Carbon Dioxide levels in atmosphere and plant sizes

[SeriousBug]

Well, I recently learned that higher levels of oxygen in the past resulted in animals that are much bigger than similiar ones living today. What this makes me think are the plants, how were they at pre-historic times? Were the trees smaller when the dinosaurs dominated the earth? Did the trees get bigger as the carbon dioxide levels rose? Or did it only result in a biomass increase rather than individual size?

[krash661]

Well, I recently learned that higher levels of oxygen in the past resulted in animals that are much bigger than similiar ones living today. What this makes me think are the plants, how were they at pre-historic times? Were the trees smaller when the dinosaurs dominated the earth? Did the trees get bigger as the carbon dioxide levels rose? Or did it only result in a biomass increase rather than individual size?

it may have to do with pure wilderness, as in

there were more tree's and plant then occupied space by humanity.

but i really do not know,

but it is an interesting thought,

well for me anyways.

interesting.

[Moontanman]

Well, I recently learned that higher levels of oxygen in the past resulted in animals that are much bigger than similiar ones living today. What this makes me think are the plants, how were they at pre-historic times? Were the trees smaller when the dinosaurs dominated the earth? Did the trees get bigger as the carbon dioxide levels rose? Or did it only result in a biomass increase rather than individual size?

 

During the Carboniferous Period oxygen levels were as much as 40% higher than today and allowed insects to get quite large, Dragon Flies as big as eagles, CO2 levels were also quite high at that time as well.

 

During the time of the dinosaurs CO2 was high as well and also resulted in lush plant growth and quite possibly larger animals but dinosaurs were able to get much bigger due to their physiology as well, even the sauropods had hollow bones and breathed similar to the way birds breath and this allowed them to get much larger than mammals ever have.

[EdEarl]

 

During the Carboniferous Period oxygen levels were as much as 40% higher than today ..., CO2 levels were also quite high at that time as well.

 

The atmosphere is currently about 78%N, 21%O, 1%Ar, and 0.04%CO2. If O is 40% higher, then it would be about 29%O.

 

Assume we can ignore the miniscule amounts of Ar and CO2, then what happened?

 

1. The total O increased, and total N remaining the same, meaning the atmosphere was thicker with increased pressure?

2. The total O remained the same, and total N reduced, meaning the atmosphere was thinner with decreased pressure?

3. The total O increased and total N decreased, meaning thickness and pressure remained about the same.

 

If 1. where did the O come from?

If 2. where did the N go?

If 3. then the answers to the above two questions answer this condition.

[SeriousBug]

Thanks for all your replies. Looking at Carboniferous Rainforest Collapse, it says that with climate getting colder and drier, the tropical rainforests were devastated, and this caused the oxygen amounts to lower and carbondioxide to rise. Still, there doesn't seem to be anything told about the sizes of plants, and I'm guessing that only biomass changed, not individual sizes.

 

Assume we can ignore the miniscule amounts of Ar and CO2, then what happened?

We can't ignore the CO₂. If you check this chart(on page 9), comparing those values with current ones shows that during Carboniferous Period the CO₂ levels were 2 or 3 thousand times higher than current levels.

Edited May 15, 2013 by SeriousBug

[EdEarl]

Thanks for all your replies. Looking at Carboniferous Rainforest Collapse, it says that with climate getting colder and drier, the tropical rainforests were devastated, and this caused the oxygen amounts to lower and carbondioxide to rise. Still, there doesn't seem to be anything told about the sizes of plants, and I'm guessing that only biomass changed, not individual sizes.

 

 

We can't ignore the CO₂. If you check this chart(on page 9), comparing those values with current ones shows that during Carboniferous Period the CO₂ levels were 2 or 3 thousand times higher than current levels.

I understand that CO2 levels control global temperature or at least strongly correlate.

 

However, my question was about O2 amounts in the atmosphere. Conversion of CO2 into O2 and sequestered C cannot account for a 40% increase in O2, because the CO2 levels are only 400 ppm (.0.04%) today, and the most CO2 in history I have ever heard reported is 1000 ppm.

 

Sorry about not making that clear before.

Edited May 15, 2013 by EdEarl

[Moontanman]

I understand that CO2 levels control global temperature or at least strongly correlate.

 

However, my question was about O2 amounts in the atmosphere. Conversion of CO2 into O2 and sequestered C cannot account for a 40% increase in O2, because the CO2 levels are only 400 ppm (.0.04%) today, and the most CO2 in history I have ever heard reported is 1000 ppm.

 

Sorry about not making that clear before.

 

 

You are assuming that before the Carboniferous gas levels were the same as today, in fact CO2 was thought to be very high well before then but O2 was very low. As the CO2 was turned into oxygen and life forms the oxygen levels soared, this resulted in lush plant growth for the first part of that period then as CO2 levels crashed the climate turned cold, plant growth slowed. The extra Carbon was sequestered as coal and oil and limestone, limestone was probably a bigger sink for CO2 than coal or oil. The extremely high oxygen levels also fell due to fires that swept through the lush forests as the climate cooled and dried. Without the lush plant growth to replenish the oxygen the levels fell. I am sure it had some effect on overall air pressure but I can't find any references to that.

 

Air pressure on the Earth has varied wildly as has it's gaseous content, before complex life and before the great oxygenation event it is thought that methane was a large part of the Earths atmosphere and quite possibly H2S as well.

[EdEarl]

Does atmospheric oxygen, including O2, CO2, NO, NO2, etc., sometimes become sequesterd in solids or liquids in significant amounts (e.g., >1%) for long periods of time (e.g, > 1 yr). For example, if much of the methane hydrate entered the atmosphere, would the additional water from burning that methane significantly decrease atmospheric oxygen.

