Editing IPCC:AR6/SROCC/Chapter-1 (section)

=== 1.5.1 Hazards and Opportunities for Natural Systems, Ecosystems, and Human Systems ===

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Hazards faced by marine and coastal organisms, and the ecosystem services they provide are generally dependent on future greenhouse gas emission pathways, with moderate likelihood under a low-emission future, but high to very high likelihood under higher emission scenarios ( ''very high confidence'' ) (Mora et al., 2013 <sup>[[#fn:r221|221]]</sup> ; Gattuso et al., 2015 <sup>[[#fn:r222|222]]</sup> ). Hazards to marine ecosystems assessed in AR5 (IPCC, 2014 <sup>[[#fn:r223|223]]</sup> ) included degradation of coral reefs ( ''high confidence'' ), ocean deoxygenation ( ''medium confidence'' ) and ocean acidification ( ''high confidence'' ). Shifts in the ranges of plankton and fish were identified with ''high confidence'' regionally, but with uncertain trends globally. SROCC provides more evidence for global shifts in the distribution of marine organisms, and in how the phenology of animals is responding to ocean change (Sections 3.2.3, 5.2). The signature of climate change is now detected in almost all marine ecosystems. Similar trends of changing habitat due to climate change are reported for the cryosphere (Sections 2.2, 3.4.3.2). The risk of irreversible loss of many marine and coastal ecosystems increases with global warming, especially at 2°C or more ( ''high confidence'' ; IPCC, 2018 <sup>[[#fn:r224|224]]</sup> ). Risk also increases for habitat displacements, both poleward (Section 3.2.4) and to greater ocean depths (Section 5.2.4), or habitat reductions, such as that caused by glacier retreat (Section 2.2.3).

Changes in the ocean and cryosphere bring hazards that affect the health, wellbeing, safety and security of populations in coastal, mountain and polar environments (Section 2.3.5, 3.4.3, 4.3.2). Some impacts are direct, such as sea level rise or coastal erosion that can displace coastal residents (4.3.2.3, 4.4.2.6, Box 4.1) . Other effects are indirect; for example, rising ocean temperatures have led to increases in maximum wind speed and rainfall rates in tropical cyclones (Section 6.3), creating hazards with severe consequences for natural and human systems (Sections 4.3, 6.2, 6.3, 6.8). The multiple category 4 and 5 Atlantic hurricanes in 2017 caused the loss of over 3300 lives and more than 350 billion USD in economic damages (Cross-Chapter Box 9; Andrade et al., 2018 <sup>[[#fn:r225|225]]</sup> ; Murakami et al., 2018 <sup>[[#fn:r226|226]]</sup> ; NOAA, 2018 <sup>[[#fn:r227|227]]</sup> ). In mountain regions, glacial lake outburst floods have caused severe impacts on lives, livelihoods and infrastructure that often extend beyond the directly affected areas (Section 2.3.2 and 6.2.2). Some hazards related to ocean and cryosphere change involve abrupt and irreversible changes (Section 1.3), which generate sometimes unpredictable risks, and multiple hazards can coincide to greatly elevate the total risk (Section 6.8.2). For example, combinations of thawing permafrost, sea level rise, loss of sea ice, ocean surface waves and extreme weather events (Thomson and Rogers, 2014 <sup>[[#fn:r228|228]]</sup> ; Ford et al., 2017 <sup>[[#fn:r229|229]]</sup> ) have damaged Arctic infrastructure (e.g., buildings, roads) (AMAP, 2015 <sup>[[#fn:r230|230]]</sup> ; AMAP, 2017 <sup>[[#fn:r231|231]]</sup> ), impacted reindeer husbandry livelihoods for Sami and other Arctic Indigenous peoples and impeded access to hunting grounds, other communities and travel routes fundamental to the livelihoods, food security and wellbeing of Inuit and other Northern cultures (Section 3.4.3). In some Arctic regions, tipping points may have already been reached such that adaptive practices can no longer work (Section 3.5).

Climate change impacts on the ocean and cryosphere can also present opportunities, in at least the near- and medium-term. For example, in Nepal warming of high mountain environments and accelerated melting of snow and ice have extended the growing season and crop yields in some regions (Section 2.3; Gaire et al., 2015 <sup>[[#fn:r232|232]]</sup> ; Merrey et al., 2018 <sup>[[#fn:r233|233]]</sup> ), while tourism and shipping has increased in the Arctic with loss of sea ice (Section 3.2.4). Moreover, rising ocean temperatures redistribute the global fish population, allowing new fishing opportunities while reducing some established fisheries (Bell et al., 2011 <sup>[[#fn:r234|234]]</sup> ; Fenichel et al., 2016 <sup>[[#fn:r235|235]]</sup> ; Section 5.4). To gain from new opportunities, while also avoiding or mitigating new or increasing hazards, it is necessary to be aware of trade-offs between risks and benefits to understand who is and is not benefiting. For example, opportunities can involve trade-offs with mitigation and/or SDGs (Section 3.5.2), and the balance of economic costs and benefits may differ substantially between the near-term and long-term future (Section 5.4.2.2).

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