People are sometimes surprised when they ask me if I believe in global warming and I say no. I always follow up by pointing out that belief is an article of faith, and faith neither seeks nor demands proof. I then continue by pointing out that I have data and mathematical models that show that human-caused global warming is happening with high enough probability to make it “actionable”, by which I mean that we must take action.
Of course, I personally do not (yet) have my own data and models. But I do have a scientists-style of understanding of how the physics work to create the problem, and am comfortable that I can use that understanding to explain to others (in my teaching mode).
When I sought the nomination to run as a Republican for a partisan public office, I visited a local College, where I addressed a room full of College Republicans (it was a small room). After the usual introductory speech about why I considered myself a conservative and a Republican (this was before the 2016 elections), I opened the floor for questions. Polling data tells us that the younger Republican voters are not denying the science of global warming, but since I am older it was no surprise that the first question they asked me was where I stood on global warming. We know there is a large divide between the older voters and the younger ones, and no doubt they were curious if I was “old school denier.”
I replied by noting that as a mathematician my sound bites took ten minutes and a whiteboard. They proceeded to scrounge up a maker and I turned to the whiteboard to explain my answer. I drew a set of circles connected by arrows. One was labeled “Temperature”, one was labeled “CO2” and the third was labeled “Orbital mechanics” (aka, Milankovitch Cycles). These three factors can explain the last 800,000 years of ice age cycles. A large arrow from orbital mechanics to temperature is used to indicate that orbits drive the Earth’s temperature, and that temperature drives the balance of CO2 between oceans and atmosphere. As the Earth heats up, the amount of CO2 in the atmosphere increases, so a larger arrow shows that temperature drives the CO2 content (so the increase in CO2 “lags behind” the temperature). Finally, a small arrow from CO2 to the temperature captures the idea that the increase in CO2 also adds to the temperature increase — this is called a feedback loop, and represents the greenhouse effect of atmospheric CO2. Then i sketched out a graph showing the temperature and CO2 over the last 800,000 years (rough, but instructive).
I then noted that this model is constructed using math that the physics students would recognize as differential equations, addressing the two economists I noted that they would recognize them as a dynamics model. Finally, pointing to the other students I commented that I did not know the right language in their areas of study.
Next, I explained, we began a global experiment in 1750 (the usual start of the Industrial Revolution) to see what happens to this system if we release several hundred million years of sequestered carbon from coal (and later oil and natural gas). Over the two hundred fifty plus years since then we have released over 500 billion tonnes of CO2. Drawing a large circle and labeling it “Industrial CO2” I noted that this new source of CO2 overwhelmed the tiny feedback between CO2 and temperature, and changed the model in a way that made human-released CO2 the driver of temperature, rather than the way it had been for the preceding 800,000 years.
Turning from the board to the College Republican students I concluded by noting that all the rest — the polar bears on ice cubes, disappearing glaciers, weird weather — all of these news stories are just politics, and the real question is what are we going to do about it?
Luckily for me, I was eventually unable to get the nomination, and Senator Draheim became the representative for District 20. I am no politician, it turns out.
About a year later, I told this story as an introduction to the idea of global warming — presenting to a room filled with about 400 8th grade science students. After the talk, as the students were leaving, one rushed down to ask me a question. His question?
“Sir, would those have been ordinary or partial differential equations?”
This is a mathematical sublety — and I could only smile as I replied, “Partial, and man, are you going to have a great life!”