Naked Science Forum
Life Sciences => The Environment => Topic started by: Petrochemicals on 02/10/2019 15:33:42
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Carbon dioxide levels in ancient times where far far higher than they are now, plants had an abundant supply to utilise for growth. Then came the carboniferous age, where trees locked away carbon and no microbes existed that where capable of decomposing wood, this carbon in the wood lay trapped in a land congested with tree trunks. The trees then became buried, fossilised and today we have fossil fuels and low co2 levels.
Aside from this trapping of co2 in wood, carbon dioxide also interacts with minerals and other media. For an example, the co2 is absorbed by the oceans producing carbonic acid, this then eats away at rocks producing the associated salts and products.
Are the carbon interactions sustainable and in balance or is the sum total of all NON MANMADE carbon reactions adding or subtracting carbon dioxide gas from the atmosphere
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In the next two or three billion years or so, it is unlikely.
Natural processes will establish some sort of steady state equilibrium that has a non-zero amount of CO2 in the atmosphere. The equilibrium will shift around somewhat on both an annual cycle due to seasonal changes in deciduous forests, and a several thousand year cycle due to changes in temperature driven by external factors (like our orbit etc.), and there will be times when CO2 levels spike due to volcanism or forest fires, or fall more quickly due to good growing years... but it will stay largely constant on a century-by-century basis.
While it is true that carbonate minerals are produced at the expense of atmospheric CO2, these are calcined in the bowels of the earth as tectonic movements cause the deposits to be subducted. This CO2 is released through volcanic eruptions as well as slower off-gassing processes.
Essentially, there are naturally occurring processes that can add to and subtract from the atmospheric CO2 levels. Many of these are negative feedback loops (on long timescales, ie 103 to 107 years) so that the more CO2 there is in the atmosphere, the faster it gets absorbed, and the more carbonate rock has been formed, the more quickly it gets consumed. Some of the components, however, are positive feedback loops (especially on short timescales, ie 1 to 104 years), like more CO2 in the atmosphere can increase the global temperatures, leading to less dissolved CO2, and more forest fires, both of which lead to more atmospheric CO2 (or the reverse). This leads to relatively rapid changes between a few distinct equilibrium points, which, once established, are fairly stable until a large forcing factor comes along, causing another rapid change to a new equilibrium point.
Once the sun turns into a red giant, our atmosphere will be stripped off, and then there isn't much point considering how much of the remainder is CO2...
check out the "carbon cycle" for more info
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In the next two or three billion years or so, it is unlikely.
Natural processes will establish some sort of steady state equilibrium that has a non-zero amount of CO2 in the atmosphere. The equilibrium will shift around somewhat on both an annual cycle due to seasonal changes in deciduous forests, and a several thousand year cycle due to changes in temperature driven by external factors (like our orbit etc.), and there will be times when CO2 levels spike due to volcanism or forest fires, or fall more quickly due to good growing years... but it will stay largely constant on a century-by-century basis.
While it is true that carbonate minerals are produced at the expense of atmospheric CO2, these are calcined in the bowels of the earth as tectonic movements cause the deposits to be subducted. This CO2 is released through volcanic eruptions as well as slower off-gassing processes.
Essentially, there are naturally occurring processes that can add to and subtract from the atmospheric CO2 levels. Many of these are negative feedback loops (on long timescales, ie 103 to 107 years) so that the more CO2 there is in the atmosphere, the faster it gets absorbed, and the more carbonate rock has been formed, the more quickly it gets consumed. Some of the components, however, are positive feedback loops (especially on short timescales, ie 1 to 104 years), like more CO2 in the atmosphere can increase the global temperatures, leading to less dissolved CO2, and more forest fires, both of which lead to more atmospheric CO2 (or the reverse). This leads to relatively rapid changes between a few distinct equilibrium points, which, once established, are fairly stable until a large forcing factor comes along, causing another rapid change to a new equilibrium point.
Once the sun turns into a red giant, our atmosphere will be stripped off, and then there isn't much point considering how much of the remainder is CO2...
check out the "carbon cycle" for more info
Forest fires are negligable in imact and are generally constant, so a small increace will only slightly increace levels. A study in the amazon said that the ammount of carbon stored in the wood in the amazon forest is worth 100 years of UsA emmisions, when you realise the ammount of forest cleared across the earth by man in the last 3000 years there is alot more carbon released by that than fossil fuel, a few square miles of forest will not massively impact the current standing. The forests cleared show that the balance is not in equilibrium.
Also whilst a big enough increace in temperature will vent gas from the water, i believe the ammount of temperature increace is not enough to offset the increace ?
