<VOICE="Homer Simpson">Global warming. Is there anything it can't do?</VOICE>:

Some climate experts have said the potential cooling of Europe was paradoxically consistent with global warming caused by the accumulation of heat-trapping "greenhouse" emissions.

How long do we have to wait to fire up our SUVs? When the ice in Chicago is higher than the Sears Tower?

This particular possible effect of global warming (shutting down the Atlantic circulation, with the cooling effect on Europe) is not a new hypothesis. It's been talked about for years in the scientific literature. There's evidence that the circulation broke down near the end of the last ice age, when fresh water from melting icecaps shut off the formation of cold, extra-salty water in the northern oceans (which sinks and drives the system). I've wondered if future geoengineers might try to counteract this by diverting the outflow of the Great Lakes (above Lake Ontario) into the Mississippi system, so as to make the N. Atlantic saltier.

Chicago isn't warmed by this Atlantic current, so why this should lead to ice there isn't clear. However, if this circulation broke down you would expect to see even higher sea surface temperatures in the tropical Atlantic, since this circulation is a major way that heat is carried to the poles. I doubt you want to see that.

Chicago isn't warmed by this Atlantic current, so why this should lead to ice there isn't clear.

I was being (slightly) tongue in cheek, Paul.

I am aware that one of the theories of global warming consequences is of the shutdown of the Atlantic circulation (though as the article says, there's no consensus on it). But I also think that we understand much less than we think we do about this, and that we shouldn't necessarily be shocked if there is instead another glacial advance (which is overdue, based on historical cycles) in this century.

However, if this circulation broke down you would expect to see even higher sea surface temperatures in the tropical Atlantic, since this circulation is a major way that heat is carried to the poles. I doubt you want to see that.

No, in my current residential situation (which I hope is non permanent) I would be extremely not down with that. Next year, we might get all the way to Omega...

Rand

What Paul neglects to mention is that at the time of the postulated shutdown of the Atlantic current that caused what is known as the Younger Dryas, there was a discharge from the edge of the ice sheet with more water than is in all of the great lakes combined within a few weeks. This was the glacial lake Agassiz which was backed up at the edge of the ice sheets and when the sheets melted to a critical point this water was discharged.

I really HATE crappy science and journalist with less brains and a chimp parroting stupid crap like this.

Dennis

I've read Rand's post a couple of times now. I don't know if it is pro or con on "greenhouse" global warming.

It is (like me) agnostic (at least on the issue of whether or not this is something that we should be counterproductively panicking about, e.g., Kyoto). It's mostly a commentary on the inability of journalists to resist tying any change in weather or climate to "global warming."

Dennis: the shutdown at the end of the last ice age did indeed involve a huge impulse of fresh water. The hypothesized shutdown with global warming would have a somewhat different cause: reduction (or, eventually, elimination) of sea ice formation. The cold, saltier water is currently produced, as I understand it, when sea water freezes, concentrating the salt in the part of the surface water that remains liquid.

Winter sea ice in the arctic has recently been thinning/receding at a rapid pace. There are projections the Northwest Passage may be traversible by ordinary ships within a few decades.

Disregard that bit about sea ice formation causing the saltier water; I think it was a misconception I picked up somewhere.

It's possible that opening the Northwest (and Northeast) Passage may have a bigger effect than any minor change in land temperatures.

I mean in terms of opening up Siberia and allowing the civilized countries of the Northern Hemisphere to ignore the barbarians of the South even more than we can today.

I'm *still* waiting for somebody to explain to me how we're causing global warming... on Mars.

Well one of the ways to counteract the effects of global warming is to fly more. Sattelite imagery suggests that the number of contrails being created by high flying aircraft are creating an abundant amount of artificial cirrus clouds and may contribute to global dimming, possibly reducing the amount of radiation that reaches the surface.

Josh: I seem to recall that cirrus clouds may actually exacerbate global warming, since they also reflect more IR back down, reducing the IR emissivity of the planet. Clouds that are more than one IR optical depth below the top of the atmosphere would not have this effect, so low altitude clouds would tend to cool the planet.