some examples:
If CO2 concentration increases in the atmosphere because of an increased rate of outgassing, global temperature will rise. Rising temperature and more dissolved CO2 will lead to increased weathering of crustal rocks as a result of faster reaction rates (temperature effect) and greater acidity. Enhanced weathering will use up the excess CO2 thereby cooling the climate. If global temperature cools as a result of some astronomical forcing or tectonic/ocean circulation effect, the lower temperatures will result in lower rates of chemical weathering. Decreased weathering means less CO2 being drawn from the atmosphere by weathering reactions, leaving more CO2 in the atmosphere to increase temperatures. If more rocks become available for rapid weathering as a result of mountain uplift the enhanced weathering will draw down atmospheric CO2 and decrease global temperatures. But the decreased temperatures will slow reaction rates, thereby using less CO2, thus allowing temperatures to moderate. | 
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发表于 2009-2-1 02:38:00
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