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Will Global Warming Devastate Crops?  Read All About It!
Volume 3, Number 35: 13 December 2000

Every once in a while - much more often, in fact, than one would hope would be the case - a great hue and cry is raised over an experimental finding reported in a peer-reviewed scientific journal.  Worse than that, much is often made of an isolated report in a non-referred science magazine.  There are even cases where word-of-mouth accounts of research that has not yet been submitted for publication, much less even written in a suitable format for journal review, make their way into the news services.  And all of a sudden, the dramatic new finding - based on only the claims of its authors - becomes the mantra of some pre-existing movement (such as the Climate Alarmist Craze) that realizes how the new information can be used to promote its own agenda.

A case in point concerns a University of Florida study that enjoyed a bit of prominence just a couple weeks ago.  Some news services (Environment News Service's AmeriScan of 1 Dec and Daily University Science News of 4 Dec) ran headlines stating that global warming could reduce rice harvests, describing the phenomenon as extremely bad news for Third World countries and the two billion people who obtain 40% of their daily calories from rice.  In addition, the story implied much the same about peanuts, soybeans and kidney beans, hinting at the possibility that most all seed-producing plants were similarly threatened.

What is one to make of such reports?  For starters, one should realize that even the best of scientists can be wrong, as almost all of us are now and then, and that nearly all researchers - whether they've published 10, 100 or 1000 papers - periodically have a paper rejected.  When this happens the authors sometimes revise the manuscript and submit it to a different journal, sometimes succeeding and sometimes failing once again to have it published.  If the paper never sees the light of day, chances are it suffered from true deficiencies; and if it is ultimately published somewhere, chances are it will be significantly different than it was in its first incarnation.  In either event, the bottom line is basically the same: the original story was not all it was cracked up to be.

Discretion thus suggests that overly dramatic scientific claims should not be given too much credence until they have in fact been published in the scientific literature.  Even then, skepticism is still in order, especially in the biological realm, where all sorts of confounding factors have the potential to affect an experiment.  A case in point is the growth response of plants to atmospheric CO2 enrichment.  In one of the largest reviews of this subject ever undertaken, Idso (1992) surveyed a total of 1,087 individual experimental results, finding that fully 93% of them were positive.  One implication of this finding is that the other studies may not have been conducted properly.  Another possibility is that they were done correctly but that 7% of the plants studied just don't respond positively to atmospheric CO2 enrichment.  In either case, the few neutral or negative responses are not characteristic of the responses of the great bulk of earth's vegetation.  And this observation highlights the importance of not relying too heavily on just one experiment, or even a small group of studies, especially in important matters about which there is much controversy.

Another thing to remember is that even if a study is correct in its findings, the spin that is put on the results by the authors and/or other interested parties may not be correct.  In the case of the claim that future warming will reduce the yields of rice, peanuts, soybeans and seed-producing crops in general, for example, one must consider additional changes in the global environment that may occur concurrently.  And in this regard, the ongoing rise in the air's CO2 content - which is even more certain than future warming - must figure prominently.

Several studies published in peer-reviewed scientific journals have conducted just such analyses.  Alexandrov and Hoogenboom (2000a), for example, recently used the output from various general circulation models of the atmosphere to assess the likely performance of soybeans and peanuts (two of the supposedly temperature-threatened crops) over the next few decades in the southeastern United States.  As was implied in the news service reports of the University of Florida study, the predicted increase in air temperature, along with predicted decreases in precipitation, implied future decreases in the yields of both soybeans and peanuts.  However, when the growth-promoting effects of the likely concomitant increase in the air's CO2 content were included in the analysis, yield increases were predicted for both crops.  And in a similar analysis of winter wheat in Bulgaria, Alexandrov and Hoogenboom (2000b) obtained the same result: yield decreases due to warming alone, but yield increases due to elevated air temperature and CO2 concentration together.

Many other peer-reviewed scientific journal studies could be cited in support of the conclusions of the analyses of Alexandrov and Hoogenboom, as well as in support of the general principle that increases in the air's CO2 content typically tend to overpower the deleterious effects of all sorts of environmental stresses, as indicated in the massive review of this subject produced by Idso and Idso (1994).  There are also many similar studies that have been produced subsequently.(1)

So, take heart, Third World countries, and do not be misled by the Climate Alarmists who wring their hands and weep great Elephant Tears for you; the future yet looms bright.  Only by overtly meddling with the world's economy in a fruitless and likely counter-productive effort to curtail anthropogenic CO2 emissions will we likely screw things up for the biosphere, including our agricultural enterprises.  The great bulk of pertinent scientific knowledge, i.e., all the evidence, clearly suggests that Kyoto spells disaster for man and nature alike, and that the rising CO2 content of earth's atmosphere is actually a godsend, a truly remarkable blessing in disguise.(2)

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

1.  Reviews of a number of these studies can be found on our website, most notably under the general Subject Index heading Growth Response to CO2 with Other Variables.

2.  See, for example, our Editorial The Fortunate Coupling of Atmospheric CO2 and Temperature Trends and our Journal Review Rising CO2 Concentrations Help Plants Adapt to Rising Temperatures.

Alexandrov, V.A. and Hoogenboom, G.  2000a.  Vulnerability and adaptation assessments of agricultural crops under climate change in the Southeastern USA.  Theoretical and Applied Climatology 67: 45-63.

Alexandrov, V.A. and Hoogenboom, G.  2000b.  The impact of climate variability and change on crop yield in Bulgaria.  Agricultural and Forest Meteorology 104: 315-327.

Idso, K.E.  1992.  Plant responses to rising levels of atmospheric carbon dioxide: A compilation and analysis of the results of a decade of international research into the direct biological effects of atmospheric CO2 enrichment.  Climatological Publications Scientific Paper #23. Office of Climatology, Arizona State University, Tempe, AZ.