List three impacts of a change in regional climate?

Answer 1

Over the past 50 years, Alaska has warmed at more than twice the rate of the rest of the United States. Its annual average temperature has increased 3.4°F, while winters have warmed by 6.3°F. The higher temperatures are already causing earlier spring snowmelt, reduced sea ice, widespread glacier retreat, and permafrost warming. The observed changes are consistent with climate model projections of greater warming over Alaska, especially in winter, as compared to the rest of the country. Climate models also project increases in precipitation over Alaska. Simultaneous increases in evaporation due to higher air temperatures, however, are expected to lead to drier conditions overall, with reduced soil moisture. Average annual temperatures are projected to rise between 5 and 13°F by late this century, with lower emissions scenarios yielding increases at the lower end of this range and higher emissions yielding increases near the high end of the range.

Key Issues

Longer summers and higher temperatures are causing drier conditions, even in the absence of strong trends in precipitation.

Between 1970 and 2000, the snow-free season increased by about 10 days across Alaska, primarily due to earlier snowmelt in the spring. A longer growing season has potential benefits, such as a longer season for summer tourism and agriculture. However, the white spruce forests in Alaska's interior are experiencing declining growth due to drought stress and continued warming could lead to widespread death of trees. The decreased soil moisture also suggests that agriculture might not benefit from the longer growing season.

Alaska Spruce Beetle Infestation

Kenai Peninsula, 1971 to 1998

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Insect outbreaks and wildfires are increasing with warming.

During the 1990s, south-central Alaska experienced the largest outbreak of spruce beetles in the world as rising temperatures allowed the beetle to survive the winter and to complete its life cycle in half the usual time. Drought-stressed trees were unable to fight off the infestation. Fires are also increasing. By the end of this century, the area burned in Alaska is projected to triple under a moderate greenhouse gas emissions scenario and to quadruple under a higher emissions scenario.

Lakes are declining in area.

Across the southern two-thirds of Alaska, the area of closed-basin lakes (lakes without stream inputs or outputs) has decreased over the past 50 years. This is likely due to the greater evaporation and thawing of permafrost that result from warming. These wetlands provide breeding habitat for millions of waterfowl and shorebirds and are important hunting and fishing grounds for Native People. A continued decline in the area of surface water would present challenges for ecosystems, Natural Resources, and the people who depend upon them.

Thawing permafrost damages roads, runways, water and sewer systems, and other infrastructure.

As permafrost thaws, the land can sink and collapse, damaging forests, homes, and infrastructure. Economists estimate that thawing permafrost will add billions of dollars in repair costs to public infrastructure (costs to private property have not yet been estimated).

Projected Coastal Erosion, 2007 to 2027

Newtok, western Alaska

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Coastal storms increase risks to villages and fishing fleets.

Alaska has more coastline than the other 49 states combined. These coastlines are increasingly threatened by a combination of losing their protective sea ice buffer, increasing storm activity, and thawing coastal permafrost. The ground beneath some communities is literally crumbling into the sea. The rate of erosion along Alaska's northeastern coastline has doubled over the past 50 years.

Displacement of marine species will affect key fisheries.

Climate change is altering marine ecosystems in ways that affect commercial fisheries. The world's largest single fishery is the Bering Sea pollock fishery, which has undergone major declines in recent years. Air and sea temperatures have increased, and sea ice has declined in this region.

Annual average temperature over the Northwest region as a whole rose about 1.5°F over the past century, with some areas experiencing increases up to 4°F. The region's average temperature is projected to rise another 3 to 10°F in this century, with higher emissions scenarios resulting in warming in the upper end of this range. Increases in winter precipitation and decreases in summer precipitation are projected by many climate models, though these projections are less certain than those for temperature. Impacts related to changes in snowpack, streamflows, sea level, forests, and other important aspects of life in the Northwest are already underway, with more severe impacts expected over the coming decades in response to continued and more rapid warming.

Key Issues

Decreasing Habitat for Cold-Water Fish

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Declining springtime snowpack leads to reduced summer streamflows, straining water supplies.

The Northwest is highly dependent on temperature-sensitive springtime snowpack to meet growing and often competing water demands such as municipal and industrial uses, agricultural irrigation, hydropower production, navigation, recreation, and in-stream flows that protect aquatic ecosystems including threatened and endangered species. Higher temperatures are causing more winter precipitation to fall as rain rather than snow and are contributing to earlier snowmelt. Further declines in snowpack are projected, reducing the amount of water available during the warm season.

