Allergies and Dr. Broecker

Guest Post by Willis Eschenbach

In yet another futile attempt to explain away what I see as the reasonable and justified skeptical American reaction to the unending stream of nonsense being peddled as climate science these days, we have an article by a Special Correspondent to the Associated Press. I don’t know what makes the correspondent so special, but I suppose “Slightly Confused Correspondent” doesn’t have that same ring to it. The article is called “The American ‘allergy’ to global warming: Why?“.

Inter alia, the report talks about a 1975 study by Dr. Wally Broecker published in Science magazine. I love finding new papers I haven’t read, particularly early ones. The study was titled “Climatic Change: Are We on the Brink of a Pronounced Global Warming?“. The AP report says:

In the paper, Columbia University geoscientist Wally Broecker calculated how much carbon dioxide would accumulate in the atmosphere in the coming 35 years, and how temperatures consequently would rise. His numbers have proven almost dead-on correct.

In other words, the Special Correspondent’s claim is that we Americans are idiots not to believe in global warming, since Wally figured it all out thirty-five years ago, duh.

Well, that’s a bit of an exaggeration. His numbers were passable, not “dead-on correct”. But the interesting part is how he got the numbers. Here’s his graph:

ORIGINAL CAPTION: Fig. 1. Curves for the global temperature change due to chemical fuel CO2, natural climatic cycles, and the sum of the two effects. The measured temperature anomaly for successive 5-year means from meteorological records over the last century is given for comparison.

Dr. Broecker claims the temperature will follow a combination of the CO2 effect plus the Camp Century cycles. So … what are these gloriously named “Camp Century cycles” when they are not out working overtime for the good Doctor?

It turns out that Dr. Broecker is utilizing an analysis of the “Camp Century” ice cores from Greenland. The data is held at the NOAA Paleoclimatology World Databank. Broecker says that there is an underlying regular cyclic temperature variation in the ice core data. He is using the change in the relative amount of an oxygen isotope (∂O18) as a proxy for the temperature. It is not clear whether he used the exact data as is currently archived at NOAA.

Broecker says that there are two strong cycles in the data, at 80 and 180 years. He then derives the smoothed sinusoidal curve of the superposition of those putative 80 and 180 year underlying cycles. This is the curve called “Camp Century cycles” in his Figure 1.

To the Camp Century cycle he then adds the CO2 effect, and says that the result shows the future evolution of the global surface air temperature. TA DA!

So what’s not to like in his analysis?

Well, first, when I analyze the Camp Century ∂O18 data I find no strong 80 or 180 year cycles. As I mentioned, this may be because he used other data. But the dataset available at NOAA doesn’t show much in the way of regular cycles at all. In addition, Dr. Scafetta has assured us that the cycles are not 80 and 180 years … they are 60 and 20 years. I’ll let him settle that with Dr. Broecker.

Second, his temperature data (shown in Figure 1 by the heavy solid black line) doesn’t agree with the modern (HadCRUT3 or GISS) data. This is not surprising, as he is using temperatures given in a reference called “J. M. Mitchell, Arid Zone Monograph 20 (UNESCO, Paris, 1963), pp. 161-181″. In Figure 2 I have overlaid his data with the actual HadCRUT data.

Figure 2. Broecker’s Figure 1, overlaid with the actual HadCRUT3 temperature data in red. I have aligned them at the 1900 mark.

My first comment is that the HadCRUT3 temperature (red line) follows the “CO2 effect” line (solid line with round black dots) much more strongly than it follows “CO2 effect plus the Camp Century cycles” (heavy dashed line). However, his combination of Camp Century cycles and CO2 does a better job of explaining the drop in temperatures from about 1945 to 1970. Overall, his results not a very good fit to either line. Are they “almost dead-on correct” as the Special Correspondent claims? Hardly.

The main issue, however, is not how poor the fit is. It is that he has gotten these results using a method which I have not seen used much, a combination of CO2 plus some presumed underlying cycles. Mainstream climate scientists don’t do that much.

So we are left with a few possibilities:

1. Broecker got it right all the way down the line, and modern climate science just hasn’t caught up with his cyclical brilliance.

2. Broecker got it kinda right, but it could just as easily be by chance.

3. Broecker didn’t get it right at all.

So this 35 year old study is thrown in my face as a reason I shouldn’t be “allergic” to global warming?? I find the title of the article risible. I have many opinions on the global warming hypothesis, but I’m not allergic to any part of it.

I am, however, allergic to claims like those of Dr. Broecker being used as a reason I should swear fealty to the gods of warming. Part of the reason Americans are “allergic” to global warming are the ridiculous claims of useful idiots like the Special Correspondent, who actually seems to believe that Dr. Broecker settled all of these questions long ago.

My regards to all, and please don’t take this as an attack on Dr. Broecker’s work. He did his best with the data and information he had at the time.

w.

(I never did figure out what was so special about the Correspondent … perhaps in addition to believing that Broecker’sresults are “almost dead-on correct”, he can believe six impossible things before breakfast.)