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Friday 17 May 2013

Why It’s Called Global Warming

We get the same kind of response from the climate change denial lobby, whichever side of the North Atlantic they operate on: Sean Hannity of Fox News Channel (fair and balanced my arse) telling “It snowed in Houston ... there’s no global warming”, or Christopher Booker telling his faithful Telegraph readers “I woke yesterday to find six inches of global warming on my lawn”.

Laugh? I thought I’d never start. But that misses the point, as does this week’s sudden shock horror to find that it’s possible to see snow in May (clearly there are a lot of folks too young to remember 1979). It may have been much cooler than usual for mid-May this week, but global temperature averages are exactly what it says on the tin: it isn’t just about one location in the UK or USA.

To illustrate this point in as straightforward a way as possible, let’s look at current temperatures for London: these are lower than average for mid-May, with a high today of just 13 Celsius and a low tonight of 9. This compares with the average high of 17.7, and low of 8.4 degrees. But, as I’ve already told, it is not just about one location, and to show this, let’s look further east.

I’ve taken three examples, the first being the Polish capital of Warsaw. Average high and low temperatures for mid-May are 19.4 and 8.6 degrees. Now look at today’s forecast from the BBC: this shows an expected high of 26 degrees, and a low of 17. That’s significantly above the average, and a rather larger positive variation than the negative one for London.

Let’s take another example from eastern Europe, the Ukranian capital city of Kiev, which lies on approximately the same latitude as Plymouth, although its winters are far more harsh. Average high and low temperatures for mid-May are 20.7 and 10.8 degrees. Moving right along to today’s forecast, this shows rather different high and low of 28 and 16 degrees respectively.

Again, the variation is significant, and the higher than average temperatures extend over a wide area: consider the Russian capital of Moscow. Average high and low temperatures for mid-May are 18.6 and 10.7 degrees respectively. The forecast for today predicts rather higher values of 29 and 16. It looks hot and probably humid, with the odd shower, for Muscovites today.

Yes, temperatures may be lower than average across the UK, but that does not give the global picture. The problem with taking average temperatures for one location is that global temperature only averages out across the whole of the globe, and so that kind of approach is meaningless – unless everywhere else is showing a similar effect or trend. And that ends today’s meteorology lesson.

What you will not read in far too many papers over the next few days.

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