[Moontanman]

Does atmospheric oxygen, including O2, CO2, NO, NO2, etc., sometimes become sequesterd in solids or liquids in significant amounts (e.g., >1%) for long periods of time (e.g, > 1 yr). For example, if much of the methane hydrate entered the atmosphere, would the additional water from burning that methane significantly decrease atmospheric oxygen.

 

If enough methane hydrate entered the earth's atmosphere it definitely would have an effect on the level of atmospheric oxygen. A huge amount of CO2 is sequestered in limestone, in fact it has been estimated that Earth and Venus have approximately the same amount of Carbon but all of the Carbon on Venus is in the atmosphere while most of Earth's Carbon is sequestered in limestone.

[EdEarl]

If enough methane hydrate entered the earth's atmosphere it definitely would have an effect on the level of atmospheric oxygen. A huge amount of CO2 is sequestered in limestone, in fact it has been estimated that Earth and Venus have approximately the same amount of Carbon but all of the Carbon on Venus is in the atmosphere while most of Earth's Carbon is sequestered in limestone.

I understand a lot of oxygen is sequestered in iron compounds, too.

 

Are there natural processes that release large amounts of oxygen from limestone? Iron compounds?

 

I think there is a process for released, burned methane hydrate to become methane hydrate again.True or False?

 

I am trying to understand varioius processes that could change atmospheric O2 levels by 40%.

[Moontanman]

I understand a lot of oxygen is sequestered in iron compounds, too.

 

Are there natural processes that release large amounts of oxygen from limestone? Iron compounds?

 

I think there is a process for released, burned methane hydrate to become methane hydrate again.True or False?

 

I am trying to understand varioius processes that could change atmospheric O2 levels by 40%.

 

 

The main process if not the only one is called photosynthesis, no other process i know of releases O2 into the atmosphere in significant quantities.

[EdEarl]

The page from Wikipedia (link below) has two graphs one of paleo CO2 levels and one of paleo O2 levels. From casual inspection, the O2 and CO2 levels do not appear to be inversely proportional. Do you know of any similar graphs that would be easier to compare.

 

http://en.wikipedia.org/wiki/Paleoclimatology#History_of_the_atmosphere

[Moontanman]

The page from Wikipedia (link below) has two graphs one of paleo CO2 levels and one of paleo O2 levels. From casual inspection, the O2 and CO2 levels do not appear to be inversely proportional. Do you know of any similar graphs that would be easier to compare.

 

http://en.wikipedia.org/wiki/Paleoclimatology#History_of_the_atmosphere

 

 

I'm not sure why you would expect them to be inversely proportional, Much of the CO2 is sequestered in limestone not biomatter, cooler temps mean more rain and erosion and the release of more CO2 which raises temps and lowers rainfall and erosion. The amount of O2 in the atmosphere is tiny compared to the CO2 sequestered in limestone...

[EdEarl]

I'm not sure why you would expect them to be inversely proportional, Much of the CO2 is sequestered in limestone not biomatter, cooler temps mean more rain and erosion and the release of more CO2 which raises temps and lowers rainfall and erosion. The amount of O2 in the atmosphere is tiny compared to the CO2 sequestered in limestone...

Oh! CO2 sequestered in limestone and comes out. That explains a lot. ty

[krash661]

interesting conversation.

[Essay]

http://www.snowballearth.org/slides/Ch13-2.gif

 

This (above) is a link to a large, more detailed image of the situation. Note the "log" scale for pO2 on right. Note O2 spikes that are associated with glaciations, which are caused by "all" the atmospheric CO2 being converted into biomass, such as when algae first evolved, and when life (plants) first came up onto land about 500Mya, and especially when wood evolved around 250 Mya--but before woodrot fungus evolved,.

 

But here is another more general picture of the situation:

 

 

Pressures of the ancient atmospheres were much higher than today.

 

http://pubs.acs.org/subscribe/archive/ci/30/i12/html/12learn.html

 

"The atmosphere could have started at higher pressure and then decreased continuously through Earth’s life to ~4–5 bar ~100 Mya and down to 1 bar today (curve C)."

 

A few years ago, in a university Atmospheric Science 101 class... I learned it was 10 to 100 bars (curve C), at least, during the early Archaen, when volcanic out-gassing regenerated an atmosphere--after the original atmosphere was blown off by the Hadaen bombardments.

 

~

[EdEarl]

tyvm Moontanman and Essay

 

 

I do not understand the ammonia, methane part of this graph...not oxygen related but curious.

 

There seems too little atmospheric CO2 at 500kyr and 250kyr to account for increased O2 levels. This graph has no spike in O2 at 2.5gyr. Interesting, but there is more to learn.

[overtone]

Tree height and mass are not carbon limited now in any tree taxon I know of (water transport and other nutrients, mechanical loading, rather), so unless there was some quite different type of large plant growing back then probably CO2 concentration made little or no difference to the maximum sizes of the plants.

 

 

There seems too little atmospheric CO2 at 500kyr and 250kyr to account for increased O2 levels

Unnecessary - atmospheric levels would be governed by the rate of supply vs the rate of removal, and as the photosynthetic biosphere kicks into gear plants and microorganisms remove CO2 and supply oxygen faster than the newer oxygen breathers or combustion/chemical combination remove oxygen and supply CO2, until a new equilibrium is reached.

Edited May 16, 2013 by overtone

[EdEarl]

tyvm

 

I finally looked up the equation for photosynthesis. The O2 comes from water, not the CO2.

[studiot]

Those who wish to trace the history of the atmosphere and its relationship to conditions, and life, would be advised to read the Oxford University book

 

The Emerald Planet by David Beerling.

 

As far as I know it is the only modern book dedicated to this subject.

 

In particular Professor Beerling discusses and answers the headline question of this thread.

 

go well

Edited May 17, 2013 by studiot