are humans the true culprit?
Essentially they give some graphical proofs that the CO2 increase is a result rather than a cause of global warming. Note here that neither side of the argument claims that there is NO global warming. The bone they are picking is what causes it ... us or the sun. I'm now on the "sunny" side. I no longer embrace the "dark" side ... I've seen the light ;o)
Of course, this documentary has been critized by the adherents to the human causation view. It is interesting to me that James Randi has even embraced the dark side in this case (he's the world's foremost "skeptic"). His page at http://www.randi.org/jr/2007-04/040607mi.html#i5 has some revealing "follower" traits that I wouldn't have expected of Mr. Randi. He is a big fan of Phil Plait and often sites his scientific wisdom. as in this page ... wherein one Carl Wunsch is cited as having been misled and misquoted in the documentary. I went back and looked into it and he was a minor figure (they only used his statement that when the oceans are warmer they release CO2). Fine. He expected to have a soap box on which to remonstrate on the horrors of oil consumption. He was "duped". No, he was "edited". They threw out what he said that didn't fit the goals of the documentary and selected out what was useful to their cause. Duh. Is this something new? This is what everybody does. They take lots of statements then pick & choose what suits their needs. To the untrained eye, I'll grant that it looks like Mr. Wunsch is probably a supporter of the view supported by Mr. Durkin (the producer). But he is not misquoted. The perceived offense is one of omission and is an expected outcome for any interview anywhere about any subject whatsoever.
The Substantive Argument Against Human Causation
A graph of sunspot counts for the past 400 years is plotted against the temperatures for those centuries. The correlation is pretty obvious ... more sunspots = lower temperature ... and ... less sunspots = warmer temperature. What is not obvious is that this correlation, if true, is an absolute proof that global temperature swings are solar driven rather than CO2 driven. It is absolute because there is no way that the observation of sunspots (initially through a pinhole camera obscura) can be caused by CO2 on earth. The causal chain can be only one way. Either solar activity causes climatic changes on Earth ... or ... the perceived correlation is a coincidence or fraud.
Knowing this, the adherents of human causation have resorted to saying that the Medieval Warm period and the Little Ice age were ... local events, i.e. the correlation is not valid ... the little ice age was cold because maybe the people cut down all the trees. They resort to ex post facto "fiddling" without any proofs. The initial reports that were accepted as valid for centuries are now invalid because ... they don't fit the human causation model. Now, that's Bad Astronomy in my book.
They showed another graph of CO2 levels (from Greenland ice cores) plotted against global temperatures (also from ice cores - how they do this I don't exactly know but apparently they do ... the scientists who took the readings). The result shows that the peaks for CO2 and peaks for temperature correlate strongly but whereas the Al Gore component sees this as proof that CO2 causes temperature rises ... the solar contingent observes that the CO2 peaks follow the temperature peaks indicating that increased temperature causes increased CO2 ... meaning that the CO2 peaks are driven by the sun or some other agent.
I don't know the pedigree of these graphs exactly. Each side accuses the other of fudging graphs. To be sure, one could also say that temperatures followed CO2 peaks but at a much greater distance (hah). However, since they claim that CO2 causes a temperature rise on the order of a decade or less later ... we have to assume that temperature followed by CO2 is the correct interpretation (by their standards). If these graphs represent truth, the human causation point of view is undercut dramatically.
As a last ditch holdfast, the human causation crowd says that there is an additional component to global warming not derived from the sun that is man-made. They are "salvaging" their theory by hanging on to an edge by their fingernails. In all probability, CO2 emission is irrelevant in the grand sweep of global climate history. This does not mean that I advocate burning all the oil under the ground. The fact is that it is dirty from more than the CO2 perspective and should be abolished at the earliest opportunity. But not at the expense of prohibiting the economic developement of third world countries. First take care of the needs of humanity ... then ... clean up the environment ... if there is any left to clean up (like the Brazilian Rain Forest :o(
The Mechanism for Solar Driven Climate
The proponents of the solar viewpoint say that cosmic rays cause increased cloud cover by ionization in the atmosphere. How this occurs, I don't really understand. The theory is that when the sun is very active, its magnetic field increases and partially shields the earth from cosmic rays (heavy atomic nuclei from super novas). When the sunspots are few, the magnetic fields diminish and the cosmic rays return causing increasing cloud cover which in turn causes increased global temperatures via the main greenhouse gas ... water vapor.
The science here is somewhat new. It may need modification and maybe it's all wrong somehow. But if the graphs are correct, something must occur ... caused by the sun during heavy sunspot activity ... which, in turn, causes global temperature decrease (and increase when the sunspots are least).
Check out the video and see for yourself. It's very rational and presents facts that are vulnerable (capable of being disproved if incorrect) which is what I expect of any Good Astronomy.