It is time to stop quivering in our boots in pointless fear of the future and just roll up our sleeves and build it.
- Ray Pierrehumbert

Thursday, January 28, 2016

Another Day, Another Attribution Question

NPR asked some of the usual climatology suspects (Mike Mann, Heidi Cullen, etc.) "how come" about the recent, impressive Northeast blizzard.

I am sure a lot of meteorologists squirmed at the result.

People like to be asked questions about their expertise, and are loath to say "I dunno", so the resulting report is a baffling series of maybe-sortas. Climatology comes off looking very lame. OK, maybe it is in some ways somewhat lame, but it comes off much worse than it should.

If you had asked a meteorologist, you would have gotten a much more confident and impressive series of answers, and neither El Niño nor climate disruption would have figured prominently.

This is very reminiscent of  my recent comments about the Indian Monsoon, which were followed up by a much more detailed exposition by Rohit Singh, a fellow who obviously thinks about the monsoon in far more detail than I do.

I made the case that statistical climatology is mute and moot on the question, and that physical climatology would indicate that climate disruption must have an effect on the monsoon.

The question of whether El Niño has an effect on a blizzard is comparable. Of course, it must, as everything is not only connected, but in the atmosphere, everything that happens on a large scale is quite closely connected. But do we know what? Nope.

A far richer and more detailed answer can be provided by meteorologists, looking at short-term causality. Their explanation of the blizzard will have much in common with Singh's explanation of the monsoon. Along the lines of:
The storm ended up occluding in classic fashion, meaning that its main coastal surface low hung back while jet-stream energy carved out an occluded front extending northeastward just off the East Coast (see Figure 7). This evolution led to prime snowmaking conditions in a region of frontal formation aloft called a deformation zone that set up inland from the surface front, putting the heavy snow along and just northwest of the urban corridor. (Here’s an NWS explanation of deformation zones.)

WU blogger Steve Gregory, like many others, saw the classic nature of this setup emerging in the NAM and GFS models on Friday, although even then he wasn’t totally convinced. “Whenever a storm occludes out, it slows down and is pulled closer to the upper low (500 mb) and the storm track. Most importantly the deformation zone was then able to spiral further outward (northward) by 100-150 nautical miles, which brought very heavy snow bands into the NYC/Long Island/Cape Cod region,” Steve told me in an email.
But all of this phenomenology is embedded in a climatological setting, where both El Niño and anthropogenic climate change play a distinct role. If you ask me whether El Niño had a hand in this, all I can say is "how could it not?" If you ask me WHAT role it played, I will, like any other physical climatologist, be rendered speechless. The models made the storm successfully, and the climate made the models do that. Can we "explain" the connection? No, there are too many steps.

If a business goes under in a recession, can you blame the economy for the failure? It's tempting. If a business thrives in a recession, or goes under in a boom, though, what can you say?

The larger economy has an effect on your business. It certainly affects your chances of success. But whether you succeed or fail depends on whether you have a sound business model and successful marketing. There will be some red ink somewhere that tells you what happened in detail. The economic "climate" will certainly have an effect, and it will show up in the aggregate statistics of all businesses. But each business succeeds or fails for particular reasons, and trying to connect a single business's profit statement to global trends is barking up the wrong tree.

In the case of severe weather, it's often worse.

I would have said that the unusually warm water off the east coast was a crucial factor, and that a global warming connection was hard to miss... But in retrospect I'm glad they didn't ask me.

The report is a mess because the question is a mess. Yes of course El Niño had an effect - it's a dominant feature of the atmosphere these days. But was it the "cause"? This is really the wrong question.

1 comment:

Kevin O'Neill said...

Dr Jennifer Francis back in 2011: "The question is not whether sea ice loss is affecting the large-scale atmospheric circulation...it's how can it not?"