Originally appeared in the Fort Collins Coloradoan on February 1, 2011

It’s refreshing to read that Gary Young (Jan. 24 Soapbox) wants to focus on physics facts rather than ideology or fairy tales. Sadly, the “facts” he wrote were almost completely wrong.

Young is correct that carbon dioxide molecules absorb and emit thermal radiation, but it’s the effect of the extra heat received by the surface that will cause our climate to warm dramatically in coming years. The extra CO2 actually cools the upper air as it radiates away heat more effectively. Water vapor in the air is a more potent greenhouse gas than CO2.

Unfortunately, the extra heat received by the oceans will cause much greater evaporation and so load the air with more water vapor on top of the extra CO2. Water vapor and CO2 don’t “compete:” they’re on the same team.
But Young’s most glaring factual error is the claim that “there are no robust definitive repeatable scientific experiments measuring how the effects of the superabundance of absorbing molecules actually heat or cool the atmosphere.”

This has been false for almost 150 years. The thermal absorption and emission properties of CO2 were first measured by John Tyndall in 1863, during the Civil War, and are about as well understood as steam locomotives.

Calculations of the warming expected to result from doubling CO2 by burning coal and oil were first published in 1896 before the invention of cars or light bulbs. Svante Arrhenius used measurements of the absorption of heat radiation from the Moon to calculate a warming of 5 degrees Fahrenheit for double CO2.

Modern estimates use much more data, but it’s remarkable that this number is almost unchanged through the last 115 years. Scientists and engineers all around the world have repeated these measurements and calculations thousands of times; the results are incredibly robust.

Another “physics fact” that Young doesn’t seem to understand is that most of the planet is covered by deep oceans, which warm much more slowly than the land because of their vast heat capacity.

The 5-degree warming estimate is a global average, but land in the northern hemisphere would warm at least twice that much. Measured trends back up the physics, so doubling CO2 should lead to about 10 degrees of average warming for inland places like Colorado.

Ten degrees of warming doesn’t sound so bad on a cold night in January, but you’d have to move to Roswell, N.M., to find a place 10 degrees warmer than Fort Collins on average.

If China and India industrialize with coal as expected, CO2 won’t just double but more than triple from 1850 levels by the time my children are old. According to simple physics, that would make Fort Collins as warm as Phoenix is now. I wonder what that will do for the stock market and real estate values?

Of course, it’s possible that something might come along and get rid of the extra heat. Maybe the sun will suddenly dim or huge clouds of interplanetary dust will cool us off.

Call me a skeptic. I’m not going to bet the farm on something like that without any evidence whatsoever.
Physics doesn’t depend on your beliefs, ideology or politics. The molecules just don’t care.

Scott Denning is Monfort professor of atmospheric science at Colorado State University. He is also the science advisor to the Fort Collins Sustainability Group.