Volume 10, Number 16: 18 April 2007
In his 21 March 2007 testimony before the United States Senate's Environment & Public Works Committee, former U.S. Vice President Al Gore talked passionately about what he referred to time and again as a "climate crisis," which he characterized as "a planetary emergency - a crisis that threatens the survival of our civilization and the habitability of the Earth." Using the word "crisis" an amazing 10 times in his 14-paragraph testimony, Gore mentioned several things designed to supposedly justify his prolific use of the scary word; yet he truly outdid himself when he ominously added that "new evidence shows that it [i.e., the climate crisis] may be even worse [our italics] than we thought." And that's saying a lot, particularly when the "thinker" is Al Gore!
So what was the ominous bad news? According to Gore, "a recent study published by the University of Alaska-Fairbanks indicates that methane is leaking from the Siberian permafrost at five times the predicted levels," and considering the possibility that this revelation might not be scary enough to convince people of his take on the issue, he added that "methane is 23 times as potent a greenhouse gas as carbon dioxide." And in case that little bit of information was not enough to do the job, he went on to say "there are billions of tons underneath the permafrost." No wonder Gore claims the situation is even worse than a crisis! But is it really?
Most people would probably conclude that if methane was escaping from such a vast and long-inert reservoir as the Siberian permafrost, and at such an unexpectedly high rate, its atmospheric concentration would also likely be rising at an unexpectedly high rate; and that's probably what Gore was counting on their thinking. However, that's not what's been happening. After rising rapidly until the early 1990s, the atmosphere's methane concentration continued to rise, but at an ever-slowing rate; and the decline in its rate-of-rise continued to the point that since the turn of the century the methane concentration of the atmosphere has essentially stabilized - ceasing to rise any further - as demonstrated by the updates of atmospheric methane concentration data provided by Dlugokencky et al. (2003) and Khalil et al. (2007). What is more, the nature of the rate-of-rise decline in methane concentration suggests that atmospheric methane concentrations could well begin to decline in the not-too-distant future, as we discuss in more detail in our editorial of 8 Jan 2003.
Why are these facts so incredibly important? The answer resides in the degree of radiative forcing induced by the increase in atmospheric methane concentration since preindustrial times. Shine and Sturges (2007) indicate that since 1800 the increase in the air's methane content has produced an enhanced radiative forcing of approximately 0.5 W m-2; and they note that because "rising methane concentrations can cause increases in ozone and stratospheric water vapor concentrations ... methane's true contribution was nearer 0.9 W m-2, equivalent to more than half the radiative forcing caused by CO2," which is estimated to have been 1.66 W m-2.
This being the case, the cessation of the historical increase in the atmosphere's methane concentration - which appears to have actually been accomplished, and without any overt help from mankind - will likely do more to slow the increase in total greenhouse-gas radiative forcing than any program humanity will ever be able to implement. And if the atmosphere's methane concentration actually starts to decline (which looks to be a real possibility in the very near future), the increase in radiative forcing due to continued increases in the air's CO2 content will be significantly countered by the decline in methane-induced radiative forcing, once again accomplishing more than anything man will ever be able to do in this regard. In fact, it allows for the important and wonderful possibility that the ongoing rise in the air's CO2 concentration will be able to continue and thereby provide the boost in agricultural productivity we are going to need by the mid-point of this century to adequately feed the planet's rapidly-rising human population without having to usurp - or steal from nature - so much of the world's remaining cultivatable land and freshwater resources (see our editorials of 13 Jun 2001 and 4 Sep 2002), and without having to worry about the increase in atmospheric CO2 creating a dangerous degree of global warming.
Sherwood, Keith and Craig Idso
References
Dlugokencky, E.J., Houweling, S., Bruhwiler, L., Masarie, K.A., Lang, P.M., Miller, J.B. and Tans, P.P. 2003. Geophysical Research Letters 30: 10.1029/2003GL018126.
Khalil, M.A.K., Butenhoff, C.L. and Rasmussen, R.A. 2007. Atmospheric methane: Trends and cycles of sources and sinks. Environmental Science & Technology 10.1021/es061791t.
Shine, K.P. and Sturges, W.T. 2007. CO2 is not the only gas. Science 315: 1804-1805.