Figure 1.4 of the Second Order Draft clearly showed the discrepancy between models and observations, though IPCC’s covering text reported otherwise. I discussed this in a post leading up to the IPCC Report, citing Ross McKitrick’s article in National Post and Reiner Grundmann’s post at Klimazweiberl. Needless to say, this diagram did not survive. Instead, IPCC replaced the damning (but accurate) diagram with a new diagram in which the inconsistency has been disappeared.

Here is Figure 1.4 of the Second Order Draft, showing post-AR4 observations outside the envelope of projections from the earlier IPCC assessment reports (see previous discussion here).



Figure 1. Second Order Draft Figure 1.4. Yellow arrows show digitization of cited Figure 10.26 of AR4.

Now here is the replacement graphic in the Approved Draft: this time, observed values are no longer outside the projection envelopes from the earlier reports. IPCC described it as follows:

Even though the projections from the models were never intended to be predictions over such a short time scale, the observations through 2012 generally fall within the projections made in all past assessments.



Figure 2. Approved Version Figure 1.4

So how’d the observations move from outside the envelope to insider the envelope? It will take a little time to reconstruct the movements of the pea.

In the next figure, I’ve shown a blow-up of the new Figure 1.4 to a comparable timescale (1990-2015) as the Second Draft version. The scale of the Second Draft showed the discrepancy between models and observations much more clearly. I do not believe that IPCC’s decision to use a more obscure scale was accidental.



Figure 3. Detail of Figure 1.4 with annotation. Yellow dots- HadCRUT4 annual (including YTD 2013.)

First and most obviously, the envelope of AR4 projections is completely different in the new graphic. The Second Draft had described the source of the envelopes as follows:

The coloured shading shows the projected range of global annual mean near surface temperature change from 1990 to 2015 for models used in FAR (Scenario D and business-as-usual), SAR (IS92c/1.5 and IS92e/4.5), TAR (full range of TAR Figure 9.13(b) based on the GFDL_R15_a and DOE PCM parameter settings), and AR4 (A1B and A1T). ,,, The [AR4] data used was obtained from Figure 10.26 in Chapter 10 of AR4 (provided by Malte Meinshausen). Annual means are used. The upper bound is given by the A1T scenario, the lower bound by the A1B scenario.

The envelope in the Second Draft figure can indeed be derived from AR4 Figure 10.26. In the next figure, I’ve shown the original panel of Figure 10.26 with observations overplotted, clearly showing the discrepancy. I’ve also shown the 2005, 2010 and 2015 envelope with red arrows (which I’ve transposed to other diagrams for reference). That observations fall outside the projection envelope of the AR4 figure is obvious.



Figure 4. AR4 Figure 10.26

The new IPCC graphic no longer cites an AR4 figure. Instead of the envelope presented in AR4, they now show a spaghetti graph of CMIP3 runs, of which they state:

For the AR4 results are presented as single model runs of the CMIP3 ensemble for the historical period from 1950 to 2000 (light grey lines) and for three scenarios (A2, A1B and B1) from 2001 to 2035. The bars at the right hand side of the graph show the full range given for 2035 for each assessment report. For the three SRES scenarios the bars show the CMIP3 ensemble mean and the likely range given by -40% to +60% of the mean as assessed in Meehl et al. (2007). The publication years of the assessment reports are shown. See Appendix 1. A for details on the data and calculations used to create this figure… The temperature projections of the AR4 are presented for three SRES scenarios: B1, A1B and A2.

Annual mean anomalies relative to 1961–1990 of the individual CMIP3 ensemble simulations (as used in

AR4 SPM Figure SPM5) are shown. One outlier has been eliminated based on the advice of the model developers because of the model drift that leads to an unrealistic temperature evolution. As assessed by Meehl et al. (2007), the likely-range for the temperature change is given by the ensemble mean temperature

change +60% and –40% of the ensemble mean temperature change. Note that in the AR4 the uncertainty range was explicitly estimated for the end of the 21st century results. Here, it is shown for 2035. The time dependence of this range has been assessed in Knutti et al. (2008). The relative uncertainty is approximately constant over time in all estimates from different sources, except for the very early decades when natural

variability is being considered (see Figure 3 in Knutti et al., 2008).

For the envelopes from the first three assessments, although they cite the same sources as the predecessor Second Draft Figure 1.4, the earlier projections have been shifted downwards relative to observations, so that the observations are now within the earlier projection envelopes. You can see this relatively clearly with the Second Assessment Report envelope: compare the two versions. At present, I have no idea how they purport to justify this.

None of this portion of the IPCC assessment is drawn from peer-reviewed material. Nor is it consistent with the documents sent to external reviewers.



