About 1 trillion tonnes of carbon is stored in permafrost.325
and you include the footnote:
325 “The new northern permafrost zone carbon inventory reports the surface permafrost carbon pool (0–3 m) to be 1,035 ±150 Pg carbon (mean ±95% confidence interval, CI).” E. a. G. Schuur et al.,‘Climate Change and the Permafrost Carbon Feedback’, Nature 520, no. 7546 (April 2015): 171–79,https://doi.org/10.1038/nature14338.
In the Nature paper you cited for a listing of permafrost carbon, you find the following quote on the same page as lists total carbon in the top 3 meters of permafrost. I list the geographic regions in braces for clarity:
Taken together, the known pool of terrestrial permafrost carbon in the northern permafrost zone is 1,330–1,580 Pg carbon, accounting for surface carbon as well as deep carbon in the yedoma region [in Siberia and Alaska] and [Arctic] river deltas, with the potential for 400 Pg carbon in other deep terrestrial permafrost sediments that, along with an additional quantity of subsea permafrost carbon, still remains largely unquantified.
So a total amount of carbon in permafrost between 1730-1980 Pg, or 1.73-1.98 trillion tonnes of carbon, not the 1 trillion tonnes you list. This is typically described as being twice the carbon currently in the atmosphere, but how quickly it causes heating given some rate of thaw depends on whether it is released as methane or carbon dioxide. As you know, methane has 100X the heating potential of carbon dioxide, but that drops off rapidly over a couple decades, so rate of release is very important.
If you look elsewhere for amounts, you find the usual figure listed is 1.5Tt for total carbon in permafrost. I think that represents updates to estimates but have not looked into it in detail. A slight rephrase of your sentence “About 1 trillion tonnes of carbon is stored in permafrost.” to either mention the top 3 meters of soil explicitly for the trillion tonnes number or to use some figure closer to 1.5Tt (NOAA’s mid-range for total northern permafrost). will bring the announced total closer to what people typically mean by total carbon in permafrost, just the permafrost in the North.
Earlier in the same Nature paper, you read:
Deeper carbon measurements were initially rare, and it was not even possible to quantify the uncertainty for the permafrost carbon pool size estimate. However, important new syntheses continue to report large quantities of deep carbon preserved in permafrost at many previously unsampled locations, and that a substantial fraction of this deep permafrost carbon is susceptible to future thaw15. The permafrost carbon pool is now thought to comprise organic carbon in the top 3 m of surface soil, carbon in deposits deeper than 3 m (including those within the yedoma region, an area of deep sediment deposits that cover unglaciated parts of Siberia and Alaska16–18), as well as carbon within permafrost that formed on land during glacial periods but that is now found on shallow submarine shelves in the Arctic.
For the reference you cite, it’s clear that carbon deeper than 3m is considered “susceptible to future thaw”, and so is relevant to discussions of permafrost contribution to global warming. In fact, some existing examples of that thaw are mentioned in that 2015 paper.
I think there are numerous taking off points for discussion of the effects of permafrost thaw aside from the box 5.1 sections of the IPCC technical report that you cite.
The parameters deciding the effects of permafrost include:
abrupt vs gradual release of carbon
carbon release as methane (CH4) vs carbon dioxide (CO2)
geological shaping of ice and organic matter within permafrost
release of ancient microbes (bacteria, viruses) and others (anthrax, smallpox) in the soil
subsidence rates (causing effects on current or future infrastructure)
biophysical rates of change to permafrost (ground fires and microbial action)
stored chemical release on permafrost lands (sump chemicals, other chemicals)
if you decide that you want to expand on those in a later version of your research.
EDIT: I included some light edits to this to make my comment more clear. Also I would love to discuss more of the topics you raise in your research report, including the models suggesting different levels of contribution from carbon release from permafrost.
I noticed this quote at the end of the box highlight on “Permafrost Carbon and Feedbacks to Climate” in Chapter 5 of the IPCC Technical Report that you cite:
In conclusion, thawing terrestrial permafrost will lead to carbon release under a warmer world (high confidence). However, there is low confidence on the timing, magnitude and linearity of the permafrost climate feedback owing to the wide range of published estimates and the incomplete knowledge and representation in models of drivers and relationships.
