[Bored chemist]

so there must be something out there which generates more CO2

Winter?

[alancalverd]

Not according to Mauna Loa. And AFAIK there have been 400,000 winters in the last 400,000 years, but only 5 large CO2 peaks.

[Petrochemicals]

Anyway, back to the ice cores.

If we ignore the CO2 lag and suppose that sudden increases of CO2 were responsible for sudden temperature changes, those of a curious nature would ask what caused those sudden bursts of CO2?   

Obviously, volcanic activity. Which projected massive amounts of CO2 and dust into the atmosphere. So we look at the ice cores and see....that the dust maxima mostly coincide with temperature and CO2 minima.

Bloody Russians.   

One thing you notice about the co2 graph is it builds slowly and then crashes, just like the temperature etc. If co2 is the cause of global warming, where does it all dissappear to so quickly if co2 is such a longterm problem?

[alancalverd]

I think you are reading the graphs back to front, and possibly upside down.

Archaeologists and geologists often draw graphs with time going into the past from left to right, as in reply # 29, because that is the order in which they discover it, whereas stuff actually happens in the conventional physics order shown in the OP here, with "more at the top".

[Petrochemicals]

I see what you mean

[Bored chemist]

Not according to Mauna Loa. And AFAIK there have been 400,000 winters in the last 400,000 years, but only 5 large CO2 peaks.

You seem to have forgotten what you were talking about.
My comment "Winter" was related to your point that

The Mauna Loa CO2 peaks quite sharply in the northern summer, when anthropogenic emission is minimal, so there must be something out there which generates more CO2 than human activity,

So, that's the seasonal variation and the thing that changes the CO2 concentration is winter.
Strictly, it doesn't create CO2, it stops the uptake, but the effect looks the same.

And before you ask, yes, I know there are two winters every year.

There's also the problem that what you said
"there must be something out there which generates more CO2 than human activity"
implies that the variation due to seasons is bigger then the anthropogenic change.

You might have more success getting people to consider the OP if you didn't say that because the graph is pretty clear..


seasonal.jpg (96.94 kB . 1106x579 - viewed 3795 times)

[alancalverd]

For those with normal vision, here's the Mauna Loa CO2 graph expanded to show the monthly variation

the thing that changes the CO2 concentration is winter. Strictly, it doesn't create CO2, it stops the uptake,

So in winter, when anthropogenic emission is greatest and foliage uptake is least, I would expect the CO2 concentration to be higher than in summer.  But as you can plainly see, it's actually the other way around.

There's also the problem that what you said
"there must be something out there which generates more CO2 than human activity"
implies that the variation due to seasons is bigger then the anthropogenic change.

You need to distinguish between change (differential) and sum (integral). All True Believers will tell you that atmospheric CO2 is very persistent, which is why the (presumed) anthropogenic contribution has accumulated year on year. I don't dispute that. My question is why does the northern hemisphere CO2 level increase more in summer than in winter?

[Bored chemist]

And before you ask, yes, I know there are two winters every year.

It seems you didn't understand why you should ask.

https://en.wikipedia.org/wiki/Keeling_Curve#Results_and_interpretation
"The Keeling Curve also shows a cyclic variation of about 5 ppmv each year corresponding to the seasonal change in uptake of CO2 by the world's land vegetation. Most of this vegetation is in the Northern hemisphere where most of the land is located. From a maximum in May, the level decreases during the northern spring and summer as new plant growth takes CO2 out of the atmosphere through photosynthesis. After reaching a minimum in September, the level rises again in the northern fall and winter as plants and leaves die off and decay, releasing CO2 back into the atmosphere"

[Bored chemist]

You need to distinguish between change (differential) and sum (integral)

OK, lets do that
If something changes from about 310 to about 410, that is a difference. It's a difference of about 100
If it changes from about 396 to about 407 that is also a difference- about 11
And since 100 is more than 11 your contention that the seasonal variation is bigger than the anthropogenic variation is plainly wrong.

Now, what did you think someone had integrated?

