Originally Posted by Trixie
I admit I dont know a lot about the Ordovician - Im a Triassic to Cretaceous nerd but I know how difficult it is to model climate in the Jurassic and how often new sampling proves us wrong!
My main problem with using Co2 in the late Ordovician to disprove Co2s importance in climate is sampling. The further back in time you go the further apart in age your sample points end up being. An example from my work in the Jurassic we talk (okay brag a bit) about really high resolution biostrat dates we are getting in some areas - down to hundreds of thousands of years, yet an Eocene worker would just laugh at us. Added to this the further back we go the more 'alien' things are. Things were quite primitive - pre vascular plants at this time.
To put it plainly Co2 Levels and glaciation appear to be coincident but the error bar here is huge in the order of millions of years. An interesting paper I found refers to some newish infill data supporting this, unfortunately only the abstract is online
The following site has a good summary of the debate:
I am not saying I am right and the sceptics are wrong here - i dont think either camp has enough evidence to prove it without a doubt.
Ah, so you're looking at the late coal measures....coal geologist I presume
I'm a geologist too.....used to be a hard rock guy...Cu/Ag/Au/Pb/Zn and U
. You softies used to amuse us hard rock guys
I used the Ordovician CO2 levels as a generalised example...not to disprove that the CO2 now wasn't doing anything to the climate. Only that given that the CO2 level for the Ordovician was around an average of 4400ppm for the period and that near the end you had an ice age and still high CO2 levels, meant that the climate (both then and now) was a lot more complicated than it appears on the surface. There are many more factors to enter into the equation before you go blaming any one culprit for causing change. But, CO2 will be a major player in driving climate change, whether it's now or in the past. I posted the example, ultimately, to get people here to think before they just write something and without knowing about the science involved.
I'm also lucky in having several years of study in climatology and remote sensing up my sleeve as well as geology, so I do have some experience with atm' radiation budgets and circulation, ocean-atm interactions and such...GCM's etc.
Those two sites you posted basically prove my point....you need to look at all the variables, not just one, CO2. But in saying that CO2 is a major driving factor in what influences the planet's climate.
I'm fully aware of sampling bias in the rock record, especially when it comes to isotope analysis and such.