Causes: Almost 100% of the observed temperature increase over the last 50 years has been due to the increase in the atmosphere of greenhouse gas concentrations like water vapor, carbon dioxide (CO2), methane and ozone. There are several greenhouse gases responsible for warming, and humans emit them in a variety of ways. Most come from the combustion of fossil fuels in cars, factories and electricity production. The gas responsible for the most warming is carbon dioxide, also called CO2. Other contributors include methane released from landfills and agriculture (especially from the digestive systems of grazing animals), nitrous oxide from fertilizers, gases used for refrigeration and industrial processes, and the loss of forests that would otherwise store CO2.Different greenhouse gases have very different heat-trapping abilities. Some of them can even trap more heat than CO2. A molecule of methane produces more than 20 times the warming of a molecule of CO2 . Nitrous oxide is 300 times more powerful than CO2. Other gases, such as chlorofluorocarbons (which have been banned in much of the world because they also degrade the ozone layer), have heat-trapping potential thousands of times greater than CO2.
Effects:The planet is warming, from North Pole to South Pole, and everywhere in between. Globally, the mercury is already up more than 1 degree Fahrenheit (0.8 degree Celsius), and even more in sensitive Polar Regions and the effects of rising temperatures aren’t waiting for some far-flung future. They’re happening right now. Signs are appearing all over, and some of them are surprising. The heat is not only melting glaciers and sea ice; it’s also shifting precipitation patterns and setting animals on the move. Some impacts from increasing temperature are already happening.
•Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice.
•Sea level rise became faster over the last century.
•Some butterflies, foxes, and alpine plants have moved farther north or to higher, cooler areas.
•Precipitation (rain and snowfall) has increased across the globe, on average.
•Spruce bark beetles have boomed in Alaska thanks to 20 years of warm summers. The insects have chewed up 4 million acres of spruce trees.
If this warming continues, then
•Sea levels are expected to rise between 7 and 23 inches by the end of the century, and continued melting at the poles could add between 4 and 8 inches.
•Hurricanes and other storms are likely to become stronger.
•Species that depend on one another may become out of sync. For example, plants could bloom earlier than their pollinating insects become active.
•Floods and droughts will become more common. Rainfall in Ethiopia, where droughts are already common, could decline by 10 percent over the next 50 years.
•Some diseases will spread such as malaria carried by mosquitoes.
•Ecosystems will change, some species will move farther north; others won’t be able to move and could become extinct. Wildlife research scientist Martyn Obbard has found that since the mid-1980s, with less ice on which to live and fish for food, polar bears have gotten considerably skinnier.
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