Alec Rawls makes the case for omitted variable fraud in global climate change models. His lengthy article is worth your time. The general idea: There is massive and well-accepted evidence for the influence of solar activity on the earth’s climate.
For the 1750-2010 period examined, two variables correlate strongly with the observed warming (and hence with each other). Solar magnetic activity and atmospheric CO2 were both trending upwards over the period, and both stepped up to much higher levels over the second half of the 20th century. These two correlations with temperature change give rise to the two main competing theories of 20th century warming. Was it driven by rapidly increasing human release of CO2, or by the 80 year “grand maximum” of solar activity that began in the early 1920′s? (“Grand minima and maxima of solar activity: new observational constraints,” Usoskin et al. 2007.)
The empirical evidence in favor of the solar explanation is overwhelming. Dozens of peer-reviewed studies have found a very high degree of correlation (.5 to .8) between solar-magnetic activity and global temperature going back many thousands of years (Bond2001, Neff 2001, Shaviv 2003, Usoskin 2005, and many others listed below). In other words, solar activity “explains,” in the statistical sense, 50 to 80% of past temperature change.
So how can IPCC and other “global warming” models find that CO2 plays a large causal role? The IPCC assumes—that’s right, assumes—that CO2 is 40 times more significant than the sun is its effects on the earth’s climate. The models then omit crucial variables. They include one variable for solar activity, but standard models for studying the sun’s effects usually include at least three. In other words, scientists committed to supporting the global warming hypothesis deliberate omit variables known to be critical for understanding the sun’s effects. Their causal influence is thus randomly attributed to other factors.
It gets worse. Comprehensive models that include those missing factors do find a correlation between temperature and CO2—but with a significant time lag. In other words, the evidence is that temperature increases cause increases in CO2, not the other way around. There may be feedback effects from CO2 to temperature, but they are small in relation to the effects of the sun and the causal relation going in the other direction between temperature and CO2.
In contrast, records of CO2 and temperature reveal no discernable warming effect of CO2. There is a correlation between atmospheric CO2 and temperature, but with CO2 changes following temperature changes by an average of about 800 years (Caillon 2003), indicating that it is temperature change that is driving atmospheric CO2 change (as it should, since warming oceans are able to hold less CO2). This does not rule out the possibility that CO2 also drives temperature, and in theory a doubling of CO2 should cause about a 1 degree increase in temperature before any feedback effects are accounted, but feedbacks could be negative (dampening rather than amplifying temperature forcings), so there no reason, just from what we know about the greenhouse mechanism, that CO2 has to be a significant player. The one thing we can say is that whatever the warming effect of CO2, it is not detectable in the raw CO2 vs. temperature data.
Rawls’s conclusion is direct:
Nothing could be more perverse in such a circumstance than to unplug the modern world in a misbegotten jihad against CO2. The IPCC’s omitted variable fraud must stop. AR5′s misattribution of 20th century warming to CO2 must stop. The evidence overwhelmingly supports the solar-magnetic warming theory. The only support for the CO2 theory is the fact that models built on it can achieve a reasonable fit to the last couple centuries of temperature history, but that is only because CO2 is roughly correlated with solar activity over this period, while these models themselves are invalidated by their demonstrable omitted variable fraud. If warming is attributed to solar-magnetic effects at all in accordance with the evidence then the warming that is left to attribute to CO2 becomes utterly benign.
There is much more detail in Richard Lindzen’s presentation to the House of Commons a few days ago. That human activity is having some effect on climate is trivially true. The question is how great that effect is. The evidence indicates that it is relatively insignificant, and not at all of a scale to produce catastrophe.
But hey, I’m sure you don’t mind paying $5 a gallon for gasoline. The Obama administration is halfway to its stated goal of $8-$10 a gallon gasoline. Why do they want that? Global warming!