Guest post by David Archibald
The story so far: in this recent post – Ap Index Neutrons and Climate, we had looked at the Dye 3 oxygen isotope-derived temperature record to see how big climate swings have been over the last few thousand years.
Figure 1: Dye 3 Temperature Record from Oxygen Isotope Ratios
As Figure 1 shows, the raw Dye 3 data shows plenty of noise and rapid swings in temperature.
Figure 2: Dye 3 Temperature Record 22 Year Smooth and less Millennial Cooling Trend
Applying a 22 year averaging to the data (the Hale Cycle) and taking off the millennial cooling trend that averages 0.00010915°C per annum produces the data in Figure 2. It is evident that the Medieval Warm Period and the Roman Warm Period occurred as a result of few excursions to the lower bounding line of activity.
Figure 3: Dye 3 Normalised Temperature Distribution
Figure 3 shows the result of sorting the normalised Dye 3 temperature record from lowest to highest and then plotting that up. The vertical lines are deciles of 377 years. What is striking is that the temperature range in the 2nd and 9th deciles is almost the same as that of the 5th and 6th deciles, which means that the average isn’t normal. What is normal is change. If temperature dwelled in the middle of the range and was subject to excursions up and down, then the curve would be flatter in the middle. In fact the temperature is only in the middle if it is on its way to somewhere else, either hotter or colder. Which means that there is no Arcadia of normal bliss – growing ranges are constantly either contracting or expanding like a concertina.
Figure 4: Lagged Dye 3 and CET Temperature with Inverted Be10 Data 1659 – 1750
Nobody lives on top of the Greenland icesheet so how does the Greenland data affect the affairs of Men? Figure 4 plots the Dye 3 temperature data, lagged three years, in red (plus 36°C) against the Central England Temperature (CET) Record in blue with the Dye 3 Be10 data in green. The interval 1659 to 1750 was chosen because this includes the fastest change in the CET record and the biggest spike in the Dye 3 Be10 record. There is a very good correlation between the Dye 3 temperature record and the Dye 3 Be10 record. There is good correlation between the Dye 3 temperature record and the CET record apart from the decades 1690 to 1710.
There is another good reason for looking at the decades 1690 to 1710 and that is that the decades 2010 to 2030 might be a re-run of them. Famines caused by the cold killed roughly 10% of the population in France 1693-94, Norway 1695-96 and Sweden 1696-97, 20% in Estonia 1696-97 and 33% in Finland 1696-97 (Elizabeth Ewan, Janay Nugent (2008) ”Finding the family in medieval and early modern Scotland” Ashgate Publishing. p.153).
Humans expand to fill the habitable zone, but the habitable zone can shrink too. This is a link to the Arbor Day Foundation’s animation of the changes they made to their hardiness zone map in 2006: http://www.arborday.org/media/mapchanges.cfm
Figure 5: Hardiness Zones Map
Figure 5 shows the current hardiness zones map. The 10°F width of these zones just about equates to the 5°C drop in temperature due to the length of Solar Cycle 24 over that of Solar Cycle 22.
The lesson from the Dye 3 temperature data, and that late 17th Century Finnish famine, is this: exploit the expansion in the habitable zone as the Sun becomes more active, but be prepared to run back towards the equator because it isn’t going to last.