Has atmospheric CO2 driven climate changes in the past?

Question

One answer this morning in this forum stated that atmospheric CO2 has never driven climate change in the past.

However, it is generally well accepted that global temperatures were much warming millions of years ago.[1] Plate tectonics, volcanic activity, solar variations, orbital changes, and collisions with meteoroid/asteroid, etc… have all played a role, but why can’t greenhouse gases play a role? Can all climate changes of the past be explained without including the affects of greenhouse gases?

[1] http://www.ncdc.noaa.gov/paleo/ctl/beyond.html

Answer 1

"Randall. Over the last 350 million years, (including the well known Jurassic and Triassic periods), atmospheric CO2 concentrations have probably not been higher than 2000 ppm"

I do not know how you concluded this from your source. The only actual measurements, by Royer et al, show CO2 concentrations much higher than 2000ppm in the last 350myrs.

"Has atmospheric CO2 driven climate changes in the past?"

It would be difficult to say definitively that CO2 has driven climate in the past. Even the records of past climate are very uncertain, let alone what drove the climatic events. Has CO2 played a role in past climatic shifts? It is very likely.

Answer 2

Plants take in CO2 and breathe out oxygen.  The CO2 you are worried about would be a byproduct of modern mass-production methods.   This didn't exist 1,000 years ago when there were Ice Ages and Dark Ages.

Ozone is another unknown.    Lots of things to think about.  have you been studying this or is it one of your general interests?

Answer 3

Its possible, but the evidence indicates that the Earths climate over the last 600 million years does not seem to change in step with radical swings of atmospheric CO2 levels.

http://www.geocraft.com/WVFossils/Carbon...

Answer 4

Come on ,give the plants credit for taking CO2 way down. Atmospheric  oxygen is 20.9% and has not changed. We live off oxygen not CO2,which plants need. The present level of CO2 is 380 ppm. now put this in percent of atmosphere and that is .000380% and that is nothing.  I doubt it that as CO2 being so heavy it is difficult to measure. The lowest point of oxygen is 19.5% . Below this U will pass out. CO2 being the heavier gass will displace the oxygen we need ,and the oxygen will decreas. CO2 will need to increas a lot to drop the oxygen  0.1%. These percents of gas comes from OSHA which establishes numbers for for the workmans safety...

Answer 5

We've certainly had greenhouse gases, maybe not as high;-{

Volcanic activity, forest fires from lightning, methane, etc.

Answer 6

That just depends on how you define 'driven'.  There has to be a source of CO2 increasing the atmospheric concentration for CO2 to drive climate change.  Usually the source of increasing CO2 is from some sort of feedback, like oceans warming to a point where they emit more CO2 than they absorb.

In that case, some other factor had caused the warming to begin, and then CO2 kicked in to 'drive' the warming afterward.

Answer 7

I hope you get some really good answers here and that I can access them this fall back in my classroom.  The last answer I read (and cannot see, now that I am answering) said that greenhouse gases were such a small percentage of the atmosphere that they couldn't influence the climate.

Does he think that seeding clouds to squeeze rain out of them is a fairytale?  While it doesn't always succeed (it isn't magic, and is a very imprecise engineering activity, due to the scale), it very often does work, and the chemicals diffused into the clouds are an extremely tiny percentage of that portion of the atmosphere.  

I think our budding scientist needs to study relative proportions.  When I first heard of building an elevator to the moon, I thought it was a crock.  Turns out it was not, it was a very practical proposal proposed by at least one eminent scientist (that is, a guy who could DO it was pushing for it).  The  whole affair would be quite vulnerable to terrorism, so it never got off the ground.  Permanence would have been too much of an issue, making the cost prohibitive.

Perhaps our friend might be interested in buying a flat bridge on the flat earth he may or may not believe in?

Answer 8

the general answer to your question is yes.  The reason that it's stated by various government officals, and those working for government controlled entities that this is not the case, is simple: Profit.  Of course, what is happening now is largely a result of natures natural shift in climates.  However, telling the public that this is the case, and that NOTHING can be done to stop it, is not making them any money.  On the other hand, this strategy allows them to gain both politically and financially, based on fears of the public, generated by such lies.  But ah, the government has us right where it wants us.

Answer 9

the reason that greenhouse gases cant play a role in making dramatic changes in the climate is simply because of the fact that the gg's (greenhouse gases) including water vapor, CO2, and methane, amount to such a small percentage in the earth's atmosphere that if the amount were to double the effect couldn't possibly change the climate. the gg's alone add up to only 0.79% of the atmosphere (or around there).

to furthur prove this, during the time of WW2 and about 10 years after, the climate dropped a good 10 degrees while CO2 was being added to the atmosphere

Answer 10

There have been plenty of past CO2-driven warming periods.

But they involved CO2 levels 1200-1500% of today's CO2 levels.

Some other factor caused a much more substantial warming than 1.2 degrees F and then a warmer, greener earth produced more CO2 which resulted in a warming spiral.

But again - the CO2 levels were 1200-1500% higher than today's level.