Since 1850 59% of atmospheric CO2 emissions have been taken up by terrestrial and marine sinks according to AR6 (see attached image). This amounts to 1430 Gt of CO2. Unlike the terrestrial sink, which is largely permanent (soil organic matter and living biomass), some of the marine sink is transitory. For example, a portion of dissolved CO2 (and the carbonate and bicarbonate is equilibrates with) will offgas when atmospheric partial pressure of CO2 drops, after accounting for the time lags in oceanic circulation.
Do any of you have references to studies that estimate what portion of the marine sink is permanent? This is important when calculating how much excess CO2 (atmospheric plus transitory marine) we need to draw down to solve climate change and ocean acidification. Thank you!
Thanks for your answer Alastair and the useful paper. If my read is right, the paper says that most (~75%) of the dissolved CO2 is permanently gone if we are talking about a timescale of >1,000 years. However, under a scenario with negative emissions (which all of the current SSPs employ), there could be drawdown of atmospheric CO2 partial pressure faster than that. This would result in an ocean-atmosphere equilibration and net offgassing of CO2. Given that ocean turnover will take several centuries, a large portion (i.e. >25%) of the dissolved CO2 currently in the ocean could be released to the atmosphere prior to removal via pH reactions in response to sequestration. Are you familiar with any literature on this phenomenon?
Thanks again!
Hi Benjamin W. Abbott,
When I wrote "None" I meant that there is no chance that we will draw down CO2 from the atmosphere so that it draws CO2 up from the oceans. Here is an article published today by the EIA "The EIA projects nearly 50% increase in energy use by 2050": https://www.eia.gov/todayinenergy/detail.php?id=49876#
In it most of the increase is provided by renewables, so they are only keeping up with energy demand. They are not replacing fossil fuels, far less providing the energy needed to remove CO2 from the atmosphere.
The only way to reduce CO2 emissions is to reduce energy use, and I can't see the politicians and the public (including scientists) agreeing to that.
OTOH, perhaps the book "Drawdown" by Paul Hawken has the answer: https://www.amazon.co.uk/Drawdown-Comprehensive-Proposed-Reverse-Warming-ebook/dp/B077QBNM8M/ref=tmm_kin_swatch_0?_encoding=UTF8&qid=1633619474&sr=8-1
If he has then here are a couple of references that may help you.
Archer, D., Eby, M., Brovkin, V., Ridgwell, A., Cao, L., Mikolajewicz, U., Caldeira, K., Matsumoto, K., Munhoven, G., Montenegro, A. and Tokos, K. (2009) ‘Atmospheric Lifetime of Fossil Fuel Carbon Dioxide’, Annual Review of Earth and Planetary Sciences, vol. 37, no. 1, pp. 117–134 [Online]. DOI: 10.1146/annurev.earth.031208.100206 (Accessed 27 April 2010). Gingerich, P. D. (2019) ‘Temporal scaling of carbon emission and accumulation rates: modern anthropogenic emissions compared to estimates of PETM onset accumulation’, Paleoceanography and Paleoclimatology, Wiley Online Library, vol. 34, no. 3, pp. 329–335.
There are also several references in section 2 of the above that you may find useful.