Last week, I gave the final exam for my Physics of Energy and the Environment class, a course for non-science-major undergraduates. Nearly all of the questions were answered correctly by a majority of students, and the individual question outcomes correlated well with overall exam performance. Surprisingly, however, there was one question that the vast majority (75%) got wrong. It didn’t require complicated analysis, or even any analysis at all. Rather, it was a simple factual question (the lowest rung in Bloom’s taxonomy), and moreover one we explicitly discussed and commented on in class. Why, then, would it fare so poorly?
The question was this:
Over 180 countries made pledges regarding their future CO2 emissions as part of the 2015 Paris climate agreement. If countries act as they’ve pledged…
- A … the planet will cool, counteracting the warming that has occurred so far.
- B … the planet’s temperature will remain stable (unchanging) for the rest of this century.
- C … the planet will warm, but the warming this century will be less than 1 °C..
- D … the planet will warm, but the warming this century will be less than 2 °C.
- E … the planet will warm more than 2 °C this century.
See if you know the answer; I’ll state it in a moment. (Someday I’ll learn how to make quizzes in WordPress…)
When covering this in class, about a week before the exam, I showed the following graph showing global greenhouse gas emissions over time, pointing out the curves this would have to follow in the future if overall warming of the planet is to be limited to 2C (greenish curve), or 1.5C (orange curve). I blocked the future curve that corresponds to what warming will be if countries follow their Paris Accord pledges. Note that in the Paris talks, about 190 countries agreed that warming should be limited to 2 C, ideally 1.5 C, to avoid major harm to people and our environment. (Graph source: ). Where will the pledged emission curve go? (To A, B, C, D, or E?):
Again, you can try to answer. I’ll reinsert today’s illustration, so your eyes don’t immediately go to the next graph…
Here’s the pledge curve (cyan):
The correct answer is A, which only 4% of students guessed. Why so few? Because, I think, it is absurd! Countries agreed that we should target warming of at most 2 C, and then promised to take actions that, even if they actually achieved them, would miss that mark by a large margin.
An analogy: Imagine you’re told that to avoid some disease you need to lower your daily calorie intake by 300 Calories. You agree to this, come up with a proposed diet that lowers your calorie intake by 100 Calories, and declare success. This seems bizarre, but this is exactly analogous to the Paris Climate Accords. This was noticed in 2015 itself. (Some other links: ) .
Worse still, most countries aren’t even meeting their pledges, but that’s another topic…
The answer to the exam question is, therefore, E. The pedagogical question is why so few answered correctly, especially since we explicitly noted this in class — not just me talking, but a poll question that required looking at the graph, plus several students commenting as well.
Here, I’m speculating, but I think one key aspect is that people have a very hard time absorbing information that contradicts their intuition or “common sense.” This comes up all the time in standard introductory physics courses — there are intuitions about motion, for example, that are hard to un-teach. Here, the intuition is of a different sort — of course one wouldn’t propose activities that don’t actually achieve one’s goals, so how could this be the case?
A second factor is that the course, this past term, was remote — I taught it by Zoom. I should write more about this, both as a post and for my own notes. In general it went better than I expected; about a quarter of the class was remarkably enthusiastic and engaged, and I got a lot of unsolicited positive comments. However, about a quarter were completely disengaged, attentive to a tiny fraction of the course content, whether live or recorded. The rest were somewhere in between. For a great many reasons, some within and some beyond their control, many students have an extremely hard time with our current remote-learning reality, and learn nearly nothing from it.
There’s more I should comment on about the course. We briefly, for example, covered nuclear power. (I try hard not to insert my views into the class, but I cannot believe that we take climate change seriously unless we increase our use of nuclear power, rather than decreasing it as we’re currently doing. The anti-nuclear arguments remind me a lot of climate denialism.) But, all this will have to wait. Among the many tasks for the week, preparing for next terms teaching: The Physics of Solar and Renewable Energy!
Your gastrointestinal tract. I felt like I needed a new illustration for a talk I gave at last week’s (virtual) American Physical Society meeting, and I’ve never been very happy with the guts I’ve drawn or painted.
— Raghuveer Parthasarathy; March 24, 2021
 Green light. The Economist (2015), (available at https://www.economist.com/international/2015/12/19/green-light)