I’m not particularly well-qualified in biology, finding it much less interesting than physics and chemistry when I was at school, so no-one should put much weight on this musing. In fact, this post was prompted by some comments I saw on someone’s blog (tell me which one and I’ll provide the link) that they were going to leave Greenhouse alone and go back to worrying about why the dinosaurs became extinct.
Dinosaur extinctions are not something that have occupied my mind too frequently, except to the point that the usual speculations about it being caused by an “extinction event” seem to be contradicted by the evidence. The age of the dinosaurs lasted between 230 and 65 million years BC, but during that time any number of dinosaur species came and went. To accept that dinosaurs all disappeared at the one time, you have to ignore their evolutionary history.
Recent research on man suggests that within 150,000 or so years we could become unable to recreate ourselves conventionally because of deterioration in male DNA. That suggests that Dinosaur DNA may have just run its course too. TS Elliott would have approved – not a bang but a whimper.
Now I’m wondering about another possibility. We know that large reptiles are a function of warmer climates, unless you can show me the arctic boa-constrictor or crocodile. We also know that the greenhouse effect is a real effect, even though we are uncertain as to the magnitude of that effect, all other things considered. We also know that the precentage of CO2 in the atmosphere at the moment is more than it has been in the last 400,000 years, but less than at other times in the earth’s past.
So, here’s the speculation (and I’m looking for some feedback on it): geosequestration of prehistoric carbon through the Triassic, Jurassic and Cretaceous periods led to less atmospheric CO2, lowered temperatures and made massive reptiles unviable. The dinosaurs may therefore have literally shivered to death (actually I don’t think cold-blooded animals shiver as that would dissipate the energy they’ve taken in from the environment, but you get the idea, they probably more coagulated) over quite a long period of time, starting with the biggest first.
As I say, no qualifications in this area at all, so could be quite off beam, but would be interested in feedback.
May 06, 2005 | Graham
Dinosaur extinction a result of geo-sequestration?
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Hey Graham, Your hypothesis doesn’t correlate with the variations in Co2 levels. The carbon sequestration during this long period was offset by various volcanic eruptions. For example, a minor mass extinction is thought to have occured 90 million years ago when volcanos erupted enmass in the Indian and Pacific oceans and belched out lots of C02 resulting in a runaway greenhouse effect! Now give us the link to that website?
Comment by Jennifer — May 6, 2005 @ 4:31 pm
Tell me more. I thought you were fairly sceptical of the possibilities of a “runaway greenhouse effect”. But now you’re citing one from 90 million years ago.
As the source of my musings was really trying to understand what might happen with higher greenhouse gases using what has actually happened in the past as a better modelling guide than anything today’s climate scientists are likely to come up with, this sounds promising as a way of exploring the issue.
It doesn’t really answer the questions about dinosaur extinctions, because there were obviously a number of them over 165 million years. Perhaps the dimming from the eruptions did for them at the time of your eruption by cooling the earth and limiting plant growth, and then another hotter period helped other dinosaurs to thrive, with final extinctions occurring because 25 million years after your event the CO2 levels had dropped back again and the earth cooled for greenhouse reasons.
Comment by Graham Young — May 6, 2005 @ 4:48 pm
On being a skeptic there is worse – I was actually quoting from a piece by Ian Plimer, Prof of Geology at Melbourne Uni and acknowledged climate skeptic, wrt the “runaway greenhouse effect”!!! But note I opened with the words “thought to have occured”!
The point I was hoping to make though, is that sequestration can be offset by volcanic eruptions.
Comment by Jennifer Marohasy — May 7, 2005 @ 9:02 am
PS Temperatures during the big ‘greenhouse’that corresponded with the about 165 million year reign of the dinasaurs are thought to have been comparable to temperatures during the previous ‘greenhouse’ (i.e. period that preceeded the Permian-Carboniferous Ice age). But Co2 levels where thought to be much much higher during the earlier ‘greenhouse’.
Comment by Jennifer Marohasy — May 7, 2005 @ 9:20 am