Coastal Impacts, Adaptation, and Vulnerabilities - Climate ...

Physical Climate Forces 23that survive within a range of elevations, seasonal temperature, precipitation, and ebband flood tides. For certain species, too much precipitation can have as much impact astoo little precipitation can have. For example, for oysters, spawning is affected by toomuch freshwater in the spring and too much saltwater in the summer, both of which caninduce diseases. An increase in extreme flooding and episodic events can increase turbidity,cause wetland loss, and induce stress to submerged plants and coral reefs.Strong scientific consensus now suggests that the frequency of some climate extremeevents is increasing and evidence exists that some extremes have increased as a result ofanthropogenic influences (Peters et al., 2011). A December 2011 news release by NOAAreported that the U.S. experiences 12 disasters in 2011 that cost a billion or more dollars,totaling losses of about $53 billion. Several were coastal storms and the 2011 losses weregreater than the previous record year in 2008. The global frequency of tropical storms isprojected to remain about the same with an increase in the number of extreme events.“Average tropical cyclone maximum wind speed is likely to increase, although increasesmay not occur in all ocean basins. It is likely that the global frequency of tropical cycloneswill either decrease or remain essentially unchanged” (IPCC, 2011). Hurricanesand episodic storm events have been observed to have many direct physical impacts.These factors are likely to contribute to increased erosion, flooding, wetland loss, anddamage to infrastructure.2.2 Sea-level Rise and Future ScenariosGlobal sea-level rise is expected to continue through the end of the next century andbeyond, which will significantly impact the U.S. and the world. Past trends providevaluable evidence in preparing for future environmental change but are insufficient bythemselves for assessing the risks associated with an uncertain future. The wide range ofestimates for global mean sea-level rise are scattered throughout the scientific literatureand other high profile assessments such as previous reports of the NCA and the IntergovernmentalPanel on Climate Change (IPCC). Currently, no coordinated, interagencyeffort exists in the U.S. to identify agreed upon global mean sea-level rise estimates forthe purposes of coastal planning, policy, and management. This is an important gapbecause identifying global mean sea-level rise estimates is a critical step in assessingcoastal impacts and vulnerabilities. At present, coastal managers are left to identify globalsea-level rise estimates through their own interpretations of scientific literature or theadvice of experts on an adhoc basis. For these reasons, the NCA Development and AdvisoryCommittee requested a report entitled Global Mean Sea-level Rise Scenarios for theU.S. NCA (Parris et al., 2012). This report provides a synthesis of the scientific literatureon global sea-level rise and a set of global mean sea-level rise scenarios to describe futureconditions and assess potential vulnerabilities and impacts.Scenario PlanningScenarios do not predict future changes; instead, they describe future potential conditionsin a manner that supports decision-making under conditions of uncertainty (Gray2011; Moss et al., 2010; Weeks et al., 2011). Scenarios are used to develop and test decisionsunder a range of plausible futures. This approach strengthens an organization’s