I was taught to always question preformed conclusions, study the facts, and read the documents. And with that, I must question why Al Gore's movie says that sea levels will rise 20 feet in the 21st century, when the IPCC Report (Gore's Bible) gives a worst case scenario of sea levels only rising 23 inches.
Why does no one question Al Gore on this glaring contradiction?
ping
Straight from Gore's mouth (Smithsonian interview):
Q: Some critics are skeptical of the 20-foot rise in sea levels that you predict. Is this just the worst-case scenario?
A: Not at all. The worst-case scenario is 140 feet, although that would be far, far into the future. There are two wild cards: one is Greenland, the other is West Antarctica. Greenland is the wilder of the two wild cards.... It's undergoing a radical discontinuity, it seems, both with a rapid increase in the [glacial] melt rate and with other developments that are quite concerning. For example, they have for the last 10 or 15 years been following the emergence of these icequakes. Icequakes are like earthquakes. They're now being picked up by seismometers all over the world, and in 1993 I believe there were 7. In 1999 that doubled to—if I'm not mistaken—14. Last year there were 30. And with these icequakes doubling twice in little more than a decade, there is growing concern. Here's the other thing: [the collapse of Antarctica's Larsen B ice shelf] was quite a significant event because the scientists that specialize in such things were genuinely forced to go back and examine what it was about their models that led them to radically [overestimate] the amount of time it would take an ice shelf like that to break up. They retrofitted into their models one new understanding that came out of that event, and that is what happens when you have surface melting resulting in pooling on the top of a large, thick ice shelf. The prior understanding had been that the water sinks down into the mass of the ice and refreezes. In this case they found that instead of refreezing it tunneled and left the ice like Swiss cheese, metaphorically, and vulnerable to a sudden breakup. It broke up in 35 days, and in fact the majority broke up in only two days. Now they see the same tunneling phenomena on Greenland. When I ask off the record, "Give me some time frames here, how realistic is it that we could see a catastrophic breakup and melting in Greenland in this century?" they cannot rule that out and privately will not."
The IPCC estimates sea level rise based on current trends. Gore's movie notes, correctly, that ice sheets are very dynamic and the processes which could cause rapid changes and catastrophic collapse are not well known. Still, most climate scientists don't think that a Greenland ice cap collapse is likely this century, so Gore's "amplification" of this potential is done for shock effect. But most climate scientists also agree that once ice cap destabilization and large scale melting begin, that process will be unstoppable. If the average global temperature rises by more than 2 degrees C in the 21st century, the eventual total melting of the Greenland ice cap will be a virtual certainty to occur during the 22nd to 24th centuries.