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By 2023-2028 period, what will happen to emissions and airborne fraction?

Emissions continue to rise at increased rate, airborne fraction increases
1 (5%)
Emissions continue to rise at increased rate, airborne fraction no noticeable change
0 (0%)
Emissions continue to rise steadily at approx existing rate, airborne fraction increases
10 (50%)
Emissions continue to rise steadily at approx existing rate, airborne fraction no noticeable change
2 (10%)
Emissions continue but at declining rate, airborne fraction increases
5 (25%)
Emissions continue but at declining rate, airborne fraction no noticeable change
2 (10%)

Total Members Voted: 19

Voting closed: January 31, 2018, 04:34:51 PM

Author Topic: 2018 Mauna Loa CO2 levels  (Read 33702 times)


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Re: 2018 Mauna Loa CO2 levels
« Reply #150 on: January 31, 2019, 11:01:40 PM »
I suggest reading

The ocean is taking up a large part of the emissions. The amount the ocean takes up in short term depends on the partial pressure of CO2 (just the proportion of CO2 in the atmosphere) compared to what was already absorbed previously (which depends on past proportion of CO2 in the atmosphere).

The main first order effect therefore, is that if you half the emissions then you also half the amount the oceans take up and this is a rapid effect (like a Edit:month?year in the tropics).

Lots of other effects:
Land also adjusts to CO2 level but doesn't take up as much and may be a bit slower.
Sequestering to deep ocean - biology and water overturning cycle
Rock weathering.

These are getting slower and weaker effects.

Edit 2
See also:
and other searches for airborne fraction.

The airborne fraction is a scaling factor defined as the ratio of the annual increase in atmospheric CO
2 to the CO
2 emissions from anthropogenic sources.[1] It represents the proportion of human emitted CO2 that remains in the atmosphere. The fraction averages about 45%, meaning that approximately half the human-emitted CO
2 is absorbed by ocean and land surfaces. There is some evidence for a recent increase in airborne fraction, which would imply a faster increase in atmospheric CO
2 for a given rate of human fossil-fuel burning.[2] However, other sources suggest that the "fraction of carbon dioxide has not increased either during the past 150 years or during the most recent five decades".[3][4]

Changes in carbon sinks can affect the airborne fraction.

This concept exist because it is fairly stable. So cut emissions in half and the ocean and land uptake are also approx cut in half keeping the airborne fraction roughly the same.

Sorry for the bad news. This means cutting emissions in half does not get the job of stabilising CO2 levels done, we need like a 95% cut in emissions eventually rising to 100% in order to stabilise CO2 levels.

Seems I have got some of this stuff wrong and I should come back and correct and add better info.

See comments commencing 12 Jan 2019 at

and some continuation at

Ok here are results from a sudden stop in emissions. Cols are years, emissions in ppm CO2 equiv, atmosphere conc and the annual increment. The drop is immediate but modest and tails away fairly quickly. Which I think is what I said. I hope :-)

The temp stays very flat, it actually drops a whisker for a few decades before increasing very gradually over the centennial time scale. Due to the deep ocean gradually warming.

[159,] 2010 3.9877255 386.2585 2.04413596
[160,] 2011 4.0634923 388.3413 2.08285478
[161,] 2012 4.1406986 390.4636 2.12230999
[162,] 2013 4.2193719 392.6261 2.16251556
[163,] 2014 4.2995400 394.8296 2.20348574
[164,] 2015 4.3812312 397.0749 2.24523507
[165,] 2016 4.4644746 399.3626 2.28777833
[166,] 2017 4.5492996 401.6938 2.33113060
[167,] 2018 4.6357363 404.0691 2.37530726
[168,] 2019 4.7238153 406.4894 2.42032396
[169,] 2020 4.8135678 408.9556 2.46619665
[170,] 2021 0.0000000 406.5635 -2.39208398
[171,] 2022 0.0000000 404.7401 -1.82341108
[172,] 2023 0.0000000 403.1955 -1.54462036
[173,] 2024 0.0000000 401.8031 -1.39232590
[174,] 2025 0.0000000 400.5070 -1.29612394
[175,] 2026 0.0000000 399.2814 -1.22562982
[176,] 2027 0.0000000 398.1137 -1.16768541
[177,] 2028 0.0000000 396.9972 -1.11655029
[178,] 2029 0.0000000 395.9275 -1.06968026
[179,] 2030 0.0000000 394.9016 -1.02591050

Hi, and thank you for the numbers. 2.392 going into sinks looks to be just a little larger than in each of the past three years and wasn't what I was expecting. Much nearer to what you said, but I'm not sure either of us were expecting increase in that first year.

Sinks of 1.0259 is less than 43% of the 2.392 in just 9 years. I would doubt that continues as an exponential decline.

Chris, this version of the model only has a 1y tilmestep so the details within that time scale are a bit imprecise. In fact the sink into deep ocean for the first year (after stopping emissions) won't see the atmospheric conc at all, whether it was +100 or -100 would make no difference. A shorter time step (but the same underlying equations) would change that just a fraction I think.

Carbon equation has 3 time scales (and 20% of emissions stay in atmosphere for ever) so a simple exponential won't describe it well. Still 340ppm at 2350 in this scenario.

This model uses "the Myhrvold and Caldeira" equations.