Editing IPCC:AR6/SR15/Chapter-3 (section)

===== 3.4.10.2 The changing structure of communities: migration, displacement and conflict =====

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'''Migration:''' In AR5, the potential impacts of climate change on migration and displacement were identified as an emerging risk (Oppenheimer et al., 2014) <sup>[[#fn:r1076|1076]]</sup> . The social, economic and environmental factors underlying migration are complex and varied; therefore, detecting the effect of observed climate change or assessing its possible magnitude with any degree of confidence is challenging (Cramer et al., 2014) <sup>[[#fn:r1077|1077]]</sup> .

No studies have specifically explored the difference in risks between 1.5°C and 2°C of warming on human migration. The literature consistently highlights the complexity of migration decisions and the difficulties in attributing causation (e.g., Nicholson, 2014; Baldwin and Fornalé, 2017; Bettini, 2017; Constable, 2017; Islam and Shamsuddoha, 2017; Suckall et al., 2017) <sup>[[#fn:r1078|1078]]</sup> . The studies on migration that have most closely explored the probable impacts of 1.5°C and 2°C have mainly focused on the direct effects of temperature and precipitation anomalies on migration or the indirect effects of these climatic changes through changing agriculture yield and livelihood sources (Mueller et al., 2014; Piguet and Laczko, 2014; Mastrorillo et al., 2016; Sudmeier-Rieux et al., 2017) <sup>[[#fn:r1079|1079]]</sup> .

Temperature has had a positive and statistically significant effect on outmigration over recent decades in 163 countries, but only for agriculture-dependent countries (R. Cai et al., 2016) <sup>[[#fn:r1080|1080]]</sup> . A 1°C increase in average temperature in the International Migration Database of the Organisation for Economic Co-operation and Development (OECD) was associated with a 1.9% increase in bilateral migration flows from 142 sending countries and 19 receiving countries, and an additional millimetre of average annual precipitation was associated with an increase in migration by 0.5% (Backhaus et al., 2015) <sup>[[#fn:r1081|1081]]</sup> . In another study, an increase in precipitation anomalies from the long-term mean, was strongly associated with an increase in outmigration, whereas no significant effects of temperature anomalies were reported (Coniglio and Pesce, 2015) <sup>[[#fn:r1082|1082]]</sup> .

Internal and international migration have always been important for small islands (Farbotko and Lazrus, 2012; Weir et al., 2017) <sup>[[#fn:r1083|1083]]</sup> . There is rarely a single cause for migration (Constable, 2017) <sup>[[#fn:r1084|1084]]</sup> . Numerous factors are important, including work, education, quality of life, family ties, access to resources, and development (Bedarff and Jakobeit, 2017; Speelman et al., 2017; Nicholls et al., 2018) <sup>[[#fn:r1085|1085]]</sup> . Depending on the situation, changing weather, climate or environmental conditions might each be a factor in the choice to migrate (Campbell and Warrick, 2014) <sup>[[#fn:r1086|1086]]</sup> .

'''Displacement:''' At 2°C of warming, there is a potential for significant population displacement concentrated in the tropics (Hsiang and Sobel, 2016) <sup>[[#fn:r1087|1087]]</sup> . Tropical populations may have to move distances greater than 1000 km if global mean temperature rises by 2°C from 2011–2030 to the end of the century. A disproportionately rapid evacuation from the tropics could lead to a concentration of population in tropical margins and the subtropics, where population densities could increase by 300% or more (Hsiang and Sobel, 2016) <sup>[[#fn:r1088|1088]]</sup> .

'''Conflict:''' A recent study has called for caution in relating conflict to climate change, owing to sampling bias (Adams et al., 2018) <sup>[[#fn:r1089|1089]]</sup> . Insufficient consideration of the multiple drivers of conflict often leads to inconsistent associations being reported between climate change and conflict (e.g., Hsiang et al., 2013; Hsiang and Burke, 2014; Buhaug, 2015, 2016; Carleton and Hsiang, 2016; Carleton et al., 2016) <sup>[[#fn:r1090|1090]]</sup> . There also are inconsistent relationships between climate change, migration and conflict (e.g., Theisen et al., 2013; Buhaug et al., 2014; Selby, 2014; Christiansen, 2016; Brzoska and Fröhlich, 2016; Burrows and Kinney, 2016; Reyer et al., 2017c; Waha et al., 2017) <sup>[[#fn:r1091|1091]]</sup> . Across world regions and from the international to micro level, the relationship between drought and conflict is weak under most circumstances (Buhaug, 2016; von Uexkull et al., 2016) <sup>[[#fn:r1092|1092]]</sup> . However, drought significantly increases the likelihood of sustained conflict for particularly vulnerable nations or groups, owing to the dependence of their livelihood on agriculture. This is particularly relevant for groups in the least developed countries (von Uexkull et al., 2016) <sup>[[#fn:r1093|1093]]</sup> , in sub-Saharan Africa (Serdeczny et al., 2016; Almer et al., 2017) <sup>[[#fn:r1094|1094]]</sup> and in the Middle East (Waha et al., 2017) <sup>[[#fn:r1095|1095]]</sup> . Hsiang et al. (2013) <sup>[[#fn:r1096|1096]]</sup> reported causal evidence and convergence across studies that climate change is linked to human conflicts across all major regions of the world, and across a range of spatial and temporal scales. A 1°C increase in temperature or more extreme rainfall increases the frequency of intergroup conflicts by 14% (Hsiang et al., 2013) <sup>[[#fn:r1097|1097]]</sup> . If the world warms by 2°C–4°C by 2050, rates of human conflict could increase. Some causal associations between violent conflict and socio-political instability were reported from local to global scales and from hour to millennium time frames (Hsiang and Burke, 2014) <sup>[[#fn:r1098|1098]]</sup> . A temperature increase of one standard deviation increased the risk of interpersonal conflict by 2.4% and intergroup conflict by 11.3% (Burke et al., 2015a) <sup>[[#fn:r1099|1099]]</sup> . Armed-conflict risks and climate-related disasters are both relatively common in ethnically fractionalized countries, indicating that there is no clear signal that environmental disasters directly trigger armed conflicts (Schleussner et al., 2016a) <sup>[[#fn:r1100|1100]]</sup> .

In summary, average global temperatures that extend beyond 1.5°C are projected to increase poverty and disadvantage in many populations globally ( ''medium confidence'' ). By the mid-to late 21st century, climate change is projected to be a poverty multiplier that makes poor people poorer and increases poverty head count, and the association between temperature and economic productivity is not linear ( ''high confidence'' ). Temperature has a positive and statistically significant effect on outmigration for agriculture-dependent communities ( ''medium confidence'' ).

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