further enhance coordination of mitigation and adaptation decision making ( [[#Auffhammer--2018|Auffhammer, 2018]] ; [[#Aldy--2021|Aldy et al., 2021]] ). Using these damages estimates can also inform other policy and tools that improve the consideration of climate impacts in markets and decision making ( [[#Report%20of%20the%20Climate-Related%20Market%20Risk%20Subcommittee--2020|Report of the Climate-Related Market Risk Subcommittee, 2020]] ).

Box 14.6

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