Republican congressional candidate Ruth McClung boasts about her education in physics. It’s too bad she didn’t get a quality education in logic.

McClung lectures Arizona’s 7th congressional district on the importance of the sun in warming the Earth:

Global warming exists. The question is, “Is man-caused global warming a significant factor in our environment?” I don’t think so, and I am in good company with a number of other scientists. To understand why I believe this, we need to know a little about the physics of global warming.

We live on a relatively warm planet. If we didn’t, then life could not exist on the earth. The background temperature of space is roughly 3 or 4 degrees Celsius above absolute zero, or about 270 degrees Celsius below the freezing point of water. If the earth was not near the sun (or some other star) the earth too would be very cold – basically the background temperature of space. But since the earth is near the sun (about 93 million miles away) we live on a relatively warm planet.

The temperature on the earth is also affected by our distance from the sun. Mercury and Venus are both closer to the sun, and their temperatures are much hotter than the earth. Mars, Jupiter, and the rest of the planets are further from the sun, and their temperatures are much colder than the earth. In fact, if the sun was just 1% closer to the earth, about 2% more energy would fall on the surface of the earth, and if the sun was just 1% further away, the earth would receive about 2% less solar energy. The earth would then be warmer or cooler respectively.

The amount of solar energy that falls on the earth also affects the temperature. It is colder in the winter than in the summer because less solar energy falls on the earth’s surface in that hemisphere. The days are shorter in the winter. Also the sun is lower in the sky, so less light hits the ground directly.

So this leads me to my first rule on global warming: The number 1 factor contributing to global warming is the sun!

Calculus, the mathematics underlying much of science, distinguishes between the magnitude of a variable and the rate of change in a variable. Ruth McClung confuses the two in a sophomore’s blunder. In all but her last paragraph, McClung uses the phrase “Global Warming” to describe the positive effect that the sun’s radiation has on the Earth in keeping it warm. That the sun warms the earth is uncontroversial and nearly universally accepted. But in her last paragraph, McClung uses the phrase “Global Warming” to describe the positive rate of change we’ve seen over the last 100 years in global temperature. But the rate of change in global temperature and the magnitude of global temperature are not the same thing, which makes McClung’s conclusion fallacious.

To put the matter in slightly different terms, just because there is a causative factor that produces an effect on some system does not mean that all changes in the system are reducible to that causative effect. Consider my life and my heart, for example. I am alive because my heart is beating. Without a heart beat, I could not possibly continue to live. And yet, if I die, is it necessarily because of something my heart did? Clearly not. Is it possible that something else caused me to die? Of course. I could have been blown to smithereens by a bomb. I could have had my lungs stuffed with mud.

Intervening variables often affect complicated systems like the Earth’s climate and like human societies. Neither the environment nor policymaking is reducible to simple bivariate relations. Ruth McClung’s overly simplistic, bivariate way of thinking does not suit her well for Congress.