Tiempo Climate Newswatch

According to Zhu Jianguo of the Institute of Soil Sciences in Nanjing, PR China, with higher levels of carbon dioxide in the air, rice and wheat may grow faster but will become less nutritious. The conclusion is based on free-air carbon dioxide enrichment experiments, in which crops are grown in open fields in an artificial local atmosphere. The Nanjing experiments are the first undertaken in a developing country.

Plants combine carbon dioxide with water to form carbohydrates, so higher concentrations of carbon dioxide in the air mean that they grow more rapidly, but this can be at the expense of the nutritional content. With a 50 per cent increase in carbon dioxide levels, yields increased by 15 per cent for rice and 14 per cent for wheat. Growth rates were enhanced by 10-14 per cent in the case of rice and 12-20 per cent for wheat. Protein levels in both crops, however, decreased by around ten per cent.

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• SciDev.Net

Klaus Keller and William E. Easterling of the Penn State Institutes of the Environment argue that typical economic analyses of the global warming problem may be biased because they neglect climate thresholds. "Economic models of climate change typically assume that changes occur gradually and reversibly," said Keller. "However, some environmental effects are not smooth and show a threshold response. For a long time nothing or very little happens and then suddenly a large change occurs." Neglecting the possibility of these effects in economic analysis favours scenarios based on limited action to control emissions.

The analysts considered two cases - widespread bleaching of corals and the collapse of oceanic circulation systems - that are difficult to forecast but might occur very rapidly. Keller concludes that "observation systems that would yield actionable early warning signals about climate thresholds have the potential to improve climate policies considerably. Implementing such observation systems could very well be a highly profitable investment for future generations."

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• ClimateBiz
• Free download of technical paper if browsing from a developing country or transitional economy domain, IDEAS

According to research led by the University of Colorado at Boulder, 2004 saw the largest ever decline in upper stratospheric ozone observed over the higher Northern Hemisphere. "This decline was completely unexpected," says Cora Randall of the Laboratory for Atmospheric and Space Physics. Ozone reductions of up to 60 per cent occurred some 40 km above high northern latitudes. The decline is attributed by the researchers to natural processes.

A record speeding up of the atmospheric circulation early in the year allowed nitrogen gases, resulting from chemical reactions triggered by energetic solar particles high in the atmosphere, to descend down into the stratosphere more easily. The increased concentration of nitrogen gases in the stratosphere then caused the ozone destruction. The Halloween solar storms of 2003 may also have played a part in increasing prevailing concentrations of nitrogen gases. Randall concluded that "scientists searching for signs of ozone recovery need to factor in the atmospheric effects of energetic particles, something they do not now do."

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• Terra Daily

• Discovery Channel