Editing IPCC:AR6/WGII/Chapter-8 (section)

==== 8.4.1.1 Exposure and Vulnerability under Different Scenarios and Alternative Development Pathways ====

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At the international and national level, the SSPs ( [[#O’Neill--2017a|O’Neill et al., 2017a]] ) have been developed to outline various development pathways, associated emissions and levels of warming, but also different possible development profiles (i.e., levels of economic growth, poverty, inequality, demographic change, etc.) that are highly relevant for adaptation.

Studies using the SSPs to understand multidimensional poverty are few but growing, and underscore that the impacts of climate change on poverty are extremely sensitive to different levels of warming ( [[#Byers--2018|Byers et al., 2018]] ). Multi-sector risks approximately double between 1.5°C and 2°C global mean temperature (GMT) change, and double again in a +3°C world. Comparing a +1.5°C world pursuing sustainable development (SSP1) to a high-poverty and high-inequality +3°C world (SSP3), [[#Byers--2018|Byers et al. (2018)]] project substantial increases in populations exposed to drought, water stress, heat stress and habitat degradation (see in detail [[#Byers--2018|Byers et al., 2018]] ). While in a +1.5°C world exposed populations increase by 7–17%, the increase within a +3°C plus world is 27–51% ( [[#Byers--2018|Byers et al., 2018]] ; [[#Frame--2018|Frame et al., 2018]] ). Populations in Asia and Africa account for more than 80% of the global population exposed to these phenomena, and within South Asia and the Sahel, up to 90% of populations are exposed. Scenario tools help us to understand the burden of increasing multidimensional poverty, and potential for poverty traps, if mitigation and adaptation measures are not taken rapidly and effectively implemented.

At the national and sub-national levels, studies on development and risk scenarios capture specific challenges, for example, urban growth, demographic change, human health and ageing (e.g., [[#Dong--2015|Dong et al., 2015]] ; [[#Chapman--2019|Chapman et al., 2019]] ). In this regard, local scenarios of human vulnerability can inform future strategies for adapting to hazards such as heatwaves in cities under different socioeconomic development strategies. These scenario approaches allow us to focus on changes in climatic and societal conditions as well as urban transformations. This provides a more comprehensive basis for defining adaptation goals (see [[#Fekete--2019|Fekete, 2019]] ; [[#Birkmann--2021b|Birkmann et al., 2021b]] ). Costs and benefits of different adaptation measures can be assessed against different future scenarios of climatic and societal change.

Contrasting with ‘top-down’ SSP scenarios, ( [[#Berkhout--2014|Berkhout et al., 2014]] ) outline how mesoscale and ‘bottom-up’ scenarios have been developed to inform spatial planning, for example, in the Netherlands. Increasing computational power has opened possibilities for large-scale ‘bottom-up’ simulations of people’s livelihoods in the context of evolving climate change impacts, such as the migration decisions of farmers facing drought in Mexico over the coming century (Bell et al., 2019) and livelihood decisions of people facing coastal flooding in Bangladesh to the year 2100 ( [[#Bell--2021|Bell et al., 2021]] ). Such ‘bottom-up’ scenarios can generate projections about future outcomes, inform mapping and assess future vulnerability, with special emphasis on livelihoods of the poor. Researchers conclude that results of respective scenarios that aim to inform adaptation and risk reduction policies in the context of climate change have to match the frames of the stakeholder ( [[#Berkhout--2014|Berkhout et al., 2014]] ; [[#Conway--2019|Conway et al., 2019]] ). Scenarios that assess potential future vulnerabilities and future capacities for adaptation require more attention, since many approaches for projecting future climate risk still largely overlook non-climatic drivers that determine future vulnerability and exposure ( [[#Windfeld--2019|Windfeld et al., 2019]] ).

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