[alancalverd]

In 2019 the seasonal fluctuation reported at Mauna Loa was from 405 to 415 than back down to  408 - a maximum excursion of 10. The underlying smoothed curve rose from 410 to 412, an excursion of 2. 10 >  2 in my book. And this cycle is repeated every year. All I am asking for at this stage of the argument is an explanation of the apparently anomalous cycle. Why is there more CO2 in the atmosphere in summer than in winter? Why is the amplitude of the annual fluctuation 5 times larger than the annual increment?

It's odd how Believers dismiss others as deniers, when it is the Believers who persistently ignore the data! For the umpteenth time, yes, the climate is changing. Yes, it must because it is inherently chaotic. And it always has, with sharp temperature rises every 100,000 years or so, followed by a slow decline. And on the basis of historic performance, we would expect to be in a rapid rise period about now.

I think you would agree that a scientific hypothesis must explain existing data and predict future data. The CO2-as-driver hypothesis manifestly does not explain historic data. The anthropogenic-CO2-as-recent-driver might  hold water but so far we have only observed a one-way correlation with a trend that began several thousand years ago, which most scientists would say is "interesting, possibly consistent with  previous data, but by no means proof of causation".

[Bored chemist]

The anthropogenic-CO2-as-recent-driver might  hold water

And, for the third time; you still have to explain how it could possibly not do so.

[evan_au]

For comparison, there is a Southern Hemisphere CO2 monitoring station at Cape Grim lighthouse in Tasmania.
- I downloaded and graphed the CO₂ concentration for the same years (2015-2020).
- Tasmania shows much less seasonal CO₂ variability than Mauna Loa - so this is a local seasonal phenomenon, rather than a global atmospheric phenomenon.
- They also measure Methane and nitrous oxides at Cape Grim - methane has greater seasonal variability, nitrous oxides less variability.

Cape_Grim_CO2_2015-2020.png (11.09 kB . 472x285 - viewed 3708 times)

Carbon dioxide concentrations show seasonal variations (annual cycles) that vary according to global location and altitude. Several processes contribute to carbon dioxide annual cycles: for example, uptake and release of carbon dioxide by terrestrial plants and the oceans, and the transport of carbon dioxide around the globe from source regions (the Northern Hemisphere is a net source of carbon dioxide, the Southern Hemisphere a net sink).
The Cape Grim baseline carbon dioxide data displayed show both the annual cycle and the long-term trend.

See: https://www.csiro.au/en/Research/OandA/Areas/Assessing-our-climate/Latest-greenhouse-gas-data

which most scientists would say is "interesting, possibly consistent with  previous data, but by no means proof of causation

This assumes that scientists are dependent on observations only.
- However, climate science is now an experimental science, with climate experiments conducted "in silico" (in silicon, in a supercomputer)
- And results have repeatedly shown that if you remove human additions of greenhouse gases, but leave background levels (including volcanoes), then you remove the warming trend we see now. That is cause and effect.
- That is taken to the next level with studies that try to attribute particular extreme events to human-induced climate change. They run many scenarios with and without human greenhouse contributions, and can come up with an estimate like "This event is 30% more likely with human contributions to climate change".

See: https://en.wikipedia.org/wiki/Attribution_of_recent_climate_change#Detection_and_attribution_studies

[alancalverd]

The problem with all simulations is that they give you the answer you want, because you input the mathematical model. If the model is good, you should be able to wind the clock back 400,000 years and generate the ice core data. Or you could start with the data and use a bit of AI to generate the model. Either approach would be honest and scientific.The question is whether the first approach shows CO2 historically lagging behind temperature, or the second approach explains why it suddenly starts leading.

[Bored chemist]

The problem with all simulations is that they give you the answer you want,

That's why the weather forecast is always so good in Alan's world.
The forecasts are mathematical simulations and, according to Alan, they will predict just the weather you want.

Other realities are available.

[Bored chemist]

Or you could start with the data and use a bit of AI to generate the model.

