How much CO2 was in the atmosplere 250 million years ago?

Question

How much CO2 was in the atmosplere 250 million years ago?

Answer 1

A whole lot.  Dana's numbers are no doubt good.  At the same time coastlines were very different, most coastal cities today would be underwater.

Frances O - Warming/cooling in the past was mostly controlled by solar radiation.  How do we know it's not that now?  Very simple; we measure the Sun.

"Recent oppositely directed trends in solar

climate forcings and the global mean surface

air temperature", Lockwood and Frolich (2007), Proc. R. Soc. A

doi:10.1098/rspa.2007.1880

http://www.pubs.royalsoc.ac.uk/media/pro...

News article at:

http://news.bbc.co.uk/1/hi/uk/6290228.st...

A bit more authoritative than the right wing blogs.

Answer 2

Possibly quite a bit, that is why scientist think there were lush tropical plants all over the earth, and there is some evidence to support that in fossilized remains. That in turn helped to create all of the Oxygen from the plants taking in to CO2 and releasing the O2

Answer 3

Well this was near the end of ~1 million years of massive huge volcanism in Siberia. The world was going thru the biggest mass extinction ever, experiencing severe oceanic anoxia, substantially decreased atmospheric oxygen, and global temperatures had increased around 6 degrees C according to the oxygen isotopes.

But direct atmospheric CO2 proxies, particularly from this time, are controversial. There is ginko leaf stomata work but material from this time isn't very good (if the method is reliable anyway). There is a massive global excursion in ∂13C of –6‰ , a little more than seems accountable by CO2 release from the Siberian traps alone (–5‰, although we can only guesstimate the original size of these lava flows). But there is little point simply calculating the CO2 release from volcanism anyway because it occurred over long time, and there are feed backs in both directions.

That said, some recent computer models seem to do a reasonable job at accounting for all the specific climate and environment proxies from this time (in a world which differed hugely from ours today). And suggest very high CO2, though I don't know exactly what right now. And they aren't by any means a definite answer.

If this is from the perspective of geological analogues for present global warming, somewhat better data exists for more recent global warming episodes, eg. the mid-Cretaceous. But the short answer is, although much research is being done on these topics, we just don't really know. And it's difficult to see how we can know with a high degree of certainty - there just aren't good CO2 proxies in rocks (yet known anyway). These were very different climate systems anyway.

By the way, Danas answer above is from Berner, which are very long term estimates (10's of millions of years scale) based on modeling of very long term geological factors, and don't factor short term perturbations. And for the idiot above, work such as this is important in general geology, the foundation of oil exploration in the first place.

Answer 4

Somewhere around 1500-2000 ppm.  Temperatures were also about 8°C higher, and solar output was less.

Answer 5

It is all a guess....no way to measure what was going on at that time..... and, anyone who tries to give a number probably works overtime making big money from taxpayer dollars on some silly computer simulation of hypothetical models......

Answer 6

That far back is hard to determine.  Samples of the ice were taken at Vostok, Antarctica and the ice provided information to the temperatures and co2 going back 500,000 years.

For CO2 graphs:

http://cdiac.esd.ornl.gov/trends/co2/gra...

For Temp graphs:

http://cdiac.esd.ornl.gov/trends/temp/vo...

If you could put these two graphs on top of each other, you would see that temperatures lead co2 by some 800 years.  

After temps spike, and start to decline, co2 continues to increase for another 800 years before it too starts following the temperature graph.