|MadSci Network: Environment|
Andrew - Based on what we know about the earth’s climate system, it seem likely that some areas may experience longer growing seasons and/or increased productivity as a result of global warming but that this effect will be far too small to slow global warming enough. Both warmer temperatures and elevated CO2 can be good for plants, especially under ideal lab conditions. However, other factors may limit or even reverse this effect in the real world. Global warming is likely to shift rainfall patterns, which may lead to drought (and possibly more wildfires) in many areas. Plants also need nutrients like nitrogen and phosphorus to grow - if there aren’t enough of these nutrients around, plants won’t increase in productivity. Finally, other changes that come with burning fossil fuels (such as air pollution) reduce the productivity of crops and natural systems. Most importantly, the increases in productivity in some areas (negative feedbacks) will not be enough to offset our continued emissions of greenhouse gasses. Most of the current models already include our best guess for the productivity gains you hypothesize and they still predict that both CO2 concentrations and temperature will continue to rise if we don’t cut our greenhouse gas emissions. Increased warming in places like polar regions may increase the growth of plants there but can also melt permafrost and trigger the release of carbon stored in the soil. These “positive feedbacks” could increase CO2 and temperature far more rapidly than the productivity gains in other areas could slow things down. Overall, we can't count on increased plant productivity to solve global warming for us. If you’re really interested, the most recent scientific consensus can be found at: http://www.ipcc.ch/ although evidence for global warming has gotten even stronger since this report was published (2001). The summaries for policy makers contain lots of details.
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