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CO2 and Temperature: The Great Geophysical Waltz
Volume 2, Number 7: 1 April 1999

In a recent news release, NASA's Goddard Institute for Space Studies declared 1998 to be "a record temperature year," the warmest ever recorded during the period of instrumental temperature assessment.  Likewise, in a new analysis of proxy temperature data, Mann et al. (1999) suggest that the past decade may well have been the warmest of the past millennium.  And once again (see our Vol. 1, No. 1 editorial: Much Ado About Tiny Temperature Trends), we have the Goddard Institute for Space Studies' James Hansen being quoted as stating that "there should no longer be an issue about whether global warming is occurring, but what is the rate of warming, what is its practical significance, and what should be done about it."

In truth, there is no issue about whether the globe has warmed over the past century or so.  Everyone accepts that it has warmed significantly, as the planet has recovered from the global chill of the Little Ice Age.  There is also beginning to be a consensus about the practical significance of the warming.  Growing seasons have lengthened and plant biomass formation has increased, as a result of both the warming and the concomitant increase in atmospheric CO2 concentration.  So what should be done about it?

We suspect that very few people would want to turn back the climatic clock to the conditions that spelled the doom of the Viking colonists on Greenland and created extreme hardship in Northern Europe and elsewhere.  Likewise, not many people have a problem with longer growing seasons and increased biomass production.  So what's all the fuss about?

It's pretty much a tempest in a computerized teapot.  For many years climate modelers have predicted that the ongoing rise in the air's CO2 content will intensify earth's natural greenhouse effect and boost surface air temperatures to levels that will create all sorts of planetary havoc, melting polar ice caps, raising sea levels, flooding some parts of the globe while turning others to deserts, reducing agricultural productivity, and on and on ad infinitum.  And now the likes of James Hanson would have us believe that because atmospheric CO2 and global temperature have both been rising over the past century or so, the rise in atmospheric CO2 must be driving the warming that is asserted to be sure to bring on the worst of the apocalyptic predictions.

In assessing such claims, it is important to remember that correlation does not prove causation, and that causation, if it does exist, may well operate in reverse fashion from what one may have originally thought.  Hence, it is important to have as much data as possible when attempting to evaluate claims of causal relationships between different parameters; and the last few weeks have given us a wealth of new data of just the type needed to determine if there is indeed any relationship between atmospheric CO2 concentration and surface air temperature.

Perhaps the most exciting new data come from Fischer et al. (1999), who examined records of atmospheric CO2 and air temperature derived from Antarctic ice cores that extended back in time across a quarter of a million years.  Over this immense time span, the three most dramatic warming events experienced on earth were those associated with the terminations of the last three ice ages; and for each and every one of these tremendous global warmings, earth's air temperature rose well before there was any increase in atmospheric CO2.  In fact, the air's CO2 content did not begin to rise until 400 to 1,000 years after the planet began to warm.

Clearly, increases in atmospheric CO2 did not trigger these massive climate changes.  In addition, there was a 15,000-year period following the second of the glacial terminations when the air's CO2 content was essentially constant but air temperatures dropped all the way down to values characteristic of glacial times.  Hence, just as increases in atmospheric CO2 did not trigger any of the major global warmings that lead to the demise of the last three ice ages, neither was the induction of the most recent ice age driven by a decrease in CO2.  And when the air's CO2 content finally did begin to drop after the last ice age was fully established, air temperatures either remained fairly constant or actually rose, doing just the opposite of what the climate models suggest should have happened if changes in atmospheric CO2 drive climate change.

In much the same vein, Indermuhle et al. (1999) determined that after the termination of the last great ice age, the CO2 content of the air gradually rose by approximately 25 ppm in almost linear fashion between 8,200 and 1,200 years ago, over a period of time that saw a slow but steady decline in global air temperature, which is once again just the opposite of what would be expected if changes in atmospheric CO2 affect climate in the way affirmed by the popular CO2-greenhouse effect theory.

So who leads who?  In the geophysical dance of carbon dioxide and temperature, which repeats itself every hundred thousand or so years, it is definitely not CO2.  Sometimes the two parameters are totally out of sync with each other, as when one rises and the other falls.  Sometimes one is in transit to a higher or lower level, while the other is in stasis.  And even when they do move in harmony, temperature seems to take the lead.

Clearly, there is no way that these real-world observations can be construed to even hint at the possibility that a significant increase in atmospheric CO2 will necessarily lead to any global warming, much less the catastrophic type that is predicted to produce the apocalyptic consequences that are driving fear-ridden governments to abandon all sense of rationality in the current hysteria over "what should be done about" the ongoing rise in the air's CO2 content.

We need to get real about this issue.  We need to look at real phenomena that have actually occurred in the real world.  And in spite of all the computer simulations to the contrary, we have got to realize what these real data are really telling us.  When this is done, the answer comes very simply, as simply as mastering the old-time waltz that the planet has been playing for a quarter million years or more.  The key is in the interaction of the participants; when you know who leads, you can avoid a lot of missteps.

Dr. Craig D. Idso
President
Dr. Keith E. Idso
Vice President

References
Fischer, H., Wahlen, M., Smith, J., Mastroianni, D. and Deck, B.  1999.  Ice core records of atmospheric CO2 around the last three glacial terminations.  Science 283: 1712-1714.

Indermuhle, A., Stocker, T.F., Joos, F., Fischer, H., Smith, H.J., Wahlen, M., Deck, B., Mastroianni, D., Tschumi, J., Blunier, T., Meyer, R. and Stauffer, B. 1999.  Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica.  Nature 398: 121-126.

Mann, M.  1999.  Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations.  Geophysical Research Letters 26: 1759-1762.