This past weekend I watched Al Gore's "An Inconvenient Truth." I wasn't going to watch it because I was sure it would be nothing more than propaganda, bald-faced assertions and half-truths. But a little voice in the back of my head kept saying "How will you answer alarmists when they say 'how can you criticize something you haven't seen?'" So I caved and watched it and am happy to announce that my initial evaluation was spot on. In reviewing the movie I would like to focus on many of the things Gore didn't say and some of the assumptions underlying the things he did say.
There were lots of scenes of melting glaciers, melting sea ice and melting permafrost, i.e. anecdotes. Mr. Gore never bothered to tell his audiences that anecdotes are not evidence.
Gore also fails to tell his audience that there is no such thing as a global climate. There are only local and regional climates and they are all interacting with each other. The sum of all these interactions is what is loosely referred to as the global climate and it is always changing. To say that tweaking one variable like CO2, among the large number of variables, will alone cause disaster is ridiculous. For that to be true there would have to be almost zero flexibility in the sum of all those interacting weather systems.
Gore claims that the more CO2 we put into the atmosphere, the more the temperature will rise. He is implying that the relationship between CO2 and temp is linear. He hides from his viewers the fact of saturation which is explained here. This simply means that the more CO2 put into the atmosphere, the law of diminishing returns kicks in, i.e. traps less and less heat.
He also has an impressive chart showing a correlation between CO2 and temperature allegedly from ice cores. It shows a significant spike in CO2 but no corresponding spike in temp. A closer look at this can be had here.
Gore also showed a graph which purports to go back about 1000 yrs. To show the insignificance of the medieval warm period there is a tiny bump. In statistics, there is a technique called smoothing and I think they used a steam roller on this one.
AIT also fails to provide a long historical context. Sure, it claims to go back 600,000 years but that's not enough geologically speaking. Gore omits the fact that the earth has been in a glacial epoch for about 3 million years. According to thissite, a glacial epoch is when ice forms at the poles and like everything else, goes through cycles in which ice grows towards the equator, called glaciations, then recedes again, called interglacials. The historical record shows that the overall climate of an earth during a glacial epoch is heavily weighted in favor of cooling, not warming. How heavily? Well, since glaciations usually last an average of 100,000 yrs, and warm interglacials like the one we are in now, average only about 20,000 years, I would say about an 80% chance of cooling.
The idea that a slight increase in GHGs would stop the next glaciation is just nuts. When they talk of global warming becoming 'irreversible', they are trying to get viewers to believe that a simple doubling of CO2 will slam the breaks on an entire glacial epoch, even reverse it!!! Now they're getting asinine.
Gore drags out the so-called study by Ms. Naomi Oreskes of 928 papers by scientists who she claims, support the AGW hypothesis with no dissenters. Gore conveniently omits the fact that Dr. Benny Peiser conducted a review of those same 928 papers plus a few hundred more in the same data bank and found Ms. Oreskes was way off. Only 13 papers explicitly endorsed the AGW theory. Obviously she was taking those papers which had no position one way or another and recording them as positive. I submit, that's not honest.
Gore also conveniently avoids telling his viewers that the USA is a net carbon sink which means that it takes out of the atmosphere more CO2 than it puts in.
While there are other things wrong with it, the whole documentary is a salad of half-truths designed to disarm viewers into accepting falsehoods garnished with croutons of truth, an exercise in convenient evasion.