The scientific consensus is that global average temperatures are rising, a phenomenon often referred to as global warming. Many scientists believe human activity has greatly contributed to the buildup of greenhouse gases in Earth’s atmosphere in the past century or so, and hence Earth’s gradual warming—around 1 degree Fahrenheit (0.5° Celsius). One recent study by an international panel of scientists predicted that the global average temperature could increase between 2.5 and 10.4° Fahrenheit (1.4 and 5.8° Celsius) by the year 2100 and that sea levels could rise by up to 2 feet (just over a half meter).

What is the biggest culprit? Although there are other gases, such as methane and chlorofluorocarbons, that increase global warming, most experts point to carbon dioxide as the worst pollutant in this case. This gas is released into the atmosphere mainly through burning of fossil fuels, such as coal, gasoline, and diesel. The gas also forms from the destruction of natural vegetation, such as the burning of forests to turn into grazing meadows for livestock. In this case, the carbon dioxide releases in two ways. First, the destruction of plant life through human actions causes less carbon dioxide to be absorbed out of the atmosphere; and secondly, rotting vegetation in clear-cut forests releases carbon dioxide.