I like to keep my eyes open for any documentaries on climate or climate change, so when I saw The History Channel had an episode of MegaDisasters titled Mega Freeze, I had to check it out. The title was actually a little misleading, as the only parts of the world heading for a Mega Freeze were the mid- to upper-latitudes. The rest of the world was dealing with Mega Heat, Mega Floods and Mega Droughts. I guess Mega Climate Meltdown was too cumbersome a name.

The point of the program was that global warming may cause too much ice melt which will cause too much "freshening" of the sea water which will shut down at least a portion of the Thermohaline circulation. The Thermohaline circulation is a broad ocean circulation which acts to transport heat from the equatorial region toward the poles. If it were to shut down, or at least if the northern extent of it were shut down, places like western Europe, eastern Canada and the northeastern part of the United States would turn sharply colder.

Here's a simple graphic of the Thermohaline circulation, from NOAA's web site:

This idea has been creeping into the media, with articles such as this one from the UK Guardian. However, at this point there seems to be little to be concerned about, and in fact RealClimate.org effectively argues that the article in the Guardian was groundless.

The program on the History Channel did make some fairly strong correlations between past climate change and periods of societal unrest which made for interesting viewing. If you've been reading this blog for any period of time though, you know I can do without the hyperbole. And that's the MegaTruth.