Lies, damned lies, and CET

I borrowed my title of course from the great Mark Twain and gave it a twist that only a blogger trying to attract new readers can come up with. But it’s basically true, you can look at any set of data and view it in such a light statically, that you can use it to prove that global warming is a reality even in Central England, or the complete opposite and prove that we are entering a new ice age. I’ve been playing around CET ever since I copied the entire monthly catalog into a program that I had written for my BBC B Computer in 1983, and I reckon one of the best ways of visualising it is by means of a 365 day centred moving average (in red), and just to reinforce that and smooth it a little I add a 14 day moving average on top of that (thick black line). I havent the faintest idea of what that’s called in statistical parlance, probably bollocks, but I like it nonetheless. So here are a few graphs to illustrate just what I’m talking about.

The no axe to grind graph

As you can see this graph (fig 1) shows the entire daily CET series since 1878. I could have extended it back to 1772, but it does get a little cramped in the x-axis department. To save any debate about what long-term average to use, I decided to generate one for the entire 1878-2015 period. Over those graphs I’ve added a simple linear trend for the whole series. The warming trend is a very modest +0.09°C per decade, a value that even our most skeptical reader shouldnt balk at.

Figure 1

The skeptics graph

Let’s use the comparatively cold 1961-1990 long-term average for the skeptics graph (fig 2), and restrict the x-axis to show only the last 20 years, which of course changes the linear trend to show a negative anomaly of -0.20°C per decade, but there’s still an awful lot of red that gives the impression that the CET series is warming.

Figure 2

But if we chose another long-term average, say for the years 1986-2015, you’ll notice (fig 3) that things get a lot bluer, even though the linear trend is showing exactly the same -0.20°C per decade cooling it just looks like there is very little going on. Wonderful, at this rate there’ll be frost fairs on the Thames gain within 50 or 60 years.

Figure 3

The true believers graph

To get the most out of the data we’ll use the 1986-2015 long-term, and using the same data restrict the x-axis to show only the recent years since 2010, which of course changes the linear trend again, and we now have a massive warming trend of +1.61°C per decade – lovely we’re now out doing GISS.

Figure 4

Personally I like the first graph. It makes best use of the maximum amount of ‘accurate’ CET data that we have. Things are warming, you don’t need a linear trend to show you that, and in the last 30 years or so that warming looks quite pronounced. I think the above graphs should please most people, be they skeptics, believers, or those just like me, sitting on the fence in the firm belief that climate is always changing just like the CET series.

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About xmetman

I am an exmetman who is passionate about all things to do with weather and climate. I have no axe to grind, and am continually upsetting people on both sides of the global warming debate with the articles that I publish, hell, I'm even banned from commenting on the Met Office's own blog! What I do fight for is the freeing up of climate, observational and forecast data collected and created on our behalf by the Meteorological Office.
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