Guest post by David Archibald
Figure 1: Ap Index 1932 – 2012
The Ap Index is the weakest of the solar activity indicators and has returned below the floor value of solar minima over the last 80 years – the green line in the chart above.
Figure 2: Solar Cycles 20 and 24 Ap Index and Neutron Count
The last time there was a cooling event in the modern instrument record was during Solar Cycle 20. Aligned on the month of minimum, Figure 2 shows that while the Ap Index and neutron count are co-incident to date in Solar Cycle 24, they were quite divergent over two thirds of Solar Cycle 20.
Figure 3: Neutron Counts over Solar Cycles 20 to 24
One big difference between Solar Cycle 20 and the other solar cycles of the modern instrument record is that just over half way through the cycle, the neutron count returned to levels of solar minima and remained there for the balance of the cycle. That is shown in Figure 3 above which also shows that the neutron count of Solar Cycle 24 is yet to depart from levels associated with previous minima, three years into the solar cycle.
Further to the post on Solar Cycle 24 length based on Altrock’s green corona diagram at:
http://wattsupwiththat.com/2012/01/08/solar-cycle-24-length-and-its-consequences/, Altrock noted the slow progress of Solar Cycle 24 in mid-2011. From Altrock, R.C., 2010, “The Progress of Solar Cycle 24 at High Latitudes”:
“Cycle 24 began its migration at a rate 40% slower than the previous two solar cycles, thus indicating the possibility of a peculiar cycle. However, the onset of the “Rush to the Poles” of polar crown prominences and their associated coronal emission, which has been a precursor to solar maximum in recent cycles (cf. Altrock 2003), has just been identified in the northern hemisphere. Peculiarly, this “rush” is leisurely, at only 50% of the rate in the previous two cycles.”
Altrock’s green corona diagram is available here: http://www.boulder.swri.edu/~deforest/SPD-sunspot-release/6_altrock_rttp.pdf
If Solar Cycle 24 is progressing at 60% of the rate of the previous two cycles, which averaged ten years long, then it is likely to be 16.6 years long. Using that figure of 16.6 years would make Solar Cycle 24 seven years longer than Solar Cycle 22. Using a solar cycle length – temperature relationship for the US – Canadian border of 0.7°C per year of solar cycle length, a total temperature decline of 4.9°C is predicted over a period of about twenty years.
Has a fall of that magnitude happened in that time frame happened in the past? A good place to look is the Dye 3 temperature record from the Greenland Plateau, available here: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/gisp/dye3/dye3-1yr.txt
Figure 4: Dye 3 Temperature Record from Oxygen Isotope Ratios
There is plenty of noise in this record and rapid swings in temperature, for example the 5.2°C fall from 526 to 531 at the beginning of the Dark Ages.
Figure 5: Dye 3 Temperature Record 22 Year Smoothed
Averaging the Dye 3 temperature record using the 22 year length of the Hale Cycle produces a lot of detail. What is evident is that there has been a very disciplined temperature decline over the last four thousand years. The whole temperature record is bounded by two parallel lines with a downslope of 0.3°C per thousand years. The fact that no cooling event took the Dye 3 temperature below the lower bounding green line over nearly four thousand years is quite remarkable. It implies that solar events do not exceed a particular combination of frequency and amplitude. From that it can be derived that this particular combination of frequency and amplitude with be ongoing – that is that cooling events will happen just as frequently as they did during the Dye 3 record.
Figure 6: North – South Transect through the Grain Belt
The relationship between temperature and growing conditions at about the latitude of the US – Canadian border is that one degree C will shift growing conditions by about 140 km. With a total 4.9°C temperature decline in train, that means a shift of about 700 km. Figure 6 shows the result of that temperature decline. Witchita will end up with the climate of Sioux Falls, which in turn will be like Saskatoon now. The growing season loses a month at each end.