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oppdatert 15.07.2014

The Global Warming Debate

Review of David Archer's book, The Long Thaw

In this book Dr. David Archer, a chemical oceanographer, argues that it is the concentration of atmospheric CO2 that drives climate changes, and consequently that global warming all in all is caused by humans.  After a thorough reading of Archer's book my impression is that his argument is highly questionable, that it in fact seems inconsistent. My conclusion is that he has not proved his case that global warming is anthropogenic.

The Long ThawI bought this book because for years I have asked myself whether global warming really is anthropogenic or not (to the extent there has been global warming). All the time we hear both views opinioned by scientists, although media and the organized environmental industry try to sell the propaganda that "we now know with certainty" that all global warming is caused humans. But has the hypothesis of anthropogenic global warming (hereafter AGW) been consistently verified by empirical findings? A review I read online claimed that Archer's book The Long Thaw was good and balanced. Since it is reasonable short and non-expensive, I bought this book along with two other books (Chris Mooney's Storm World and Farmer and Cook's Climate Change Science: A Modern Synthesis).

The book turned out to be a disappointment. Instead of being thoroughly explanatory and balanced, it is in fact marred with alarmist tendencies, inconsistent inferences, and a conjecture claiming that there are no other plausible explanations than that global warming is caused by humans. The text does not consistently back up that this assertion. The representation of adjoining subjects and statements are not contiguous; does not move logically from 'a' to 'b' to 'c', etc., but are spread around in different parts of the book, making "connecting the dots" a "detective job" that should have been entirely unnecessary. Having read other reviews on different Internet sites I discovered that I'm not the only one to experience this. Reading The Long Thaw will not make you believe that Archer is right about what drives climate changes. On me it had an almost opposite effect. Not only am I not any closer to be able to make any sound conclusion, but my skepticism has increased a little.

IPCC 1995 vs Hockey-stickOne "short cut" commonsense way of evaluating a book like Archer's is this: If you have a strong view about some topic such that X causes Y, and you want to argue your case, what would you do? Naturally you would show the necessary number of graphs that makes it impossible to deny a strong and consistent correlation between X and Y. Then you would add scientific explanations connecting cause and effect to these graphs. All along you would make sure that every claim and every graph and every scientific explanation (or plausible explanation or reasonable conjecture) is backed up by solid scientific references, so that the reader in principle can check "everything" the author claims. Following this commonsense way of evaluating Archer's book is close to impossible, because of a fundamental lack of references. Only in a few instances does Archer offer references to back up his assertions and inferences. One would believe that since it is Archer's aim to show that CO2 essentially drive climate changes, he would publish the necessary number of graphs (based on established empirical findings) that would confirm his beliefs to the extent that is becomes "near impossible" (given one is honest and reasonably intelligent) to deny a strong and consistent correlation between atmospheric CO2-concentration and global temperature (GT). That is, in such a way that every time atmospheric CO2-concentration increases, there is an increase in GT, and every time there in a decrease in atmospheric CO2-concentration, there is a decrease in GT. In addition; the faster the increase in CO2-concentration, the faster the GT will increase.

Naturally, there are other causes for GT to increase or decrease. That is what makes climate change science very complex and difficult. Archer explains several of the different kinds of climate forcing agents, like the Milankovitch cycles (eccentricity, axial tilt, and precession), changes in the Earth's albedo, etc. So all proxy climate data must be adjusted for all the different kinds of climate forcings and the resulting graphs should then confirm a correlation between atmospheric CO2-concentration and GT. But Archer does not reproduce as much as a single graph that correlates CO2-concentration and GT. Why not if that would help confirm his hypotheses? That really is a mystery to me! The only related graph Archer reproduces is one based on the famous Antarctic Vostok ice core data. However, the graph in Archer's book does not show correlation between atmospheric CO2-concentration and GT (page 76), but between sea-surface levels and CO2-concentration. Why choose this one when other graphs are available, namely precisely the one we ought to see – a correlation between atmospheric CO2-concentration and GT from the time same period? See graph below.  The problem here is that since it takes a long time for ice to melt (hundreds if not thousands of years according to the author, page 77), it takes a long time for the sea-surface level to rise. That means that correlating CO2-concentration with sea-surface levels will not directly support Archer's hypotheses (that atmospheric CO2-concentration forces GT) – unless increased CO2-concentration precede a rise in sea-level by "several centuries, if not thousands of years". It turns out that this is not the case. On the contrary, the Antarctic Vostok ice core data converted and time adjusted to showing atmospheric CO2-concentration correlated with GT that I have seen reproduced in other periodicals shows that GT usually increased before an increase in CO2-concentration; actually by several centuries. So a correlation surely exists, but if an inference should be made on this last mentioned graph, it would be that it is Global Temperature that forces atmospheric CO2-concentration because an effect cannot in time happen before the cause. Now, on first thought, this might sound absurd. How can a rise in GT lead to an increase in CO2-concentration in the atmosphere? However, it is common knowledge that the warmer the ocean, the less CO2 it can contain. And since CO2 is easily dissolvable in sea-water – in enormous amounts over thousands of years – CO2 will naturally be forced out of the ocean and into the atmosphere when ocean temperature naturally increase as a consequence of increasing GT.

Vostok ice core dataNow, other climate change scientists claims that feedback mechanisms can cause problems so that graphs can be misinterpreted in the sense that what seems to be cause and effect is not so. According to this claim, an increase in atmospheric CO2-concentration can force GT up, even if GT started to rise first. Because the CO2-release from the ocean can then cause a further increase in GT. Now it is unclear how such a feedback mechanism plausible can cause the kind of "perfect curves" we see in graphs like the Antarctic Vostok ice core data. Nowhere have I found a plausible explanation for how this can happen. However, and that is the point, Archer completely bypasses any such discussion. He does not even mention it. Therefore one can only conclude that on this particular subject, Archer's claim is unsatisfactory.

