Consequences of Global Warming
Unless we act now, our children will inherit a hotter world, dirtier air and water, more severe floods and droughts, and more wildfires
Barrow
McCall Glacier
Shismaref
Yukon River
Fairbanks
Wasilla
Kenai Peninsula
ALASKA HEATS UP
Warming temperatures are already having an impact on the people, wildlife and landscape of Alaska. Click on the numbers on this map to see what's happening on the front lines of global warming.
1. Barrow 2. Shismaref 3. Yukon River 4. Wasilla 5. Kenai Peninsula 6. McCall Glacier 7. Fairbanks
The latest scientific data confirm that the earth's climate is rapidly changing. Global temperatures increased by about 1 degree Fahrenheit over the course of the last century, and will likely rise even more rapidly in coming decades. The cause? A thickening layer of carbon dioxide pollution, mostly from power plants and automobiles, that traps heat in the atmosphere.
Scientists say that unless global warming emissions are reduced, average U.S. temperatures could rise another 3 to 9 degrees by the end of the century -- with far-reaching effects. Sea levels will rise, flooding coastal areas. Heat waves will be more frequent and more intense. Droughts and wildfires will occur more often. Disease-carrying mosquitoes will expand their range. And species will be pushed to extinction. As this page shows, many of these changes have already begun.
CLIMATE PATTERN CHANGES
Consequence: warmer temperatures
Average temperatures will rise, as will the frequency of heat waves.
Warning signs today
* Most of the United States has already warmed, in some areas by as much as 4 degrees Fahrenheit. In fact, no state in the lower 48 states experienced below average temperatures in 2002. The last three five-year periods are the three warmest on record.
* Many places in North America had their hottest seasons or days on record in the late 1990s.
* Since 1980, the earth has experienced 19 of its 20 hottest years on record, with 2005 and 1998 tied for the hottest and 2002 and 2003 coming in second and third.
Consequence: drought and wildfire
Warmer temperatures could also increase the probability of drought. Greater evaporation, particularly during summer and fall, could exacerbate drought conditions and increase the risk of wildfires.
Warning signs today
Wildfire
Greater evaporation as a result of global warming
could increase the risk of wildfires.
* The 1999-2002 national drought was one of the three most extensive droughts in the last 40 years.
* In 2002, the Western United States experienced its second worst wildfire season in the last 50 years; more than 7 million acres burned. Colorado, Arizona, and Oregon had their worst seasons.
* The period from April through June of 1998 was the driest three-month period in 104 years in Florida, Texas, and Louisiana.
* Dry conditions produced the worst wildfires in 50 years in Florida in 1998.
* April through July of 1999 was the driest four-month stretch in 105 years of record-keeping in New Jersey, Delaware, Maryland, and Rhode Island.
* Montana, Colorado, and Kansas experienced severe dust storms in 2002, a product of dry conditions.
* September 2001 to February 2002 was the second driest six-month period on record for the Northeast.
Consequence: more intense rainstorms
Warmer temperatures increase the energy of the climatic system and lead to more intense rainfall at some times and in some areas.
Warning signs today
* National annual precipitation has increased between 5 and 10 percent since the early 20th century, largely the result of heavy downpours in some areas.
* Vermont, New Hampshire, Rhode Island, and Massachusetts each got more than double their normal monthly rainfall in June 1998.
* Severe flooding in the Texas, Montana, and North Dakota during the summer of 2002 caused hundreds of millions of dollars in damage.
HEALTH EFFECTS
Heat wave in Chicago
More frequent and more intensive heat waves could result in more heat-related deaths. Photo: Gary Braasch, Chicago, July 1995. See the World View of Global Warming website for more Gary Braasch photos illustrating the consequences of the changing climate.
Consequence: deadly heat waves and the spread of disease
More frequent and more intensive heat waves could result in more heat-related deaths. These conditions could also aggravate local air quality problems, already afflicting more than 80 million Americans. Global warming is expected to increase the potential geographic range and virulence of tropical diseases as well.
