IPCC Report.pdf - Adam Curry

Chapter 4Changes in Impacts of Climate Extremes: Human Systems and EcosystemsMurray-Darling Basin in Australia, as it accounts for most of the waterfor irrigated crops and pastures in the country.New Zealand has a high level of economic dependence on agriculture,and drought can cause significant disruption for this industry. The1997-1998 El Niño resulted in severe drought conditions across large areasof New Zealand with losses estimated at NZ$ 750 million (2006 values)or 0.9% of GDP (OCDESC, 2007). Severe drought in two consecutivesummers, 2007-2009, affected a large area of New Zealand and causedon-farm net income to drop by NZ$ 1.9 billion (Butcher and Ford, 2009).Drought conditions also have a serious impact on electricity production inNew Zealand where around two-thirds of supply is from hydroelectricityand low precipitation periods result in increased use of fossil fuel forelectricity generation, a maladaptation to climate change. Auckland,New Zealand’s largest city, suffered from significant water shortages inthe early 1990s, but has since established a pipeline to the WaikatoRiver to guarantee supply (OCDESC, 2007).Climate change may cause land use change in southern Australia.Cropping could become non-viable at the dry margins if rainfallsubstantially decreases, even though yield increases from elevated CO 2partly offset this effect (Luo et al., 2003).4.4.7.4. WildfireWildfires around Canberra in January 2003 caused AUS$ 400 milliondamage (Lavorel and Steffen, 2004), with about 500 houses destroyed,four people killed, and hundreds injured. Three of the city’s four waterstorage reservoirs were contaminated for several months by sedimentladenrunoff (Hennessy et al., 2007). The 2009 fire in the state of Victoriacaused immense damage (see Box 4-1 and Case Study 9.2.2).An increase in fire danger in Australia is associated with a reducedinterval between fire events, increased fire intensity, a decrease in fireextinguishments, and faster fire spread (Hennessy et al., 2007). Insoutheast Australia, the frequency of very high and extreme fire dangerdays is expected to rise 15 to 70% by 2050 (Hennessy et al., 2006). Bythe 2080s, the number of days with very high and extreme fire dangerare projected to increase by 10 to 50% in eastern areas of New Zealand,the Bay of Plenty, Wellington, and Nelson regions (Pearce et al., 2005),with even higher increases (up to 60%) in some western areas. In bothAustralia and New Zealand, the fire season length is expected to beextended, with the window of opportunity for fuel reduction burningshifting toward winter (Hennessy et al., 2007).Floods are New Zealand’s most frequently experienced hazard (OCDESC,2007) affecting both agricultural and urban areas. Being long and narrow,New Zealand is characterized by small river catchments and accordinglyshorter time-to-peak and shorter flood warning times, posing a difficultpreparedness challenge. Projected increases in heavy precipitationevents across most parts of New Zealand (Table 3-3) is expected tocause greater erosion of land surfaces, more landslides, and a decreasein the protection afforded by levees (Hennessy et al., 2007).4.4.7.6. Storm SurgesOver 80% of the Australian population lives in the coastal zone, andoutside of the major capital cities is also where the largest populationgrowth occurs (Harvey and Caton, 2003; ABS, 2010). Over 500,000addresses are within 3 km of the coast and less than 5 m above sealevel (Chen and McAneney, 2006). As a result of being so close to sealevel, the risk of inundation from sea level rise and large storm surgesincreases with climate change (Hennessy et al., 2007). The risk of a1-in-100 year storm surge in Cairns is expected to more than double by2050 (McInnes et al., 2003). Projected changes in coastal hazards fromsea level rise and storm surge are also an issue for New Zealand (e.g.,Ministry for the Environment, 2008).4.4.8. Open OceansThe ocean’s huge mass in comparison to the atmosphere gives it a crucialrole in global heat budgets and chemical budgets. Possible extremeimpacts can be triggered by (1) warming of the surface ocean, with amajor cascade of physical effects, (2) ocean acidification induced byincreases in atmospheric CO 2 , and (3) reduction in oxygen concentrationin the ocean due to a temperature-driven change in gas solubility andphysical impacts from (1). All have potentially nonlinear multiplicativeimpacts on biodiversity and ecosystem function, and each may increasethe vulnerability of ocean systems, triggering an extreme impact(Kaplan et al., 2010; Griffith et al., 2011). Surface warming of the oceanscan itself directly impact biodiversity by slowing or preventing growth intemperature-sensitive species. One of the most well-known biologicalimpacts of warming is coral bleaching, but ocean acidification can alsoaffect coral growth rates (Bongaerts et al., 2010). The seasonal sea icecycle affects biological habitats. Such species of Arctic mammals aspolar bears, seals, and walruses depend on sea ice for habitat, hunting,feeding, and breeding. Declining sea ice can decrease polar bear numbers(Stirling and Parkinson, 2006).4.4.7.5. Intense Precipitation and FloodsThere has been a likely decrease in heavy precipitation in many parts ofsouthern Australia and New Zealand (Table 3-2), while there is generallylow to medium confidence in projections due to a lack of consistencybetween models (Table 3-3).4.4.9. Polar Regions4.4.9.1. IntroductionThe polar regions consist of the Arctic and the Antarctic, includingassociated water bodies. The Arctic region consists of a vast treeless261