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Sea level rise

Page history last edited by PBworks 16 years, 9 months ago

Sea level rise of up to 20 feet (7 metres) will be caused by melting of either West Antarctica or Greenland in the near future.

 

TRANSCRIPT

 

I want to focus on West Antarctica, because it illustrates two factors about land-based ice and sea-based ice. It's a little of both. It's propped on tops of islands, but the ocean comes up underneath it. So if the ocean gets warmer, it has an impact on it. If this were to go, sea levels worldwide would go up 20 feet. They've measured disturbing changes on the underside of this ice sheet. It's considered relatively more stable, however, than another big body of ice that is roughly the same size. Greenland

 

In 1992 they measured this amount of melting in Greenland. 10 years later this is what happened. And here is the melting from 2005. Tony Blair's scientific advisor has said that because of what is happening in Greenland right now, the map of the world will have to be redrawn. 

 

If Greenland broke up and melted, or if half of Greenland and half of West Antarctica broke up and melted, this is what would happen to the sea level in Florida. This is what would happen in the San Francisco Bay. A lot of people live in these areas. The Netherlands, the low-countries: absolutely devastating.

 

The area around Beijing is home to tens of millions of people. Even worse, in the area around Shanghai, there are 40 million people. Worse still, Calcutta and, to the East Bangladesh the area covered includes 50 million people. Think of the impact of a couple hundred thousand refugees when they are displaced by an environmental event and then imagine the impact of a hundred million or more. Here is Manhattan. This is the World Trade Center Memorial Site. After the horrible events of 9/11 we said never again. But this is what would happen to Manhattan. They can measure this precisely, just as the scientists could predict precisely how much water would breech the levy in New Orleans. The area where the World Trade Center Memorial is to be located would be under water. Is it possible that we should prepare against other threats besides terrorists? Maybe we should be concerned about other problems as well.

 

 

RULING

 

1. Sea level rise of up to 20 feet (7 metres) will be caused by melting of either West Antarctica or Greenland in the near future.

In scene 21 (the film is carved up for teaching purposes into 32 scenes), in one of the most graphic parts of the film Mr Gore says as follows:

"If Greenland broke up and melted, or if half of Greenland and half of West Antarctica broke up and melted, this is what would happen to the sea level in Florida. This is what would happen in the San Francisco Bay. A lot of people live in these areas. The Netherlands, the Low Countries: absolutely devastation. The area around Beijing is home to tens of millions of people. Even worse, in the area around Shanghai, there are 40 million people. Worse still, Calcutta, and to the east Bangladesh, the area covered includes 50 million people. Think of the impact of a couple of hundred thousand refugees when they are displaced by an environmental event and then imagine the impact of a 100 million or more. Here is Manhattan. This is the World Trade Center memorial site. After the horrible events of 9/11 we said never again. This is what would happen to Manhattan. They can measure this precisely, just as scientists could predict precisely how much water would breach the levee in New Orleans."

This is distinctly alarmist, and part of Mr Gore's 'wake-up call'. It is common ground that if indeed Greenland melted, it would release this amount of water, but only after, and over, millennia, so that the Armageddon scenario he predicts, insofar as it suggests that sea level rises of 7 metres might occur in the immediate future, is not in line with the scientific consensus.

 

COMMENTARY

 

William:

 

Pupils might get the impression that sea-level rises of up to 7m (caused by the complete melting of Greenland or half of Greenland and half of the West Antarctic shelf) could happen in the next decades. The IPCC predicts that it would take millennia for rises of that magnitude to occur. However, pupils should be aware that even smaller rises in sea level are predicted to have very serious effects. or Burton: "This is distinctly alarmist, and part of Mr Gore's 'wake-up call'... not in line with the scientific consensus."

 

Yeah, I think Gore was misleading on this, and said so before.

 

mt:

 

             I do not agree. Gore avoided saying anything about the "near future", I believe. Current thinking indicates that ice sheets may fail rapidly, but to be fair that mostly postdates the film.

 

Inel finds this in the AR4:

The Greenland Ice Sheet is projected to contribute to sea level after 2100, initially at a rate of 0.03 to 0.21 m per century for stabilisation in 2100 at A1B concentrations. The contribution would be greater if dynamical processes omitted from current models increased the rate of ice flow, as has been observed in recent years. Except for remnant glaciers in the mountains, the Greenland Ice Sheet would largely be eliminated, raising sea level by about 7 m, if a sufficiently warm climate were maintained for millennia; it would happen more rapidly if ice flow accelerated. Models suggest that the global warming required lies in the range 1.9°C to 4.6°C relative to the preindustrial temperature. Even if temperatures were to decrease later, it is possible that the reduction of the ice sheet to a much smaller extent would be irreversible.

 

mt:

 

but this postdates the film. Perhaps similar text is in TAR. However, this text hardly suffices to justofy the ruling.

 

Steve B: 

 

Recall that the dynamical effects were obvious no later than five years ago, and that Jim Hansen has been talking about "reticent" glaciologists for at least a couple of years (reticent meaning that they were expressing concerns privately that they were unwilling to repeat in public).  I think it's very likely that there were conversations between some of those scientists and Gore plenty early enough for those concerns to be reflected in the film.  The AR4 says "more rapidly" but notably avoids saying how much more rapidly, and at this point has anybody hazarded more than a guess about what the upper limit of the speed of such a process might be?  Not that I've seen.   

 

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