The climate on a large and small scale
A publication by American climate scientists underscores the importance of regional analyzes of climate change. The researchers found that regional effects are quite at odds with the global average. Volcanic eruptions or phenomena like El Niño can cause temperatures around the world to rise or fall within months. However, their major effects on the Earth's biosphere may not appear until one to three years later. This is the thesis of scientists in a study published in Science (October 31 issue).
Regional analyzes show different influences of such events on the growth activity of plants. Global warming is causing increased plant growth in temperate and polar zones. On the other hand, growth in hot tropical and semi-arid regions initially slows down.
The results were presented by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. They support the thesis that reactions of biological systems to global changes can vary greatly across the globe. According to David Schimel, a staff member at NCAR and one of the study's authors, the results underscore the potential of such data collections on global change, as well as the usefulness of computer models linking the atmosphere and biosphere.
"In the study, we specifically looked for lagged ecosystem responses because they were predicted by the models," notes Schimel.
The global temperature record reveals various annual climate patterns, including warming caused by El Niño in the 1980s. These patterns have so far been attributed to prevailing carbon dioxide concentrations globally and to vegetation growth regionally. The carbon dioxide concentrations, which are constantly increasing worldwide due to human activities, initially rose faster than usual in the first few months after a global temperature peak. They then increased more slowly during a one to three year period after the temperature peak, again followed by a further slight acceleration.
In their study, the scientists compared the connection between temperature and vegetation in data sets from regions separated by a degree of longitude and latitude. This means a distance of about 85 to 110 kilometers. At the maximum of a warm period, plant growth increased in polar and temperate zones. At lower latitudes, including tropical rainforests and drier savannas and grasslands, growth slowed."This difference suggests that … temperature may have direct adverse effects on plant growth or may exacerbate water stress in moderately arid ecosystems," the authors note.
However, during the first year to three years after a temperature peak, the pattern appears to be reversed: plant growth increases in the warmer and drier areas, while it decreases in the higher latitude regions.
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