Cosmic Influence on Climate; Mann Reacts to Paleoclimate Study; Urban Heat Islands Mean Fewer Ice Storms

Cosmic Influence on Climate

In new research published in GSA Today, a publication of the Geological Society of America, researchers Nir Shahiv and Jan Veizer conclude that cosmic rays emanating from dying stars account for 75 percent of the change in the Earths climate over the past 500 million years. This means that carbon dioxide accounts for much less of the recent mild warming trend than commonly postulated.

The theory is that cosmic rays increase the number of charged particles in the atmosphere, which then leads to the formation of more low-level clouds that cool the atmosphere. Shaviv and Veizer have put together a model that looks at the interaction of cosmic rays with historical climate data.

The researchers were able to place an upper limit on the role of CO2 that translates to a temperature increase of about 0.75 C. associated with a doubling of CO2. This is about one-third the amount of radiative forcing assumed in most general circulation models. The findings are also consistent with the suggestion that much of the warming seen over the last century is associated with increased solar activity rather than greenhouse gases. (Nature, July 8).

Mann Reacts to Paleoclimate Study

Michael Mann of the University of Virginia and a group of other paleoclimatologists have responded to the recent study by Wille Soon et al on the evidence that the Medieval Warm Period and subsequent Little Ice Age were worldwide phenomena. The Soon study refutes the "hockey stick" graph contained in the Third Assessment Report of the IPCC, which appears to show that the 20^th Century experienced unusual warming.

The critique by Mann et al appears in the July 8 issue of the American Geophysical Union publication Eos. It alleges three main flaws in Soon et als work. First, that it misinterprets proxy data indicative of drought or excess moisture as evidence of temperature.

Second, that the specific time periods of warmth or coolness in the two alleged climate eras varied from place to place, meaning that applying the labels "medieval warm period" or "little ice age" to them reflected Eurocentrism. The claim of Eurocentrism, at least concerning the Little Ice Age, was demolished in a book, The Little Ice Age, published in 2001 by archeologist Gale Christensen, which finds evidence for that climatic event all over the world.

Finally, Mann alleges that using the entire twentieth century as the temperature base with which to compare previous periods is inappropriate. Soon and his colleagues are preparing a scientific response to the criticisms, which they hope will be published in Eos.

Scientific American Charge Refuted

In a sidebar to an article also criticizing the Soon study in the June 24 issue, Scientific American repeated allegations that the publication of the study in the journal Climate Research was influenced by politics. The sidebar suggested that peer review had failed in this instance.

However, as Ross McKittrick pointed out in a July 10 article on Tech Central Station, "Prof. Otto Kinne, the Director of Inter-Research (the publisher of Climate Research) personally reviewed the file, including the four referee reports and the process leading up to the publication decision. He dismissed the misconduct accusation, finding that the article was properly reviewed and that the editor, Prof. Chris de Freitas, did a good and correct job as editor."

Urban Heat Islands Mean Fewer Ice Storms

A new study in the Journal of Applied Meteorology adds more details about the urban heat island effect. Researchers from the University of Illinois found that large cities such as New York or Chicago experience significantly fewer days of freezing rain and ice storms than surrounding rural areas. Smaller cities experience less of an effect, although it is still noticeable.

Hashem Akbari of the Heat Island Group at the Lawrence Berkeley National Laboratory in California told Nature that studies of this type, "help us understand how heat islands generate their own weather patterns, change wind direction and modify air quality." As the magazine pointed out, "Some cities are up to 11 C warmer than the surrounding suburbs. Traffic, buildings, and air-conditioning units all release heat. Tarred roofs and roads soak up solar energy which they give up at night, when the largest temperature differences between city and country occur." (Nature, July 1)

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