Permafrost

     Changes in the size of each Earth system carbon pool in response to the addition of permafrost carbon to the UVic ESCM.  That is, the difference in the size of each carbon pool between simulations with and without permafrost carbon.  All values are relative to the size of the frozen permafrost carbon pool.  A summation of all the pools adds up to 100% for each year.

     Results are given for two emissions pathways (DEPs 4.5 and 8.5) and for 3 climate sensitivities to a doubling of CO2 (2.0, 3.0, and 4.5°C).  Soil layers that thaw, but are subsequently returned to a permafrost state, continue to be administered by the active soil carbon pool, leading to the apparent high rate of transfer of carbon to the active soil carbon pool in the 20th century.

     Permafrost (not including whatever is under the ice in Greenland and Antarctica) holds about twice as much carbon as the atmosphere does today.  In the worst case shown, if current net carbon sinks fail, atmspheric CO2 levels could more than double, even if humans ceased carbon emissions today.

     In fact, the permafrost carbon pool is twice the amount of carbon now in the atmosphere.  Putting 85% (680 ppm) of that in the air (worst-case scenario RCP 8.5) would almost triple (+170%) our current atmospheric CO2 level.  That's on top of 820 ppm added from fossil fuels in RCP 8.5: in all, 1900 ppm of CO2 in the air by 2300.