We saw Al Gore's An Inconvenient Truth this weekend. I had actually already read the book, and was curious to see his Apple Keynote based presentation, just to see what state of the art is in presentations (not a bullet-point to be seen), as well of course to be warned that the world as we know it is coming to an end, and if I do nothing, it is my own damn fault. The movie basically stars Keynote, with Al Gore as a supporting actor.
Lots has been said about if this Al Gore was what we saw in 2000, ... maybe he would have been elected President. I am not sure the average American really wants to hear about environmental problems though, but at least he wouldn't have been quite so stiff or in search of himself. He certainly could have pulled some votes from the left, but would he have lost the center?
Unfortunately, this movie is an eye-opener for people. I say unfortunately, for their eyes should have been opened before. The CO2 data is not new, though some of the pictures of receding glaciers are.
The movie remains a brilliant piece of propaganda. (It is propaganda, not science, not even science reporting, since it is in the end a call to action, not merely information). Al Gore asserts consensus in the scientific community about the direction of global climate change (on average it is getting warmer and more carbon dioxidic) and in a bit of a shell game implies there is also consensus about the magnitude of change, and its consequences.
In particular, it is worthwhile to consider the Daisyworld Model as a possible framework for considering consequences.
What happens when CO2 goes up? Temperature rises. What happens when temperatures rise? Things that thrive in a warmer environment are more successful. One question is, does that success then dampen the increase? I.e. does the life in the warm environment (e.g. the increased proliferation of life in what once was polar bear country, the giant frozen landmasses and sheets of ice of the northern hemisphere) then absorb more CO2, limiting the effect? The second question is: how long does it take? (And what people and what species get displaced in the meantime).
The Figure used from the Vostok Antarctica ice core, which was also in the movie, correlates dust, CO2 and temperature over the past 400,000 years. Note that every increase is followed by a crash (there does not seem to be a secular trend). (Interestingly the rises are faster than the falls.)
Some of the variation is due to solar-earth variations, e.g. (Milankovitch cycles), clearly an exogenous source (the earth's weather and biology is not changing the Earth's tilt (we hope)), but that must be coupled with biological responses.
A manmade exogenous force (CO2) might be expected to have effects on climate as well, but perhaps those are self-limiting (see Daisy World or the cyclic evidence), or maybe they will run amok (see the planet Venus), we don't know. It is all very complicated.
That doesn't mean we shouldn't act, but why do humans need propoganda and false certainties presented to us to act?
So, see the film, and act. Or don't see the film and act. Or see the film and don't act. Or don't see the film and don't act. Those are your choices.