Their abstract claims:
"We use statistical methods for nonstationary time series to test the anthropogenic interpretation of global warming (AGW), according to which an increase in atmospheric greenhouse gas concentrations raised global temperature in the 20th century.
"Specifically, the methodology of polynomial cointegration is used to test AGW since during the observation period (1880–2007) global temperature and solar irradiance are stationary in 1st differences whereas greenhouse gases and aerosol forcings are stationary in 2nd differences. We show that although these anthropogenic forcings share a common stochastic trend, this trend is empirically independent of the stochastic trend in temperature and solar irradiance.
"Therefore, greenhouse gas forcing, aerosols, solar irradiance and global temperature are not polynomially cointegrated. This implies that recent global warming is not statistically significantly related to anthropogenic forcing. On the other hand, we find that greenhouse gas forcing might have had a temporary effect on global temperature."
"One of the weaknesses of the ADF test in the presence of a trend is that it assumes the trend is linear. But it isn’t. How might we overcome that problem? There’s more than one way to skin this cat. One is to use the CADF (Covariate-Augmented ADF test), and supply a covariate to represent the trend. Namely: climate forcing. That will give us a much better picture of the right trend to use since 1880, than just a straight line, and will eliminate that weakness of the ADF test. Fortunately, the “CADFtest” package for R implements the covariate-augmented ADF test." . . .
It’s a regression of the form:
I've selected from the more interesting comments in order to expose why we should show a great deal of skepticism when drawing conclusions from Beerstock et al's adventure in statistics.}
Maybe it’s actually both: a Whiskey Sour.
After all, the idea of global warming as Bourbon Myth ...
Though the effect is real, climate scientists (at NASA GISS, for example) have made a considerable effort to identify and minimize its effects within the surface temperature record.
Some global warming "skeptics" have nevertheless greatly exaggerated its significance, claiming that it has been responsible for much (if not all) of the measured upward global temperature trend in recent decades, a claim that does not hold up under examination.
Posted by Horatio Algeranon~ ~ ~ ~ ~ ~ ~ ~
Has VS found an analysis he wants to stick with, or does he keep introducing new ones?
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[Response: I've got no beef with the ADF test, but the PP test seems better. The ADF test is also known to have low statistical power when there's strong autocorrelation. Mainly it must be borne in mind that failure of the ADF test does NOT demonstrate the existence of a unit root -- contrary to the impression some give -- it simply fails to reject it. When there's little data and a nonlinear trend, that happens all too easily.
B&R isn’t even published…it’s a paper someone put on their webside (with a rather hopeful filename, containing “nature”) and which is now waved around in the deniosphere as “the final nail in the coffin of AGW”.
As you seem to have missed the crux the paper, allow me to re-iterate. Specifically, the paper set out to reject the null hypothesis, and instead rejected AGW. The paper was testing the null hypothesis, and the methodology used WAS appropriate for testing **that** hypothesis. Instead it finds evidence that strongly supports the null hypothesis and therefore the probability level of AGW being a reality to be very small. As previously pointed out [self quote]:
"The null hypothesis does **not** assert the existence of any forcings. That refutes the alleged refutation of using cointegration tests." - So, pllease refrain from shifting your goalposts.
Do you understand that rejection of the null hypothisis is standard hypothesis testing?
With what you are trying to state, the paper should have not been published in the first place. Your statements (although intelligent sounding) are rather quite nonsensical.
Do you think you know better than the editor?
Cole does follow with another comment, but it's repetitious and side steps the points made by the SkepticalScience science guys.