EARTH HAS A FEVER
Throughout its long history, Earth has warmed and cooled time and again. Climate has changed when the planet received more or less sunlight due to subtle shifts in its orbit, as the atmosphere or surface changed, or when the Sun’s energy varied. But in the past century, another force has started to influence Earth’s climate: humanity Scientists say it’s “extremely likely” that human activity is boosting the planet’s temperature. Earth has a fever. Scientists are more certain now than ever before that people are largely to blame. It is “extremely likely” that human activities have contributed greatly to Earth’s increasing temperature, reports an international group of climate change researchers. How likely is that? Scientists say they are now 95 to 100 percent certain that people have had a big role in warming. A summary of the latest report, released September 27, was based on information published through 2012. Researchers from the Intergovernmental Panel on Climate Change, a United Nations group known as IPCC, analyzed thousands of studies. Most of those studies contained evidence suggesting a link between peoples’ actions and global warming. The new report’s conclusions are even more confident of humanity’s role in climate than the last IPCC assessment, issued in 2007. But even back then, IPCC considered that human activities “very likely” have been boosting global warming. Those activities include burning fossil fuels, such as coal and gas. That burning releases a greenhouse gas called carbon dioxide. In the atmosphere, this gas traps heat close to Earth’s surface. And that helps warm the planet. According to the report, carbon dioxide levels have increased by 40 percent since people started burning fossil fuels for energy, about 260 years ago. In the last 60 years, “the atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased,” the...
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