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What is the net zero CO2 level?

gez

gez

pfm Member
First off. I know what net zero means. So I do not need that explaining.

What I'm trying to find out and have been unsuccessful so far is:

What is the absolute CO2 output of the globe in tonnes of CO2 (or whatever unit) required to be balanced by the earths absorbtion of CO2. In other words what exatly is the "net zero" CO2 output requirement.

I can find plenty of site explaining what net zero means as a concept, even sites saying we need to reduce to net zero output by 2050 to avoid the worst consequences, but what I can't find anywhere is:

Exactly what level of CO2 ouput, in absolute terms, do humans have to reduce their CO2 output to, in order to reach net zero.

Can somebody provide a link to an authoratative site (i.e. not a newspaper or green lobby etc site, I want a science paper), which states the absolute level of CO2 output required to attain net zero. Please, thank you very much :)
 
While we’re on the subject, net zero seems likely to be an equilibrium point and presumably at that point, the CO2 ppm in the atmosphere stabilises, but doesn’t reduce. So still contributes to warming. We would appear to need to then take the next step, to reduce the % of atmospheric CO2, if not to pre-industrial levels, at least to a concentration which gives rise to manageable impacts on climate.
 
Sue Pertwee-Tyr said:
While we’re on the subject, net zero seems likely to be an equilibrium point and presumably at that point, the CO2 ppm in the atmosphere stabilises, but doesn’t reduce. So still contributes to warming. We would appear to need to then take the next step, to reduce the % of atmospheric CO2, if not to pre-industrial levels, at least to a concentration which gives rise to manageable impacts on climate.
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My understanding is that has been calculated in to the required net zero level already? As in the level that's been agreed would mean that the global temps would not only not continue to rise but would actually drop back down to a lower level than they are now even. I could be wrong, but that's how I've understood the levels to have been calculated?

Not sure what you're meaning by "global warming". Do you mean it in the sense of "contributes to the average temp of the planet" or "is continuing to increase the average temp of the planet"? Because, as I'm sure you know, any level of CO2 will contribute to global warming by the first definition.
 
gez said:
My understanding is that has been calculated in to the required net zero level already? As in the level that's been agreed would mean that the global temps would not only not continue to rise but would actually drop back down to a lower level than they are now even. I could be wrong, but that's how I've understood the levels to have been calculated?

Not sure what you're meaning by "global warming". Do you mean it in the sense of "contributes to the average temp of the planet" or "is continuing to increase the average temp of the planet"? Because, as I'm sure you know, any level of CO2 will contribute to global warming by the first definition.
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The latter, because there seems to be a correlation between the % of atmospheric CO2 above pre-industrial levels and global temperature rise. I am presuming that some sort of equilibrium had been reached in pre-industrial times, though there were clearly fluctuations (eg, the medieval ‘little ice age’). On the basis that we probably don’t want more ‘little ice ages’ I’m supposing there is a level above the pre-industrial level of, IIRC c250ppm, which is pretty benign and perhaps optimal for ecosystems as we know them. Perhaps something around 300-320 ppm but that’s little more than a slightly educated guess.

On your first point, I’ve never heard it acknowledged that ‘net zero’ is any more than an equilibrium between anthropogenic CO2 and natural sequestration of CO2, and no specific indication that it represents a tolerable level of atmospheric concentration. But I’m quite prepared to be corrected on that.
 
gez said:
an somebody provide a link to an authoratative site (i.e. not a newspaper or green lobby etc site, I want a science paper), which states the absolute level of CO2 output required to attain net zero
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Net-zero article. Essentially it’s zero. The ocean is in equilibrium with atmosphere over decadal timescales. Lower the total concentration of CO2 in atmosphere and the ocean becomes a source, not sink.
 
Life depends on the carbon cycle. Stop it and all life on this planet as we know it extinguishes. Maybe some simple lifeforms such as those supposed to live in rocks deep in the Earth will survive.

Global warming does exist and this warming and cooling has been going on for billions of years and a long time before we came into being. The Earth is heated by the Sun and the amount received also depends on the planets precession neither of which we can control so its really out of our hands.

The amount of carbon locked up in fossil fuels is enormous and if we were to burn it all then we'd replace the oxygen in the atmosphere with carbon dioxide i.e. around 20% of the total - today its around 0.05% up in my lifetime from 0.03% so you can already see the trend. It makes sense to leave the fossil fuels in the ground rather than burning them. If we did that then the Carbon cycle would eventually reduce the carbon dioxide level and reach an equilibrium. What that is nobody knows as its dependant on so many factors and unknowns.

DV
 
Joe P said:
@horta,



Your best answer, please. No more than three enigmatic words.