And this is why considering the highs and lows in a bit of depth is worth doing.
It is projected that CO2 released from permafrost will be 18 (3.1–41) PgC /°C by 2100, with the relative contribution of CO2 vs CH4 remaining poorly constrained. Permafrost carbon feedbacks are included among the under-represented feedbacks quantified in Figure 5.29.
Those projections, if we accept them as accurate, do not address nonlinear release of carbon, particularly as Methane. That leaves it to you to summarize expected heating over the short term of an abrupt release of carbon involving significant amounts of CH4. As I wrote, CH4 has 100X the heating potential of CO2 but over the longer term of a century, that drops to 25X.
Would abrupt release of a large amount of CH4 create a jump in average temperature of 1-2C? What would the impact of that be? How would it amplify other feedbacks and with what consequences for humanity, give that the effect is temporary?
Your report could address those questions with more interest than it does.
Hi, John.
In your research report, you wrote:
and you include the footnote:
In the Nature paper you cited for a listing of permafrost carbon, you find the following quote on the same page as lists total carbon in the top 3 meters of permafrost. I list the geographic regions in braces for clarity:
So a total amount of carbon in permafrost between 1730-1980 Pg, or 1.73-1.98 trillion tonnes of carbon, not the 1 trillion tonnes you list. This is typically described as being twice the carbon currently in the atmosphere, but how quickly it causes heating given some rate of thaw depends on whether it is released as methane or carbon dioxide. As you know, methane has 100X the heating potential of carbon dioxide, but that drops off rapidly over a couple decades, so rate of release is very important.
If you look elsewhere for amounts, you find the usual figure listed is 1.5Tt for total carbon in permafrost. I think that represents updates to estimates but have not looked into it in detail. A slight rephrase of your sentence “About 1 trillion tonnes of carbon is stored in permafrost.” to either mention the top 3 meters of soil explicitly for the trillion tonnes number or to use some figure closer to 1.5Tt (NOAA’s mid-range for total northern permafrost). will bring the announced total closer to what people typically mean by total carbon in permafrost, just the permafrost in the North.
Earlier in the same Nature paper, you read:
For the reference you cite, it’s clear that carbon deeper than 3m is considered “susceptible to future thaw”, and so is relevant to discussions of permafrost contribution to global warming. In fact, some existing examples of that thaw are mentioned in that 2015 paper.
I think there are numerous taking off points for discussion of the effects of permafrost thaw aside from the box 5.1 sections of the IPCC technical report that you cite.
The parameters deciding the effects of permafrost include:
abrupt vs gradual release of carbon
carbon release as methane (CH4) vs carbon dioxide (CO2)
geological shaping of ice and organic matter within permafrost
release of ancient microbes (bacteria, viruses) and others (anthrax, smallpox) in the soil
subsidence rates (causing effects on current or future infrastructure)
biophysical rates of change to permafrost (ground fires and microbial action)
stored chemical release on permafrost lands (sump chemicals, other chemicals)
if you decide that you want to expand on those in a later version of your research.
EDIT: I included some light edits to this to make my comment more clear. Also I would love to discuss more of the topics you raise in your research report, including the models suggesting different levels of contribution from carbon release from permafrost.
I noticed this quote at the end of the box highlight on “Permafrost Carbon and Feedbacks to Climate” in Chapter 5 of the IPCC Technical Report that you cite:
And this is why considering the highs and lows in a bit of depth is worth doing.
Those projections, if we accept them as accurate, do not address nonlinear release of carbon, particularly as Methane. That leaves it to you to summarize expected heating over the short term of an abrupt release of carbon involving significant amounts of CH4. As I wrote, CH4 has 100X the heating potential of CO2 but over the longer term of a century, that drops to 25X.
Would abrupt release of a large amount of CH4 create a jump in average temperature of 1-2C? What would the impact of that be? How would it amplify other feedbacks and with what consequences for humanity, give that the effect is temporary?
Your report could address those questions with more interest than it does.