A VERY MUCH MALIGNED GAS

With our almost religious fervor to embrace the idea of global warming, carbon dioxide in our atmosphere is getting a bad rap. Rarely mentioned are the other so-called green house gases: water vapor and methane. With about three-quarters of the Earth covered by water, water vapor is tough to do much about. And methane is emitted by many living things notably we humans, cattle and termites.

Carbon dioxide occupies less than 0.04% of the air we breath, but has admittedly a profound effect on our planet. Without it, the average temperature of the Earth would be well below freezing. Our distance from the Sun, makes its warming effect not enough to keep us toasty. Even more importantly, carbon dioxide keeps us from starving. It is the crucial source of all our food. Plants use the sun's energy to break apart carbon dioxide and turn it into the carbon-based molecules that make up our food. Every year some 100 billion tons of carbon dioxide are converted into plant material. This provides the foodstuff that feeds every animal and human on Earth.

Unfortunately, when anything is burned for energy to drive our world--be it wood, oil, coal or natural gas, carbon dioxide is produced as a by-product. Even the slow burning of food in animal or human metabolism creates carbon dioxide. Plants convert water and carbon dioxide into sugars and starches and give off oxygen as a by-product. We and other animals eat plant tissues and burn them with oxygen for energy while exhaling carbon dioxide. This is how nature preserves the cycle of life.

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