Monday, November 17, 2014

Green Geoengineering means raking up a lot of leaves



         Atmospheric CO2 concentrations continue to increase in spite of "Green Geoengineering"

"Green" geoengineering solutions are very appealing because they don't involve any complicated technology or geochemistry.  Wouldn't it be great if all we had to do to stop sea level rise and avert the Greenhouse Warming was to plant a garden or farm Christmas Trees or cabbages or wheat, and let the plant growth pump down the CO2 that our cars and factories and homes are expelling into the atmosphere?  Wouldn't it great if we didn't have to do anything at all?

Plants do pump down CO2, as shown by a strong annual cycle in the CO2 concentration in the atmosphere (figure above).  CO2 in the atmosphere increases from Oct to April, and then rapidly decreases by 3-4 ppm from April to Oct---i.e. during summer in the northern hemisphere.   The burst in plant growth and the appearance of leaves pumps down huge amounts of CO2.   But alas, as fall arrives and then winter, then leaves fall off the trees, the plant growth slows down, and natural soil process produce decay which returns the CO2 to the atmosphere.  

This shows the basic problem with "Green" Geoengineering---putting CO2 into plants is not a one-way trip.  The CO2 is released back to the atmosphere when the leaves decay and crops are harvested, when the christmas tree is cut, decorated, and then stacked up in landfills, or when trees in old growth forests crash to ground and rot.  The only way "Green" geoengineering can work would be to somehow preserve all the biomass and prevent it from decaying.  For starters, someone would have to rake up every single leaf dropped by all maple and oak trees across the United States, put the leaves in a giant garbage bag, and then keep that garbage bag sealed up in their basement ..... forever.


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