Widespread Impacts

​Impacts related to climate change are already evident in many sectors and are expected to become increasingly disruptive across the nation throughout this century and beyond. 

Climate change is already affecting societies and the natural world. Climate change interacts with other environmental and societal factors in ways that can either moderate or intensify these impacts. The types and magnitudes of impacts vary across the nation and through time. Children, the elderly, the sick, and the poor are especially vulnerable. There is mounting evidence that harm to the nation will increase substantially in the future unless global emissions of heat-trapping gases are greatly reduced. 

Because environmental, cultural, and socioeconomic systems are tightly coupled, climate change impacts can either be amplified or reduced by cultural and socioeconomic decisions. In many arenas, it is clear that societal decisions have substantial influence on the vulnerability of valued resources to climate change. For example, rapid population growth and development in coastal areas tends to amplify climate change related impacts. Recognition of these couplings, together with recognition of multiple sources of vulnerability, helps identify what information decision-makers need as they manage risks. 

Impacts are particularly severe when critical systems simultaneously fail. We have already seen multiple system failures during an extreme weather event in the United States, as when Hurricane Katrina struck New Orleans. Infrastructure and evacuation failures and collapse of critical response services during a storm is one example of multiple system failures. Another example is a loss of electrical power during heat waves or wildfires, which can reduce food and water safety. Air conditioning has helped reduce illness and death due to extreme heat, but if power is lost, everyone is vulnerable. By their nature, such events can exceed our capacity to respond. In succession, these events severely deplete resources needed to respond, from the individual to the national scale, but disproportionately affect the most vulnerable populations.

Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds., 2014: Highlights of Climate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, pp. 32–33, Print.