The fit of the CSALT model to global temperature data is so close that it makes some sense to do a detailed analysis of the occasional glitches in the data.  This could tell us if there are other noise components that could fill the gap.

Initially what I want to do is a subjective interpretation — if one can isolate the parts of the model that don’t work so well, this may open up areas for further investigation.  For example, was the large warming spike at the end of WWII (starting in late 1943) real or was it due to calibration issues [1]?

Figure 1: Residual of the CSALT model fit to GIS data. Note the largest warming discrepancy starting in late 1943.

The following annotated fit (Figure 2) of the GISS temperature record to the CSALT model uses the GISS aerosol optical thickness data and a 12-month window to get rid of seasonal noise.

Figure 2: Peak-by-peak analysis of CSALT model to GISS temperature anomaly. Main volcanic eruptions shown as lower-case. Dark Blue is CSALT model and Green is GISS data.

To guide the eye, and as an example, the annotation labelled R indicates a period of time corresponding to the a warming residual shown in Figure 1 near 1943-1944. The individual volcanic eruptions are listed below.

The subjective interpretation is described next for each of the points on the curve. Characterizing a portion of the fit as Excellent means that the shape, timing, and intensity of the model peak (and surrounding valley) matches the data clearly.  Labeling it Good means that the overall fit works but something is a bit off, and Marginal means that it is only showing signs of incipient matching.

A – Excellent, Krakatoa time frame
B – Excellent, shoulder dips not as deep in model
C – Excellent, model peak of SOI not as high
D – Marginal, wide peak, lots of volcanic activity may be occluding the SOI.
E – Excellent
F – Excellent
G – Marginal, cooling trough which is elevated in model
H – Good, Novarupta time frame
I – Excellent
J – Excellent
K – Poor, Small, narrow peak missing
L – Excellent
M – Excellent, two fluctuations followed by a dip
N – Good, missing valley
O – Marginal, Peak OK, but no troughs on either side
P – Marginal, Not high enough peak in 1938
Q – Excellent
R – Poor, Suppressed warming peak in 1943
S – Excellent, trough occurs
T – Excellent
U – Excellent
V – Good, follows a cooling trend
W – Excellent, recovery from Agung eruption
X – Excellent
Y – Excellent
Z – Excellent, low peak from St. Augustine eruption
1 – Excellent, narrow peak
2 – Good, Timing of peak OK but not strong enough
3 – Excellent
4 – Excellent
5 – Excellent, Pinatubo
6 – Excellent
7 – Excellent, strong El Nino of 1998, model not quite as warm as data
8 – Marginal, Shifted peak position, extra fluctuation
9 – Excellent
0 – Excellent
# – Excellent
! – Poor, Heating predicted by model not observed — until this last month.

Of the 37 total annotations the count is :
Poor – 3
Marginal – 5
Good – 4
Excellent – 26

Most of the fits are good enough that they don’t need much commentary, but we can further decompose the Marginal and Poor fits.

The Marginal peak fits are :
– D – Not as much cooling suppression in the GISS aerosol model in spite of lots of volcanic activity
– G – Deeper cooling trough than the neutral SOI shows.
– O – Neutral SOI conditions not providing enough peak-to-peak
– P – Not strong enough SOI event, note that SST bucket measurement procedures are changing during this time [1]
– 8 – SOI neutral peaks seemed to have shifted by a year or two after temperature

The Poor peak fits are (shown in Figure 3) :
– K – A very small narrow peak that may be related to a rebound from a cooling dip in 1921
– R – No SOI event during end of 1943.  Again the SST calibration may be important or war efforts may have caused some issues in collection or measurements.
– ! – The current year is not close to the degree of warming that SOI neutral conditions would imply

Timely that September’s GISS data was recently made available. The last few month’s data points is shown in the right-most panel below. For the model to continue to hold, any gap between model and data can not persist. It is indeed possible that this gap is closing with a temperature anomaly of 0.74C for September. This is something to keep an eye on.

Figure 3: Close up of poor fitting areas, K, R, ! and a marginal area P

The lag time of SOI to a globally averaged temperature anomaly is 6 months, so that we could pay special attention  on a monthly basis to how well the CSALT model is capturing the actual temperature profile . The fact that it can do so well over 130+ years (save for the occasional odd excursion) implies that it will continue to work, unless of course a different climate regime takes over.  Some believe this could happen if the circulation patterns controlled by Arctic warming start to shift the jet stream [2][3].

 Related

1. CSALT model 
2. Climate Variability and Inferring Global Warming

References