Posted by: ericgrimsrud | March 9, 2015

The missing CO2/warming link discovered!

As most of us know, the concentration of CO2 in our atmosphere is now extraordinarily high as shown in the following figure.

Measurements of this sort are commonly referred  to as the “Keeling Curve” in honor of the man who initiated these background measurements back in 1958.  Additional perspective on the significance of these results is provided by the next figure – where the Keeling Curve is shown again (dark data points) along with CO2 concentrations dating back to the preindustrial year of 1700 (these data come from the ice core record).

Yes, our atmospheric CO2 levels have increased from 280 to just over 400 ppm (about 40%) over the Industrial Age.  This excess CO2 has been shown to come largely from mankind’s combustion of fossil fuels. In addition, the complete ice core record shows that our atmospheric CO2 levels had never been above 290 ppm over the last 800,000 years – until the onset of the Industrial Age.

So yes, our present CO2 level is extraordinarily high and it currently continues to increase even further at a rate of about 2.2 ppm per year .

Therefore, the big question before us today is – do we know for sure that the extra CO2 we have shown above is causing a significant amount of warming and if so, how much? While we have had a pretty good idea, to date, of  how much heating will result from our increased CO2 levels, those estimates have come from lab-based experiments and theory along with observations of the recent and deep past. While that enormous body of evidence has been very convincing, it must also be admitted that up to last week science had not yet provided direct measurements of the ground level heating that was being caused specifically by excess levels of CO2. This is why an upcoming research publication in Nature by D. R. Feldman, W. D. Collins, P. J. Gero, M. S. Torn, E. J. Mlawer, and T. R. Shippert, entitled Observational determination of surface radiative forcing by CO2 from 2000 to 2010 is of landmark importance.  It provides the last hard scientific link that quantitatively connects our increasing levels of CO2 to the magnitude of global warming.

So what did these scientists do and what did they discover?  In essence, they very accurately measured the infrared radiation emitted by atmospheric CO2 molecules that is directed downwards back to the Earth’s surface. They did this at two locations, Lamont, Oklahoma, and Barrow, Alaska, continuously over the ten-year period between 2000 and  2010.

In doing so, they found that the extra CO2 accumulated between the years 2000 and 2010 resulted in an increase in this so called “backradiation” of CO2 at both of the measurement locations.  As indicted by the first figure shown above, the extra CO2 accumulated over this ten-year period is 22 ppm.  The magnitude of the additional CO2-induced heat observed over that period was found to be 0.20 watts per square meter. When applied to the entire surface area of the Earth, this amounts to about 0.10 billion watts of additional energy in the year 2010 relative to that of 2000 – due to the extra 22 ppm CO2.

A major point of this paper is that its result is in excellent agreement with the previous predictions of warming by CO2 that  have been based on laboratory experiments and theory – as have been repeatedly reported by the International Panel on Climate Change (IPCC).  Therefore, our quantitative understanding of the relationship between atmospheric CO2 and surface temperatures can no longer to be called “just a theory” – even though the theory turns out to be correct.  It is also now linked from beginning to end by solid observational science.  Another important consequence of this paper is that it makes clear that the relation between CO2 and warming is that of “causation” and not just accidental “correlation”.  We now know from direct observations exactly how much additional heat is provided to the Earth’s surface with each increment of CO2 increase.


  1. Eric,
    The concentration of CO2 in the atmosphere is rising monotonically as you point out. If CO2 was the “Control Knob” of climate as claimed by Richard Alley (Penn State) we should be noticing an uptick in temperature. Mother Nature has a wicked sense of humor:

    • To galloping,

      Most of the heat is going into the oceans (see one of my recent posts). Also natural T cycles can mask surface T rises for a short time (such as a decade). Nevertheless, surface T’s last year were the hottest on record (would you consider that to be a T rise?

      • That “Hottest Year on Record” meme is a joke. Please send me a link to the data file that “proves” it.

        In the meantime here is a link to another data file that disproves it:

        The satellite record coverrs 37 years and it shows that 1998 was the hottest followed by 2010. At best, 2014 was the third hottest year in the last 37.
        Have you compared 1998 with 1934?

        [Response from EPG: The reference you requested has been provide before on this post at Note that it concerns surface Ts where people happen to live and goes back into 19th century. Now tell us where Spencer’s T’s were measured. Somewhere high in the atmosphere, I suspect and only go back 3 or 4 decades. ]

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