North America: Climate Change Impacts

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North America: Climate Change Impacts

Introduction

North America, the third-largest continent, is home to approximately 515 million people. It stretches from the Central American peninsula north to the Arctic, and will experience a wide range of effects from climate change. These effects will be most intense in the Arctic. The region will not only suffer impacts from climate change, but is having a large impact on climate change: North America has produced a greater share of greenhouse gas emissions over time than any other continent. This is due mostly to the contribution of the United States, historically the world's largest single emitter of human-released greenhouse gases. The United States is now the second-largest emitter of greenhouse gases in the world, just behind China. Climate change is already being observed in North America, including shifted rainfall patterns and dramatic warming in the Arctic.

Historical Background and Scientific Foundations

Various effects of climate change have already been observed in North America. Average air temperature increased from 1955 to at least 2005, with most

warming occurring in Alaska, northwestern Canada, and the continental interior. The growing season has increased by about two days per decade since 1950 in Canada and the United States, mostly due to earlier springs. This warming has been caused both by a combination of human-released gases and fine particles (aerosols) and by natural causes. Annual precipitation (rain and snow) has increased for most of North America, but has decreased in the southwestern United States, eastern Arctic, and Canadian prairies. Water flowing in streams has increased by 25% in the eastern United States over the last 60 years but has decreased by about 2% per decade in the Rocky Mountains.

WORDS TO KNOW

AEROSOLS: Particles of matter, solid or liquid, larger than a molecule but small enough to remain suspended in the atmosphere. Natural sources include salt particles from sea spray and clay particles as a result of the weathering of rocks, both of which are carried upward by the wind. Aerosols can also originate as a result of human activities and in this case are often considered pollutants.

DROUGHT: A prolonged and abnormal shortage of rain.

EROSION: Processes (mechanical and chemical) responsible for the wearing away, loosening, and dissolving of materials of Earth's crust.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC): Panel of scientists established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) in 1988 to assess the science, technology, and socioeconomic information needed to understand the risk of human-induced climate change.

PERMAFROST: Perennially frozen ground that occurs wherever the temperature remains below 32°F (0°C) for several years.

IN CONTEXT: UNCERTAINTY IN REGIONAL PREDICTIONS

According to the National Academy of Sciences, there are uncertainties in determining “exactly how climate change will affect different regions. Although scientists are starting to project regional climate impacts, their level of confidence is less than for global climate projections. In general, temperature is easier to predict than changes such as rainfall, storm patterns, and ecosystem impacts. It is very likely that increasing global temperatures will lead to higher maximum temperatures and fewer cold days over most land areas.”

SOURCE: Staudt, Amanda, Nancy Huddleston, and Sandi Rudenstein. Understanding and Responding to Climate Change. National Academy of Sciences, 2006.

In 2007, the United Nations' Intergovernmental Panel on Climate Change (IPCC) released the report of its Working Group II, Climate Change 2007: Impacts, Adaptation and Vulnerability. The report noted the following points, among others, about the impact of climate change on North America:

North America has seen severe damage to local economies, ecosystems, and social systems from recent extreme weather, including floods, storms, droughts, heat waves, and wildfires. Although no single event, such as Hurricane Katrina, can ever be attributed entirely to global warming—extreme weather events were happening long before human beings began to release greenhouse gases in large quantities—an increase in the frequency of such events has been a predicted effect of global warming, and is now being observed.
North America has more capacity to adapt to climate change than most other continents. However, vulnerability depends on whether adaptation is actually attempted, and when. Native peoples and the poor will remain more vulnerable than others to climate-change impacts. North American traditions and institutions have tended to build adaptations that are decentralized, unevenly distributed, and are focused on reacting to problems rather than preventing them.
Coastal development and pollution will interact with climate change impacts to stress coastal communities and habitats. Storm impacts are likely to be more severe, thanks to rising sea levels, along the Atlantic and Gulf coasts. Settlement continues to accelerate along coasts, increasing the monetary value of the property at risk.
Disturbances like wildfires and insect infestations are already increasing and will increase further as soils become more dry and growing seasons longer. These changes will offset the carbon uptake of increased vegetation growth encouraged by recent changes.

Impacts and Issues

The U.S. Environmental Protection Agency (EPA) has forecast a number of likely impacts on the country by region, based largely on the IPCC's 2001 climate report, as follows:

Northeast. Northward shifts in the ranges of plants and animals. Coastal erosion, loss of wetlands, and increased storm-surge risk from rising sea level. Decreased skiing, increased warm-season activities (e.g., golf).

Southeast and Gulf Coast. Loss of barrier islands and wetlands. Risk to developments in coastal floodplains from sea-level rise and extreme precipitation events (heavy rains) that cause flooding. Increased fire and insect outbreaks in forests, changing forest character. Reduced winter cold stress, increased summer heat stress.

Midwest and Great Lakes. Lower lake and river levels, with impacts on recreation and shipping. Increased agricultural productivity. Reduced winter cold stress, increased summer heat stress.

Great Plains. Northward shift of agricultural activity, with increased potential for drought.

The West. Earlier runoff of snowmelt, stressing water reservoirs (reserves will peak earlier in the year). Significant problems obtaining enough water for drinking, household use, power generation, and agriculture. Increased wildfires. Reduced winter cold stress, increased summer heat stress.

Alaska. Disrupted forests from warming and insect outbreaks. Warming will cause increased overall biological production, but will disrupt polar bears, marine mammals such as walruses and seals, and other wildlife. Infrastructure such as buildings and roads will be damaged by permafrost melting. Traditional lifestyles will be altered by retreating sea ice and earlier melting of snow in spring.

BIBLIOGRAPHY

Books

Parry, M. L., et al, eds. Climate Change 2007: Impacts, Adaptation and Vulnerability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.

Web Sites

“Climate Change Impacts on the United States: The Potential Consequences of Climate Variability and Change.” U.S. Global Change Research Program, November 11, 2000. <http://www.gcrio.org/NationalAssessment> (accessed October 16, 2007).

Frumhoff, Peter C., et al. “Confronting Climate Change in the U.S. Northeast: Science, Impacts, and Solutions.” Union of Concerned Scientists, July, 2007. <http://www.ucsusa.org/global_warming> (accessed October 16, 2007).

Larry Gilman

Climate Change: In Context