There Are No Shortcuts

What sounds logical can deceive

There are no shortcuts in science. A scientist studying a natural phenomenon must first determine what factors are relevant and then isolate them to determine how they contribute. One cannot just string together logical statements, reach a conclusion and declare your theory is proved. Unfortunately, this is how science is often communicated in public.

To help make this point, I’d like to give an example outside the realm of science. Let us say that,

1.       All flights attendants know how to swim

2.       Ralph knows how to swim

3.       Conclusion: Ralph is a flight attendant

You probably view this conclusion as suspect. This is an example of a valid deductive argument that reaches a false conclusion. Assuming the first two propositions are true, it is not logical to reach the conclusion. There is nothing in the propositions that integrates flight attendants, Ralph and swimming. The swimming is coincidental but not a determining factor in Ralph’s employment. We simply need more information to determine if swimming is the deciding factor in Ralph’s career choice.

Now let’s see how this error creeps into the public debate regarding climate change.

I have seen on-line some people try to explain human caused climate change in the following way:

1.       The Earth is heated by sun at shorter wavelengths and cools by radiating heat to space at longer wavelengths.

2.       CO₂ absorbs energy at long wavelengths (the same spectral region that cools the Earth)

3.       The physics of thermodynamics teaches us that temperature rises when more energy is absorbed than can be released.

4.       Conclusion: CO₂ is warming the Earth.

This conclusion leaves out quite a bit of context and ignores many other factors that are relevant to the rise in global temperatures.

It is absolutely true that the Earth is warmed by shortwave radiation coming from the sun and cools by long-wave radiation to space. But the science isn’t entirely clear how much sunlight heats the Earth. There are about a dozen different databases with measurements of the energy coming from the Sun. Depending on which one that is used, a study may conclude that the Sun has had a steady output or it has been variable with a steadily rising output.

It is equally true that CO₂ absorbs the long-wave radiation coming from the Earth, slowing the escape of heat to space. But it is unclear how large a role it plays in regulating the Earth’s temperature. It certainly contributes to warming. It is most likely that CO₂ is only one of several factors, however.

The final point regarding thermodynamics is also misleading. Physics textbooks deal with simple systems to teach about energy transfer. The Earth’s climate is a complex interplay between land, air and water. While we know quite a bit about how heat is exchanged between these systems, it is not well known how long-term, large-scale changes take place.

So, similar to our initial statement about Ralph, it is important to understand the full context of the science.  It is also crucially important that any conclusions be tightly tied to the propositions that led us to that conclusion. Each proposition must be true under all circumstances and they should relate to each other. Science communication needs to be clear on this point.