IPCC Report.pdf - Adam Curry

Changes in Impacts of Climate Extremes: Human Systems and EcosystemsChapter 4The number and size of coastal settlements and their associatedinfrastructure have increased significantly over recent decades(McGranahan et al., 2007; Hanson et al., 2011; see also Case Study9.2.8). In many cases these settlements have affected the ability ofnatural coastal systems to respond effectively to extreme climate eventsby, for example, removing the protection provided by sand dunes andmangroves. Small island states, particularly small island developingstates (see Case Study 9.2.9), may face substantial impacts from climatechange-related extremes.Urbanization exacerbates the negative effects of flooding throughgreatly increased runoff concentration, peak, and volume, the increasedoccupation of flood plains, and often inadequate drainage planning(McGranahan et al., 2007; Douglas et al., 2008). These urbanizationissues are universal but often at their worst in informal settlements,which are generally the most exposed to flooding and usually do nothave the capacity to deal with the issues (Hardoy et al., 2001). Floodingregularly disrupts cities, and urban food production can be severelyaffected by flooding, undermining local food security in poor communities(Douglas, 2009; Aggarwal and Singh, 2010). A further concern for lowandmiddle-income cities as a result of flooding, particularly in developingcountries, is human waste, as most of these cities are not served byproper water services such as sewers, drains, or solid waste collectionservices (Hardoy et al., 2001).Slope failure can affect settlements in tropical mountainous areas,particularly in deforested areas (e.g., Vanacker et al., 2003)and hillyareas (Loveridge et al., 2010), and especially following heavy prolongedrain (e.g., see Case Study 9.2.5). Informal settlements are often exposedto potential slope failure as they are often located on unstable land withno engineering or drainage works (Alexander, 2005; Anderson et al.,2007). Informal settlements have been disproportionately badly impactedby landslides in Colombia and Venezuela in the past (e.g., Takahashi etal., 2001; Ojeda and Donnelly, 2006) and were similarly affected in 2010during unusual heavy rains associated with the La Niña weatherphenomenon (NCDC, 2011). Densely settled regions in the Alps (Crostaet al., 2004) and Himalayas have been similarly impacted (Petley et al.,2007).Cities can substantially increase local temperatures and reducetemperature drop at night (e.g., see Case Study 9.2.1). This is the urbanheat island effect resulting from the large amount of heat-absorbingmaterial, building characteristics, and emissions of anthropogenic heatfrom air conditioning units and vehicles (e.g., Rizwan et al., 2008; for acritical review of heat island research, see Stewart, 2011). Heat wavescombined with urban heat islands (Basara et al., 2010; Tan et al., 2010)can result in large death tolls with the elderly, the unwell, the sociallyisolated, and outdoor workers (Maloney and Forbes, 2011) beingespecially vulnerable, although acclimatization and heat health-warningsystems can substantially reduce excess deaths (Fouillet et al., 2008).Heat waves thus pose a future challenge for major cities (e.g., Endlicheret al., 2008; Bacciniet al., 2011; for London, Wilby, 2003). In urban areas,heat waves also have negative effects on air quality and the number ofdays with high pollutants, ground level ozone, and suspended particleconcentrations (Casimiro and Calheiros, 2002; Sanderson et al., 2003;Langner et al., 2005).The largest impacts from coastal inundation due to sea level rise (and/orrelative sea level rise) in low-elevation coastal zones (i.e., coastal areaswith an elevation less than 10 m above present mean sea level; seeMcGranahan et al., 2007) are thought to be associated with extremesea levels due to tropical and extratropical storms (e.g., Ebersole et al.,2010; Mozumder et al., 2011) that will be superimposed upon the longtermsea level rise (e.g., Frazier et al., 2010). An increase in the meanmaximum wind speed of tropical cyclones is likely over the 21st century,but possibly not in all ocean basins (see Table 3-1). The destructivepotential of tropical cyclones may increase in some regions as a resultof this projected increase in intensity of mean maximum wind speedand tropical cyclone-related rainfall rates (see Section 3.4.4). Stormsgenerally result in considerable disruption and local destruction, butcyclones and their associated storm surges have in some cases causedvery substantial destruction in modern cities (e.g., New Orleans andDarwin; see also Case Study 9.2.5). The impacts are considered to bemore severe for large urban centers built on deltas and small islandstates (McGranahan et al., 2007; Love et al., 2010; Wardekker et al.,2010), particularly for those at the low end of the international incomedistribution (Dasgupta et al., 2009). The details of exposure will becontrolled by the natural or human-induced characteristics of the system,for example, the occurrence/distribution of protecting barrier islandsand/or coastal wetlands that may attenuate surges (see, e.g., Irish et al.,2010; Wamsley et al., 2010) or changes such as land reclamation (Guoet al., 2009). Recent studies (Nicholls et al., 2008; Hanson et al., 2011)have assessed the asset exposure of port cities with more than onemillion inhabitants (in 2005). They demonstrated that large populationsare already exposed to coastal inundation (~40 million people or 0.6%of the global population) by a 1-in-100-year extreme event, while thetotal value of exposed assets was estimated at US$ 3,000 billion (~ 5%of the global GDP in 2005). By the 2070s, population exposure wasestimated to triple, whereas asset exposure could grow tenfold to someUS$ 35,000 billion; these estimates, however, do not account for thepotential construction of effective coastal protection schemes (see alsoDawson et al., 2005), with the exposure growth rate being more rapid indeveloping countries (e.g., Adamo, 2010). Lenton et al. (2009) estimated asubstantial increase in the exposure of coastal populations to inundation(see Figure 4-5).4.3.5.2. InfrastructureWeather- and climate-related extremes are expected to produce largeimpacts on infrastructure, although detailed analyses of potential andprojected damages are limited to a few countries (e.g., Australia,Canada, the United States; Holper et al., 2007), infrastructure types(e.g., power lines), and sectors (e.g., transport, tourism). Inadequateinfrastructure design may increase the impacts of climate and weatherextremes, and some infrastructure may become inadequate where climate248