Re: [Phys-l] Still More Global Warming

[John Mallinckrodt <ajm@csupomona.edu>]

Daryl,

You wrote:

> if anyone would bother to look at the data, none of the past
> warming periods coincides with an increase in atmospheric CO2. In  
> fact, CO2
> levels have been hugely huge in the past and never associated with  
> causing
> climate change. Why now? See http://www.darylscience.com/ 
> CO2-1.bmp . I'll
> dig out where I found that if you need. It is a basic little graph  
> of 'time
> ago' and CO2 levels. As you can see, the highest levels are quite a  
> while
> ago. Many folks argue that what was happening 400 million years ago  
> has
> nothing to do with today. I beg to differ and ask that they try to  
> view the
> 'big picture'. However, most interestingly, within the last 100  
> Million
> years, the CO2 levels were about ten times what they are now.

I'm not sure what to make of the graph you have provided because I'm  
not entirely sure what it is showing or especially how it supposedly  
demonstrates an anticorrelation of CO2 levels with temperatures.  I  
do note, however, that it covers a period of approximately 10% of the  
age of the Earth and must, therefore, rely on methods quite different  
than those used to produce the more well-known graphs based on ice  
core data, e.g.

  http://en.wikipedia.org/wiki/Image:Co2-temperature-plot.svg

that cover only one one-thousandth of that period of time--"only" the  
last half million years or about six glacial cycles.  This data does  
make use of a deuterium proxy for temperature, but it is not a  
simulation and the correlation between CO2 levels and the inferred  
temperatures is completely unmistakable.  Thus, it seems to me that  
it is wrong to say that "none of the past warming periods coincides  
with an increase in atmospheric CO2" at least on the one million year  
time scale unless you take on the methodology.

Things may look different over the 1000 million year time frame, but  
I don't know if there is any good evidence of that. Things may also  
look different over the 0.01 million year time frame, but I'm a  
little skeptical that we have accurate enough temperature or CO2 data  
to say much about the relatively minute variations that have occurred  
during that period.

John Mallinckrodt
Cal Poly Pomona