We’ll have another feature article up in a couple of days.
Meanwhile, any topic is fair game as commentary to this article (though as always we prefer comments that are interesting, thoughtful and kind over ones that are boring, trite or mean).
In the event that y’all are tongue-tied in coming up with a topic, I’d like to propose an increasingly common question and increasingly important question that is likely to get some special attention in the next few weeks, and which I expect to be at the center of a legitimate controversy for a long time to come.
(Wow. A legitimate controversy.)
The question is how we should be thinking about extreme events. Notably, extreme weather events, and extreme environmental events of sorts that are connected to weather and climate, such as wildfires and infestations.
There is a tendency for those of us who are alarmed to look at every such event, and say “See! We’ve gone too far already!” Meanwhile those who tend to be more sanguine will flip through the history books, find analogous events, and say “it was ever thus”. These claims seem like they ought to be reducible to objective questions. But there is considerable controversy within science as to how to think about them.
I hope my paraphrases are not too far off the mark, but as I understand it Kevin Trenberth suggests that the human influence on climate is already so profound that every event is a climate change driven event to some extent. On the other hand, Myles Allen suggests that no event has occurred to date that is demonstrably impossible in the preindustrial climate. Both of these claims are cogent and reasonable, indeed undeniable. Yet their cogency carries the same sense as it does in the following anecdote, commonly told of engineers, but here repurposed for atmospheric scientists.
Two men in a hot air balloon lose their bearings, and yell down to somebody on the ground “Where arrrreee weeee?”. To which the distant response is heard: “In an Balloooooon!” One of the two daredevils turns to the other and says “That must be a climate scientist. Every word he says is true and still we have no better idea what to do than before we asked.”
The simple answer seems to be that no individual event has any established connection to climate change, yet all events are causally related to it.
This one is not just the usual political back-and-forth between the groups that have associated their identity politics with one or another side of the question. This is important, because how hard we work to avoid climate change depends on the associated risks, among which severe events figure prominently.
Whil we have many many observations of common events and can determine with astonishing precision the measures of the mundane. Even with terribly calibrated instruments, after all, we have essential unanimity in the global mean temperature trajectory! But the statistics of the extraordinary are much harder, both in practical and in theoretical terms.
Right now there are astonishing floods in Thailand. How, for example, should we think of them? Are they once-in-a-lifetime floods? Or unheard-of floods? If they are once-in-a-lifetime floods, are they becoming twice-in-a-lifetime floods? How much does that matter?
I have seen some images that make me wonder if Thailanders don’t take floods in stride more than most of us. One picture showed a family, perched up on tables and sofa backs, watching television in their knee-deep flooded house. People seem to be grinning and bearing it. Maybe I am misreading it, but perhaps the lack of presence of the Thai floods on the front pages is appropriate. This is a rare event, but not an unheard of one, and people are prepared for it, like a blizzard in Montreal or a hurricane in Texas. Yet if a comparable area were underwater in most countries it might be much more severe, because it would have no precedent.
This past summer, the ongoing drought in all of Texas, most of the neighboring states, and half of Mexico took hold. In Texas, it yielded a summer without a close precedent in the evaporation rate in Texas or any other state. (The high desert states tend to have cool nights.) How should we think about this?
Is it the combination of an unprecedented drought, unrelated to global warming, plus some additional warming from the background trend? Note that while most models dry the southwest in the upcoming century, they are somewhat equivocal on the fate of Texas. Should what the models say work into our degree of attribution of particular events? Are we already seeing the effects of climate change in the occurrence of severe events? If not, how will we know when that happens? And if it does occur, how should it figure into our risk calculations?
This looks likely to be an ongoing theme for a while. Comments welcome here. Longer articles are more than welcome here ( firstname.lastname@example.org ) and links to such articles elsewhere would also be appreciated.