20 April 2009

why carbon sinks?

Everybody is talking about reduction of green house gases and carbon-cuts. What a lot of people don't realise is that even if carbon amounts in the atmosphere are reduced today, the effects of current levels of carbon already present is going to be felt for atleast 100 years - this is how long it takes for carbon to dissipate. In other words: even if we reduce carbon emissions now, the carbon already present can contribute to global warming.

This realization is the reason why there is a current scramble for carbon sequestration technologies. The idea behind this is to capture carbon and then bury it under the earth, in the sea-bed or to come up with a method where the conversion of carbon is accelerated.

Currently forests have been acting as a great 'carbon sink' whereby carbon is naturally captured. However due to global warming there have been speculations that forests could release huge quantities of carbon and create a situation in which they do more to accelerate warming than to slow it down. While deforestation is responsible for about 20% of greenhouse gas emissions from human activities, forests currently absorb more carbon than they emit.

But the problem is that the balance could shift as the planet warms, the report concludes, and the sequestration service provided by the forest biomes could be lost entirely if the Earth heats up by 2.5C or more.
Droughts, more pest invasions, and other environmental stresses would trigger considerable forest destruction and degradation. This could create a dangerous feedback loop, it adds, in which damage to forests from climate change would increase global carbon emissions that then exacerbate global warming.

The other biggest natural carbon sink are the oceans of the world which are already showing stress due to acidification because of excess carbon. Plankton in the ocean also act as a carbon sink and they will slowly die as the oceans become more acidic and warm up. The other big carbon sink is the permafrost which is said to contain large amounts of methane. Global warming will cause it to melt which will release all the methane which is more potent than CO2 as a GHG.

The need for reducing carbon emissions as well as to reduce the amount of carbon already in the atmosphere is pressing. So there is a twin objective to be met in order to combact enhanced global warming. Does this make it harder to reach our objectives? Perhaps. But it also impresses upon us the incredible delicacy of the Earth's natural regulating systems.

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