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2 Vulnerabilities and Impacts
Pages 29-60

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From page 29...
... Climate-related changes can create new or interact with existing vulnerabilities to cause impacts, including changes in: • Temperature, both averages and extremes; • Precipitation, both averages and extremes; • The intensity, frequency, duration, and/or location of extreme weather events; • Sea level; and • Atmospheric carbon dioxide (CO2) concentrations.
From page 30...
... These changes are causing impacts that should promote adaptation regardless of whether the trends are permanent. In many circumstances, projected increases in the frequency and intensity of many extreme weather events over the next several decades will initially drive adaptation more than changes in mean weather variables.
From page 31...
... A key fact about climate change impacts is that stabilization of atmospheric GHG concentrations will not immediately stabilize the climate, which will continue to change for some time because of the delayed response of the climate to the buildup of GHGs emitted in the recent past. A companion to this report (ACC: Limiting the Magnitude of Future Climate Change; NRC, 2010c)
From page 32...
... . According to this summary report, future climate change impacts in the United States will include warmer average temperatures, changes in precipitation patterns, more frequent heat waves and severe storms, rising sea level, and decreases in sea ice and permafrost, which will be particularly rapid in the Arctic.
From page 33...
... For example, a day so hot that it is currently experienced once every 20 years would likely occur every other year or more frequently by the end of the century under the higher emissions scenario. Although uncertainties remain about whether the number of hurricanes could increase with climate change, the destructive energy of Atlantic hurricanes is likely to increase in this century as sea surface temperature rises (USGCRP, 2009)
From page 34...
... Globally, under the higher emissions scenarios, average sea level is estimated to rise by 3 to 4 feet (USGCRP, 2009)
From page 35...
... . DETERMININg vuLNERAbILITIES TO PROJECTED CLIMATE CHANgES As defined earlier, vulnerability is a function of the character, magnitude, and rate of climate change to which a system is exposed, as well as the system's sensitivity and its adaptive capacity.
From page 36...
... Examples of other sources include population shifts and development choices, such as dense urban development in drought-prone areas; and places and 
From page 37...
... Changes in ecosystem function, in turn, affect human communities that depend on natural ecosystems to maintain clean water supplies, soil fertility, and other vital services (USGCRP, 2009)
From page 38...
...  TAbLE 2.1 Summary of regional climate-related impacts Climate-Related Impacts Extreme Urban Rainfall Sea Early Degraded Air Heat Heat Tropical with Level United States Census Regions Snowmelt Quality Island Wildfires Waves Drought Storms Flooding Rise New England • • • • • • • ME VT NH MA RI CT Middle Atlantic • • • • • • • • NY PA NJ DE MD East North Central • • • • • • WI MI IL IN OH West North Central • • • • • ND MN SD IA NE KS MO South Atlantic • • • • • • • • WV VA NC SC GA FL DC East South Central • • • • • • KY TN MS AL West South Central • • • • • • • • TX OK AR LA Mountain • • • • • • • MT ID WY NV UT CO AZ NM Pacific • • • • • • • • • AK CA WA OR HI SOURCE: Adapted from CCSP (2008f )
From page 39...
... Recent events suggest that changes in extreme weather events, including heat waves, floods, droughts, windstorms, and wildfires, will likely be particularly challenging for communities and sectors to adapt to. The combination of climate change and trends in population growth also poses serious adaptation challenges.
From page 40...
... . FIguRE 2.7 Projected changes in annual average runoff for 2041-2060 relative to a 1901-1970 baseline by water resource region, based on analyses using emissions that fall between the lower and higher emissions scenarios.
From page 41...
... Under the higher emissions scenario, widespread decreases of 30 percent and more are projected. Greater conflicts over water resource allocations between agriculture, urban areas, and natural ecosystems are likely in many areas.
From page 42...
... . In addition, societal vulnerability to future water stress and related conflicts is increased by some current laws and practices such as those governing interstate water allocation and reservoir operations, and by the relatively low price that is paid for water in most regions of the United States.
From page 43...