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Forest fires are negligable in imact and are generally constant, so a small increace will only slightly increace levels. A study in the amazon said that the ammount of carbon stored in the wood in the amazon forest is worth 100 years of UsA emmisions,
These statements seem contradictory to me. 100 years of USA emissions (at current rates) is quite significant, so even burning 0.5% would be a significant event. And while I would agree that there isn't typically that much variability in forest fires from year to year, there are also instances of major fires that can both release a significant amount of CO2 as a direct product of combustion, and reduce the rate at which CO2 can be absorbed in the near term.
when you realise the ammount of forest cleared across the earth by man in the last 3000 years there is alot more carbon released by that than fossil fuel, a few square miles of forest will not massively impact the current standing. The forests cleared show that the balance is not in equilibrium.
A few points:
(1) yes there is not currently an equilibrium--*we* are significantly disrupting that equilibrium, and pushing the system to a new equilibrium with significantly higher CO2 concentrations than have been in the atmosphere at any point in the last million years or so.
(2) Comparing the deforestation we have caused over the last few millennia with the burning of fossil fuels over the last 200 years is not really a reasonable comparison.
(3) When I mentioned forest fires, I was not talking about a few square miles. I'm talking about epic rashes of forest fires like those that are likely to have occurred after major meteorite strikes or geologic activity. In just thee last few decades there have been examples of individual fires burning thousands of square kilometers of forest, and those are likely to be very small compared to what has happened (and will happen) on a scale of millions of years.
Also whilst a big enough increace in temperature will vent gas from the water, i believe the ammount of temperature increace is not enough to offset the increace ?
This was one of the examples of a positive feedback loop, so "offest" doesn't apply. (the hotter it gets, the more carbon dioxide comes out of the water, making it hotter, which drives more out of the water...)
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Forest fires are negligable in imact and are generally constant, so a small increace will only slightly increace levels. A study in the amazon said that the ammount of carbon stored in the wood in the amazon forest is worth 100 years of UsA emmisions,
These statements seem contradictory to me. 100 years of USA emissions (at current rates) is quite significant, so even burning 0.5% would be a significant event. And while I would agree that there isn't typically that much variability in forest fires from year to year, there are also instances of major fires that can both release a significant amount of CO2 as a direct product of combustion, and reduce the rate at which CO2 can be absorbed in the near term.
It may seem contradictory but a very small percent of the amazon burned and this is accounted for by other areas not having fires this year. There are fires every year somewhere on earth. Paradise california last year, non this year. It is healthy and natural to have forest fires. There is a percentage of forest of fire pretty much continually, the carbon cycle releasing and sequesting carbon at a contsant rate
The point is that most of europe africa asia where forests 3000 years ago, must have gone, this must be at least 1000 years of co2 emmisions gone without trace.
when you realise the ammount of forest cleared across the earth by man in the last 3000 years there is alot more carbon released by that than fossil fuel, a few square miles of forest will not massively impact the current standing. The forests cleared show that the balance is not in equilibrium.
A few points:
(1) yes there is not currently an equilibrium--*we* are significantly disrupting that equilibrium, and pushing the system to a new equilibrium with significantly higher CO2 concentrations than have been in the atmosphere at any point in the last million years or so.
(2) Comparing the deforestation we have caused over the last few millennia with the burning of fossil fuels over the last 200 years is not really a reasonable comparison.
(3) When I mentioned forest fires, I was not talking about a few square miles. I'm talking about epic rashes of forest fires like those that are likely to have occurred after major meteorite strikes or geologic activity. In just thee last few decades there have been examples of individual fires burning thousands of square kilometers of forest, and those are likely to be very small compared to what has happened (and will happen) on a scale of millions of years.
1)yet done slowly over 3000 years far more carbon has dissapeared
2)it is an inconveniant truth for some. Point is the carbon has gone somewhere.
3)yep and this much carbon has to go somewhere, 3000 years of deforestation has not led to other trees elsewhere, nor high levels of carbon
Also whilst a big enough increace in temperature will vent gas from the water, i believe the ammount of temperature increace is not enough to offset the increace ?
This was one of the examples of a positive feedback loop, so "offest" doesn't apply. (the hotter it gets, the more carbon dioxide comes out of the water, making it hotter, which drives more out of the water...)
But as a percentage of gasses there is more carbondiox dissolved due to higher levels. Depends on the increace of temperature and carbon dioxide percent.
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Then came the carboniferous age, where trees locked away carbon and no microbes existed that where capable of decomposing wood, this carbon in the wood lay trapped in a land congested with tree trunks.
Wait, how do we know that no microbes existed at the time? Weren't they simply didn't leave fossils?
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Substitute "not enough" microbes to decompose all the dead trees. The evidence is coal.
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Then came the carboniferous age, where trees locked away carbon and no microbes existed that where capable of decomposing wood, this carbon in the wood lay trapped in a land congested with tree trunks.
Wait, how do we know that no microbes existed at the time? Weren't they simply didn't leave fossils?
https://en.m.wikipedia.org/wiki/Carboniferous
Interesting time rammed full of oxygen due to levels of c02 dropping from 2000ppm to about 500ppm. Full of giant creatures that collapsed when the celulose in trees became degradable.