IPCC_Managing Risks of Extreme Events.pdf - Climate Access

Chapter 4Changes in Impacts of Climate Extremes: Human Systems and EcosystemsThese statistics imply the increasing cost of such disasters to society,regardless of cause. It is also important to note that the number ofweather- and climate-related disasters has increased more rapidly thanlosses from non-weather disasters (Mills, 2005; Munich Re, 2011; SwissRe, 2011). This could indicate a change in climate extremes, but thereare other possible explanations (Bouwer, 2011). Drought and floodlosses may have grown due to a number of non-climatic factors, such asincreasing water withdrawals effectively exacerbating the impact ofdroughts, decrease in storage capacity in catchments (urbanization,deforestation, sealing surfaces, channelization) adversely affecting bothflood and drought preparedness, increase in runoff coefficients, andgrowing settlements in floodplains around urban areas (see Section4.2.2; Field et al., 2009).4.5.4.2. Potential Trends in Key Extreme ImpactsAs indicated in Sections 3.3 to 3.5 and Tables 3-1 and 3-3, climateextremes may have different trends in the future; some such as heatwaves are projected to increase over most areas in length, frequency,and intensity, while projected changes in some other extremes are givenwith less confidence. However, uncertainty is a key aspect of disaster/climate change trend analysis due to attribution issues discussed above,incomparability of methods, changes in exposure and vulnerability overtime, and other non-climatic factors such as mitigation and adaptation.A challenge is ensuring that the projections of losses from futurechanges in extreme events are examined not for current populationsand economies, but for scenarios of possible future socioeconomicdevelopment. See Box 4-2 for a discussion of this with respect tocyclones.It is more likely than not that the frequency of the most intense tropicalcyclones will increase substantially in some ocean basins (Section 3.4.4).Many studies have investigated impacts from tropical cyclones (e.g.,ABI, 2005a, 2009; Hallegatte, 2007; Pielke Jr., 2007; Narita et al., 2009;Bender et al., 2010; Nordhaus, 2010; Crompton et al., 2011). Table 4-3presents the projected percentage increase in direct economic losses fromtropical cyclones from a number of these studies, scaled to the year 2040relative to a common baseline (year 2000). There is high confidence thatincreases in exposure will result in higher direct economic losses fromtropical cyclones and that losses will also depend on future changes intropical cyclone frequency and intensity. One study, building on globalclimate model results from Bender et al. (2010), found that to attributeincreased losses to increased tropical cyclone activity in the UnitedStates with a high degree of certainty would take another 260 years ofrecords, due to the high natural variability of storms and their impactsUS$ billions2502000Overall Losses in 2010 ValuesOf Which Insured in 2010 Values15010005001980198519901995200020052010Figure 4-8 | The overall losses and insured losses from weather- and climate-related disasters worldwide (in 2010 US$). These data for weather- and climate-related ‘great’ and‘devastating’ natural catastrophes are plotted without inclusion of losses from geophysical events. A catastrophe in this data set is considered ‘great’ if the number of fatalitiesexceeds 2,000, the number of homeless exceeds 200,000, the country’s GDP is severely hit, and/or the country is dependent on international aid. A catastrophe is considered‘devastating’ if the number of fatalities exceeds 500 and/or the overall loss exceeds US$ 650 million (in 2010 values). Data from Munich Re, 2011.271