... These trends are likely to continue. In the western United States, the frequency of large wildfires and the length of the fire season increased substantially in recent decades, due primarily to earlier spring snowmelt and higher spring and summer temperatures (although annual area burned may have been just as high in the 1920s)
From page 44...
... It is uncertain how these animals could adapt to significantly less sea ice. As in other sectors, current policies to manage the impacts of human activities on the natural environment -- including fisheries, wildlife, and forest management; pollution control; and habitat protection -- were based on the assumption that the Earth's climate was relatively stable.
From page 45...
... Projected sea level rise could inundate portions of major cities such as Miami or New York during storm surges or even extreme high tides. Sea level rise can also lead to saltwater intrusion of freshwater aquifers in coastal areas that could reduce freshwater supplies (USGCRP, 2009)
From page 46...
... . Although data are limited to estimate the health impacts that may result from changes in extreme weather events other than heat waves, such events create potentially serious health consequences.
From page 47...
... during the worst heat waves (Ebi and Meehl, 2007)
From page 48...
... Locations, Systems, and Populations Will be Affected by Climate Change Responses As Well As by Climate Change Itself Impacts of climate change that may require adaptation by human and natural systems will not be limited to the direct effects of changes in temperature, precipitation, storm behavior, and sea level. Climate change is also likely to create indirect effects through the impacts of climate change policies.
From page 49...
... . Examples of impacts of climate change policies that might require an adaptive response include the following: • If climate change policies emphasize reductions in GHG emissions, as ex pected, then regional economies dependent on fossil fuel production and use (especially coal)
From page 50...
... In addition, growing biomass intended for long-term carbon storage can be complicated by climate change impacts on regional ecological systems, along with associated adaptive land use strategies. Other possible impacts of climate change policies -- not all of them negative -- include effects on choices of energy production and use technologies, on environmental emissions, and on international energy technology and service markets (for additional details see ACC: Limiting the Magnitude of Future Climate Change; NRC, 2010c)
From page 51...
... To be precise, the aggregate metrics, as applied to the United States in Figure 2.9, include the following: 1. Risk of extreme weather events.
From page 52...
... . It should be emphasized that this figure calibrates risks to increases in global mean temperature.
From page 53...
... 2. Conversely, dangerous anthropogenic interference in the climate system will likely be discovered at all levels as climate change alters the intensities, fre quencies, and regional distributions of extreme weather events.
From page 54...
... seeks to understand the causes of observed changes in climate by comparing observed changes with those simulated by climate models under rising atmospheric GHG concentrations and against background climate variability in model simulations with no rising GHGs. For statistical reasons, D&A is most successful at large spatial scales.
From page 55...
... . Projected increases in the frequency and intensity of extreme weather events highlight the need to increase understanding of those most at risk, both today and in future societies with possibly different risk profiles.
From page 56...
... Science and engineering needs include reevaluation of boundaries of flood plains, better flood maps, and redesign or retrofitting of hospitals and other critical infrastructure so that services would not be disrupted during an extreme weather event. Effective adaptation will thus require consideration of climate change risks along multiple dimensions: increasing resilience to warmer temperatures and average changes in the water cycle while at the same time increasing resilience to extreme weather events -- and doing both while considering current and future changes in other driving forces.
From page 57...
... All of these changes could reduce the resilience of natural ecosystems and make them more vulnerable to threshold changes. These and other broad changes in the ground rules by which ecosystems operate create significant scientific challenges in understanding and predicting the patterns and consequences of changes in natural ecosystems.
From page 58...
... . Another source of uncertainty comes from the fact that current global climate models operate at relatively coarse spatial scales (hundreds of kilometers or miles)
From page 59...
... In summary, the panel finds that climate change impacts are certain to increase throughout this century, requiring significant effort to adapt in order to avoid socially, economically, and environmentally disruptive changes in systems with high value to society. Adaptation options need to address current and projected changes in mean weather variables as well as increases in the frequency and intensity of many extreme events.
From page 60...
... Many scientific challenges remain in assessing impacts and vulnerabilities and providing the specific and localized information needed to guide adaptation decisions. Conclusion: Many current and future climate change impacts require immediate actions to improve the ability of the nation to adapt.


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