Where does the politics end and the science begin? A few basic questions may help clear some of the smog.
Who came up with this greenhouse gas concept and how seriously is it taken?
According to physicist and historian Spencer Weart, the idea can be traced to French mathematician Joseph Fourier. Back in the 1820s, Fourier did some calculations to show that a rock like Earth orbiting at 93 million miles from the sun should be a big snowball. He suggested our balmy temperatures could be attributed to our atmosphere, which might hold in heat - sort of like a greenhouse.
There wasn't much experimental evidence to back this up until the 1850s, when British scientist John Tyndall started shining infrared light through various gases.
Tyndall knew the Earth absorbs solar radiation and emits infrared. If the greenhouse theory was right, gases that make up the atmosphere would absorb some of this infrared, thus raising the temperature.
At first he almost disproved the greenhouse effect by showing that infrared passes straight through oxygen and nitrogen - the main components of our atmosphere. But before he quit, Tyndall tried a few other gases, including CO2, and found it was a powerful absorber of infrared. Water vapor had the same property.
That suggested that while carbon dioxide makes up less than 0.001 percent of our atmosphere, it's working along with water vapor to prevent infrared radiation from escaping to space. These gases also emit radiation, some of which is directed back toward the ground. "As a dam built across a river causes a local deepening of the stream, so our atmosphere . . . produces a local heightening of temperature at Earth's surface," Tyndall wrote.
