Climate Nonlinearity in Simple Terms (video)

click here for videoI’m making this video during a cold wave here in the USA. Climate change is bringing everyone more extreme weather, both colder and warmer. But the overall trend is warmer.

In 1990 the United Nations Advisory Group on Greenhouse Gases said (quote)

Temperature rise beyond one degree centigrade may elicit rapid, unpredictable and nonlinear responses that could lead to extensive ecosystem damage.

(end of quote) “Nonlinear”?? What does that mean?

Well, my name is Eric Schechter, and I’m an emeritus professor of mathematics at Vanderbilt University, and I will explain “nonlinear.”

A process is called “linear” if its graph is nearly a straight line; that is, next year’s change is nearly the same as last year’s change. Well, that’s not happening; the temperature rise is SPEEDING UP.

arrows smallThere are two kinds of nonlinearities that I’m particularly worried about. One is a FEEDBACK LOOP. That’s a process whose consequences are also causes.

For example, as a CONSEQUENCE of warming, the ice on the Arctic Ocean is melting. The white ice, which used to REFLECT sunlight, is replaced by dark water, which ABSORBS sunlight. That’s a CAUSE of more warming. And what happens in the Arctic doesn’t stay in the Arctic.

There are many feedback loops in global warming. And some of them, such as the melting of polar ice, won’t be stopped by the end of fossil fuels or even the end of civilization. We need drastic remedies NOW.

As a feedback loop gets bigger, so do its consequences, and thus its causes. So it grows FASTER AND FASTER. The result is EXPONENTIAL growth, and the graph of that is VERY different from a straight line. We math professors teach about exponential growth in calculus. By the way, I urge all my fellow math professors to start talking about global warming, both inside your classes and outside your classes, if you’re not doing that already.

The other nonlinearity that worries me is tipping points. If you gradually lean back in your chair, at first it’s quite comfortable. But when you lean back just a little too far, you pass the TIPPING POINT, and suddenly WHAM! you’re on the floor. Similarly, when the temperature rises past certain critical levels, we may experience abrupt systemic changes.

methaneFor instance, methane is already leaking slowly from the Arctic. When the temperature gets just a little higher, the rest of the methane may suddenly be released. There’s a lot of it, and it’s a very powerful greenhouse gas.

And the ecosystem may have tipping points too. Already, the temperature is rising faster than species can adapt, and they’re going extinct. The ecosystem is losing diversity, and that makes it fragile. At some point it may pass a tipping point, and WHAM! it may collapse, like a tower of blocks with one too many removed.

That would be bye-bye to humanity and most other species. We humans are the most adaptable species, but without the other species, we’ll have nothing to eat.

Some crop failures have already begun. Even the rich will run out of canned food, and they can’t eat their money.

We’re near the edge. We might still avoid extinction, but only if we make big changes in a big hurry. Our governments are doing too little about climate, because they’re in the pocket of the fossil fuel companies.

Don’t be fooled by greenwashing. Regardless of what they may say, corporations put short-term profit ahead of all else, to keep up with their rivals and survive in a competitive market. That’s the nature of capitalism. But you and I must COOPERATE, to save the ecosystem. Join the protests. Spread the word.


2021 Feb 19, version 1.01. I think it’s much better with all the pictures (if you can make out the audio track); this is the transcript of a video.