Your Questions: Carbon Power : NPR
CO2 is actually important to have in the atmosphere. Without enough of it, the Earth would get too cold for us. In fact, when we say humans are producing CO2, it does NOT mean the total amount of CO2 on Earth has changed. It stayed the same. Human beings don't create it out of nowhere. It's better to say human beings release CO2. That's more believable isn't it? Most CO2 is locked in ice and permafrost and in fossil fuels. When we burn fossil fuels we release CO2. This released CO2 heats the earth a small amount which leads to ice melting, and that releases even more CO2. Yes, ice melts every year, but there is some ice that hundreds of thousands of years old. When this old ice melts it adds to the net amount of CO2 we wouldn't have otherwise.First, the sun bathes the Earth in radiation. Some of that radiation we can see – visible light — and some of it we can't, like ultraviolet light.
When solar radiation strikes Earth, the atmosphere reflects some of it back into space. The rest is absorbed by the atmosphere or penetrates through to the surface, where it is absorbed by land and water. Think of how a paved parking lot or puddle of water warms on a sunny day.
Then — and this is key — the Earth beams part of that heat back up to space — in the form of infrared energy. But while the transparent gases in the atmosphere let incoming sunlight pass through (that's where the name "transparent" comes from) they absorb or trap some of the infrared radiation sent up by the Earth. This infrared energy heats up the gas molecules, which then release some of that heat, helping warm the Earth. (In a real greenhouse, this "re-radiation" doesn't play a big role — the glass simply traps the warm air in the greenhouse.)
Also, it turns out that different atmospheric gases have different abilities to trap and radiate heat. The four major warming gases are water vapor, carbon dioxide, methane and nitrous oxide.
We know all this because ice cores can look much farther back than just 200 years, they can look back 650,000 years.
Q. How far outside of the historical range for CO2 levels are we at this point? — Jim Foreman, Sacramento, Calif.
Pretty far. Scientists studying air bubbles trapped in ice cores have found that over the last 650,000 years, CO2 levels in the atmosphere ranged from about 180 parts per million (ppm) to 300 ppm. Just prior to Britain's Industrial Revolution, levels hovered at 280 ppm, according to the latest report from the United Nation's Intergovernmental Panel on Climate Change. CO2 levels had risen to 379 ppm by 2005, and are increasing at an average of nearly 2 ppm per year.
The trend is pretty similar for other major greenhouse gases produced by human activities. Methane concentrations have more than doubled from 715 parts per billion (ppb) in pre-industrial times to 1774 ppb in 2005. And nitrous oxide levels have spiraled from 270 ppb to 319 ppb.