|The Week That Was
June 21-27, 1999
We start this week with some late science news that's going to bust popular myths:
For example, the claimed close association between paleo-temperatures and past CO2 concentrations has long been used to support the Greenhouse Warming theory. But this argument is no longer in vogue as new research results come to the fore.
First of all, the analysis of the Vostok ice core by Fischer et al. (1999) shows CO2 increases lagging with a delay of about 600 years behind the temperature increases of the three deglaciations of the last 400,000 years. While higher CO2 levels may well amplify the warming somewhat, they clearly are not the primary cause for the rapid temperature rises signaling the end of an ice age.
Next, according to a general review by Berner, CO2 levels were about 5 times greater than present values some 200 million years ago. Most analyses had shown a steady decrease since then, together with a general cooling. Looks like Greenhouse Warming at work, doesn't it? Now comes a new result referring to the middle Eocene, about 45 million years ago. Pearson and Palmer conclude that the CO2 level then was probably similar to modern concentrations or only slightly higher. Their method is based on determining seawater pH by measuring the boron-isotope composition of planktonic foraminifera. (The pH values reflect the amounts of CO2 dissolved in seawater, and therefore its atmospheric levels.) They conclude that the global cooling since the Eocene was not primarily due to decreases in CO2 levels (as believed…hoped for?), but to changes of ocean circulation resulting from the tectonic opening and closing of oceanic gateways, as continents move around. [Pearson, P., and M. Palmer. 1999. Middle Eocene Seawater pH and Atmospheric Carbon Dioxide Concentrations. Science, 284, 1824-1826.]
In a news report ["Slide into Ice Ages Not Carbon Dioxide's Fault?" Science 284, 1743-1746, 1999], Richard Kerr quotes paleo-climatologist Thomas Crowley (Texas A&M): "It could be the whole carbon dioxide paradigm is crumbling," at least for explaining long-term climate changes.
Finally, an interesting new method for measuring ancient levels of carbon dioxide relies on the inverse relation between CO2 levels and the frequency of stomata [breathing holes] in tree leaves. By counting stomata in fossil birch leaves preserved in a Dutch bog, Wagner et al obtained a detailed record of CO2 levels in the early Holocene [the present warm interglacial period that began about 15,000 years ago]. Contrary to accepted wisdom the CO2 concentrations were in excess of 300 ppm, and thus even greater than the pre-industrial value. Our comment: Another nail in the coffin of the theory. [Wagner, F., S. Bohncke, D. Dilcher, W. Kurshner, B. van Geel, and H. Visscher. 1999. Century-Scale Shifts in Early Holocene Atmospheric CO2 Concentration. Science, 284, 1971-1973.]
More news about carbon dioxide…to complicate life for theorists:
Increasingly, detailed measurements of CO2 are being used to study the sources and sinks. It is known that the equatorial oceans are the dominant oceanic source to the atmosphere. The net flux amounts to 0.7 to 1.5 Gigatons of carbon (about what is emitted in the United States), of which up to 72 percent emanates from the equatorial Pacific Ocean. During the 1991 to 94 El Nino period the annual fluxes were 30 to 80 percent of normal, accounting for up to one-third of the observed atmospheric anomaly (the difference between the annual and the long term average increases in global atmospheric CO2). This may explain the significant decrease in the annual CO2 growth rate between 1991 and 1993, falling from a mean value of 1.5 ppm per year to about 0.7 ppm per year in 1992. [Feebly, R., R. Wanninkhof, T. Takahashi, and P. Trans. 1999. Influence of El Nino on the equatorial Pacific contribution to atmospheric CO2 accumulation. Nature, 398, 597-600.]
Canadian agriculture experts have figured out that agricultural soils can be used as a carbon sink; if proper farm management is implemented over the next decade, this could achieve 10% of Canada's CO2 reduction goal. Unfortunately, at the Kyoto Conference, other countries opposed Canada's plan to include soils. Ideologists want cuts in energy use to inflict suffering. But our friends in Canadian West are not giving up the fight.
We end by quoting the distinguished physicist Freeman Dyson, who has written a skeptical article about the science and politics of climate. It appeared in the May 1999 issue of APS News, published by the American Physical Society. He is mainly concerned with the great emphasis given to the predictions of General Circulation Models, and the little attention paid to observations. He concludes: "[Climate models] are not yet adequate tools for predicting climate. If we persevere patiently with observing the real world and improving the models, the time will come when we are able both to understand and to predict. Until then, we must continue to warn the politicians and the public: don't believe the numbers just because they come out of a supercomputer."
Readers asked for literature refences on items from TWTW (June 14 - 20):
Bleaching of coral reefs? Kleypas et al. [Science 284, 118, 1999]
Computer model calculation that points to a collapse of the North Atlantic Thermohaline Circulation? Joos F., G. Plattner, T.F. Stocker, O. Marchal, and A. Schmittner. 1999. Global Warming and Marine Carbon Cycle Feedbacks on Future Atmospheric CO2. Science, 284, 464-467. Unfortunately, the postulated feedbacks are difficult to detect by atmospheric carbon isotope measurements, making this whole matter even more speculative.