When I was a postgraduate researcher at the Jodrell Bank Radio Observatory I was given advice by Professor Sir Bernard Lovell that has stayed with me ever since. One evening we unrolled the pen recorder data in a long ribbon down the corridor outside the main observing room. “Now,” he said, “look at the data. Get to know it.” His point was that before us was what the universe was saying, and that it was more important than any theory.” Data is never inconvenient. It beats theory every time.
I met another kind of scientist earlier this year. He had won many awards for his contributions to climate science, and he introduced himself as a “scientist, which means my main interest is in modeling.” I let the, what I thought contentious statement, pass, as our subsequent discussion made me realise, as if I needed reminding, that awards are not always an indicator of knowledge.
Those two approaches to science are in my mind as I look at the latest predictions for the global temperature over the next few months.
2011 is bound to be a relatively cold year, probably outside the top ten warmest years (all in the past decade) in the instrumental record (post-1880.) To some this data has to be fitted into the hypothesis that the world is getting ever warmer. You would have thought that interpreting a temperature reading lower than previous years would have been straightforward. But no.
You will recall what some said about 2010 which was relatively warm though not statistically significantly warmer than any other year of the past decade. Some said it was ‘proof’ that global warming was continuing. Well, if a relatively warm year is proof of the continuation of global warming, then expect a relatively cool year to be…err…also considered proof that global warming continues.
The Washington Post article says, “The fact that this year is currently running cooler than last year does not in any way invalidate the fact that the world is warming, and that this warming is very likely due mostly to manmade greenhouse gas emissions.”
This is a sleight of hand with the English language. The plain logic is that whilst we live in the warmest decade, it has not been “warming” for over a decade. Therefore the statement made by the Washington Post is untrue. It comes from the same kind of logic that states that global warming increases the incidence of extreme events, but it is impossible to attribute an individual extreme event to global warming. The logic of such a statement, seen in many places, is nonsense. An extreme event is an extreme event, did it happen because of global warming or not? If not then more of them does not reverse the conclusion.
So we have two approaches to the temperature of 2011 and they couldn’t be more different. One says there has been no warming, the other that warming continues unabated!
One should of course look at these things over a longer timescale.In decadal terms the 80’s were warmer than the 70’s, the 90’s warmer than the 80’s and the past decade the warmest of all.
But look at the data a little more carefully.
Up, Down Or Stable?
The thing that is striking about global temperature data in most datasets is that there is not much gradient. By this I mean that its main feature is long periods where no increase is evident. What seems to change is the decadal baseline. Given the error bars one would be hard-pressed to say that there had been a temperature increase between 1980 – 1995. The super El Nino of 1998 is obvious, but after it (after the subsequent la Nina died down) the temperature remained stable. Transition between one plateau and another is one way to look at the annual average global temperature dataset. Bear in mind that I am not talking about any hypothesis or theory here, just describing the data.
Click on image to enlarge.
[Notes on Fig 1, taken from Dr Roy Spencer’s website. In the section prior to 1997 there are two dips, around 1984 and 1993, due to the El Chichon and Pinatubo volcanoes. Other than that there is no upward trend from 1979 -97 that is statistically significant. Note the period 2002 – 2011 also shows no change bearing in mind the large la Nina and El Nino fluctuations in the later part of this period.]
The obvious question is; what was the effect of the 1998 super El Nino? Did it mask a linear rise in temperature, or did it signify a change from one plateau to another?
Prediction of the course of the current la Nina suggests that it will increase in intensity in the next six months, so it will probably depress the temperature of 2012 as well. I wonder if this strong la Nina might presage another baseline change in global temperature at a level below that of the last decade.
If this is so, and I am only thinking out loud, then it would be hard to reconcile this with current thinking about continuing global warming. recall that for many years after it became obvious in the data that the temperature in the past decade was unchanging, many groups, scientists among them, refused to accept it as a reality. then when the inconvenient data would not go away we saw more theories advanced to account for the standstill than you can shale a stick at!
Under the current hypothesis the annual average global temperature must start increasing. One can invoke natural decade cycles to hold it back for so long, but they must eventually give way to greenhouse gas forcing. Eventually the temperature must increase at a faster rate than it would have done to make up for its temporary suppression.
The problem is, of course, the data. We are at the stage where theory is becoming unable to explain what is going on. We have had no global temperature increase since the 1998 super El Nino, and now have the prospect of 2011 and 2012 being significantly cooler than the temperature plateau of the past decade.
So what kind of scientist are you? Do you look at data in terms of what it is, or through the prism of models and expectation?
Look at the data and think without prejudice. What do you think will happen? Perhaps the temperature will go up. Perhaps it might stay the same…but if it goes down significantly…