What Really Is the Worst That Can Happen?

Someone on the Facebook group “Global Warming Fact of the Day” (GWFotD to its Friends) brought up the famous and excellent Greg Craven video, and wondered why nobody had ever really answered Greg’s question.

So, what really IS the worst that could happen? Shouldn’t we calibrate our actions against that? Shouldn’t science try to answer that question?

This is especially true given the appearance of a community of people who believes that a climate-driven catastrophe is so imminent and so enormous that humans will be literally extinct within two decades. (Yes, some people apparently believe this so deeply that they express contempt for those who do not.) Can we refute them?

It turns out that it’s sort of an ill-posed question.

It’s certainly true that the whole ball of wax is at risk of being utterly ruined by humans. There’s some disagreement about how close to the edge we are and how much we can do about it. That it’s within our capacity to do that is no longer in doubt.

But there isn’t really a scientifically sound way to answer the question of what the worst case is.

For complex questions, rigorous thought is best done statistically. Are you talking about 99-to-1 bad news or 999999 to 1 bad news? The worst thing that can happen? 99999999999 to 1? Who knows? Complex science is weakest at these fringes exactly where traditional physics is strongest.

But we have good ways to think about the last percentile, or the last decile. The more extreme the outlier, the weaker our ammunition. To the most extreme question, the “worst case”, there is no really rigorous answer.

Regarding near term extinction, humans are now thriving in a way that no species known ever anywhere has previously. To suggest that a globally dominant population of seven billion specimens would go extinct in less than a generation is what, a 0.9999999 event? It seems more likely to be caused by a rogue asteroid than by anthropogenic climate change in any case. Right now, we have enough to worry about with the more-likely-than not scenarios, which really is Greg’s point.

The Disappearing Hiatus

This has been known behind the scenes for a while, but the publication is useful. It again demonstrates that the scientific literature is performing a very unusual function in the climate policy arena. The very clear accessible presentation of the work in this video is enormously helpful as well.

I think another thing to consider is this. This demonstrates is how very un-robust the “slowdown” is. It did not take much of a correction to eliminate the trend.

Indeed, the conclusions allude to this:

While short term trends are generally treated with a suitable level of caution by specialists in the field, they feature significantly in the public discourse on climate change.

There’s another aspect to this, though, and it may be a bigger deal than might at first be apparent. It adds up to a pretty scary situation.

That’s because the “slowdown” or “hiatus” has also had a number of alternative explanations. Decreased solar activity. Increased volcanic activity. A prevalence of cool-phase El Nino oscillations. Increase in aerosol loading from rapid and dirty Chinese industrial expansion. Heat export to deeper ocean layers.

To be sure, we are somewhat at risk of post hoc reasoning here. If there had been no sign of a “hiatus”, it is likely that less effort would have gone into explaining it! But all of these explanations appear individually to be sound, and with the possible exception of the last, likely to be reversed at any time. What that would mean is that in reality the underlying rate of warming is still accelerating. Ouch.