Why not use real intelligence?
You know- stuff like actual physics where we can put in parameters like the absorption spectrum of CO2.

[alancalverd]

Actual physics begins with the observation that temperature leads CO2,  historic temperature rises have been very rapid and not associated with an obvious geological source of CO2, and the subsequent decreases in temperature has always been slow.. All I'm asking for here, is an explanation of the data we have.

If I look to the future, it is clear that the temperature has been rising rapidly for the last 25,000 years or so, with or without human intervention, on pretty much the same shape curve as all previous cycles. Therefore it makes sense to  plan for a future where global temperature is at least as high as it has ever been in the last million years. Faffing about measuring CO2 is "weighing the pig". It would be scientifically interesting and economically sensible to reduce anthropogenic CO2 before we run out of fossil fuels and it happens anyway, but it is far more important to plan for the humanitarian disaster that history suggests is inevitable, rather than blaming ourselves for what is entirely beyond our control.

I heard of a shareholders' meeting of a company that was in serious trouble. It was proposed to pay the directors in shares rather than money.  Lots of pompous small shareholders took it in turns to complain about the dilution of their hundred or thousand shares, until a very old man stood up and said "I have five million shares in this company. I bought them at $15 and now they are worth 10 cents. Gentlemen, the plane is on fire and you are arguing about the pilot's salary."

[evan_au]

you should be able to wind the clock back 400,000 years and generate the ice core data

It comes back to the constants vs variables in your computer simulation.
- If you are going back 400,000 years, then the eccentricity and inclination of Earth's orbit become variables.
- Computer modeling has tried to match the Milankovitch cycles (and claimed some success), but it needs to be integrated with lags in the takeup of gases in rocks and other slow processes that are poorly understood.

However, to produce a valid climate forecast of the next 200 years (rather than 200,000), we can just leave these unknowns as constants.

See: https://en.wikipedia.org/wiki/100,000-year_problem

Actual physics begins with the observation that temperature leads CO2

In the Cape Grim records, it appears that:
- daylight hours increase and temperatures rise from August to February, in the Southern Hemisphere spring & summer
- this leads to growth in oceanic algae, which absorbs CO₂
- This is enough in most years to cancel the human-induced annual growth in CO₂ concentration (and even reverse it, in some years)
- As winter approaches, the algae dies off, releasing some CO₂ into the atmosphere, and taking some of it to the bottom of the ocean.
- This annual cycle of algal growth is independent of and superimposed upon human-caused greenhouse gas emissions.

But it is meaningless to talk of "lag" or "lead" in an annual cycle.
- "leads by 6 months" is identical to "lags by 6 months"
- And this sheds no light on a lag of thousands of years in the 100,000-year climate cycle. They are entirely different processes

[Bored chemist]

Actual physics begins with the observation that temperature leads CO2

Actual physics of absorption of IR by CO2 began nearly a hundred years before the ice core data was known.
It also has the massive advantage of being amenable to experiment and testing.

[alancalverd]

- this [summer] leads to growth in oceanic algae, which absorbs CO2

That's particularly interesting because you might expect Mauna Loa to behave pretty much the same way - fairly close to the sea and also surrounded by trees....but it doesn't.

If you are going back 400,000 years, then the eccentricity and inclination of Earth's orbit become variables.

If Milankovitch is responsible for the most recent 25,000 years, that really does make CO2 seem irrelevant. The problem I have, however, is that all the Milankovitch inputs are sinusoidal and independent, so whatever the resultant waveform, you'd expect the resultant temperature curve over 400,000 years to be time-symmetric with variable peaks rather than a bounded sawtooth: something very nonlinear is going on.

[Bored chemist]

something very nonlinear is going on.

Gosh!

Quote from: Bored chemist on 24/01/2021 10:58:03
Only MarkPawelek is naive enough to think that there's no positive feedback.
There are at least 3 major pathways for it
1 Ice is reflective
2 Methane trapped as hydrates would be a very potent greenhouse gas
3 water vapour