Place your bets -- Epsilon redux

Tamino asks:

What’s the chance that if we continue with business-as-usual, man-made global warming will lead to disastrous climate change? It isn’t zero. It isn’t one. What is epsilon?

My estimate (with links added):

Even if benefits were somehow remotely comparable to costs (2% chance of that, maybe?), benefits will be concentrated among the rich, while harms will be concentrated among the poorest and most vulnerable. So disaster is highly likely.

Enough disruption and direct harm to reverse the overall trend to greater wealth and prosperity — 10% — 70% (highly uncertain) — say 40% over the next few centuries.

Collapse of civilization, barbarism, going a long way backwards in terms of knowledge and human adaptive capacity even as impacts continue for centuries — 5%.

About the first estimate I (and most economists who have studied the issue) are very confident, and it’s easy to make the case for mitigation based on that alone. The other estimates are highly uncertain, and many analyses ignore them, foolishly in my view.

Add your own estimates at Tamino's and/or over here. He forbids much supporting argumentation, to avoid distractions, but not being cursed with his degree of popularity, I think we can differentiate ourselves by welcoming rationales and arguments for the numbers. 

Tamino is watching the food

Open Mind takes on what I have argued is the critical "final common pathway" of global warming risks -- crop and supply chain failures (which may start small, and end up big) leading to a situation in which -- there's no way to say this gently -- people will starve.

It's hard for us to imagine that society to break down in that way -- for people in the developed world, their only experience of food is as something they get in exchange for money. That we could have money and not be able to buy the things we need is so far out of our experience that it may seem preposterous. It's not. It's closer to such as us than we like to think.

Tamino rocks the graphs to analyze the cause of the recent explosive spike in food prices:



Money quote:

The 2010-2011 rise in food prices was triggered by a rise in cereals prices. It started in July of 2010, and still hasn’t relented. Sure, there are other factors too — and as usually happens, an increase in cereals prices can cause a “ripple effect,” leading to increased prices in other commodities. But the root cause is something that happened to cereals prices in July of 2010.

And what on earth could that be?

“Cereals” includes wheat. What if one of the world’s largest wheat producers had devastating crop losses, reducing their production by a third? What if they were one of the world’s biggest wheat exporters, but production was so reduced that their exports dropped to zero? That’s exactly what happened in Russia. And the trouble started in July of 2010.

Why did the Russian wheat harvest suffer so? Because of the record-breaking heat wave and drought which plagued a massive region, at just the wrong time for Russian agriculture. And one of the contributing factors is: global warming.

That’s the ugly, deadly dangerous secret the denialists don’t want you to think about. That’s why they sank so low as to try to blame inflation of food prices on attempts to fight global warming, when it’s really due to: global warming.

All I can add to Tamino's analysis is this: we live in a highly complex and interrelated civilization, and I'm a fan. I wouldn't want to be a hunter-gatherer. Art, science, literature, philosophy and engineering all cease to exist without the specialization that has increasingly characterized human societies since the adoption of settled agriculture. But specialization comes with a price. A more complex machine is more prone to failure and more difficult to repair.

Picture two wells. When you replace a well that is a hole in ground, a bucket, and a rope with a diesel generator, water pump, and a set of pipes, you improve the functionality of that well immensely, but you also add many, many more points of failure. Similarly, as our society becomes more and more sophisticated, greater caution is called for, more redundancy, more effort to anticipate problems, more humility. Yet the wealth and comfort we enjoy engenders the opposite attitude -- we have developed an exaggerated idea of our power over nature, come to take our technology for granted, developed an expectation of a constant increase in prosperity which may be possible, but is not inevitable by any means.

We are drawing the wrong lessons from the explosive change that the scientific method and the rule of law have brought us over the last 250 years. I very much fear that there is a rude awakening ahead.