European Climate

July 9, 2006 9:12 AM

The Source of Europe's Mild Climate
posted by Gyan (17 comments total)

Is this something that I would have to be a warm ocean current to understand?
posted by Balisong at 9:38 AM on July 9, 2006

Interesting.
posted by martinrebas at 9:41 AM on July 9, 2006

Is this something that I would have to be a warm ocean current to understand?

Well, it helps to have taken an atmospheric sciences course :).

Very interesting. But unfortunately, I have a feeling that any debate it generates will be focused on the last two sections.
posted by sbutler at 9:46 AM on July 9, 2006

This article seems to be somewhat polemic against climate scientists perpetuating a myth .. but in fact if you read carefully what climate scientists (who specialize in this area) have been saying for a while they don't think a slow-down in the stream would have a major effect on Europe's climate.. it's the popular press and media that has been hyping it.
posted by stbalbach at 9:50 AM on July 9, 2006

totally interesting...so they luck out both with the mild winters, and even if the rest of us get little ice-aged (or worse) again?
posted by amberglow at 9:53 AM on July 9, 2006

And what about the rising temperatures in summer there?
posted by amberglow at 9:54 AM on July 9, 2006

Wow that's unfriendly writing -- and it's peppered with first person rambling. From what I can make out, the clear and easy-to-understand explanation is wrong, mostly, and the dense and poorly-explaned explanation is correct.

I wonder why the clear and easy-to-understand one continues to prosper? Hmm.
posted by bonaldi at 10:05 AM on July 9, 2006

How well accepted is this? I ask, because this rather harsh statement appears aimed at some group of researchers:

"The blame lies with modern-day climate scientists who either continue to promulgate the Gulf Stream-climate myth or who decline to clarify the relative roles of atmosphere and ocean in determining European climate. This abdication of responsibility leaves decades of folk wisdom unchallenged, still dominating the front pages, airwaves and Internet, ensuring that a well-worn piece of climatological nonsense will be passed down to yet another generation.
posted by batou_ at 10:06 AM on July 9, 2006

I'd ask batous question too (And also if i was in an ultra paranoid mood I'd be curious if Richard Seager had an ties to oil companies, but perhaps that's a little silly).

The point about the similarities of the climate of Northern Europe and the Pacific Northwest despite the lack of a gulf stream there is an interesting one though. It;s certainly something I'd like to know about.
posted by Artw at 10:19 AM on July 9, 2006

Summary by the same author here.
posted by weapons-grade pandemonium at 10:21 AM on July 9, 2006

it might be an interesting subject, but a very lame post. any additional information? supporting links? a little bit of information as to WHY i should read 5 pages worth of text?
posted by lemonfridge at 10:23 AM on July 9, 2006

How well accepted is this? I ask, because this rather harsh statement appears aimed at some group of researchers

It's going to be hard to say because much of the article was "Here's what our models told us." For a rebuttal, you really need to be a climate scientists with access to models of your own.

However, I don't think that there was anything revolutionary in the paper. This was the most technical part of the discussion:

The conservation of angular momentum, it turns out, causes the mountains of North America to contribute substantially to the dramatic difference in temperatures across the Atlantic. To fathom why, you must first understand that the troposphere (the lower part of the atmosphere, where weather takes place) is bounded at the top by the tropopause, a region of stability where temperature increases with height and which acts somewhat like a lid. Thus when air flows over a mountain range—say, the Rockies—it gets compressed vertically and, as a consequence, tends to spread out horizontally. When a spinning ice skater does as much, by spreading his arms, the conservation of angular momentum slows his spin. An atmospheric column going up a mountain behaves in a similar way and swerves to the south to gain some clockwise spin, which offsets part of the counterclockwise planetary component of its spin.

On the far side of the Rockies, the reverse happens: The air begins to stretch vertically and contract horizontally, becoming most contracted in the horizontal when it reaches the Atlantic. And as with an ice skater pulling in his arms, conservation of angular momentum demands that the air gain counterclockwise spin. It does so by swerving to its left. But having moved to the south after crossing the mountains, it is now at a latitude where the planetary component of its angular moment is less than it was originally. To balance this reduction in angular momentum, the air acquires more counterclockwise spin by curving back around to the north. This first southward and then northward deflection creates a waviness in the generally west-to-east flow of air across North America and far downwind to the east.

To me, that sounds like a simplification of the principal of potential vorticity conservation and Lee cyclogenesis (what?). Pretty basic and unexciting stuff.
posted by sbutler at 10:26 AM on July 9, 2006

More on the thermohaline circulation, with links and references:

Nature news feature

(a good summary of "the state of play").

Article by Carl Wunsch (MIT), who has a great reputation for rigour and skepticism:

Science review (PDF)

Summary of the debate at Real Climate.org, with lots of links:

Atlantic circulation changes
posted by bumpkin at 2:44 PM on July 9, 2006

Adding to bumpkin's links: Regarding Seager's work, there is a discussion in this Real Climate thread (as an aside to the main topic, starting at comment 3).
posted by talos at 3:51 PM on July 9, 2006

interesting, if difficult read, thanks for that.

I'm quite surprised the "usual suspects" haven't been 'round to complain that "Gore lied to us!" in "An Inconvenient Truth" [ducks!]
posted by I, Credulous at 5:44 PM on July 9, 2006

Interesting. The possible shutdown of the Gulf Stream was one of the potential scenarios described by Gore in An Inconvenient Truth. Seager describes the conventional wisdom:

Evidence from ocean sediments suggests that at times during the last Ice Age the North Atlantic thermohaline circulation was considerably weaker than it is today, or perhaps it even shut down entirely. One such event took place about 12,900 years ago, during the last deglaciation, and is called the Younger Dryas (after a European cold-dwelling flower that marks it in some terrestrial records). The Younger Dryas began with a dramatic reversal in what was a general warming trend, bringing near-glacial cold to the North Atlantic region. This episode ended with an even more dramatic warming about 1,000 years later. In Greenland and western Europe, the beginning and end of the Younger Dryas involved changes in winter temperature as large as 20 degrees taking place in little more than a decade. But the Younger Dryas was not a purely North Atlantic phenomenon: Manifestations of it also appeared in the tropical and southern Atlantic, in South America and in Asia.

For many years, the leading theory for what caused the Younger Dryas was a release of water from glacial Lake Agassiz, a huge, ice-dammed lake that was once situated near Lake Superior. This sudden outwash of glacial meltwater flooded into the North Atlantic, it was said, lowering the salinity and density of surface waters enough to prevent them from sinking, thus switching off the conveyor. The North Atlantic Drift then ceased flowing north, and, consequently, the northward transport of heat in the ocean diminished. The North Atlantic region was then plunged back into near-glacial conditions. Or so the prevailing reasoning went.

According to Seager, the conventional wisdom is wrong.

I would expect that any slowdown in thermohaline circulation would have a noticeable but not catastrophic effect on climate.

More discussion at talos's link (thanks!).
posted by russilwvong at 9:05 PM on July 9, 2006

The last line on the penultimate page is classic:

Instead of creating catastrophe in the North Atlantic region, a slowdown in thermohaline circulation would serve to mitigate the expected anthropogenic warming!

Can't you just picture Dan Ayckroyd's character in Ghostbusters shouting this?
posted by LondonYank at 7:00 AM on July 10, 2006