Not so; they are keeping up. As seen upthread, there isn’t a long-term trend in the airborne fraction.
DB2
The airborne fraction is the fraction of human CO2 emissions remaining in the atmosphere. If carbon sinks were keeping up with emissions the airborne fraction would be zero. Then, all the emitted carbon would absorbed, and atmospheric CO2 would be constant.
If I were running a race and every lap I fall further behind by the same fraction, I wouldn’t say I was keeping up.
If inflation was 3% and my salary increase was 2%, my salary fraction might be constant, but I wouldn’t say I was keeping up.
If I turn on my bathtub faucet but only crack open the drain, the tub fraction might remain constant but if it’s bigger than zero, my bathroom will flood.
An airborne fraction bigger than zero, constant or not, means CO2 accumulates in the atmosphere.
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The airborne fraction is the percentage of CO2 that remains in the atmosphere. As CO2 has increased the amount that is sequestered in the land and ocean also has increased, keeping the percentage essentially constant over the decades.
True, but that wasn’t the question discussed in the Ke article you linked. With an more or less constant fraction, the amount of CO2 has been increasingly sequestered as emissions have increased.
Of course we are putting more carbon dioxide into the air. And more carbon dioxide is being sequestered (about half). Since half of the increasing emissions are still be sequestered, then the sinks are keeping up.
DB2
I apparently don’t understand your position.
The airborne fraction is " defined as the ratio of the annual increase in atmospheric CO2 to the CO2 emissions from human sources" Airborne fraction - Wikipedia
About half of human CO2 gets sequestered by sinks, the rest go in the air. That is why atmospheric CO2 levels are rising. I assume we all agree on that.
Since atmospheric CO2 levels are continuing to rise in what possible way are the CO2 sinks keeping up?
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They are still absorbing half of the (increasing) CO2 emissions, as they have been for decades. That is keeping up. This would be opposed to “filling up” or reaching a limit on the amount of carbon dioxide sequestered.
You are probably familiar with the concept of tithing. One gives a tenth of one’s income to your church or charity. As your income increases your annual donation increases, keeping up with your increased affluence.
DB2
Got it. It is still the case though that more CO2 is emitted than the sinks can take up, so I think it is an odd use of “keeping up”.
If I increase my exercise level so that I am gaining a constant 2 lbs a week I wouldn’t describe that as my exercise is “keeping up” with my calorie intake.
I am still getting fatter.
The world is still getting warmer.
The change in the carbon sink is not really surprising. Back in 2019 Bennedsen et al. calculated that since 1960 there is “no statistical evidence of an increasing airborne fraction, but we do find statistical evidence of a decreasing sink rate.”
DB2
Plants Absorb 31% More CO2 Than Previously Thought
https://scitechdaily.com/scientists-were-wrong-plants-absorb-31-more-co2-than-previously-thought/
New research shows plants absorb 31% more CO2 than previously estimated, raising the global GPP [Gross Primary Production] to 157 petagrams [billion metric tons] per year…
“Figuring out how much CO2 plants fix each year is a conundrum that scientists have been working on for a while,” Gu said. “The original estimate of 120 petagrams per year was established in the 1980s, and it stuck as we tried to figure out a new approach. It’s important that we get a good handle on global GPP since that initial land carbon uptake affects the rest of our representations of Earth’s carbon cycle.”…
Understanding how much carbon can be stored in land ecosystems, especially in forests with their large accumulations of biomass in wood, is essential to making predictions of future climate change.
DB2
And this week…
New Study Reveals Oceans Absorb More CO2 Than Previously Thought
https://scitechdaily.com/new-study-reveals-oceans-absorb-more-co2-than-previously-thought/
The new study – led by researchers from the University of Exeter’s Penryn Campus in Cornwall – used precision measurements to confirm that the temperature of the ocean skin does indeed aid carbon absorption.
Carried out in the Atlantic, the findings suggest this ocean absorbs about 7% more CO₂ each year than previously thought. It might sound small, but when applied across all oceans this additional carbon absorption is equivalent to one and half times the carbon captured by annual forest growth in the Amazon rainforest.
DB2