IPCC_Managing Risks of Extreme Events.pdf - Climate Access

Chapter 4Changes in Impacts of Climate Extremes: Human Systems and EcosystemsBox 4-1 | Evolution of Climate, Exposure, and Vulnerability – The Melbourne Fires, 7 February 2009The fires in the Australian state of Victoria, on 7 February 2009, demonstrate the evolution of risk through the relationships between theweather- and climate-related phenomena of a decade-long drought, record extreme heat, and record low humidity of 5% (Karoly, 2010;Trewin and Vermont, 2010) interacting with rapidly increasing exposure. Together the climate phenomena created the conditions formajor uncontrollable wildfires (Victorian Bushfires Royal Commission, 2010).The long antecedent drought, record heat, and a 35-day period with no rain immediately before the fires turned areas normally seen aslow to medium wildfire risk into very dry high-risk locations. A rapidly expanding urban-bush interface and valuable infrastructure (Berry,2003; Burnley and Murphy, 2004; Costello, 2007, 2009) provided the values exposed and the potential for extreme impacts that wasrealized with the loss of 173 lives and considerable tangible and intangible damage. There was a mixture of natural and human sourcesof ignition, showing that human agency can trigger such fires and extreme impacts.Many people were not well-prepared physically or psychologically for the fires, and this influenced the level of loss and damage theyincurred. Levels of physical and mental health also affected people’s vulnerability. Many individuals with ongoing medical conditions,special needs because of their age, or other impairments struggled to cope with the extreme heat and were reliant on others to respondsafely (Handmer et al., 2010). However, capacity to recover in a general sense was high for humans and human activities throughinsurance, government support, private donations, and nongovernmental organizations (NGOs) and was variable for the affected bushwith some species and ecosystems benefitting (Lindenmayer et al., 2010; Banks et al., 2011; see also Case Study 9.2.2).Chapter 3 details projected changes in climate extremes for this region that could increase fire risk, in particular warm temperatureextremes, heat waves, and dryness (see Table 3-3 for summary).where soil and bio-productive resources became permanently degraded(Dregne, 1986). An extreme example of a human-made, pronouncedhydrological drought comes from the Aral Sea basin in Central Asia. Dueto excessive and non-sustainable water withdrawals from thetributaries (Syr Darya and Amu Darya), their inflow into the Aral Sea hasshrunk in volume by some 75% (Micklin, 2007; Rodell et al., 2009)resulting in severe economic and ecological impacts.The changing impacts of climate extremes on sectors, such as water andfood, depend not only on changes in the characteristics of climaterelatedvariables relevant to a given sector, but also on sector-relevantnon-climatic stressors, management characteristics (includingorganizational and institutional aspects), and adaptive capacity(Kundzewicz, 2003).There also may be increasing risks from possible interactions of hazards(Cruz, 2005; see Sections 3.1.3 and 3.1.4 for discussion of interactionsand feedbacks). One hazard may influence other hazards or exacerbatetheir effects, also with dependence on scale (Buzna et al., 2006). Forinstance, temperature rise can lead to permafrost thaw, reduced slopestability, and damage to buildings. Another example is that intenseprecipitation can lead to flash flood, landslides, and infrastructure damage,for example, collapse of bridges, roads, and buildings, and interruptionof power and water supplies. In the Philippines, two typhoons hittingthe south of Luzon Island in 2004 caused a significant flood disaster aswell as landslides on the island, leading to 900 fatalities (Pulhin et al.,2010). It is worthwhile to note that cascading system failures (e.g.,among infrastructure) can happen rapidly and over large areas due totheir interdependent nature.4.3. System- and Sector-Based Aspectsof Vulnerability, Exposure, and Impacts4.3.1. IntroductionIn this subsection, studies evaluating impacts and risks of extremeevents are surveyed for major affected sectors and systems. Sectors andsystems considered here include water; ecosystems; food systems andfood security; human settlements, infrastructure, and tourism; andhuman health, well-being, and security. Impacts of climate extremes aredetermined by the climate extremes themselves as well as by exposureand vulnerability. Climate extremes, exposure, and vulnerability arecharacterized by uncertainty and continuous change, and shifts in anyof these components of risk will have implications for the impacts ofextreme events. Generally, there is limited literature on the potentialfuture impacts of extreme events; most literature analyzes currentimpacts of extreme events. This focus may result in part from incompleteknowledge and uncertainties regarding future changes in some extremeevents (see, for example, Section 3.2.3 and Tables 3-1 and 3-3) as wellas from uncertainties regarding future exposure and vulnerabilities.Nonetheless, understanding current impacts can be important fordecisionmakers preparing for future risks. Analyses of both observedand projected impacts due to extreme climate and weather events are239