Carbon dioxide explained

Six years ago, for the first time in 800,000 years, the world’s carbon dioxide level passed 400 parts per million (ppm). This was the milestone we’d long been anticipating.

It was just 330 ppm when the Beatles were big. Earlier, when some of us were in kindergarten, CO2 was 315 PPM.  It had taken a long time to get there.  Before the Industrial Revolution, and going back for almost a million years, the level was 280 PPM. It now stays above 400 ppm permanently. 

Still, carbon dioxide makes up only 1/25th of one per cent of the air. When you take a breath, you inhale 500 times more oxygen than you do carbon dioxide. So why the fuss?


We’ve all heard about greenhouse gases, and know that carbon dioxide, along with methane and water vapor, are the big players in this arena. But you may not know how simple is the mechanism by which it does its dirty work. In half a minute you can fully grasp how it works.

Sunlight warms the ground during the day, and at night this energy radiates back into space in the form of infrared rays. Our air is about 80 percent nitrogen, 20 percent oxygen and one percent argon. Nitrogen and oxygen atoms commonly bond into twosomes to form the molecules N2 and 02, while argon is a loner and exists as just a plain atom. The key point is this: When infrared from the ground travels up through the air and encounters these atoms and molecules, it keeps going in a straight line and continues into space. This lets the ground cool during the night.

But a molecule with three or more atoms acts very differently during its infrared encounters. Methane (CH4), carbon dioxide (CO2) and water vapor (H20) have between three and five atoms apiece. When infrared strikes any of them, it gets absorbed by the molecule, which then re-radiates it in random directions, so instead of continuing upward into space the infrared now goes sideways or upward or downward. The downward ones return to the ground to re-heat the surface a bit. 

This explains why on cloudy nights when there’s lots of water vapor overhead, the ground doesn’t cool as much as it does on a clear night. The more methane, water vapor, or carbon dioxide is in the air, the less each night can cool down. Simple.

So greenhouse gases mainly do their work during the night. They raise a region’s nightly low temperatures. It’s as inevitable as the sunrise. We see carbon dioxide in action on other worlds and the effect is always to warm things up.

Right now, the two brightest nocturnal objects after the moon are Venus — dazzling in the east just before dawn — and Mars, brilliant in the east soon after nightfall, and then out all night long. Both worlds’ atmospheres are almost pure carbon dioxide. So both have much warmer surfaces as a result. Venus is the hottest planet in the known universe, while the Martian surface is boosted to a comfortable 45 degrees because of the CO2. 

If you know any skeptics regarding carbon dioxide, or who are not freaked by the earth’s still-new milestone of hitting 400 parts per million, just point upward any night, and show them how it operates elsewhere in the universe. 

And 400 is just a waypoint. In 25 years it will reach 450 PPM. And when today’s kindergartners are in their mid-fifties, carbon dioxide will probably reach 500 PPM. Nobody knows how much warming this will produce. A lot more than now, and opportunistic plants, insects and bacteria will find their way to new places, some of which may include sites within our own bodies. Untreatable medical conditions may result.

Fortunately for us, the northeastern United States is one of the few regions where NOAA’s climate modeling computers predict continued ample rainfall and minimal consequences. So if the recent migration to our area seems energetic, wait until the world catches on that ours will be one of the sanctuaries from the grossest effects of climate change.