My last diary entry (
Global Warming Counteroffensive: Send Out the Skeptics) concerned a "debate" to be held following a local showing of
An Incovenient Truth in Columbus, Ohio. The event was set up by some local global warming skeptics associated with the Unitarian Universalist Church, who said in their advertisement: "If you are interested in knowing both sides of the argument about global warming, this is a golden opportunity for an excellent education on this issue from those who claim to be experts."
The debaters were Prof. Robert Essenhigh of Ohio State, and Harvey Wasserman, longtime environmental activist.
dKos user jrooth, a commenter on my previous diary, suggested that if I attended the debate I should ask the good professor about carbon isotope studies that effectively disprove his ideas about atmospheric carbon dioxide. Great suggestion--I did attend the debate and pose that question, which Essenhigh was unable to address--he predictably wasn't aware of these studies. My account follows.
The debate followed a 7:00pm showing of
An Inconvenient Truth at the Drexel Gateway Theater in Columbus, near the Ohio State campus. The film has been showing locally since June 15th. I was there for the opening night full house, and can report that the film is still packing 'em in three weeks later. The people who brought the film here hope that it will run all summer at this theater.
It really wasn't a debate, for a couple of reasons. One, the format was that first Harvey Wasserman gave a talk on his Solartopia vision of a green, post-industrialized, renewable-energied, mass-transited world achievable by the year 2030. This was followed by Prof. Essenhigh's talk about his alternative explanation for the correlation of carbon dioxide and temperature, based on the recent rise of carbon dioxide resulting not from the burning of fossil fuels, but rather the natural process of being outgassed from the oceans' vast carbon dioxide stores. There was no back-and-forth of a debate.
Secondly, back-and-forth between the parties wasn't really appropriate anyway, since one is a scientist and the other a grass-roots environmentalist. For a proper debate Prof. Lonnie Thompson, also an OSU prof (mentioned in Gore's film), should have been there to rebut Essenhigh's claims.
While Wasserman outlined his environmental vision ably, he didn't really address any of Essenhigh's points directly, other than offer a vague "what if you're wrong?", several appeals to Gore's film as convincing to him personally, and sidesteps like, well, even if carbon dioxide isn't causing global warming we should move to a greener future anyway. Not very effective in the traditional debate framework I'd say.
On top of this, the UU organizer was playing some kind of impartial referee, barking out Essenhigh's main points from time to time for emphasis, and strangely calling off Wasserman on occasion.
Anyway, Essenhigh's argument--which hasn't basically changed in years--is that the graph highlighted in An Inconvenient Truth charting the correlation between carbon dioxide levels and temperatures over the 400,000 years doesn't show causation. That is, Essenhigh says, while the global warming idea is that the CO2 levels are driving temperature, it could be that the temperature is driving the CO2 level. Here's a graph showing the correlation at issue:
To the classic global warming model, Essenhigh objects that no one has explained why the CO2 levels go up and down naturally. That is, where is the CO2 coming from and where is it going as these fluctuations run their course. He counters that if the causation is rather the other way around--that temperature drives CO2--he has an explanation. To wit, that as tempertures rise--due to, say, orbital factors--the oceans heat up and the solubility of CO2 in seawater decreases and CO2 is therefore outgassed into the atmosphere. He says that the cycle reverses when the arctic icecap melts, exposing more seawater to evaporation, and the resulting increase in precipitation causes more snowfall and the glaciers start growing again. He totally discounts that the CO2 increase observed today is from anthropogenic sources, even though it is at 30% higher levels than anytime in the last 400,000 years.
The carbon isotope studies referred to above present a problem for Essenhigh's model of the oceans as source for the CO2 increase. I asked if he was aware of the isotopic carbon studies which show that the industrial-age CO2 increase is coming from fossil fuel burning. He first said "oh, it's mostly C12 (carbon-12) anyway" as if that was relevant to anything. I replied that the point is the other isotopes are there, specifically C13, and the fingerprint can be used to trace whether the observed CO2 increase is coming from fossil fuels or seawater--and the answer is fossil fuels, case closed. He seemed not to be aware of C13 studies, because he then went into another off-topic tangent on radioactive C14, and how a lot of it is from atmospheric nuclear tests of the 1950s and 60s, and that it's decaying, yadda yadda. C14 is neither here nor there for the C13/C12 studies in question. It ended when he said, "show me the data" which of course I didn't have in my hands, so I just said I'd send him an email.
So, here's a quick primer on these studies for those interested:
C13 is a stable isotope of carbon, accounting for about 1% of naturally-occuring carbon in the air. The C13 concentration is less in fossil fuels (ultimately derived from C12 fixed preferentially by plant photosynthesis) and somewhat higher in seawater. This difference allows the source of the measured CO2 increase to be atributed to the proper source, in this case fossil fuel combustion. Here's a chart showing the different C13 signatures:
The quantity derived, delta-13C, is kind of a quirky measure that atmospheric scientists use--suffice it to say that the more negative the number, the less C13 is present. So it can be seen that fossil fuels have a delta-13C at -20 or less, compared to -8 or so for atmospheric levels, compared to positive numbers for the oceans.
