As a simple example, the two chemistry professors write that "the average temperature of Earth is increasing." In reality, however, it is not increasing, as the mean temperature of the globe has remained fairly steady for about the last decade and a half. But will it continue that way? Or will it soon begin to once again warm? Or actually begin to cool? Although many scientists hold one position or the other, no one really knows.

Shakhashiri and Bell also write that "extreme weather events are more frequent," when, in fact, nearly all types of extreme weather events are not more frequent now than they were in either the recent or more distant past, as may readily be seen from the many journal reviews we have archived under the general heading of Weather Extremes on our website. In addition, they say that the combustion of fossil fuels is "a major driver of climate change," when this is merely the opinion of one (albeit a large) segment of the scientific community.

Continuing, the two chemists state that "to share this knowledge with the public and be credible as a 'scientist-citizen,' a scientist must acquire a good grasp of the science of climate change." Clearly, however, this is not enough; for there are many people with "a good grasp of the science of climate change" that have widely divergent ideas about the subject. And in such cases, a true scientist-citizen should readily acknowledge that there is no scientific unanimity on this issue.

This being the case, it should be clear that neither is there any unanimity on the question of what should or should not be done about the still-unsettled subject. And, therefore, Shakhashiri and Bell's contention - that "supporting elected officials who promote policies and practices aimed to decrease the effects of global warming is another step that individuals and citizens' groups should take" - could someday be found to be just the opposite of what really should have been done.

Especially is this the case when it is realized, as indicated by Bruinsma (2009), that in order to "meet the growing demand for crops" - due mainly to the increasing population of the planet - the production of major crops "will need to increase by 70% by 2050," which increase in production would require far more extra land and water than could realistically be made available for the task. Under these real-world conditions, therefore, the only hope we might possibly have is that the CO2 content of earth's atmosphere would continue to rise, bestowing its aerial fertilization and water-use efficiency amplification effects upon our major crops, which is something that literally thousands of laboratory and field experiments have demonstrated it truly has the power to do.

Consequently, and in contrast to the contention of Shakhashiri and Bell that people should support officials who promote policies and practices aimed at decreasing anthropogenic CO2 emissions, we would hope that most rational men and women would seek to determine - as best they can, based upon real-world observations rather than theoretical models - which of the two opposing scientific factions seems to them to be the more likely to have the more correct view of the matter.

Sherwood, Keith and Craig Idso

References
Bruinsma, J. 2009. The resource outlook to 2050: By how much do land, water use and crop yields need to increase by 2050. In: Technical Papers from the Expert Meeting on "How to Feed the World in 2050." Food and Agriculture Organization, Rome, Italy.

Shakhashiri, B.Z. and Bell, J.A. 2013. Climate Change Conversations. Science 340: 9.