Increased insect outbreaks, wildfires, and changing species composition in forests will pose challenges for ecosystems and the forest products industry.

Higher summer temperatures and earlier spring snowmelt are expected to increase the risk of forest fires by increasing summer moisture deficits; this pattern has already been observed in recent decades. Drought stress and higher temperatures will decrease tree growth in most low- and mid-elevation forests and will also increase the frequency and intensity of mountain pine beetle and other insect attacks, further increasing fire risk and reducing timber production, an important part of the regional economy.

Northwest Cities at Risk to Sea Level Rise

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Salmon and other coldwater species will experience additional stresses as a result of rising water temperatures and declining summer streamflows.

Northwest salmon populations are already at historically low levels due to variety of human-induced stresses. Climate change affects salmon throughout their life stages and poses an additional stress. Studies suggest that about a third of the current habitat for the Northwest's salmon and other coldwater fish will no longer be suitable for them by the end of this century due to climate change.

Sea-level rise along vulnerable coastlines will result in increased erosion and the loss of land.

Climate change is expected to exacerbate many of the stresses and hazards currently facing the coastal zone. Sea-level rise will increase erosion of the coast and cause the loss of beaches and significant coastal land areas. Among the most vulnerable parts of the coast is the heavily populated south Puget Sounds region, which includes the cities of Olympia, Tacoma, and Seattle, Washington.

Climate change presents U.S.-affiliated islands with unique challenges. Small islands are vulnerable to sea-level rise, coastal erosion, extreme weather events, coral reef bleaching, ocean acidification, and contamination of freshwater resources with saltwater. The islands have experienced rising temperatures and sea level in recent decades. Projections for the rest of this century suggest continued increases in air and ocean surface temperatures in both the Pacific and Caribbean, an overall decrease in rainfall in the Caribbean, an increased frequency of heavy downpours nearly everywhere, and increased rainfall during the summer months (rather than the normal rainy season in the winter months) for the Pacific islands. Hurricane wind speeds and rainfall rates are likely to increase with continued warming. Island coasts will be at increased risk of inundation due to sea-level rise and storm surge with major implications for coastal communities, infrastructure, natural habitats, and resources.

A note on the emissions scenarios

None of the emissions scenarios used in this report assume any policies specifically designed to address climate change. All, including the lower emissions scenario, assume increases in heat-trapping gas emissions for at least the next few decades, though at different rates.

Agriculture, ranching, and natural lands, already under pressure due to an increasingly limited water supply, are very likely to also be stressed by rising temperatures.

Agriculture covers 70 percent of the Great Plains. As temperatures continue to rise, the optimal zones for growing certain crops will shift. Pests will spread northward and milder winters and earlier springs will encourage greater numbers and earlier emergence of insects. Projected increases in precipitation are unlikely to be sufficient to offset decreasing soil moisture and water availability due to rising temperatures and aquifer depletion.

Climate change is likely to affect native plant and animal species by altering key habitats such as the wetland ecosystems known as prairie potholes or playa lakes.

Climate change is likely to combine with other human-induced stresses to further increase the vulnerability of ecosystems to pests, invasive species, and loss of native species. Breeding patterns, water and food supply, and habitat availability will all be affected by climate change. Grassland and plains birds, already stressed by habitat fragmentation, could experience significant shifts and reductions in their ranges.

Ongoing shifts in the region's population from rural areas to urban centers will interact with a changing climate, resulting in a variety of consequences.

As young adults move out of small, rural communities, the towns are increasingly populated by a vulnerable demographic of the very old and the very young, placing them more at risk for health issues that are projected to increase with climate change. The region is also home to 65 Native American tribes; the people on tribal lands have limited capacities to respond to climate change. Many reservations already face severe problems with water quality and quantity and these problems are likely to be exacerbated by climate change.

Southeast annual average temperature has risen 2°F since 1970, with the greatest seasonal increase in the winter months. There has been a 30 percent increase in fall precipitation over most of the region but a decrease in fall precipitation in South Florida. Summer precipitation has decreased over almost the entire region. The percentage of the Southeast in moderate to severe drought increased over the past three decades. There has been an increase in heavy downpours. The power of Atlantic hurricanes has increased since 1970, associated with an increase in sea surface temperature.

Continued warming is projected, with the greatest temperature increases in summer. The number of very hot days is projected to rise at a faster rate than average temperatures. Average annual temperatures are projected to rise 4.5°F under a lower emissions scenario and 9°F under a higher emissions scenario with a 10.5°F increase in summer and a much higher heat index. (See the full report for information on the emissions scenarios.) Sea-level rise is projected to accelerate, increasing coastal inundation and shoreline retreat. The intensity of hurricanes is likely to increase, with higher wind speeds, rainfall intensity, and storm surge height and strength.

