The Great European Corn Borer
More prowling through the latest National Climate Assessment has uncovered some additional concerns. On page 158 of the NCA, the authors for the agriculture section make the following claims:
Insects are directly affected by temperature and synchronize their development and reproduction with warm periods and are dormant during cold periods. Higher winter temperatures increase insect populations due to overwinter survival and, coupled with higher summer temperatures, increase reproductive rates and allow for multiple generations each year. An example of this has been observed in the European corn borer (Ostrinia nubialis) which produces one generation in the northern Corn Belt and two or more generations in the southern Corn Belt. Changes in the number of reproductive generations coupled with the shift in ranges of insects will alter insect pressure in a given region.
The NewScientist magazine focused on risks surrounding the European corn borer in its mainstream coverage of the NCA, noting that "warmer winters mean that some insect pests will be able to reproduce year round, swelling their numbers and impacting crops and livestock. Already, the European corn borer produces two generations in the warmer south for every one born in northern states." Back in 2008, the media also covered some Purdue University research focused on threats from warming in the U.S. corn belt and its effects on the corn borer.
There are some key pieces of information missing from the overly simplistic coverage of this issue by the NCA and in the media.
Simply put, summertime temperatures are not increasing in the corn belt. The June-August, July-September, and June-September periods all have non-significant temperature trends since 1895, regardless of whether parametric or non-parametric approaches are employed. Corn belt summertime temperatures during the 1930s were far higher than anything we have seen in recent years. Neither are there any clear trends over the past 20 to 30 years.
Wintertime temperature trends in the corn belt aren't changing, either. Since the 1910s, there haven't been consistent significant trends during either the December-February, January-March, or December-March periods. Indeed, since 1990, the correlation is negative (i.e., toward cooler winter temperatures in the corn belt).
The impression I, and I suspect many other readers, received from that paragraph in the NCA was that both summer and winter temperatures in the corn belt are increasing, have significantly increased, and will continue to increase, and that – as a result – the threat from the European corn borer in the American corn belt is increasing due to anthropogenic climate change.
Virginia Burkett, the chief scientist for global change at the U.S. Geological Survey, is already on the record as saying unequivocally that "all areas are getting hotter," which is clearly incorrect. There has been no significant trend in annual temperatures in the corn belt for the past century. There is also clearly no trend in annual corn belt temperatures over the past 20 or 30 years, either.
So if average annual, summertime, and wintertime temperatures in the corn belt haven't exhibited any significant trends in a century, and more recently over the past two to three decades, how do we clearly reconcile the food security concerns expressed in the NCA with reality? Appears to be a challenge.
A number of research publications have linked corn borer life cycles to growing degree days (GDDs). So perhaps GDDs are uniformly increasing throughout the corn belt, and that is what the NCA meant to discuss? Thus, I had a good look at GDD trends over the available historical records for the 26 climate divisions/cities that constitute the corn belt in the NOAA database.
First off, the majority of stations show no GDD trend, and for most of them the correlation is actually negative, not positive. Only three stations have an increasing trend, and of these, two have what must be considered only marginal significance at best (i.e., differing conclusions obtained depending on whether parametric or non-parametric methods are employed). Contrast that with the four stations that have unequivocally strong declining GDD trends.
Overall, one would conclude there is no evidence that GDDs are increasing over time in the corn belt. Coupled with the absence of average temperature trends, that would seem to quench excessive climate alarmism regarding the corn borer. But rather than release the superficial paragraph the NCA did, why didn't they analyze the issue comprehensively in the report and present the detailed results to the public and the agricultural community? Good question, but I think we know that the alarmists love the ambiguity of a potential threat as opposed to a rigorous analysis of the subject matter which may dismiss, or at least severely lessen, any real climate change-related concerns.
And the NCA's corn borer paragraph is a classic example of sloppy and incomplete referencing. There are a host of studies on the European corn borer and climate change, yet none of them were cited. If the NCA is going to bring up an important issue like this, it should have completed the intellectual task instead of just throwing out alarmist possibilities and/or perceived likelihoods absent any rigorous context.
Of course, over at The Guardian, they are now advocating for less science in climate communication, and a move over to the subjective and nebulous domain of "human stories." Essentially, if you can't baffle them with scientific BS, baffle them with non-scientific BS. As justification for this transition from objective to subjective climate communication, Adam Corner notes that "stories are everywhere; in myth, comedy, and stained glass windows. But for the most part, they are absent from climate change communication."
Oh, this is mistaken. As we've seen so far as we dig into the NCA, there is already plenty of myth and comedy in climate change communication from the alarmists. Perhaps the alarmists want to move away from discussing objective science because they know many of their supposedly scientific claims and predictions made to date aren't holding water, and it is time to shift gears into the realm of "human stories" as a classic smokescreen to avoid a possible blowback once shoddy science is publicly exposed?
These are the complex issues that arise from critically analyzing just one paragraph of the 841-page National Climate Assessment. As we start to pull on the threads from this climate sweater, it is likely much more of it will start to unravel.