Dear Don & Yaël, 

     I've been reading a lot about climate lately, and I know that the earth stores lots of   carbon in different places, like in the ocean and in plants. Are there any other major carbon stores?

Yaël: Great question. And the answer might surprise you. While plants and oceans do store a lot of carbon, much of the planet's carbon is stored in soil. When forests and crops and other plants absorb carbon dioxide from the atmosphere, they channel      most of it into the soil.

D: Hmm...So I guess the next question is, does global warming have any affect on this soil-carbon-capture system?

Y: Actually, it does. When soil warms, the microorganisms in it grow feistier and eat more of the carbon stored in soil. When all those millions of tiny organisms aspirate,  or breathe, they release that carbon back into the atmosphere in the form of carbon dioxide...

D: Which is the main greenhouse gas that causes global warming. So warming soil  creates a sort of global warming feedback loop-- the warmer soil gets, the more CO2 it releases.

Y: Right. But there are things we can do to stop or at least slow the process. For example, farmers could increase the amount of carbon stored in soil by planting more cover crops, like legumes, that protect and enrich soil between harvests. Farmers can also do less tilling, because stirring up soil riles its microorganisms and makes  them consume more carbon. So keeping more carbon in soil is good for the atmosphere, and good for the soil.

D: So it's a win-win.

Y: Right.