A note on the emissions scenarios

None of the emissions scenarios used in this report assume any policies specifically designed to address climate change. All, including the lower emissions scenario, assume increases in heat-trapping gas emissions for at least the next few decades, though at different rates.

Key Issues

Number of Days per year with Peak Temperature over 90° F

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Projected increases in air and water temperatures will cause heat-related stresses for people, plants, and animals.

Effects of increased heat include more heat-related illness; declines in forest growth and agricultural crop production due to the combined effects of heat stress and declining soil moisture; declines in cattle production; increased buckling of pavement and railways; and reduced oxygen levels in streams and lakes, leading to fish kills and declines in aquatic species diversity.

Decreased water availability is very likely to affect the region's economy as well as its natural systems.

Increasing temperatures and longer periods between rainfall events coupled with increased demand for water will result in decreased water availability. The 2007 water shortage in the Atlanta area created serious conflicts between three states, the U.S. Army Corps of Engineers (which operates the dam at Lake Lanier), and the U.S. Fish and Wildlife Service, which is charged with protecting endangered species. Such competition for limited water supplies is expected to continue.

Land Lost During 2005 Hurricanes

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Sea-level rise and the likely increase in hurricane intensity and associated storm surge will be among the most serious consequences of climate change.

Low-lying areas, including some communities, will be inundated more frequently -- some permanently -- by the advancing sea. Current buildings and infrastructure were not designed to withstand the intensity of the projected storm surge, which would cause catastrophic damage. If sea-level rise increases at an accelerated rate (dependent upon ice sheet response to warming) a large portion of the Southeast coastal zone could be threatened.

Ecological thresholds are likely to be crossed throughout the region, causing major disruptions to ecosystems and to the benefits they provide to people.

Ecosystems provide numerous important services that have high economic and cultural value in the Southeast. Climate change may result in abrupt changes to these ecosystems, such as hurricane-induced sudden loss of landforms that serve as storm surge barriers and homes for coastal communities.

Quality of life will be affected by increasing heat stress, water scarcity, severe weather events, and reduced availability of insurance for at-risk properties.

The Southeast "sunbelt" has attracted people, industry, and investment. The population of Florida has increased by 100 percent during the past three decades and growth rates in most other southeastern states were between 45 and 75 percent. The challenges associated with climate change will affect the quality of life for these residents and affect future population growth.

Northeast annual average temperature has increased by 2°F since 1970, with winter temperatures rising twice this much. Warming has resulted in many other climate-related changes including more frequent very hot days, a longer growing season, an increase in heavy downpours, less winter precipitation falling as snow and more as rain, reduced snowpack, earlier break-up of winter ice on lakes and rivers, earlier spring snowmelt resulting in earlier peak river flows, rising sea surface temperatures, and rising sea level. These trends are projected to continue, with more dramatic changes under higher emissions scenarios compared to lower emissions scenarios. Some of the extensive climate-related changes projected for the region could significantly alter the region's economy, landscape, character, and quality of life.

A note on the emissions scenarios

None of the emissions scenarios used in this report assume any policies specifically designed to address climate change. All, including the lower emissions scenario, assume increases in heat-trapping gas emissions for at least the next few decades, though at different rates.

Key Issues

Projected Days per Year over 90° F in Boston

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Extreme heat and declining air quality are likely to pose increasing problems for human health, especially in urban areas.

By late this century under higher emissions scenarios, hot summer conditions would arrive three weeks earlier and last three weeks longer into fall. Cities that currently experience just a few days above 100°F each summer would average 20 such days per summer. Cities like Hartford and Philadelphia would average nearly 30 days over 100°F per summer. In addition, cities that now experience air quality problems would see those problems worsen with rising temperatures, if no additional controls were placed on ozone-causing pollutants.

Agricultural production, including dairy, fruit, and maple syrup, are likely to be adversely affected as favorable climates shift.

Large portions of the Northeast are likely to become unsuitable for growing popular varieties of apples, blueberries, and cranberries under higher emissions scenarios. The climate conditions suitable for maple/beech/birch forests are projected to shift dramatically northward, eventually leaving only a small portion of the Northeast with a maple sugar business and the colorful fall foliage that is part of the region's iconic character.

Severe flooding due to sea-level rise and heavy downpours is likely to occur more frequently.

