Natural Cycle Confounds Global Warming; Where Has all the Carbon Gone?; Fossilized Leaves Challenge Climate Models

Natural Cycle Confounds Global Warming

One of the most important scientific questions that remains unanswered is the role of natural variability in the climate. As noted by Dr. Richard Lindzen in the Wall Street Journal (June 11, 2001), "Distinguishing the small recent changes in global mean temperature from the natural variability, which is unknown, is not a trivial task."

A new study in the July 6 issue of Science adds another piece to the natural variability puzzle. The North Atlantic Oscillation (NAO) is a climate pattern of winds that blow counterclockwise around the Arctic. In its "high-index phase" it does so at latitude even with the Great Lakes and eastern Europe. In its "low-index phase," it extends south to the Ohio Valley and westward into France. It is an important climatic cycle that exerts "a strong influence on wintertime climate, not only over the Euro-Atlantic half of the hemisphere as documented in previous studies, but over the Pacific half as well."

The study found that "High-index days are, on average, ~5 degrees C warmer over much of the Midwestern United States, central Canada, and Europe." Low-index days exhibit colder conditions. "The NAO," according to the study, "has exhibited a pronounced trend towards its high-index polarity since the late 1960s that is evident in its time series and is also reflected in the relative numbers of low- and high-index days in different decades," leading to "warmer wintertime-mean temperatures across much of the NH [Northern Hemisphere] high-latitude continents."

One of the authors of the study, Dr. David Thompson, of Colorado State University, noted in a July 5 Canadian Broadcasting Company article, "Public perceptions that winters are becoming less wintry appear to be as much or more due to the change in the Arctic Oscillation as to global warming."

Where has all the Carbon Gone?

As environmentalists continue to harp on the evils of carbon dioxide, they may want to notice the lack of carbon dioxide in the atmosphere. Although carbon dioxide emissions are up almost 40 percent in the past 20 years, the amount of carbon dioxide in the atmosphere has decreased or remained the same, according to an article in Science (July 6, 2001). The author of the article Steven C. Wofsy with the Atmospheric Sciences Program, Department of Earth and Planetary Sciences at Harvard University, notes, "The reason for this discrepancy is that increasing amounts of anthropogenic CO₂ are being removed by forests and other components of the biosphere."

About 25 percent of carbon dioxide emitted by fossil fuels is sequestered according to the Wofsys estimates. "But," said Wofsy, "analyses of forest inventories (which measure forest areas and timber volume) seem to indicate that forests sequester much smaller amounts of carbon. Thus we have a mystery: If our forests are sequestering billions of tons of carbon annually, why cant we find it? Evidently, we have not been looking in the right places."

Right now, scientists are not entirely sure where the extra carbon dioxide is hiding, but they have some thoughts. Many organic materials, such as woody debris, soil, wood products and woody plants, are not reported in forest inventories because they are not economically valuable. All of these things can absorb carbon dioxide. Professor S. Pacala of Princeton University, et al. estimates that more than 75 percent of carbon sequestration takes place in organic matter that is not inventoried (Science, June 22, 2001). Indeed, Pacala et al. estimates that carbon uptake in the U.S. equals 20 to 40 percent of worldwide CO₂ emissions.

According to S. Fang et al., the carbon might be holed up in Asia (Science, June 22, 2001). Forests in China have absorbed substantial amounts of carbon dioxide thanks to reforestation and afforestation projects. When China planned its reforestation policy, it was not for carbon sequestration, but to restore ecosystems and produce wood for fuel. Wofsey points out that carbon sequestration will not stop the increase of carbon dioxide in the atmosphere, but it could significantly slow it.

Fossilized Leaves Challenge Climate Models

A new study of fossilized leaves cast further doubt on the reliability of climate models. An international team of scientists gathered Cretaceous era leaf fossils from Europe, Asia, and North America in an effort to calculate the temperatures at ancient sites. The leaf temperature calculations matched ocean bed oxygen isotope measurements. The surprise came when the scientists tested modern climate models, ability to predict ancient temperatures.

The results from the different models varied greatly. At most of the sites, the results of the models did not match the actual temperature data. "Were talking about an error on the order of 20^oC, so its not small-not by any means" says modeler Paul Valdes from the University of Reading. What could cause such large errors in the climate models? Researchers think the answer lies in the way that climate models simulate the effects of clouds. "Its a generic problem with all climate models," says Valdes.

The discrepancies between climate models predictions and actual temperatures leads to troubling conclusions about their ability to predict the future (New Scientist, July 9, 2001).

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