Guest essay by David Archibald
This post drew attention to the similarity between the recent warm decades and the period leading up to the extremely cold year of 1740. Now let’s investigate how a 1740-type event might play out. This graph shows the average of the monthly temperatures for the years 1736 to 1739 plotted with the monthly temperatures of the year 1740:
With respect to growing conditions, the 1740 season was a month later than the average of the previous five years and the peak months of the season were 2.5°C cooler. To get a perspective on how a repeat of 1740 might affect growing conditions in the Corn Belt, Bill Fordham, advising the grain industry in the Midwest, has kindly provided an update on the current season:
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“So far here in the center of the Midwest, the 2013 growing season is almost identical to 2009 in regards to Growing Degree Days (GDD).
In 2009 48% of the corn was planted by May 12 and 62% was planted by May 19.
In 2013 18% of the corn was planted by May 12 and 71% was planted by May 19.
In 2009, we never received a killing frost until November 5 when the low was at 28F. The Midwest had a huge crop that was wet and light test weight, but never got killed by a frost. In 2009, the total GDD accumulation from May 15 thru September 30 was 2,530 GDD.
The bulk of the corn planted in the Midwest ranges from 2,300 to 2,700 GDD (based on Fahrenheit). With the volcanoes that have been erupting in Alaska and Russia, especially with Mt Sheveluch erupting to 7.4 miles on June 26, I will be surprised if we get through the month of September in 2013 without an early killing frost. If the heat dome and high pressure ridge stays centered in the west and over Alaska until Labor Day, the clockwise rotation will pump the cold air south over the Midwest along with the ash. There are millions of acres at risk in IA and MN, that are 2-3 weeks behind normal.
After silking, it takes 24-28 days to reach the Dough Stage when kernel moisture is about 70% and about 50% of the total dry matter has accumulated in the kernel.
After silking, it takes 35-42 days to reach the Dent Stage when kernel moisture is about 55% and about 70% of the total dry matter has accumulated in the kernel.
It takes about 55-65 days after silking for a corn plant to mature and for the kernel to reach black layer, normally at 30-35% moisture.
A killing frost, <30F, will do damage whenever it occurs before black layer, the earlier the frost, the more severe the damage. A hard killing frost <28F can reduce the yield up to 25%, or more depending on the variety, even a week before black layer.
In 1974 I experienced severe loss on some late planted corn when I got rained out on May 7 and didn’t get back in to finish planting for 3 weeks. The May 7 corn yielded 190 bushels per acre and the May 28 corn yielded 90 bushels per acre, same variety.”
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Based on Bill Fordham’s experience of 1974, planting three weeks later reduced the crop yield by 50%. If the peak growth months of June, July and August are 2.5°C (4.5°F) cooler as per the CET record of 1740, that would reduce the GDD by 414.
A repeat of the climate of 1740, with a late planting and reduced heat in the three months prior to harvest can be expected to reduce crop yield by well more than 50%.
John Finn says:
“Each increment on the Y-axis appears to be 10deg F.”
No. Each 10 degrees is labeled. But you can discern 1º increments between the 10) labels. Further, you ignore the second chart I posted.
This comment relates to the misleading graph posted by dbsealey, i.e.
http://suyts.files.wordpress.com/2013/02/image_thumb265.png?w=636&h=294
Note the vertical (Y) axis is incremented by 10 units. The graph indicates a global temperature of just under 60 degrees – implying that each increment represents 10 degrees F.
The last glacial maximum saw mean global temperatures fall by about 5 degrees C (9 degrees F). In other words one increment on dbsealey’s graph represents the difference between modern day temperatures and those during the last ice age. Not content with one totally misleading and inappropriate graph, dbsealey then links to another (see Goldilocks comment) which this time uses increments of 5 degree C, so again a fall in temperature equivalent to one increment would be enough to plunge us into a catastrophic ice age – which is exactly what I said in my earlier post.
1. In the first graph the sub-increments are 2 degrees F. But, in any case, the choice of scale is totally inappropriate. The earth’s mean temperature has remained within a range of no greater than 10 degrees C (18 degrees F) over the past several million years yet your graph uses a scale between 0 and 120 degrees F. Why not use the Kelvin scale then you go from 0 to over 300 K? Your graph is meaningless junk.
2. The second graph uses increment of 5 degrees C so same criticism applies.
In both graphs the ‘labelled’ increments represent huge differences in earth’s climate.
John Finn says:
“This comment relates to the misleading graph posted by dbsealey”
John Finn, I suggest you quit digging your hole. If what you meant was that a 10-degree decline in global temperatures would cause a new stadial, then say what you mean. Otherwise, you’re just digging yourself a deeper hole with your own misleading nitpicking over ‘increments’.
I am fully capable of continuing to bruise your ego over this issue, just keep on with your comments about my so-called ‘misleading graph’ and we will see where this goes [and as noted above, I posted two graphs that show the same thing]. But if what you meant to say was that a global change of ten degrees would have a catastrophic effect, then just say so, and we will be on the same page.
Finally, thank you for pointing out that the current global temperature id decidedly on the cool side:
http://members.shaw.ca/sch25/FOS/globaltemp.jpg
that’s pretty much what I did say … and I also said that the graphs you linked to used increments on the vertical axis of 10 degrees F and 5 degrees C respectively. I also claimed (correctly) that this was a deliberate attempt to mislead the reader. Finally I’d like to add that nonsense like this does nothing to add to the debate and is generally damaging to the sceptic case.
John Finn,
You are wrong [and your comment of “pretty much” what you meant doesn’t cut it. Your comment was sloppy].
You originally wrote:
“…a single increment of the Y-axis…”
As everyone can see, the y-axis is divided into discrete 2º increments, with each ten degrees labeled for easy reference. And as we can see, 1º out of each 2º increment can be plainly seen. Further, my handy on-line dictionary defines ‘increment’ as: An increase or addition, esp. one on a fixed scale. A discrete increase. That exactly defines each ‘discrete increment’. Sorry about that, if you don’t like the definition, go argue with the dictionary. If there were no discrete divisions between each ten degree marker, you might have a leg to stand on. In this case, you do not.
The fact is that you screwed up with your sloppy original comment, which I read literally. But now you are trying to back and fill by trying to contradict the dictionary definition. Next time, maybe you will be more careful with the language you use when commenting on the charts that I posted. And I note that you have posted none of your own. Post your own charts, and you can define them. I will define per the dictionary the charts that I post. Within reason, of course. I am nothing if not reasonable.
Finally, I refer you to the essence of my argument, as stated above:
“The entire CO2-based conjecture that claims “carbon” causes global harm has been thoroughly deconstructed. It is a false alarm. The planet itself proves that beyond any doubt.”
You can go on nitpicking about what you mistakenly believe ‘discrete increment’ means; no one else but you cares. The important point is that the false alarm regarding the putative effect of “carbon” has been decisively deconstructed: CO2 does not cause any measurable global warming at current concentrations. None at all. And with that verifiable scientific fact, your entire belief system has been falsified.