The densely populated coasts of the Northeast face substantial increases in the extent and frequency of storm surge, coastal flooding, erosion, property damage, and loss of wetlands. New York state alone has more than $2.3 trillion in insured coastal property. Much of this coastline is exceptionally vulnerable to sea-level rise and related impacts.

Ski Areas at Risk under Higher Emissions Scenario†

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The projected reduction in snow cover will adversely affect winter recreation and the industries that rely upon it.

The length of the winter snow season would be cut in half across northern New York, Vermont, New Hampshire, and Maine, and reduced to just a week or two in southern parts of the region by late this century under a higher emissions scenario. Winter snow and ice sports, which contribute $7.6 billion annually to the region's economy, will be particularly affected by warming.

The center of lobster fisheries is projected to continue its northward shift and the cod fishery on Georges Bank is likely to be diminished.

Lobster catches in the southern part of the region have declined dramatically in the past decade, associated with a temperature-sensitive bacterial shell disease. Analyses also suggest that lobster survival and settlement in northern regions of the Gulf of Maine could increase under warmer conditions. Cod populations, also subject to overfishing and other stresses, are likely to be adversely affected as temperatures continue to rise.

Average temperatures in the Midwest have risen in recent decades, with the largest increases in winter. The length of the frost-free or growing season has been extended by one week, mainly due to earlier dates for the last spring frost. Heavy downpours are now twice as frequent as they were a century ago. Both summer and winter precipitation have been above average for the last three decades, the wettest period in a century. The Midwest has experienced two record-breaking floods in the past 15 years. There has also been a decrease in lake ice, including on the Great Lakes. Since the 1980s, large heat waves have become more frequent than anytime in the last century, other than the Dust Bowl years of the 1930s. The observed patterns of temperature increases and precipitation changes are projected to continue, with larger changes expected under higher emissions scenarios.

A note on the emissions scenarios

None of the emissions scenarios used in this report assume any policies specifically designed to address climate change. All, including the lower emissions scenario, assume increases in heat-trapping gas emissions for at least the next few decades, though at different rates.

Key Issues

Climate on the Move

Changing Summers in the Midwest

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During the summer, public health and quality of life, especially in cities, will be negatively affected by increasing heat waves, reduced air quality, and increasing insect and waterborne diseases. In the winter, warming will have mixed impacts.

Heat waves that are more frequent, more severe, and longer-lasting are projected. The frequency of hot days and the length of the heat-wave season will both be more than twice as great under a higher emissions scenario than a lower one (see full report for information on emission scenarios). Insects such as ticks and mosquitoes that carry disease will survive winters more easily and produce larger populations in a warmer Midwest.

Projected Changes in Great Lakes Levels

under Higher Emissions Scenario†

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Significant reductions in Great Lakes water levels, which are projected under higher emissions scenarios, lead to impacts on shipping, infrastructure, beaches, and ecosystems.

Higher temperatures will mean more evaporation and hence a likely reduction in Great Lakes water levels. Reduced lake ice increases evaporation in winter, contributing to the decline. This will affect shipping, ecosystems, recreation, infrastructure, and dredging requirements. Costs will include lost recreation and tourism dollars and increased repair and maintenance costs.

The likely increase in precipitation in winter and spring, more heavy downpours, and greater evaporation in summer would lead to more periods of both floods and water deficits.

The projected pattern of increasing precipitation in winter and spring and heavy downpours is expected to lead to more frequent flooding, increasing infrastructure damage, and impacts on human health. Heavy downpours can overload drainage systems and water treatment facilities, increasing the risk of waterborne diseases. In summer, with increasing evaporation and longer periods between rainfalls, the likelihood of drought will increase and water levels in rivers and wetlands are likely to decline.

While the longer growing season provides the potential for increased crop yields, increases in heat waves, floods, droughts, insects, and weeds will present increasing challenges to managing crops, livestock, and forests.

Spring flooding is likely to delay planting. An increase in disease-causing pathogens, insect pests, and weeds cause additional challenges for agriculture. Livestock production is expected to become more costly as higher temperatures stress livestock, decreasing productivity and increasing costs associated with the needed ventilation and cooling equipment.

Native species are very likely to face increasing threats from rapidly changing climate conditions, pests, diseases, and invasive species moving in from warmer regions.

All major groups of animals including birds, mammals, amphibians, reptiles, and insects will be affected by climate change impacts on local populations and by competition from species moving into the Midwest. The potential for animals to shift their ranges to keep pace with the changing climate will be inhibited by major urban areas and the presence of the Great Lakes.