On page 42 the author argues: "But the natural world is a complicated and subtle place… For the sake of argument, suppose a phenomenon undreamed-of exists that causes the observed buildup of heat." However, instead of discussing such possibilities he instantly counters: "But we already have a satisfactory explanation" etc... The problem here is the author's failure to mention and discuss existing alternative hypotheses, like Danish scientist Henrik Svenmark's hypothesis that holds that changes in the sun's magnetic field affects the amount of cosmic rays reaching the Earth's atmosphere. According to this hypothesis an increase in the strength of the Sun's magnetic field will decrease the amount of cosmic rays received by the Earth's atmosphere, which again will cause less cloud cover globally speaking. This should cause GT to rise. This rather famous hypothesis has been known for a long time (since 1997). It seems to offer a reasonable alternative explanation, and therefore Archer cannot just disregard this hypothesis. Not when he actually, in writing, asks if not other explanations might exist. How can readers become informed and come to reasonable conclusions when other existing hypotheses are not even mentioned? They can't if they only read Archer's book.

What might be a very serious inconsistency in Archer's book are statements that add up to the claim that the Sun might not have been stable in the past, but that the Sun is stable now. Archer on page 40: "Solar variations are the smallest of all, typically in the order of 0.1 Watts/m2." Farmer and Cook's above mentioned book shows a graphic representation of the Earth's energy balance on page 92: according to this the Earth's surface receives in average 168 Watts/m2 from direct solar radiation. This confirms what we often hear: The Suns output of sun-rays is very stable (variation less than two percent). What makes Archer believe it could be have been otherwise in the past, like during the Maunder Minimum (less radiation) and during The Medieval Climate Optimum (more radiation)?

Spenser 2007Here is what Archer writes on page 41: "The intensity of the Sun further back in time can be estimated by measuring the products of cosmic rays, depositing in ice cores. When the Sun is brightest, it has a strong magnetic field which shields the Earth from cosmic rays (my italic). The cosmic rays, when they reach the atmosphere, produce radioactive elements like beryllium-10 and carbon-14. A brighter Sun means less cosmic rays reaching the atmosphere and so less carbon-14 and beryllium-10 in the ice core." Archer then claims on page 61: "If the year 1000 A.D. was as warm as the year 2000 A.D., then one might argue that our warming is natural, not an indication of global warming at all. But the Medieval Optimum warmth was probably the result of a warmer Sun, according to the solar proxies. In our time, the Sun has not been getting warmer since 1970."

But here Archer seems to get seriously confused since he mixes together solar radiation and the mentioned solar proxy data. These proxy data, according to Archer himself (as the citation from page 41 shows), was not caused by solar radiation but by the Sun's magnetic field. The proxy data is a measure of variations in the Sun's magnetic field, not of the Sun's radiation (sun-rays - energy output). The fact that Sun radiation is stable (or near stable) does not mean that the Sun's magnetic field is stable too. To spell it out: The proxy data is a measure of how strong the Sun's magnetic field was in the past, e.g. during the Medieval Climate Optimum. That means it is irrelevant that solar radiation is stable, because the Sun's magnetic field is not stable! According to information found on the Internet, like NASA's web-pages, the Sun's magnetic field, since measurements started after World War Two, has shown a variation by a factor of at least two. Indeed, on Wikipedia (see below) we find a graph showing what Archer is writing about (the "magnetic part"). This graph shows that during the Medieval Climate Optimum, the Sun's magnetic field was not stronger than it is today, while it was considerably weaker during the Maunder Minimum. In fact, according to this graph, there has been a dramatic increase in the Sun's magnetic field the last 80-90 years. It has even been given its own name: "The Modern Maximum". This could easily mean that the Sun's energy output has been roughly the same for thousands of years, since we know that today "sunray" output is stable while the Sun's magnetic field is not!

Solar magnetic field activity by C-14 Of course, there does not have to be a connection between the Sun's magnetic field and GT. But given that it apparently is false to base an inference of the causes of temperature maximums at earlier historic times on solar radiation, and given that there actually does exist a hypothesis connecting not solar radiation, but the strength of the Sun's magnetic field to changes in global temperature, one cannot just exclude such a possibility. However, that is precisely what Archer does. These three objections I have mentioned and discussed in this review,  in sum, I believe, rather obviously shows that Archer has not proved his case. Far from it! It still might be the case that atmospheric CO2-concentration drives climate changes, but Archer has not plausibly demonstrated this at all. Archer's argument even stands out – possibly – as fundamentally inconsistent. 

So, I conclude: If you want to find out whether global warming is anthropogenic or not, it is a waste of time to read Archer's book. Because you will be unable to reach such a conclusion, given that you read his book carefully. That does not mean there is nothing of interest in Archer's book. Interesting stuff is revealed about earlier climate changes that are fascinating to read about. But that is another matter.

Bent Andreassen.


Book data - David Archer: The Long Thaw - How Humans are Changing the Next 100 000 Years of Earth's Climate. Princeton University Press. 2009, 180 pages + xii pages.

ps: En artikkel i Dagsavisen kan være av interesse. Det viser seg at flere og flere klimaforskere "hopper av lasset" som IPCC og "klima-lobbyen" ellers. Se: Vitenskapen snur ryggen til Klimapanelet.