Climate change impacts
The effects of warming on our world can be seen today
The Earth could warm another 2 to 11.5°F this century if we fail to reduce emissions from burning fossil fuels and deforestation—devastating our livelihoods and the natural world we cherish.
Impacts on the world around us
Thousands of species risk extinction from disappearing habitat, changing ecosystems and acidifying oceans. According to the IPCC, climate change will put some 20% to 30% of species globally at increasingly high risk of extinction, possibly by 2100.
Decline in polar bears
Arctic sea ice is the polar bear's feeding habitat. As sea ice disappears, bear mortality rises. In 2008, the polar bear became the first animal to be added to the Endangered Species Act list of threatened species because of global warming.
The U.S. Geological Survey has warned that two-thirds of the world's polar bear populations could be lost by mid-century as sea ice continues to retreat.
About one-third of the CO2 pollution from smokestacks and tailpipes is absorbed by the world's oceans, where it forms carbonic acid. A 2010 study published in Nature Geoscience warns that unchecked greenhouse gas emissions could cause oceans to acidify at a rate unprecedented in at least the last 65 million years.
Coral reefs are highly sensitive to small changes in water temperature. Heat triggers corals to shed the algae that nourish them—a bleaching event that leaves coral white.
In 1998, the world's coral suffered its worst year on record, which left 16% bleached or dead. (ISRS statement [PDF]) Continued warming could cause mass bleachings to become an annual event within the next few decades, wiping out many reef ecosystems.
Photo: Dr. Dwayne Meadows, NOAA/NMFS/OPR.
As the mercury rises, plants and animals are shifting their ranges toward the poles and to higher altitudes, and migration patterns for animals as diverse as whales and butterflies are being disrupted.
Threats to Western forests
The U.S. Geological Survey reports that slight changes in the climate may trigger abrupt ecosystem changes that may be irreversible.
All told, the Rocky Mountains in Canada and the U.S. have seen nearly 70,000 square miles of forest die – an area the size of Washington state – since 2000 due to outbreaks of tree-killing insects.
Thinning ice, rising seas
Rising seas are one of the most certain effects of global warming as warming ocean waters expand and melting glaciers, ice caps and ice sheets add more water to the oceans. The IPCC estimates that melting ice caps and glaciers—which are some of our most visible indicators of climate change—accounted for about 25% of sea level rise from 1993 to 2003.
Arctic sea ice is shrinking
Satellite images show that the extent of Arctic summer sea ice has decreased by almost 9% per decade since 1979. The Arctic summer could be ice-free by mid-century, according to a study by the National Oceanic and Atmospheric Administration.
Video: The three lowest minimum extents of Arctic sea ice were reached in 2007, 2008 and 2010. Source: NOAAVisualizations
Sea level rise
During the 20th century, sea level rose an average of 7 inches after 2,000 years of relatively little change. The 2007 IPCC report conservatively predicts that sea levels could rise 10 to 23 inches by 2100 if current warming patterns continue.
In the U.S., roughly 100 million people live in coastal areas within 3 feet of mean sea level. Low-lying cities such as Boston, Miami and New York are vulnerable.
The U.S. Geological Survey, EPA and NOAA issued a joint report [PDF] in 2009 warning that most mid-Atlantic coastal wetlands from New York to North Carolina will be lost with a sea level rise of 3 feet or more. North Carolina's barrier islands would be significantly breached and flooding would destroy the Florida Everglades.
A 2005 survey of 442 glaciers from the World Glacier Monitoring Service found that 90% of the world's glaciers are shrinking as the planet warms.
Glacier National Park now has only 25 glaciers, versus 150 in 1910. At the current rate of retreat, the glaciers in Glacier National Park could be gone in a matter of decades, according to some scientists.
Threats to people around the globe
Extreme weather will become more frequent—and more dangerous.
The World Meteorological Organization reported that 2000-2009 was the hottest decade on record, with eight of the hottest 10 years having occurred since 2000.
It's not just the heat that poses threats. Scientists say global warming is speeding up the cycling of water between the ocean, atmosphere and land, resulting in more intense rainfall and droughts at the same time across the globe.
A surge in wildfiresHot, dry conditions create a tinderbox ideal for wildfires. This could have a devastating impact on America's Southwest.
Increased floodingThe 2007 IPCC report concludes that intense rain events have increased in frequency during the last 50 years and that human-induced global warming has been a factor.
Increased droughtThere have also been increased periods of drought, particularly in famine-stricken areas of Africa and Asia. According to the National Center for Atmospheric Research, the percentage of Earth's surface suffering drought has more than doubled since the 1970s. In Africa alone, the IPCC projects that between 75 and 250 million people will be exposed to increased water stress due to climate change.
More intense hurricanesAs the oceans warm, scientists predict that hurricane intensity could increase. The associated storm surge poses particular risk to low-lying coastal cities like Miami, Charleston (SC) and Wilmington (NC).
Threats to human health
A warming planet threatens people worldwide, causing deaths, spreading insect-borne diseases and exacerbating respiratory illnesses. Extreme weather will also put more people in harm's way.
The World Health Organization believes that even the modest increases in average temperature that have occurred since the 1970s are responsible for at least 150,000 extra deaths a year—a figure that will double by 2030, according to WHO's conservative estimate.
Devastating heat waves
Recent studies show extreme heat events that now occur once every 20 years will occur about every other year in much of the country, if current trends continue.
In 1995, Chicago suffered a heat wave that killed more than 700 people. Chicagoans could experience that kind of relentless heat up to three times a year by 2100.
Spread of disease
Diseases such as malaria and dengue fever could become more difficult to control in areas where it's currently too cold for them to spread year-round. The malaria parasite itself is generally limited to certain areas by cooler winter temperatures since it is not able to grow below 16°C. As temperatures rise, diseases can grow and disease vectors (the carriers that transmit disease, such as mosquitoes) will mature more rapidly and have longer active seasons.
Worsening air quality
More hot days mean ripe conditions for ground-level ozone, or smog, which forms when pollutants from tailpipes and smokestacks mix in sunny, stagnant conditions. Higher temperatures cause higher emissions of one type of pollutant, namely hydrocarbons and other volatile organic compounds, as well as speeding up the chemical reactions that form ozone smog.
Smog triggers asthma attacks and worsens other breathing problems. The number of Americans with asthma has more than doubled over the past two decades to 20 million. Continued warming will only worsen the problem.
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