North America

North America has considerable adaptive capacity, which has been deployed effectively at times, but this capacity has not always protected its population from adverse impacts of climate variability and extreme weather events (very high confidence).

Damage and loss of life from Hurricane Katrina in August 2005 illustrate the limitations of existing adaptive capacity to extreme events. Traditions and institutions in North America have encouraged a decentralised response framework where adaptation tends to be reactive, unevenly distributed, and focused on coping with rather than preventing problems. "Mainstreaming" climate change issues into decision making is a key prerequisite for sustainability [14.2.3, 14.2.6, 14.4, 14.5, 14.7].

Emphasis on effective adaptation is critical, because economic damage from extreme weather is likely to continue increasing, with direct and indirect consequences of climate change playing a growing role (very high confidence).

Over the past several decades, economic damage from hurricanes in North America has increased over fourfold (Figure TS.15), due largely to an increase in the value of infrastructure at risk [14.2.6]. Costs to North America include billions of dollars in damaged property and diminished economic productivity, as well as lives disrupted and lost [14.2.6, 14.2.7, 14.2.8]. Hardships from extreme events disproportionately affect those who are socially and economically disadvantaged, especially the poor and indigenous peoples of North America [14.2.6].

Coastal communities and habitats are very likely to be increasingly stressed by climate change impacts interacting with development and pollution (very high confidence).

Sea level is rising along much of the coast, and the rate of change is likely to increase in the future, exacerbating the impacts of progressive inundation, storm surge flooding, and shoreline erosion [14.2.3, 14.4.3]. Storm impacts are likely to be more severe, especially along the Gulf and Atlantic coasts [14.4.3]. Salt marshes, other coastal habitats and dependent species are threatened now and increasingly in future decades by sea-level rise, fixed structures blocking landward migration, and changes in vegetation [14.2]. Population growth and rising value of infrastructure in coastal areas increases vulnerability to climate variability and future climate change, with losses projected to increase if the intensity of tropical storms increases. Current adaptation to coastal hazards is uneven and readiness for increased exposure is low [14.2.3,14.4.3,14.5].

Warm temperatures and extreme weather already cause adverse human health effects through heat-related mortality, pollution, storm-related fatalities and injuries, and infectious diseases, and are likely, in the absence of effective countermeasures, to increase with climate change (very high confidence).

Depending on progress in health care, infrastructure, technology and access, climate change could increase the risk of heatwave deaths, water-borne diseases and degraded water quality [14.4.1], respiratory illness through exposure to pollen and ozone, and vector-borne infectious diseases (low confidence) [14.2.5, 14.4.5].

Climate change is likely to exacerbate other stresses on infrastructure, and human health and safety in urban centres (very high confidence).

Climate change impacts in urban centres are very likely to be compounded by urban heat islands, air and water pollution, ageing infrastructure, maladapted urban form and building stock, water quality and supply challenges, immigration and population growth, and an ageing population [14.3.2, 14.4.1, 14.4.6].

Climate change is very likely to constrain North America's already intensively utilised water resources, interacting with other stresses (high confidence).

Diminishing snowpack and increasing evaporation due to rising temperatures are very likely to affect timing and availability of water and intensify competition among uses [B14.2, 14.4.1]. Warming is very likely to place additional stress on groundwater availability, compounding the effects of higher demand from economic development and population growth (medium confidence) [14.4.1]. In the Great Lakes and some major river systems, lower water levels are likely to exacerbate issues of water quality, navigation, hydropower generation, water diversions, and bi-national co-operation [14.4.1, B14.2].

Disturbances such as wildfire and insect outbreaks are increasing and are likely to intensify in a warmer future with drier soils and longer growing seasons, and to interact with changing land use and development affecting the future of wildland ecosystems (high confidence). Recent climate trends have increased ecosystem net primary production, and this trend is likely to continue for the next few decades [14.2.2]. However, wildfire and insect outbreaks are increasing, a trend that is likely to intensify in a warmer future [14.4.2, B14.1]. Over the course of the 21st century, the tendency for species and ecosystems to shift northward and to higher elevations is likely to rearrange the map of North American ecosystems. Continuing increases in disturbances are likely to limit carbon storage, facilitate invasives, and amplify the potential for changes in ecosystem services [14.4.2,14.4.4].

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