Warning signs today
* In 2003, extreme heat waves caused more than 20,000 deaths in Europe and more than 1500 deaths in India.
* More than 250 people died as a result of an intense heat wave that gripped most of the eastern two-thirds of the United States in 1999.
* Disease-carrying mosquitoes are spreading as climate shifts allow them to survive in formerly inhospitable areas. Mosquitoes that can carry dengue fever viruses were previously limited to elevations of 3,300 feet but recently appeared at 7,200 feet in the Andes Mountains of Colombia. Malaria has been detected in new higher-elevation areas in Indonesia.
WARMING WATER
Consequence: more powerful and dangerous hurricanes
Warmer water in the oceans pumps more energy into tropical storms, making them more intense and potentially more destructive.
Warning signs today
* The number of category 4 and 5 storms has greatly increased over the past 35 years, along with ocean temperature.
Consequence: melting glaciers, early ice thaw
Rising global temperatures will speed the melting of glaciers and ice caps, and cause early ice thaw on rivers and lakes.
Warning signs today
* At the current rate of retreat, all of the glaciers in Glacier National Park will be gone by 2070.
* After existing for many millennia, the northern section of the Larsen B ice shelf in Antarctica -- a section larger than the state of Rhode Island -- collapsed between January and March 2002, disintegrating at a rate that astonished scientists. Since 1995 the ice shelf's area has shrunk by 40 percent.
* According to NASA, the polar ice cap is now melting at the alarming rate of nine percent per decade. Arctic ice thickness has decreased 40 percent since the 1960s.
* In 82 years of record-keeping, four of the five earliest thaws on Alaska's Tanana River were in the 1990s.
Collapse of Larsen B ice shelf
The satellite photo at far left shows the Larson B ice shelf on Jan. 31, 2002. Ice appears as solid white. Moving to the right, in photos taken Feb. 17 and Feb. 23, the ice begins to disintegrate. In the photos at far right, taken Mar. 5 and Mar 7, note water (blue) where solid ice had been, and that a portion of the shelf is drifting away. Photos: National Aeronautics and Space Administration
Consequence: sea-level rise
Current rates of sea-level rise are expected to increase as a result both of thermal expansion of the oceans and of partial melting of mountain glaciers and the Antarctic and Greenland ice caps. Consequences include loss of coastal wetlands and barrier islands, and a greater risk of flooding in coastal communities. Low-lying areas, such as the coastal region along the Gulf of Mexico and estuaries like the Chesapeake Bay, are especially vulnerable.
Warning signs today
* The current pace of sea-level rise is three times the historical rate and appears to be accelerating.
* Global sea level has already risen by four to eight inches in the past century. Scientists' best estimate is that sea level will rise by an additional 19 inches by 2100, and perhaps by as much as 37 inches.
ECOSYSTEM DISRUPTION
Alpine meadow
Warmer temperatures may cause some ecosystems, including alpine meadows in the Rocky Mountains, to disappear.
Consequence: ecosystem shifts and species die-off
The increase in global temperatures is expected to disrupt ecosystems and result in loss of species diversity, as species that cannot adapt die off. The first comprehensive assessment of the extinction risk from global warming found that more than one million species could be committed to extinction by 2050 if global warming pollution is not curtailed. Some ecosystems, including alpine meadows in the Rocky Mountains, as well as tropical montane and mangrove forests, are likely to disappear because new warmer local climates or coastal sea level rise will not support them.
Warning signs today
* A recent study published in the prestigious journal Nature found that at least 279 species of plants and animals are already responding to global warming. Species' geographic ranges have shifted toward the poles at an average rate of 4 miles per decade and their spring events have shifted earlier by an average of 2 days per decade.
* In Washington's Olympic Mountains, sub-alpine forest has invaded higher elevation alpine meadows. In Bermuda and other places, mangrove forests are being lost.
* In areas of California, shoreline sea life is shifting northward, probably in response to warmer ocean and air temperatures.
* Over the past 25 years, some penguin populations have shrunk by 33 percent in parts of Antarctica, due to declines in winter sea-ice habitat.