IPCC AR5 Chapter 11 – Maintaining the Spin

Guest post by David M. Hoffer

In my first article on the leaked AR5 Chapter 11 draft, I focused on the extraordinary lengths to which the IPCC has gone to surround their projections with caveats that make it nearly impossible for any of them to be outright wrong. But what of the alarmist narrative? I am sad to report that it is alive and breathing. On the other hand, it appears to be on life support. I chose two examples to bring to everyone’s attention. One because I think it is amusing, and the other because it is a whopper that I doubt will survive to the final draft.

The amusing one relates to ice extent. The models are still projecting reduced ice extent for both the Arctic and Antarctic. For those of us who’ve been following that story line, that’s another indication that the models are deeply flawed. While ice extent in the arctic is down, the Antarctic extent has been setting new records. So how does AR5 Ch11 handle this contradiction?

In early 21st century simulations, Antarctic sea ice cover is projected to decrease more slowly than in the Arctic in the CMIP5 models, though CMIP3 and CMIP5 models simulate recent decreases in Antarctic sea ice extent compared to slight increases in the observations (Chapter 12, Section 12.4.6.1 and Figure 12.31).

Excuse me? Slight increases? When Hank Aaron hit his 715^th home run, putting him ahead of Babe Ruth by just one, I don’t recall anyone calling it a “slight increase”. I remember “record setting” and “history making” and “unprecedented”. Interesting way to spin an extreme event, is it not? But having minimized the record ice extent in the Antarctic by characterizing it as a “slight increase” they just can’t help but throw some alarmist narrative in as well:

Periods of rapid summer-time retreat of the Arctic sea ice margin, such as that which occurred in the late 2000s (see Chapter 4) has been noted to occur in a climate model, raising the possibility of abrupt sea ice retreat events sometime in the next 50 years (Holland et al., 2006).

Oooooh, I’m scared. They’ve got dozens of models that they’ve run thousands of times with all kinds of different initial conditions. They barely agree with each other, they don’t agree with observations on any number of fronts, there’s many pages of excuses in Chapter 11 as to why…. But they have “a model”, yes, just one, that raises the possibility of some sort of “abrupt” event. One gets the impression they wiggled that one in just so it could be quoted completely out of context in the Summary for Policy Makers.

Now for the WHOPPER!

For years we’ve been subjected to horror stories of increased numbers of major storms like hurricanes, and increased intensity as well. More and worse, all due to global warming. But basic physics suggests that a warmer world should be a more tranquil world, and the observational data agrees. Ryan Mau has had several articles on this site showing that over the last 20 years, tropical cyclones have become less frequent and less intense, the exact opposite of the alarmist narrative. In the face of overwhelming evidence, it would have been embarrassing for the IPCC to not take a step back from their position. They did. In the executive summary of Chapter 11, it says:

We have low confidence that over the next few decades there will be global and regional increases in the intensity of the strongest TCs, and the decrease in global TC frequency as is projected for the end of the 21st century in response to increasing greenhouse gases (Chapter 14).

Well that statement is a bit ambiguous, is it not? It seems to imply that tropical cyclones will be about the same, or maybe a little bit worse, a bit less frequent, not a big enough change for them to make any statements with any degree of certainty. I first read it as a climb down from the frantic alarmism of the past few years on this topic.

That statement is, by omission, is a WHOPPER!

We already know from experience with AR4 that what the science says, what the AR4 report says, and what the Summary for Policy Makers says are three rather different things. We’ve got a healthy serving of the same strategy in this case. Read the statement from the Chapter 11 Executive Summary above again, and then see what they buried in the body of the report itself:

Two recent reports, the SREX (IPCC, 2012; particularly Seneviratne et al., 2012) assessment and a WMO Expert Team report on tropical cyclones and climate change (Knutson et al., 2010) indicate the response of global tropical cyclone frequency to projected radiative forcing changes is likely to be either no change or a decrease of up to a third by the end of the 21st century.

Ooops! So the science says nothing about intensity, but on frequency, somewhere between no change and a one third decrease. One would think that a projection of up to a one third decrease in tropical cyclone frequency would be important enough to make it into the Executive Summary?

Well, if record setting ice extent in the Antarctic is just a “slight increase”, I guess by extension that a one third decrease in tropical cyclones is equally un-noteworthy.

Chapter 11 can be downloaded here (PDF)