David A. says, "Ed makes a big deal that his model works for 14C. Well, of course it does -- there is only a single source of atmospheric 14C (cosmic rays), and a single sink (radioactive decay"
That's erroneous, on two counts.
First of all, there are two sources, not one, for atmospheric 14C. The other source of 14C is the "bomb spike," from atmospheric testing of nuclear weapons (which ended in the early 1960s)..
Atmospheric 14C concentration soared due to those tests, and then began rapidly falling when the atmospheric test ban treaty brought atmospheric nuclear weapon tests to a halt.
It is the famous, beautifully-exponential decay curve of 14C levels, following the atmospheric test ban, from which we derive the 16.6 year 14C "residence time" figure. Here’s a log-scale graph of the famous 14C “bombspike:”
Secondly, the main sink for atmospheric 14C is not radioactive decay, it is exchange with other carbon reservoirs: mostly the oceans and biosphere, but also lakes, soil, etc. That's why, after the bomb spike, 14C levels fell with a half-life of only about 11.5 years, rather than 5,730 years.
David A. says, "humans are responsible for all of the excess carbon in today's atmosphere. And, in fact, nature still absorbs not only as much CO2 as it admits, but also about 50% more, of what humans emit -- the so-called airborne fraction."
That's mostly correct.
It is true that humans are responsible for increasing the CO2 level by about 130 ppmv, but I object to the word "excess" -- that's an ideological judgment, not a scientific one. The reality is that the 130 ppmv increase has merely eased the Earth's chronic shortage of atmospheric CO2.
The only other thing wrong with that statement is that David A. got the definition of "airborne fraction" backwards. It's the fraction of human CO2 emissions that remains in the atmosphere, not the fraction of human CO2 emissions removed by nature.
David A. says, "Consider this -- Ed has been trying to get his paper published for almost two years now. It has been rejected -- he won't say how many times. And he wonders why.... The answer is, because his claims are full of shit!"
Even though I agree that Ed's paper is flawed, those journal rejections are very weak evidence of it.
<RANT> (feel free to skip over my long, off-topic rant)
In quite a few fields, including climate science, the quality of the work has little to do with whether a paper is accepted for publication.
In fact, many refereed journals are dominated by junk science. Have you seen this expose of "grievance studies?"
A lot of what is published in the academic journals on climate science is as bad as "grievance studies." It is political hackery, masquerading as science.
Consider, for example, the recently concluded Jasper Ridge grasslands studies, from Stanford. They sought to find evidence that the "fertilization" benefits of eCO2 (elevated CO2) are countered by the warming effect of higher CO2 levels, so look at what they did.
First, note that it is generally understood that a doubling of CO2 should produce an average ground level irradiance increase of 3.7 ±0.4 W/m² before feedbacks (though Prof. Will Happer has found evidence that CO2's forcing is commonly overestimated by about 40%, due to inaccuracies in the modeling of the far fringes of CO2's fine line spectrum).
So the Stanford folks installed heat lamps over their experimental grass plots, to see the effect of that increased IR radiation on plants.
But to stunt the growth of the wild grasses at Jasper Ridge, Stanford researchers did not add 3 or 4 W/m² of ground level irradiance. They added 80 W/m² — equivalent to >20 “doublings” of CO2 (when the reality is that it is unlikely that mankind will ever drive outdoor CO2 levels up to even one doubling of the current level).
I’m not kidding! Yet they still got their papers published in the most prestigious journals!
When 80 W/m² proved insufficient to stunt the grasses enough, they increased it to 250 W/m² — equivalent to about 67 doublings of CO2.
Here's a photo of the heat lamps they use at Jasper Ridge:
The amazing thing is that the journals aren't embarrassed to publish such drek. You can google search for “Jasper Ridge Global Change Experiment” to find out more.
But that's no more ridiculous than the anti-scientific "carbon budget" nonsense.
Note also that the processes which remove CO2 from the atmosphere cannot be significantly affected by the emission rate of "fossil" (anthropogenic) CO2. There simply is no plausible physical mechanism for such a coupling. It is the atmospheric CO2 level, not the CO2 emission rate, which primary governs the CO2 removal rate.
Now, as it happens, the CO2 removal rate has generally been approximately half the anthropogenic CO2 emission rate, for many years, with the result that CO2 levels have risen only about half as fast as would have happened without the negative feedbacks that remove CO2 at an accelerating rate. (Note: that acceleration apparently came as a big surprise for Hansen et al (1988), and is one of the main reasons their predictions 30 years ago were so far off.)
