Quote:
Originally Posted by glenc
" Carbon dioxide levels are the lowest they have been in 500 million years"
" Carbon dioxide has never been a driver of global temperature over 500 million years"
" When the carbon dioxide levels were 10 times higher than today the Earth was in the depths of an iceage"
This graph does not show that: http://en.wikipedia.org/wiki/File:Vo...core-petit.png |
Glen, that graph is meaningless. It's only for the last 800Ka. A blip in time. For most of Earth's history, the CO2 levels have been appreciably higher (much higher in most cases) than what they've been for the last 2.5 million years. How do you account for a CO2 level of 600-800ppm for most of the Tertiary/Quaternary Periods, and a high of 1200-1250ppm for the Palaeocene/Eocene epochs. Or an average of 1800ppm for the entire Mesozoic. Or an average of 2500-3000ppm for the Palaeozoic, apart from the mid to late Carboniferous, where temps were nearly as low now and so were the CO2 levels. During the Cambrian they were around 7000-8000ppm. The Earth at present is the coldest it's been for 500Ma, even during the Carboniferous period the average global temp was about a degree warmer than now.
Those Vostock ice core measurements are being taken during an ice age. The temps and the CO2 levels are going to go up and down like a yoyo!!!.
What is ultimately in dispute here is human input into the causes for climate change. Whether you believe it or not will depend on your own PoV and how much you actually know about the subject.