Module 4: Global Warming - Physics


Module 4 Overview

Video: Physics, Not Politics (2:06)

Click here for a video transcript of "Physics, not Politics".

I was down in Washington, not that long ago, talking to the staff of an important congressional committee. Which committee? Which party? Doesn’t matter. The bright young lawyer looked at me and said, “I didn’t take science in college. I don’t know science. I don’t like science, but I know that you’re wrong about your science, because Global Warming is based on a hockey stick and it’s broken." The hockey stick she referred to is a history of climate change showing recent rapid warming that’s been confirmed multiple times, and really isn’t broken, nor is it the basis of global warming.

And so my answer to her was, “No, actually global warming is based on physics.” It’s physics that’s been known for more than a century. It’s physics that’s confirmed everyday. And, it’s physics that was really worked out by the Air Force right after World War 2, not for climate, but for things such as sensors on heat seeking missiles. And in some real sense, if you deny the warming influence of the CO2 from our fossil fuels, you’re claiming that the Air Force doesn’t know what kind sensor to put on a heat seeking missile. The discussion we had after that was absolutely fascinating.

Now it’s certainly true that no all aspects of the global warming story are as solid as those physics of radiation in the atmosphere. So let’s go look at the parts that are solid, and see where they start to get speculative or where they start to get arguable.

Dr. Alley relates a true story of a confidently mistaken person in high places.
Richard B. Alley

The science of global warming involves a lot of physics, plus chemistry, biology, climatology, geology, glaciology, ... The science is not that difficult, but the whole story is fairly long. We look at some of this story in Modules 4 and 5.

Not too many years ago, a staff member of an important government committee told Dr. Alley, in approximately these words, “I didn’t study science in college. I don’t know science. I don’t like science. But, I know you’re wrong about your science, because global warming is based on a broken hockey stick.” To which Dr. Alley replied, more or less in these words “No, global warming is based on physics known for over a century, and really refined by the US Air Force after World War II when they were working on issues such as sensors for heat-seeking missiles. If you deny global warming, in some sense you’re denying that the Air Force knows what type of sensor to put on a missile.” The conversation that followed was fascinating.“ (The “hockey stick” that the staff member referred to is the history of temperature over the most recent centuries, based on tree-ring and other records as well as thermometer measurements, and actually has proven to be surprisingly accurate as more data have been collected.)

Public discussion of climate and energy in much of the world, including the US, often involves the question of whether someone or some group “believes in global warming”. Usually, “global warming” is understood to mean that humans are primarily responsible for an ongoing increase in the average temperature of the atmosphere near the Earth’s surface. But, to a scientist working in the field, asking whether they “believe” in global warming from the CO2 from fossil-fuel burning, is a little like asking whether they “believe” that gravity will pull a dropped pencil downward; both are unavoidable consequences of well-understood physics.

You might note that if you dropped your pencil just at the moment a tornado blew the roof off the building, the pencil might go upward; it also might go upward if you dropped it just at the moment that someone turned on a giant and properly aligned electromagnet and the pencil contained enough metal, or if an earthquake suddenly accelerated you just as you were dropping the pencil. We can never be absolutely positive what the future holds.

But, most people accept the tendency for a dropped pencil to fall downward, without asking whether you “believe” in gravity. If they could see in the infrared, they would probably hold similar beliefs about global warming. Within this module, we will explore the Physics of Global Warming.