While they still act as net carbon sinks at present, it's possible that wildfires could help flip that role in the future by making these ecosystems a source of carbon dioxide and methane emissions that accelerate global warming. (climatecentral.org)
The oceans are net carbon sinks at present, not sources; part of the gigantic amounts of carbon dioxide injected in the atmoshere go into solution in the oceans, and lead to acidification. (skepticalscience.com)
By using dual radioactive tracers with differing lifetimes, Wilson et al. [2017] found short term increases in CH4 and CO2 release during periods of thaw in a discontinuous permafrost were generally offset by long - term accumulation of peat in the ensuing millennia, leading the regions to continue to be net carbon sinks with negative atmospheric radiative forcing, given the long life - time of atmospheric CO2. (eos.org)