The American Geophysical Union’s Official

By | February 6, 2008

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Reprinted with permission of the Center for the Study of Carbon Dioxide and Global Change, Tempe AZ,

The American Geophysical Union (AGU) document entitled Human Impacts on Climate begins with the statement that "the earth’s climate is now clearly out of balance and is warming." It sounds ominous, doesn’t it? But if mere warming or cooling is a sign of being out of balance, one could truthfully say that earth’s climate is almost always "out of balance," which suggests that its current condition is actually normal.

The second declaration of the document says that many components of the climate system "are now changing at rates and in patterns that are not natural." And unnatural climate change sounds even more ominous. But is this really the case?

Enlarging upon the claim that earth’s current climate is unnatural, the recently revised position statement — which was adopted by the AGU Council on 14 December 2007 — says that "evidence from most oceans and all continents except Antarctica shows warming attributable to human activities." Now if one is talking about localized human activities, such as urbanization, this contention is clearly correct. But when one is talking about regions as large as oceans and continents — which, by definition, is what is involved in global warming — the situation is much more murky. And, again, there is still the problem of how to determine what is natural warming and what may be of anthropogenic origin.

One way of approaching this dilemma is to compare climatic conditions over the past century with those of the thousands of years that preceded it, when the use of fossil fuels was non-existent. The AGU Council does this in their second paragraph, where they speak of "recent millennia of relatively stable climate." They use this characterization in order to make it appear that the planet has subsequently experienced unnatural warmth, which climate alarmists typically characterize as being unprecedented. In employing this characterization, however, the AGU Council refuses to recognize reality, for it was much warmer than it is nowadays over thousands of years during the Climatic Optimum of the mid-Holocene; and it was also warmer than it is currently during the centuries-long Medieval Warm Period of only one millennium ago, as demonstrated by the voluminous and continually-accumulating evidence for this warmer-than-current period of earth’s climatic history in our Medieval Warm Period Project[1], where we report how medieval warmth has been detected on all continents during a period of time when the atmosphere’s CO2 concentration was fully 100 ppm less than it is today. These palaeoclimate findings clearly indicate that earth’s current temperature is not in any way unnatural; and they demonstrate that today’s much-less-dramatic warmth (compared to that of "recent millennia of relative stable climate") need not have been caused by its current elevated level of CO2.

The AGU Council next describes some of the climatic projections that are used to scare people into believing we must act decisively and soon if we are to prevent the mother-of-all-catastrophes. To their credit, however, they note that "with such projections, there are many sources of scientific uncertainty." But to their discredit, they add that "none are known that could make the impact of climate change inconsequential," implying there is nothing that can significantly change the model-based projections. In reality, however, there could well be several factors — all largely unknown to them — that may in fact be able to do what the Council essentially infers is impossible. When faced with the amazing complexity of nature, therefore, humility is much to be preferred over hubris.

In much the same vein, the AGU document states "there can be surprises that may cause more dramatic disruptions than anticipated from the most probable model projections." Again, this is true; but it is equally true that there can be surprises that may cause less dramatic disruptions than anticipated from the most probable model projections. In fact, there can be surprises that may actually change the projections from something hurtful to something helpful. Indeed, that is the essence of surprises: they are things that are totally unexpected. And as everyone knows, surprises happen!

In light of these several observations, the leadership of the American Geophysical Union would do well to restrict themselves to purely scientific matters and not delve into policy prescriptions, as they do in the final paragraph of their official statement. If the science of the subject ever becomes clear, the people of the world will know what to do about it; they are not dumb. Therefore, to try to tell them how to act now, when the science is not clear, is actually an admission of that fact, i.e., the fact that the science is not clear, just as it is also an indication of the possibility that something other than science alone may have prompted the Council’s recent reaffirmation of their "position" on this scientific matter.

American Geophysical Union. 2008. Human Impacts on Climate. Retrieved from:

Source: CO2 Science, Volume 11, Number 6: 6 February 2008