The Divergence Problem

The damp squib which is the Summary Report for Policymakers (SOP) for the IPCC’s AR5 has arrived, been torn apart by the sceptics and lauded by the warmists. Mainstream media noted the arrival, parroted the general idea that humans are to blame (for what exactly is unclear) and, judging from today’s papers and sites, moved on. Climate alarmism is no longer of any great interest to the public and the coverage accorded to the SOP illustrates this.

Yet the SOP is important because, unless I miss my bet, when the full report is released on Monday, the entirely political nature of the IPCC enterprise will be starkly revealed. Plus, the IPCC itself has walked back in two critical areas.

The SOP itself is interesting simply because it reflects what green bureaucrats don’t want to discuss about the science. Which is not the same thing as saying the science does not exist; it almost certainly does and that science will be in the full report.

First up: sensitivity. The sensitivity of temperature to CO2 is a, indeed, the critical question at the intersection of climate science and policy. But in the SOP no actual sensitivity estimate was given.

The implication of this footnote is that sensitivity estimates are uncertain. Assuming for the moment that the full report supports the footnote’s conclusion, the key is going to be to examine what actual science that report discusses and why there is such uncertainty.

As I wrote yesterday, without a sensitivity estimate the SOP and the full report are effectively useless for policy purposes. Why would a politician take any measure – sure to be expensive – to reduce CO2 emissions without having at least some idea of what effect such reduction would have on temperature?

It is not as if the IPCC is unaware of this political fact, so why no sensitivity estimate? My own speculation is that the science will suggest that the sensitivity is at the low to extremely low end of the scale. 2 degrees Celsius or below per doubling of CO2. From an alarmist perspective this would be very bad news because it renders attempts to reduce emissions either pointless or cost ineffective. Speculatively, it was better to suppress the science rather than give the IPCC imprimatur to a relatively benign number.

Model failure: A fair amount of ink was spilt in the SOP trying to explain, contextualize, or dismiss the “pause” in global temperature. The SOP invoked faulty end points, ocean hidden heat and a newly discovered 30 year rule for climatic trends to discount the importance of the pause. What the SOP did not do is notice the real importance of the pause.

From the warmist’s perspective the pause is an inconvenient climate fact that nasty deniers are, wrongly, using to suggest global warming is over. While some sceptics have taken that position, most see the pause in quite another light: the pause invalidates the models which failed to predict it.

Whether or not a 17 year pause means global warming is over is not, in my view, a useful question. All the pause is is data. In itself it proves very little about climate save that Nature is complicated.

However, a 17 year period of temperatures and CO2 rise which none of the models predicted is very strong evidence that the models are wrong.

Their excuse for the absence of warming over the past 17 years is that the heat is hiding in the deep ocean. However, this is simply an admission that the models fail to simulate the exchanges of heat between the surface layers and the deeper oceans. However, it is this heat transport that plays a major role in natural internal variability of climate, and the IPCC assertions that observed warming can be attributed to man depend crucially on their assertion that these models accurately simulate natural internal variability. Thus, they now, somewhat obscurely, admit that their crucial assumption was totally unjustified. Dr. Richard Lindzen

The discussion of models in the full report should be illuminating. Politically, there is a great deal of investment in model based climate science. Similarily, the mainstream media has been running model based stories of the form “According to a model of sea level rise Victoria will be under three feet of water in 2100” without, for a second, questioning if the models are valid. Now the IPCC has, in trying to explain the pause, admitted the models are fundamentally wrong.

For many years sceptics have been routinely dismissed because their positions contradict the consensus position of the IPCC. Now, on two fronts – sensitivity and climate models – the sceptic position that we simply do not have science strong enough to use for policy purposes has been vindicated by the IPCC. These are not issues at the margins, they go to the heart of the alarmist position.

The next time a Greenie says “We have to cut CO2 emissions or face _________.” a sceptic can and should say, “That is not what the IPCC says. It says we don’t know what effect cutting CO2 emissions will have.” And the next time a lazy journalist writes a “Models say…” story the sceptic can respond “The IPCC says the models don’t get nature right. The models are wrong.”

No doubt this is not what the IPCC intended; but the fact is that the shaky foundations of a relatively new science could not support the policy weight they have been asked to bear. The gradual collapse of the IPCC edifice comes as no surprise.

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