Recent work on antarctic ice cores has now given us a good record of atmospheric composition over the last 650,00 years. The work shows that CO2 and other “greenhouse” gasses are now at their highest levels ever over that period. All the news stories are quoting scientists saying that this new information proves that human-emitted gasses are causing global warming.
They’re wrong. In fact, the core samples might just show the opposite.
(Note: I’m working from secondary sources here as I can’t bring myself to plink down the $10 to get the actual paper from Science. If I get more information later I will update this post.)
The fundamental problem is that the core samples show very little correlation between levels of greenhouse gasses and global temperatures. For example, the core samples showed conclusively that atmospheric gasses have no effect on the cycles of ice ages. Since the last ice age, there have been several periods of unusual global warming or cooling that also do not correlate strongly with greenhouse gas levels.
Even the weak correlations that do exist may not tell us much, because a changing climate changes the composition of the atmosphere. For example, methane, which is about 23 times more powerful as a greenhouse gas than CO2, arises from the decomposition of biomass by bacteria. Since warmer periods sustain more biomass, they also create more methane. So methane levels rise and fall with warming and cooling cycles even though the levels may have little to do with driving the cycles themselves. Conversely, CO2 levels may fall as a climate warms because an expanding biomass absorbs carbon. (Or maybe increased biomass leads to increased CO2 production. There is a lot of debate.) So as a general rule, we would expect warmer periods would produce more greenhouse gasses than cooler periods just by creating more biomass. The cause-and-effect relationship could be the exact reverse of that portrayed by anthrogenic-global-warming advocates.
What the core samples really show is that atmospheric gasses are not the primary drivers of global temperature change. Ice ages are the result of the Milankovitch cycles in the precession of the earth’s axis. Shorter term climate changes, on the order of decades or centuries, correlate with sunspot activity. Volcanos cause spikes of cooling followed by warming over the span of a few years. In the climatological record, it is more likely that atmospheric gas-level changes result from climate change than that the gas levels drive the climate change. (Of course, feedback loops exist which complicate any analysis.)
In order to determine whether human-emitted gasses drive climate change we first have to eliminate the effects of all the natural drivers. In the main, this has not been done. For example, even though we know that increased sunspot activity correlates with increased temperature on earth, we do not know why, even on a theoretical basis, this is so. None of the sophisticated climate models on which the anthrogenic-global-warming hypothesis are based account for sunspot activity at all. Interestingly enough, the last 30 years of increasing global temperatures have also tracked 30 years of unusually high sunspot activity.
One of the reasons I persist in viewing anthrogenic global warming as more of a social and political phenomenon than a scientific one is the way in which a kind of scientific-media-political complex bends every observation to fit the hypothesis, with few if any qualifications. Every media story I have read on the antarctic ice cores says that the cores show that humans are causing global warming, when in fact the cores merely show that greenhouse gas levels are high. To assert that the high levels of the gasses cause warming one must first assume that the gasses drive the warming. (This is a logical fallacy called begging the question.)
Even if information is included that would contradict the hypothesis, it is often couched in terms that appear to support it. For example, the story linked to above uses the lack of correlation between gas levels and ice ages to attack those who argue that increased CO2 levels might fend off an impending ice age. The fact that the lack of correlation shows that atmospheric gasses are not primary drivers of major climate change isn’t even mentioned as a possibility.
I think that significant segments of the population are so invested in the idea that industrial production must be placed under political control that they will instantly glom onto any idea that gives them the slightest justification for doing so. They try to panic the rest of the population with predictions of cataclysm while vilifying anyone who questions the premise. I think that cataclysmic anthrogenic global warming has all the earmarks of a politically driven hysteria. I think it will turn out to be as much of an exercise in mass self-deception as the “Energy Crisis” of the ’70s turned out to be.
The way that the results of the antarctic core sampling project have been portrayed just reinforces my belief that this will be so.