Joe
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The Carbon Cycle

Carbon flows between the atmosphere, land, and ocean in a cycle that encompasses nearly all life and sets the thermostat for Earth's climate. By burning fossil fuels, people are changing the carbon cycle with far-reaching consequences.
earthobservatory.nasa.gov earthobservatory.nasa.gov

DV
 
Darth,

It was a joke. The Horta is a life form based on silicon, not carbon. It is native to the planet Janus VI but appears on pfm from time to time with a poignant yet pithy post.

Fun, no?

Joe
 
Not our Horta. Our Horta is sensible and very much driven by sound science and competent engineering.

Joe
 
Dan,

dan m said:
Net-zero article. Essentially it’s zero. The ocean is in equilibrium with atmosphere over decadal timescales. Lower the total concentration of CO2 in atmosphere and the ocean becomes a source, not sink.
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I have to admit my hope that humanity will lower CO2 emissions is evaporating with each passing year. What’s the feeling among climate scientists in your field?

Joe
 
I think all would say we are not moving anywhere near fast enough. Sadly with each passing year it’s going to be harder and harder to dig ourselves out of this mess.

Dan
 
Dan,

dan m said:
I think all would say we are not moving anywhere near fast enough. Sadly with each passing year it’s going to be harder and harder to dig ourselves out of this mess.

Dan
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It’s nuts. The evidence is staring us in the face and yet we're still doing far too little. I’m in Canada, it’s winter, and the temp is +14C right now.

Joe
 
Joe P said:
Dan,



It’s nuts. The evidence is staring us in the face and yet we're still doing far too little. I’m in Canada, it’s winter, and the temp is +14C right now.

Joe
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Really? Wow. It's similar in the N of Englan d right now but we are blessed with the Gulf Stream, the N Atlantic winds and the constant pissing rain that ensues, so we don't expec subzero temps lasting for weeks.

and I'm about to walk to work, and it's pissing down. Again.

we had a drought in 1996.
 
Given that it's a dynamic equilibrium, there won't be an actual figure because it will shift with the equilibrium point. I don't know the mechanics of this particular equilibrium but having spent an inordinate length of time studying enzyme kinetics at university I know that all equilibria shift their point of stasis according to input levels. I don't know, but I have a hypothesis that the system may behave like the weight of a fat man. He may have a healthy weight of 70-80kg, for which he needs 2500 cals per day, as is reckoned to be the normal requirement for an average man. However he is stable at 120kg, and he eats 3500 cals a day. If he cuts his input to 3000 cals a day, it's still more than a healthy amount, but his weight will fall to let's say 100 kg and stabilise again. It will remain here as long as he eats 3000 cals a day. Conversely if he goes on a proper diet and eats only 2000 cals a day, he will lose weight. If he then carries on with this, it's less than he needs, but he won't starve to death. Given enough time he'll lose weight to below his 70kg amount, but he will eventually stabilise. He'll be rather thin, but still alive. This is what I mean by the equilibrium settling point varying with input levels, and I suspect that the global CO2 cycle is similar.
 
@stevec67 It doesn’t really work that way. The planet doesn’t consume CO2 “on average” unless you’re talking over thousands and thousands of years. CO2 dumped into the atmosphere stays there. Yes, there’s a seasonal cycle but the trend comes from the integrated burden put into the atmosphere. So if we stop all CO2 production it will stay at current levels. The atmosphere will continue to warm until the Earth System comes into a new equilibrium with the new radiative balance. Yep, cold turkey on CO2 doesn’t reverse warming. To do that we need to actively remove carbon and not put any more in - think massive afforestation then cut the trees down and store them.

Determining the carbon budget is tricky, but I think about half of the additional CO2 put into the atmosphere over the last 150 years went into the ocean. That means if you remove 1kg of CO2 from the atmosphere, it only nets you half that in terms of decreasing the CO2 mixing ratio. The ocean will emit CO2 to come into equilibrium with the lower CO2 in the atmosphere. This is why the focus right now is on shorter lived GHGs such as methane. Also, why the recent COP statement was so disappointing (refusing to acknowledge we must phase out fossil fuels).
 
Steve,

stevec67 said:
Really? Wow. It's similar in the N of Englan d right now but we are blessed with the Gulf Stream, the N Atlantic winds and the constant pissing rain that ensues, so we don't expec subzero temps lasting for weeks.

and I'm about to walk to work, and it's pissing down. Again.

we had a drought in 1996.
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Aye, it’s warm and soggy, with ginormous puddles everywhere. Of course, if the temp drops everyone will have a hockey rink nearby but so far it’s a liquid rink.

Man, if only the sun didn’t heat the Earth…

Joe
 
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