Why does Schneider claim such governmental intervention is required?  The answer to this question has a lot to do with storylines, risks and the precautionary principle.

The storylines are several specific greenhouse gas emission scenarios concocted by the Intergovernmental Panel on Climate Change (IPCC), which when combined with a wide range of climate sensitivities to greenhouse-gas-induced radiative forcing lead to a range of mean global temperature increases between 1990 and 2100 that reach as high as 5.8°C (Wigley and Raper, 2002), which is about the degree of warming the earth experienced while recovering from the last great ice age!  Schneider, however, postulates even more warming, with a worst-case-scenario temperature increase by 2100 in excess of 13°C.  The fact that this temperature rise is twice as large as the warming associated with most deglaciations would tend to suggest that it is totally beyond the realm of reality.

The risks, as defined by Schneider, are the "probabilities x consequences" of projected effects of global warming, some of which he enumerates in a table he adapted from McCarthy et al. (2001).  Among the items listed there are "increased deaths and serious illness in older age groups and urban poor," with a probability estimate of 90-99% likelihood.  However, as may be confirmed by perusing the second of our Major Reports (Enhanced or Impaired? Human Health in a CO2-Enriched Warmer World), this risk more likely has a probability of zero, as warming typically results in more lives saved at the cold end of the temperature spectrum than lives lost at the warm end.

One of the risks included by Schneider in the 67-90% likelihood category is an "increase in tropical cyclone peak wind intensities."  Real-world data, however, contradict him on this point [see Tropical Cyclones (Atlantic Ocean - El Niņo Effect, Global Warming Effect) Tropical Cyclones (Global), as well as Tropical Cyclones (Indian Ocean and Pacific Ocean) in our Subject Index].  Schneider also lists "intensified droughts and floods" in this likelihood category.  Once again, however, real-world data indicate otherwise [see Drought (Africa, Asia, Miscellaneous, North America) and Floods (Asia, Europe, General, North America) in our Subject Index].  Yet another risk he puts in this category is "increased Asian summer monsoon precipitation variability," which he equates with "increase in flood and drought magnitude and damages in temperate and tropical Asia."  As one by now might suspect, however, this risk, too, is not only way over-blown, it is non-existent [see Monsoon in our Subject Index].

Another risk that is mentioned several times in Schneider's testimony is that of warming-induced species extinction.  With respect to this topic, he says "it is sobering to consider what major movements -- and extinctions -- would likely take place in plant and animal communities if the climate changes by several degrees or more."  Fortunately, we have considered this possibility; and we have found it to be very close to zero.  In the first of our Major Reports (The Specter of Species Extinction: Will Global Warming Decimate Earth's Biosphere?), we carefully analyze the two major references Schneider cites in defense of this hypothesis -- Root et al. (2003) and Parmesan and Yohe (2003) -- demonstrating that several of the studies they list as supporting this concept actually refute it.

We come at last, then, to the precautionary principle.  With respect to enacting laws such as the one he promotes in his testimony, Schneider says that "decision-makers must decide whether to adopt a 'wait and see' policy approach or follow the 'precautionary principle' and hedge against potentially dangerous changes in the global climate system."  If we lived in a vacuum, that might be a good idea; but we live in the real world, where potential CO2-induced climate change is only one of many CO2-related phenomena that must be considered in arriving at a decision to regulate or not regulate anthropogenic CO2 emissions.

We broached this subject in the first of our Editorials on the McCain Senate Hearing (8 Oct 2003), where we briefly described the work of Tilman et al. (2001) and Wallace (2000).  The first of these studies demonstrates that even with expected advances in agricultural expertise, we will not be able to produce enough food to feed the human population that will exist in the year 2050 without appropriating approximately half of all potentially suitable remaining land to agriculture, which could, in Tilman et al.'s words, "lead to the loss of about a third of remaining tropical and temperate forests, savannas, and grasslands."  The second study likewise indicates that we will need to appropriate nearly all of the world's remaining freshwater to grow the extra food we will need at that point in time.  But if the air's CO2 content is allowed to rise unimpeded by governmental regulation, Idso and Idso (2000) have calculated that we will be able to overcome both of these problems -- but only just barely -- as a result of the productivity-boosting aerial fertilization effect of atmospheric CO2 enrichment and its water-saving antitranspirant effect.  Clearly, these phenomena, as well as several others having a CO2-plant physiological connection, must be considered within the context of the precautionary principle before any rational decision can be made regarding the wisdom of regulating anthropogenic CO2 emissions, as these phenomena provide proven and powerful benefits to both man and nature alike.

In conclusion, it seems fair to say that Stephen Schneider not only ignores many critical factors that need airing in high-level debate and deliberations over what to do (or not do) about the ongoing rise in the air's CO2 content, he also misrepresents many things of pertinence to these proceedings.  Our elected officials cannot be expected to act in the best interests of the nation and world without access to the facts he either fails to mention or turns upside-down.  Everyone must do his or her part to insure that the particulars of this matter are brought to the attention of their personal representatives at all levels of government.

References
Idso, C.D. and Idso, K.E.  2000.  Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration.  Technology 7S: 33-55.

McCarthy, J.J., Canziani, O.F., Leary, N.A., Dokken, D.J. and White, K.S., Eds.  2001.  Impacts, Adaptation, and Vulnerability.  Contribution of Working Group II to the IPCC Third Assessment Report.  Cambridge University Press, Cambridge, UK.

Parmesan, C. and Yohe, G.  2003.  A globally coherent fingerprint of climate change impacts across natural systems.  Nature 421: 37-42.

Root, T.L., Price, J.T., Hall, K.R., Schneider, S.H., Rosenzweig, C. and Pounds, J.A.  2003.  Fingerprints of global warming on wild animals and plants.  Nature 421: 57-60.

Tilman, D., Fargione, J., Wolff, B., D'Antonio, C., Dobson, A., Howarth, R., Schindler, D., Schlesinger, W.H., Simberloff, D. and Swackhamer, D.  2001.  Forecasting agriculturally driven global environmental change.  Science 292: 281-284.

Wallace, J.S.  2000.  Increasing agricultural water use efficiency to meet future food production.  Agriculture, Ecosystems & Environment 82: 105-119.

Wigley, T.M.L. and Raper, S.C.B.  2002.  Reasons for larger warming projections in the IPCC Third Assessment Report.  Journal of Climate 15: 2945-2952.