A response to Middleton: Ice Cores vs. Plant Stomata
David Middleton posted a pretty interesting piece about high frequency CO2 changes and differences in Holocene mid-latitude CO2 as derived from leaf stomata and that found in ice cores. It seems it was latter picked up by WUWT. Learned lots, but the conclusion of the piece is over-reaching. I had a short chat with Middleton about it. It was clear I would have to be more precise to make my point.
Here is the chart of David Middleton’s that is in question. It seeks to compare recent (1000+ year) temperature history (as defined by Moberg 2005) and CO2 levels as defined by Kouwenberg. Note that there is no error envelope around either series – but the envelope around both is pretty huge. But we will proceed without it.
Instead of eyeballing the alignment, I have taken his chart and slipped the CO2 series back to line up the dashed line at the end of the LIA circa 1610 CO2 with the corresponding dashed line of temperature at the beginning of the LIA about 1120 temperature. Now we can make some rate calculations for CO2 response to temperatures.
For pixel interpolation, I found the cells to be about:
The shift (or lag) displayed is approximately 240 years.
Values rounded to two significant digits.
For comparisons, I divided the series into 4 sections: A, B, C, D.
Section C was defined by Middleton.
End = 940
Start = 770
Years = 170
End = -0.31
Start = -0.31
Temp = 0
End = 254
Start = 307
CO2 = -53
In section A, for NO change in Temp, we have a change of -53 ppm CO2
End = 1120
Start = 940
Years = 180
End = -0.02
Start = -0.31
Temp = +.29
End = 318
Start = 254
CO2 = +64
In section B, for a +0.29 in Temp, we have a change of +64 ppm CO2
64/.29 = 220 ppm CO2 for every 1C increase
End = 1610
Start = 1120
Years = 490
End = -0.72
Start = -0.31
Temp = -0.41
End = 281
Start = 318
CO2 = -37
In section C, for a -0.41 in Temp, we have a change of -37 ppm CO2
-37/-0.41 = 90 ppm CO2 for every 1C increase
End = 1745
Start = 1610
Years = 135
End = -0.61
Start = -0.76
Temp = +0.15
End = 357
Start = 281
CO2 = +76
In section D, for a +0.15 in Temp, we have a change of +76 ppm CO2
+76/+0.15 = 510 ppm CO2 for every 1C increase
So to recap, CO2 response to 1C change for each section is:
Section A: (no response or slightly negative)
Section B: 220 ppm
Section C: 90 ppm
Section D: 510 ppm
If sections A, B, and C offer a clue as to CO2 response to temperature in the preindustrial world, then the natural CO2 accumaltion due to warming from 1610-1745 should be in the range of 0ppm to 33ppm (220ppm/C * 0.15C). The actual increase in section D is 76ppm which suggests that more than half the CO2 increase by ~1980 (1745 + 235) is from sources other than “a response to rising temperatures 240 years earlier.”
If a CO2 response to temperatures from 240 years earlier is the primary component of the rise in current CO2, we should expect a drop in CO2 accumalation beginning around 2040 corresponding to the drop in temperature just after 1800.