How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

In Defense of James Hansen's "Alternative Scenario" for Fighting Global Warming
Volume 5, Number 29: 17 July 2002

In a recent issue of Climatic Change, Wuebbles (2002) takes on a pair of formidable foes: James Hansen and the press.  His gripe with Hansen concerns various ideas expressed in the paper of Hansen et al. (2000), wherein it is suggested that the warming predicted to occur in response to the ongoing rise in the air's CO2 content may be effectively thwarted without any economically wrenching actions.  Similarly, his gripe with the press appears to center on all the attention they accorded this aspect of the paper, although his stated complaint is that "the Hansen et al. paper has clearly been misunderstood by the press."

Fortunately, Hansen was allowed to respond in the very same issue of Climatic Change (Hansen, 2002), where he emphatically states - and who should know better than he? - that "most of the media did not misunderstand the thrust of our recent paper."  Also, he reiterates his belief that "it is possible to achieve such a climatically brighter path with actions that are not 'economically wrenching,' indeed, actions that make economic sense independent of global warming."

Actions that make economic sense independent of global warming.  Now that sounds like something we could endorse.  In fact, it sounds a lot like a proper application of the precautionary principle, which is usually so badly twisted by most climate alarmists that it is essentially turned inside-out.  So what does Hansen propose?

One thing is to halt the growth of air pollution.  Hansen notes, for example, that black carbon or soot currently has a radiative forcing of approximately 1 Wm-2, while ozone has a radiative forcing of about 0.4 Wm-2.  Together, these two forcings are equivalent to the current excess CO2 forcing.  Hence, eliminating them eliminates half of the perceived global warming problem.  Although going that far may clearly not be possible, it is nevertheless true, as Hansen notes, that "halting the growth of air pollution can make a significant contribution to slowing global warming."

These actions also, as Hansen says, "make economic sense independent of global warming."  That is, they are actions that have virtue in and of themselves.  He notes, for example, that "particulate air pollution in France, Austria and Switzerland takes 40,000 lives annually with health costs equal to 1.6% of [those countries'] gross national products" and that "270,000 Indian children under 5 years old die annually from acute respiratory infections caused by air pollution."  In Hansen's plan, therefore, society tackles a serious problem that deserves far more attention than it currently gets, with the end result that humanity reaps the direct benefits of that action, as well as the ancillary climatic benefits that accrue from the concomitant reduction in global warming potential.

In this regard, it is instructive to review the illogical and tortured reasoning of Cifuentes et al. (2001), who tout the "hidden health benefits of greenhouse gas mitigation" while trying to convince us that we should fight global warming in order to reduce the deleterious and often deadly effects of air pollution (see our Editorial of 5 September 2001: The Distempered Brain Strikes Again!).  The primary objective of their approach is to reduce the concentrations of the atmosphere's major greenhouse gases (the most important of which is CO2); but this action does little to solve the health problems they identify, which can clearly be ameliorated by more direct and efficient means that are much less costly.  Also, the forced withdrawal of CO2 from the atmosphere would actually be detrimental to the well-being of essentially all of earth's plant life, as CO2 is the world's most effective aerial fertilizer.  Consequently, in addition to not aggressively addressing the problem they hold up as a cause for action, i.e., the adverse health effects of air pollution, the approach of Cifuentes et al. would actually harm the biosphere.  The approach advocated by Hansen, on the other hand, attacks air pollution-induced health problems head-on, reduces a major impetus for global warming, and does not harm the biosphere.

Hansen also advocates more research to better understand the global methane cycle, which could well lead to the development of "practices that reduce methane emissions while saving money," which, again, is a virtue in its own right.  And with a global climate forcing of 0.7 Wm-2, which is fully half that of the current CO2 forcing, the ancillary climatic benefits may be truly huge.

Another point made by Hansen is that his approach "emphasizes observations" over projections.  Harkening back to methane, for example, he notes that the "observed growth of CH4 is not accelerating, contrary to assumptions in many climate scenarios."  In fact, he reports that the growth rate of methane has declined by fully two-thirds over the past 20 years.  Clearly, it would be good to know why, and more research could provide the answer.

Then there's CO2 itself, whose atmospheric growth rate has fallen below typical model business-as-usual scenarios over the entire past decade.  In spite of this demonstrable fact, Hansen notes that "current IPCC scenarios have a growth rate in the 1990s that is almost double the observed rate," which he clearly deplores but says "is consistent with their failure to emphasize data."  This "flattening of the CO2 growth rate," according to Hansen, "is probably due in part to an increased CO2 sink."  Interestingly, this decrease in the rate of rise of the air's CO2 content was predicted by one of us before it ever became apparent (Idso, 1991a,b); and the driving force behind the prediction was the increase in the air's CO2 content itself, which stimulates earth's plant life to sequester ever more carbon via a whole suite of phenomena that are described in our Carbon Sequestration Commentaries.

In concluding, we can think of no better words to express our sentiments than those of Hansen himself: There is no fixed "truth" delivered by some body of "experts."  Doubt and uncertainty are the essential ingredient[s] in science.  They drive investigation and hypotheses, leading to predictions.  Observations are the judge.

Dr. Sherwood B. Idso
Dr. Keith E. Idso
Vice President

Cifuentes, L., Borja-Aburto, V.H., Gouveia, N., Thurston, G. and Davis, D.L.  2001.  Hidden health benefits of greenhouse gas mitigation.  Science 293: 1257-1259.

Hansen, J.E.  2002.  A brighter future.  Climatic Change 52: 435-440.

Hansen, J., Sato, M., Ruedy, R., Lacis, A. and Oinas, V.  2000.  Global warming in the twenty-first century: An alternative scenario.  Proceedings of the National Academy of Sciences USA 97: 9875-9880.

Idso, S.B.  1991a.  The aerial fertilization effect of CO2 and its implications for global carbon cycling and maximum greenhouse warming.  Bulletin of the American Meteorological Society 72: 962-965.

Idso, S.B.  1991b.  Reply to comments of L.D. Danny Harvey, Bert Bolin and P. Lehmann.  Bulletin of the American Meteorological Society 72: 1910-1914.

Wuebbles, D.J.  2002.  Oversimplifying the greenhouse.  Climatic Change 52: 431-434.