15 October 2007

An Inconvenient Truth mostly gets it right

In my previous post, I only covered three of the nine points that a UK judge ruled were incorrect in “An Incovenient Truth”. Just to be thorough, below are the other six points.

One, the judge said that the film claimed global warming was “shutting down the ocean conveyor”, or Gulf Stream current that brings warm water from the tropics up to Northern Europe. He ruled that that statement is incorrect the since the Intergovernmental Panel on Climate Change found that recent research indicates that the ocean conveyor is likely to be more resilient than previously thought.

A couple of points on this, the first is that much of the research finding that the Gulf Stream may be more robust than previously thought came out after the film was shot. If the film makers had mentioned the conclusions of research that hadn’t been completed yet, I would be very interested in their stock market and horse race predictions as well.

Another point is that the ocean conveyor current is driven by a 0.4% difference in salinity of ocean surface water in the tropics and the North Atlantic. More evaporation in the tropics makes the water saltier. The concern originally grew because scientists noticed that the Greenland ice sheet, which sits next to that current, is melting faster than previous predictions estimated because those earlier models didn’t account for the greater heat absorption of melted water versus ice. Basically, ice being white reflects sunlight and melted water being darker absorbs more sunlight, creating a feed back loop that increases melting. This drops fresh water into the current reducing its salinity. If the current’s salinity drops to 0.0% difference, the conveyor stops and Northern Europe freezes. While the judge is correct in stating that the film’s statements are more frightening than IPCC’s findings, the magnitude of the disaster that would befall Northern Europe if the current did stop, make concern appropriate. Also, given the feed-back loop in Greenland, there is still a real possibility of run away melting of the ice sheet, which could well shut down the current.

Two, the judge said that the film’s claim that melting glaciers in west Antarctica or Greenland “in the near future” could cause sea levels to rise by “up to 20 feet” is “distinctly alarmist”. The judge conceded that melting of major glaciers would raise sea levels by this much, only that it would take place over millennia.

Well, maybe, we really don’t know. Some models predict that it will take millennia for major glaciers to melt, some don’t. What we do know is that Antarctic and Greenland melt is much faster than previously estimated and that there appears to be feed-back loops that may well speed melt rates. Indeed, many scientists now are worried that such melting will occur in the next century or two. So the whole ruling depends on the definitions of “up to 20 feet” and “in the near future”. The guidance notes that will now accompany the film should probably point out that “in the near future” should be “in the not-too-distant future”.

Three, the film says that coral reefs are bleaching all over the world because of global warming and other factors. The judge said that teasing out global warming from other factors such as over-fishing and pollution is difficult.

Well, duh. But the film doesn’t claim that global warming is solely responsible. A study released in August by researchers from the University of North Carolina Chapel Hill found that Pacific coral reefs are dying faster than previously thought and that rising ocean temperatures due to global warming are one of the key factors. The judge was just plain wrong on this one.

Four, the film attributes Hurricane Katrina to global warming. The judge found that there was “insufficient evidence to show that”.

Well, yeah, sort of in a pedantic way. We know that global warming is raising ocean temperatures. Higher ocean temperatures create more and stronger storms. Katrina was a storm. The obvious conclusion is that global warming was partly responsible.

Five, the film said the disappearance of snow on Mount Kilimanjaro was due to human-induced climate change. The judge said that the scientific consensus was that that could not be established.

One point for the judge. The disappearance of snow, and 90% of the glaciers on Kilimanjaro appear to be caused by a lack of snow, which may have nothing to due with global warming.

Six, the film gave the drying up of Lake Chad as an example of global warming. The judge said, “It is apparently considered to be more likely to result from … population increase, over-grazing and regional climate variability”.

Give another point to the judge. The shrinking of Lake Chad is due to poor rainfall over the past 40 years or so and large irrigation projects that have diverted water from the lake. Gore was just wrong on this one.

If those nine points, of which only two were valid, is the best that opponents of the film could do, the rational conclusion is that the film pretty much hits the nail on the head. I’m sure those who try to deny global warming will use the court case to claim that the film is riddled with errors and that Gore has been proven in a court of law of bald-faced lying. Such a position is a conscious misinterpretation of the facts, in other words, a lie.

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