David Whitehouse: Don’t Mention The ‘Pause’
The press conference associated with the release of the AR5 Summary for Policymakers was notable by the elephant in the room – the lack of warming the surface of the world has experienced over the past 16 years. Many observers have called this fact ‘the greatest problem in climate science,’ and it certainly is its most discussed aspect these days. However, nobody on the IPCC panel wanted to say anything about it. When they did, reluctantly, they were evasive, and inaccurate.
Although the panel, aided by the moderator, dealt with other things, the press conference was really all about the ‘pause,’ and trying not to say anything about it or take any questions on it. When it was unavoidable Prof Thomas Stocker put down the hiatus as a statistical illusion related to cherry picking a particular start date which he said was 1998. Different start dates tell a very different picture he added. Those who have taken any interest in the growing discussion of the standstill in global surface temperatures are well aware of the 1998 problem. This was the date of a very powerful El Nino, and subsequent temperatures have not exceeded it. That is why almost nobody, except uninformed critics, ever use this as a start date.
Prof Stocker seemed to think that the ‘pause’ depended upon what dates were chosen for it’s start and end. Actually it doesn’t. It’s more statistically sophisticated than that. All one needs to do is to start at the most recent annual datapoint – 2012 – and work backwards to find the earliest date when there is no statistically significant warming. Let the data make the choice, not humans. This way one arrives at January 1997.
The key point is that the strong 1998 El Nino is statistically counteracted by two La Nina years in 1999 and 2000. Taking data from 2001 gets over this problem, even though there are several El Nino’s and La Nina’s since then, and it is also flat.
This is why no one with any knowledge of the data would ever start looking for a trend starting with the La Nina years of 1999 and 2000. But on the IPCC’s press panel the WMO’s Secretary General Michel Jarraud told reporters that if you start the data in 1999 you get a positive trend! This really is rather poor knowledge of the global surface temperature data or a deliberate misrepresentation of it to what, with some strong exceptions, was a rather scientifically unsophisticated audience.
At the start of the press conference Prof Stocker showed average decadal temperatures showing that the 2000s was warmer than the 1990s which was warmer than the 1980s. As we have said before decadal binning the data is only one way to look at the data and just looking at the data like this is an example of cherry picking. Looked at another way, with say 5-year data bins reveals a very different story. Indeed one that highlights the importance of the past 15-years unchanging surface temperature.
The Ocean Hypothesis
Prof Stocker and Rajendra Pachauri mentioned that one of the reasons for the ‘pause’ could be the heat going into the oceans. Prof Stocker initially admitted that the data for this was not very good. Curious that later on in the press conference such qualifications as to the quality of the ocean heat data was glossed over.
One of the most interesting stories of the week which will undoubtedly be told is how the ‘pause’ was all over the draft summary but almost completely excised from the final summary. For some this automatically relegated the importance of the ‘pause’ allowing it to be dismissed as irrelevant. Actually, it was treated this way for exactly the opposite conclusion.
David Rose of the Mail on Sunday newspaper, who has written much about the ‘pause,’ must have had a frustrating start to the press conference. Clearly wanting to ask a question he was obviously ignored by the moderator until the moderator pointed to another journalist sitting next to him. At this point David grabbed the microphone much to the moderator’s dismay.
David asked a simple question. How many more years will the ‘pause’ have to go on for until the climate models are questioned? Prof Stocker evaded the question, saying that no warming in 30 years time was not an IPCC predicted outcome!
Finally Prof Stocker said that the ‘pause’ in global surface temperatures was relatively new science. He clearly hasn’t been reading the substantial discussion of this hot topic in the peer-reviewed scientific literature over the past 5 years.
The real story of the IPCC’s summary for policy makers is not the upgrading of scientific confidence from 90% to 95% – whatever that really means – but the attempt at burying the ‘pause.’ It won’t matter in the long run because the IPCC hierarchy, just like many climate scientists, know that if the ‘pause’ continues for a few more years then everything will change.
As scientists Profs Stocker and Jarraud should have had a better grasp of the global temperature data. It is surely at the heart of the climate change debate and should not be treated in such a hand waving manner. Despite what the IPCC said at the end of a week-long process to distil the science and communicate it simply, the ‘pause’ is still the biggest problem in climate science. Overall, for a press conference about the science of climate change, those scientists answering the questions behaved like politicians, and slippery ones at that.