“The earth is a natural greenhouse and is kept warm by water vapors, carbon dioxide (CO2), and other gases in the atmosphere, which absorb the sun’s energy and radiate it back toward the earth. This type of warming is called ‘natural greenhouse effect’. ‘Enhanced greenhouse effect’, on the other hand, causes global warming due to excessive levels of CO2 in the atmosphere.”
Facts
Average temperatures have climbed 1.4 degrees Fahrenheit (0.8 degree Celsius) around the world since 1880, much of this in recent decades, according to NASA's Goddard Institute for Space Studies.
The rate of warming is increasing. The 20th century's last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies.
The United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that 11 of the past 12 years are among the dozen warmest since 1850.
The Arctic is feeling the effects the most. Average temperatures in Alaska, western Canada, and eastern Russia have risen at twice the global average, according to the multinational
Arctic Climate Impact Assessment report compiled between 2000 and 2004. Arctic ice is rapidly disappearing and the region may have its first completely ice-free summer by 2040 or earlier. Polar bears and indigenous cultures are already suffering from the sea-ice loss.
Glaciers and mountain snows are rapidly melting—for example, Montana's Glacier National Park now has only 27 glaciers, versus 150 in 1910. In the Northern Hemisphere, thaws also come a week earlier in spring and freezes begin a week later.
Coral reefs, which are highly sensitive to small changes in water temperature, suffered the worst bleaching—or die-off in response to stress—ever recorded in 1998, with some areas seeing bleach rates of 70 percent.
Experts expect these sorts of events to increase in frequency and intensity in the next 50 years as sea temperatures rise.
An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and
strong tropical storms, is also attributed in part to climate change by some experts.
According to ‘The Intergovernmental Panel on Climate Change’ humans have caused all or most of the current planetary warming. Human-caused global warming is often called
anthropogenic climate change.Industrialization, deforestation, and pollution have greatly increased atmospheric concentrations of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse gases that help trap heat near Earth's surface.
Cars amount to three-quarters of all transportation emissions. At the current rate, the world will be driven on by more than a billion cars in 2030 and a billion more by 2050.
The earth’s atmosphere now contains 40% more CO2 than before the Industrial Revolution.
These gases persist in the atmosphere for years, meaning that even if such emissions were eliminated today, it would not immediately stop global warming.
Humans are pouring carbon dioxide into the atmosphere much faster than plants and oceans can absorb it.
Some experts point out that the natural cycles in Earth's orbit can alter the planet's exposure to sunlight, which may explain the current trend. Earth has indeed xperienced warming and cooling cycles roughly every hundred thousand years due to these orbital
shifts, but such changes have occurred over the span of several centuries. Today's changes have taken place over the past hundred years or less.
Other recent research has suggested that the effects of variations in the sun's output are
"negligible" as a factor in warming, but other, more complicated solar mechanisms could possibly play a role.
Consequences
Global warming could lead to large scale food and water shortages and have cata- strophic effects on wildlife.
Sea level could rise between 7 and 23 inches (18 to 59 centimeters) by century's end. Rises of just 4 inches (10 centimeters) could flood many South Seas islands and swamp
large parts of Southeast Asia.
Some hundred million people live within 3 feet (1 meter) of mean sea level, and much of the world's population is concentrated in vulnerable coastal cities.
Glaciers around the world could melt, causing sea levels to rise while creating water shortages in regions dependent on runoff for fresh water.
Strong hurricanes, droughts, heat waves, wildfires, and other natural disasters may become commonplace in many parts of the world. The growth of deserts may also cause food shortages in many places.
More than a million species face extinction from disappearing habitat, changing ecosystems, and acidifying oceans.
The ocean's circulation system, known as the ocean conveyor belt, could be permanently altered, causing a mini-ice age in Western Europe and other rapid changes.
At some point in the future, warming could become uncontrollable by creating a so-called positive feedback effect. Rising temperatures could release additional greenhouse gases by unlocking methane in permafrost and undersea deposits, freeing carbon trapped in sea ice, and causing increased evaporation of water.
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