Daniel Kuehn on the Depression of 1921
Are There Any Changes in the Paperback Edition of SuperFreakonomics?

Polar Bears...

Can anybody tell me why and how making fun of Al Gore on polar bears became a wingnut talking point? Seems to me that what The Inconvenient Truth says about polar bears is correct, and unexceptionable...

Al Gore, An Inconvenient Truth http://www.admc.hct.ac.ae/hd1/blog/gw/An%20Inconvient%20Truth%20Transcript.pdf:

I went up to the North Pole. I went under that ice cap in a nuclear submarine that surfaced through the ice like this. This thing started patrolling in 1957. They have gone under the ice and measured with their radar looking upward to measure how thick it is because they can only surface where the thickness of the ice is 3 and half feet thick or less. So they have kept a meticulous record and they wouldn’t release because it was national security. I went up there in order to persuade them to release them, and they did. And here’s what that record showed. Starting in 1970 there was a precipitous drop off in the amount and extent and thickness of the arctic ice cap. It has diminished by 40 percent in 40 years. There are two studies showing that in the next 50 or 70 years in summertime it will be completely gone. Now you might say, “Why is that a problem? How could the arctic ice cap actually melt so quickly?” When the sun’s rays hit the ice, more than 90 percent of it bounces off right back into space like a mirror. But when it hits the open ocean more than 90 percent is absorbed.

As the surrounding water gets warmer, it speeds up the melting of the ice. Right now the arctic ice cap acts like a giant mirror. All the sun’s rays bounce off, more than 90 percent, to keep the earth cooler. But as it melts and the open ocean receives that sun’s energy instead more than 90 percent is absorbed. So there is a faster build up of heat here at the North Pole in the Arctic Ocean and the Arctic generally than any where else on the planet. That’s not good for creatures like polar bears that depend on the ice. A new scientific study shows that for the first time they’re finding polar bears that have actually drowned, swimming long distances up to 60 miles to find the ice. They did not find that before. What does it mean to us to look at vast expanse of open water at the top of our world that used to be covered by ice? We ought to care a lot because it has planetary effects.

Monnett and Gleason:

SpringerLink - Polar Biology, Volume 29, Number 8: Charles Monnett and Jeffrey S. Gleason: "Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea": Abstract: During aerial surveys in September 1987–2003, a total of 315 live polar bears were observed with 12 (3.8%) animals in open water, defined for purposes of this analysis as marine waters >2 km north of the Alaska Beaufort Sea coastline or associated barrier islands. No polar bear carcasses were observed. During aerial surveys in early September, 2004, 55 polar bears (Ursus maritimus) were seen, 51 were alive and of those 10 (19.9%) were in open water. In addition, four polar bear carcasses were seen floating in open water and had, presumably, drowned. Average distance from land and pack ice edge for live polar bears swimming in open water in 2004 (n=10) were 8.3±3.0 and 177.4±5.1 km, respectively. We speculate that mortalities due to offshore swimming during late-ice (or mild ice) years may be an important and unaccounted source of natural mortality given energetic demands placed on individual bears engaged in long-distance swimming. We further suggest that drowning-related deaths of polar bears may increase in the future if the observed trend of regression of pack ice and/or longer open water periods continues.