Wednesday, 5 July 2017

Soil carbon release accelerating global warming.

Could the release of carbon from the soil be  accelerating global warming and climate change?  The answer from the latest research published in Nature appears to be a resounding 'yes'.  This is perhaps not surprising given that the soil acts as a major store of global carbon.  It isn't simply locked in place. Organic processes release it to the atmosphere. 

Carbon is a vital ingredient of our living planet and plays a major role in the balance of our ecosystem.

All life on earth is 'made' of carbon and, simply put, carbon circulates. Carbon enters the atmosphere as carbon dioxide from respiration and combustion. It is absorbed by plants to make carbohydrates in photosynthesis using energy from the sun.

Animals feed on the plants passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled back into the atmosphere as carbon dioxide. The animals and plants eventually die and these dead organisms are eaten by decomposers (microbes and animals in the soil), and carbon is returned to the atmosphere as carbon dioxide.

The  bulk of the planet's terrestrial carbon is retained in the soil. In this sense the soil acts as a carbon buffer or 'store', and it is this way that the exchange of carbon between the soil and atmosphere represent a restraint on atmospheric carbon dioxide and on global warming. 

This carbon cycle is driven by organisms (plants, microbes and animals) living in the soil, and these organic processes are enhanced when temperature rises.  Thus, a key question is whether anthropogenic (man-made) global warming in turn acts to increase the amount of carbon released from the soil.  

A recent study shows not only that this is the case,  but also suggests that this release of carbon from  the soil is now having a significant impact on global warming.

In a major international collaboration, scientists from universities and climate centres across the world have analysed soil samples from across the globe, from the arctic permafrosts to the dry Mediterranean forests.   They found the effects of temperature on soil carbon were variable but predictable.  The amount of carbon 'stored' in the soil varied inversely with temperature.

The findings of this study provide support for the contention that the release of carbon from the soil is having a significant effect on atmospheric carbon.  As global temperatures rise more carbon will be released into the atmosphere accelerating global warming.

As the authors of the study warn, reducing greenhouse gas emissions is vital if we want to avoid the most damaging effects of this carbon feedback over the course of the century.

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