Essential climate data

I do not want any person concerned with global warming, of the natural or human variety, to discuss the issue without at least pondering this vastly informative graph for at least ten minutes. It affords a rare and cheap education.

Note especially the little coloured insert near the top. Atmospheric CO2 has been sharply declining since the age of the dinosaurs, from about the middle Jurassic period onward, from about 2,750 parts per million to about 300 parts per million. Average global temperature has dropped from a balmy 25 degrees Centigrade about 50 million years ago to about 10C today. The temperature drop began around 100 million years after the drop in atmospheric CO2. That is some lag time!

I am not saying this is the complete or final picture of atmospheric or temperature changes over time. Rather, I am saying that it successfully shows

  • the immensity of time over which the planet has been changing from one dominated by CO2 in the atmosphere to one where CO2 is a trace element;
  • the irrelevance of man to most of this picture; and
  • the possible relevance of human-produced CO2 to the latest warm period, post 1860. Note the sharp upswing in average global temperature post-1980 (see bottom right inset into chart).
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Thank you for posting the graph. Even though I have some issues with the assumptions that scientists make about temperatures from times before those temperatures could be verified by human observation, nevertheless, it raises the valid question as to how we avoid arbitrariness in deciding what point of reference we use as a basis for determining that the earth has warmed or cooled. After all, “warmer” and “cooler” are relative terms. Do we compare today’s average temperature to 50 years ago? 5000 years ago? 50,000 years ago? and so on. Futhermore, the claim that warming is bad assumes that the earth’s average temperature should be less than what it is, or not climb. But that assumes knowledge of what the earth’s temperature is supposed to be. How does one determine that? And if earth’s temperatures warm apart from human activity, what are the factors that cause that? and why does the IPCC assume they are no longer a cause of warming? It’s not good enough to challenge the IPCC’s data. We need to also challenge their assumptions.


Jerry, thank you for posting, I agree with the contention that the reference frame for cooling or warming is arbitrary. I applaud your idea of changing the IPCC’s assumptions, but I think that effort would be futile, for reasons I expressed in the posting on Maurice Strong (“not just another climate skeptic”). At its core it is a political plot, not merely an intellectual fashion. They know what they are doing, these people.

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