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For reasons that we don't entirely comprehend yet, nature gives
us a break. Of the total 6-7 billion tons (Gt) of carbon we put
in the air, only about half remains there, for a net increase of
about 3 Gt a year. The other half is taken up by ocean water or
marine organism, stored in plant tissues during photosynthesis
(which uses the power of sun-light to assemble carbohydrates
from water and CO2), buried in sediments or peat bogs or se-
questered in one of several other natural carbon-holding systems
known as reservoirs, or 'sinks'.
It's not clear how much more these sinks can hold because their
various mechanisms to store and release carbon are complex and
incompletely understood.
In addition, oceans warm much more slowly than land. So even if greenhouse gas concentrations were stabilized tomorrow, surface temperatures would continue to rise for years or decades. To keep the concentration of CO2 in the atmosphere at its current level, civilization would have to reduce emissions by 50 to 70 percent immediately and more in years to come.
Excerpted from 'Climate Change Primer' |