As CO2 emission rates have increased, CO2 levels have also unsurprisingly increased, and as CO2 levels have risen, CO2 removal rates have also unsurprisingly risen. The one surprising thing is the certainlycoincidentalfact that CO2 removal rates have been consistently around half the anthropogenic CO2 emission rates.
Back in 1988, Hansen & his seven illustrious co-authors equated emissions with level increases, which means they wrongly assumed that rising CO2 levels would not cause an acceleration in the processes that remove CO2. But now a remarkable number of supposed authorities on climate change make almost the opposite mistake: they suffer from the delusion that CO2 removal rates are governed by the emission rates, and that it is some sort of law that "half of the CO2 we emit stays in the atmosphere." That leads to imbecilic claims that anthropogenic CO2 emissions must be lowered to zero to stop the rise in CO2 levels, and to the idiotic notion of a "carbon budget."
Actually, if anthropogenic CO2 emission rates were merely halved, CO2 levels would completely cease rising, at least for quite a while.
...the selling point of Dr. Berry's work is the fact that absorption of 14C by the environment is a perfect match to the use of the continuity equations in atmospheric science when the correct residence time is applied, in this case, 16.5 years.
The 16.6 year 14C residence time derived from the bomb spike gives us an absolute lowerbound on the effective residence time of anthropogenic CO2 emissions.
We know that the effective residence time of anthropogenic CO2 emissions must be longer than that, because we know that some of the processes which lower the 14C concentration in the atmosphere do so by exchanging molecules of 14CO2 with molecules of 12CO2, thus lowering the 14C concentration without lowering the total amount of CO2 in the atmosphere.
But Ed nevertheless claims that the effective residence time of CO2 in the atmosphere is muchshorter than 16.5 years. In his Apr 14, 2019, 4:51 PM email he estimated "4 years." That is impossible.
To thoroughly understand the CO2 emission lifetimes, you’d need to understand all the important processes which affect CO2 levels in the atmosphere — and some of those processes are not well understood.
Isotope studies don’t work well for attributing CO2 emission effects, because they get confused by the enormous fluxes of carbon between the atmosphere and other carbon reservoirs. When such fluxes are balanced, so they don’t affect atmospheric CO2 level, they still can greatly affect the isotope ratios. So all you can get from the isotope studies is a lowerbound on the effective residence time. (Radioactive 14CO2 is 4.5% heavier than 12CO2, which causes very slight differences in rates of chemical & biological processes, but the differences are negligibly tiny, for our purposes.)
The low 14C “fossil” carbon we put into the atmosphere is (nearly) bio-equivalent to high-14C carbon, so the plants take up whichever CO2 molecules they encounter. Likewise, the oceans are happy to dissolve either kind of carbon dioxide. The atmospheric CO2 is constantly being exchanged with carbon in plants, animals, soil, and oceans.
So, even though mankind's CO2 emissions have elevated atmospheric CO2 levels by about 130 ppmv (over 45%), and even though the “fossil carbon” we've added to the atmosphere contains almost no 14C, there’s been only a modest drop in 14C percentage, after accounting for the bombspike. That’snotbecause our emissions aren’t responsible for the increase in CO2 level, as some people suppose. It’s because most of the low-14C CO2 we put into the atmosphere has been exchanged for other CO2 in the oceans or biosphere.
It’s as if you had $280 in common $1 bills, and I gave you another $130 in Sacagaweas. At that point, 31.7% of your money would be in coins. But then you go play poker all night. You break even, so you still walk out with the same amount of money that you started with, but now you have only a few Sacagaweas, because most of them have been exchanged for other people’s money.
Even though you have only a few coins left in the morning, the reason you have $410 instead of $280 is that I gave you that big stack of coins.
In the Q&A after this (excellent!) lecture, Prof. Dick Lindzen reasons that the practical lifetime of emitted CO2, defined as the amount of time for atmospheric CO2 level to drop by 2/3, if CO2 emissions suddenly ceased, is about fifty years:
We have good measurements of atmospheric CO2 levels (starting in 1958), and we have good data for the greatest part of anthropogenic CO2 emissions (from economic data on the production and use of various fossil fuels), so we can do a reasonable calculation for the airborne fraction, and for the net CO2 removal rate.
Using Dr. Spencer's "simple model," I wrote a tiny Perl program to simulate the effect on atmospheric CO2 level of a sudden cutoff of CO2 emissions. Counting 280 ppmv as "pre-industrial," 2/3 of the anthropogenic CO2 is gone from the atmosphere in 60 years:
# estimate CO2 removal rate in ppmv/yr as a function of CO2 level in ppmv, per Dr. Roy Spencer's "simple model"