Why We Must Act

The greenhouse effect is not a bad thing.  In fact, without greenhouse gases like carbon dioxide, life on earth would not be sustainable.  Without greenhouse gases, solar radiation would simply bounce off the planet and escape into space.  The earth would be a frozen ball of ice.  Greenhouse gases serve as a global blanket, keeping the earth warm enough to sustain life.  Thank goodness for the greenhouse effect, and thank goodness for greenhouse gases.

But what if human activity dramatically altered the natural levels of greenhouse gases in the atmosphere?  If greenhouse gases dropped significantly, the global blanket would be threadbare and the planet would cool.  If greenhouse gases rose substantially, the insulating effect would increase and the earth would warm.  That's the theory, and we are all living through the experiment.  

In any one place, the temperature can change by many degrees from day to day, or even hour to hour. A one degree change in the average global temperature, however, is huge. As NASA's Earth Observatory explains: A one-degree global change is significant because it takes a vast amount of heat to warm all the oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age. A five-degree drop was enough to bury a large part of North America under a towering mass of ice 20,000 years ago. As the same article points out, "the average global temperature on Earth has increased by about 0.8°Celsius (1.4°Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade." As the ClimateInteractive Scoreboard shows, with a business as usual approach to climate change, the average global temperature is expected to rise almost 5° Celsius, approximately the same magnitude of change as between now and the last Ice Age.