"Global warming" means the same thing as "climate change" or "global climate change." Simply put, it describes the increase in the average ground and atmospheric temperatures across the planet. Temperatures have risen between 1.08 and 1.62 degrees Fahrenheit over the past century. The consensus among scientists is that humans are to blame, largely due to vehicles, power plants, factories and other energy users burning fossil fuels such as coal and oil, and to land being cleared for development. Such actions send tons of greenhouse gases into the atmosphere, which causes the warming.
While a 1-degree temperature rise may sound puny, global warming has set in motion lots of changes: glaciers are melting, many birds are beginning their migrations earlier, some islands are becoming submerged by rising seas, melting ice is causing polar bears to starve and so on. One study found 1,700 plants, animals and insect species moved an average four miles per decade in the last half of the 20th century in search of more suitable homes. A 2006 NASA study found that the world's temperature already is reaching a level not seen in 12,000 years.
If nothing is done, an international consortium of 2,000 scientists (called the Intergovernmental Panel on Climate Change) predicts temperatures could rise 11 degrees by century's end. Already, NASA scientist James Hansen says there's been a 1-degree change in the past 30 years, with another 1-degree warming in the pipeline due to gases already in the atmosphere. Yet another 1 degree is in the pipeline because of the energy infrastructure in place, such as existing power plants and vehicles.
Skeptics while few in number loudly disagree humans cause global warming or, in some cases, that a problem even exists. U.S. Senator Jim Inhofe of Oklahoma famously has called global warming "the greatest hoax ever perpetrated on the American people." The most vocal skeptics have done relatively little recent peer-reviewed scientific research on the topic. And they represent a distinct minority among scientists.
We're on a path to turn Earth into a different planet, one without sea ice in the Arctic, with continuously rising seas and other changes, says NASA's Hansen, who has warned about the problem since the 1980s.
"It may seem impossible to imagine that a technologically advanced society could choose, in essence, to destroy itself, but that is what we are now in the process of doing," Elizabeth Kolbert wrote as the ending of her acclaimed climate-change book, Field Notes from a Catastrophe.
There is hope!
Many cities, counties and state governments, as well as businesses, are taking action. Hansen calls for improving energy efficiency, putting a moratorium on building coal-fired power plants, and putting a price on emissions (while encouraging renewable energy).
To avoid the most dangerous effects of warming, scientists say an 80 percent reduction in greenhouse-gas emissions is needed by 2050. How could you reduce your personal emissions by 80 percent? Figure out your current impact and find tips for reducing it here.
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