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

==== 3.4.4.3 Storms and coastal runoff ====

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Storms, wind, waves and inundation can have highly destructive impacts on ocean and coastal ecosystems, as well as the human communities that depend on them (IPCC, 2012; Seneviratne et al., 2012) <sup>[[#fn:r574|574]]</sup> . The intensity of tropical cyclones across the world’s oceans has increased, although the overall number of tropical cyclones has remained the same or decreased ( ''medium confidence'' ) (Section 3.3.6; Elsner et al., 2008; Holland and Bruyère, 2014) <sup>[[#fn:r575|575]]</sup> . The direct force of wind and waves associated with larger storms, along with changes in storm direction, increases the risks of physical damage to coastal communities and to ecosystems such as mangroves ( ''low to medium confidence'' ) (Long et al., 2016; Primavera et al., 2016; Villamayor et al., 2016; Cheal et al., 2017) <sup>[[#fn:r576|576]]</sup> and tropical coral reefs (De’ath et al., 2012; Bozec et al., 2015; Cheal et al., 2017) <sup>[[#fn:r577|577]]</sup> . These changes are associated with increases in maximum wind speed, wave height and the inundation, although trends in these variables vary from region to region (Section 3.3.5). In some cases, this can lead to increased exposure to related impacts, such as flooding, reduced water quality and increased sediment runoff ( ''medium-high confidence'' ) (Brodie et al., 2012; Wong et al., 2014; Anthony, 2016 <sup>[[#fn:r578|578]]</sup> ; AR5, Table 5.1).

Sea level rise also amplifies the impacts of storms and wave action (Section 3.3.9), with ''robust evidence'' that storm surges and damage are already penetrating farther inland than a few decades ago, changing conditions for coastal ecosystems and human communities. This is especially true for small islands (Box 3.5) and low-lying coastal communities, where issues such as storm surges can transform coastal areas (Section 3.4.5; Brown et al., 2018a) <sup>[[#fn:r579|579]]</sup> . Changes in the frequency of extreme events, such as an increase in the frequency of intense storms, have the potential (along with other factors, such as disease, food web changes, invasive organisms and heat stress-related mortality; Burge et al., 2014; Maynard et al., 2015; Weatherdon et al., 2016; Clements et al., 2017) <sup>[[#fn:r580|580]]</sup> to overwhelm the capacity for natural and human systems to recover following disturbances. This has recently been seen for key ecosystems such as tropical coral reefs (Box 3.4), which have changed from coral-dominated ecosystems to assemblages dominated by other organisms such as seaweeds, with changes in associated organisms and ecosystem services ( ''high confidence'' ) (De’ath et al., 2012; Bozec et al., 2015; Cheal et al., 2017; Hoegh-Guldberg et al., 2017; Hughes et al., 2017a, b) <sup>[[#fn:r581|581]]</sup> . The impacts of storms are amplified by sea level rise (Section 3.4.5), leading to substantial challenges today and in the future for cities, deltas and small island states in particular (Sections 3.4.5.2 to 3.4.5.4), as well as for coastlines and their associated ecosystems (Sections 3.4.5.5 to 3.4.5.7).

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