Here's an explanation of the differences from the source at Carleton University:
There are a few features in this figure that are worth discussing. One is that land plants, soil organic matter, soil CO2, marine organic matter, and fossil fuels all tend to hover in the -20 to -30 °/°° range. This reflects the fact that photosynthesis -- on land or in the sea -- always takes more of the lighter carbon from the mix of available CO2. This means that the carbon fixed by plants will always have a d13C value that is less than that of the source CO2. This shift is generally in the range of -20 to -30 °/°°, depending on a variety of environmental factors, and the details of the process of photosynthesis. This fractionation or discrimination involved with photosynthesis explains several other features of Figure 7.17. The shallow oceans are more positive than the deeper oceans because planktonic organisms take the lighter carbon out of the shallow water to make everything but their shells. Removing the light carbon will naturally leave the sea water depleted in the lighter carbon, so the sea water itself becomes more positive. When these organisms die, they sink to the deeper parts of the oceans, where their organic remains are largely decomposed, returning the carbon to the water, causing the deeper waters to be less positive than the surface waters.
Therefore if the delta-13C value is dropping (becoming more and more negative), we can infer that the carbon dioxide is not coming from the oceans, rather, from fossil fuels. This is in fact what's happening.
In recent years measurements of C13 have been made at Mauna Loa, and show the following trend from 1980 through 2002:
C13 levels are trending downward as C12 released from fossil fuel burning becomes more and more predominant. There is no way that C13-rich CO2 coming from the oceans is consistent with this trend. Essenhigh clearly has a reason to remain ignorant of these results, as his whole stale idea that he has been promoting for the last five years goes up in a cloud of dust.
This is how a document at the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge puts it:
The d13C of atmospheric CO2 is an indicator of either plant photosynthesis or air-sea
exchange of CO2. This is because terrestrial plants preferentially fix 12C in photosynthesis,
thereby leaving remaining CO2 relatively 13C heavy, while the dissolution and evaporation of
CO2 to and from ocean waters is practically non-fractionating isotopically. In addition, the
burning of fossil fuel has significantly increased the CO2 content of the atmosphere, with a
corresponding decrease in the d13C signal toward more negative values.
For a longer trend, here's a normalized curve going back to the 1700s (source at Christian-Albrechts-Universität zu Kiel, Uptake and Pathways of
Anthropogenic Carbon Dioxide):
That chart shows the C14 spike as well as CFC curve irrelevant to the current discussion. As for C13, it can be seen that C13 levels diminish as general CO2 increases, exactly as expected from the fact that the CO2 increase comes from fossil fuels.
The decline of C13 due to fossil fuel burning is known in the literature as the Suess effect.
It really is true, as Al Gore points out, that the so-called global warming "debate" is a sham promoted by fossil fuel interests and totally against sound science. Essenhigh's theory has been well and truly critiqued by climate scientists over the years, yet here he is again dusting off his original, debunked notes and coming out for yet another dog-and-pony show aimed at producing an illusion of some kind of equal balance, pro and con.
I was glad to see one audience member bring up Essenhigh's career specialty of the study of industrial coal combustion techniques--this coal industry connection was not mentioned by the organizers, and is never mentioned in popular accounts. The questioner asked why we should believe a mechanical engineer specialist in coal versus the bulk of climate scientists. Indeed. I don't know if this fellow saw my diary on exactly those connections, but it was good to see him there bringing up the same points.
Interestingly, there was a shill (I'm guessing from the UU organizers group) in the audience who instead of asking a question, stood up and in a swaggering manner went into a long laundry list of nearly every specious skeptical claim extant on the net. He basically had all the skeptical talking points. For example, he kept fixating on a claim that Mauna Loa studies were a fraud, because they are combined with Antarctic ice core data, despite being in a volcanic region. He was taking the unbelievable position that the observed Mauna Loa CO2 levels are coming from the volcanoes nearby. Anybody who knows anything about this subject (generally precluding the talking-point skeptics) knows that CO2 levels are measured at dozens of points around the globe. The data sets are consistent and there is absolutely nothing wrong with the Mauna Loa data. But there was this guy with this specious claim and many others. Then he sits down with a smug little grin, like a self-congraulatory cat that ate the canary, like his stream of nonsense was actually some kind of tour de force. I've seen that look before--generally from idiotic right wing commentators like Rush Limbaugh, Hannity, O'Reilly, etc. There no doubt where this "debate" issues from. It's not science and is rather pure smoke.