The Science Behind Climate Change: the Facts to Convince a Your Friends and Family that Climate Change is Real

Often, people like to point to the latest talking point on denying climate change to argue that the science is not settled. This tactic is, of course, usually science-free. It is an argumentative tool in many denialists’ drawer. The actual scientific content of pointing to most denialist arguments is nil. One can find similar strategies and even entire books by flat-Earthers claiming that the round Earth is a hoax.

So, let’s turn the discussion and actually talk about the science of climate change and see why the physics of it is not exceedingly complicated. Some basic physical principles are required in order to even start discussing the climate science. The first physics principle is that things radiate heat energy at a rate given by the Stefan-Boltzmann Law,

where P is the power radiated, T is its temperature, e is the emissivity of the body, and σ is a constant that defines the relation. The simplest model we can create captures why increasing carbon dioxide increases the Greenhouse Effect and the temperature of the Earth’s surface. It’s called the two-box model. (This description follows the general-education level undergraduate textbook I use for a class on Energy and the Environment.)

The two boxes are the atmosphere and the Earth’s surface. Both the atmosphere and Earth’s surface radiate heat energy, in infrared light, with an amount given by the Stefan-Boltzmann law. The atmosphere radiates as

and Earth surface as

The atmosphere is partially transparent, absorbing a fraction of the emission given by

There is always solar energy going into the Earth’s surface. The infrared radiation going back into space is the total of the atmospheric radiation

and that from the Earth that makes it through the atmosphere

Some basic algebra is necessary now. The total power radiated into space is

with some rearranging becomes

The last term in red is the greenhouse effect term. It reduces the amount of energy radiating into space, and warms the Earth’s surface. Two things can make it be stronger: the emissivity of the atmosphere e is bigger, or the difference between the surface and radiating atmosphere temperatures is bigger,

It is often thought that the emissivity e increasing due to increased carbon dioxide, which has a high e, is the driving mechanism of the greenhouse effect, but this is subdominant. (This is often used by denialists to confuse the issue.) The main effect is that increased carbon dioxide in the atmosphere increases the altitude that the main radiation comes from the atmosphere, which is colder. Therefore, the temperature difference, between the Earth’s surface and the radiating atmosphere is larger. And, voila, this increase increases the Greenhouse Effect and more heat is trapped. Learning more about the science behind climate change is the number one reason denialists change their mind.

Now, this is a little bit technical, but is very basic physics. I teach the two-box model in a general education course at UC Irvine that has no math or science prerequisites. If your friend or family member does not know about the Stefan-Boltzmann law is, or cannot follow the algebra that shows how carbon dioxide increases the Greenhouse Effect term above, he or she should not be claiming to know anything about the science of climate change. There are more than a few such folks who are on Congress’ House Science Committee that still do just that: argue about settled science with empty talking points. This is one place to start to talk about the science.