Richard North, 11/01/2022  

I've spent a good deal of my professional life taking temperatures – mostly with hand-held electronic devices, fitted with a variety of probes - measuring a variety of foods, equipment and internal environments. Even at this level, without factoring in instrument error, I know how difficult it is to achieve accurate and consistent results.

When it comes to measuring the temperature of the planet, therefore, it takes little imagination to appreciate how the difficulties must multiply, more so when one is trying to construct an historic record spanning not just decades but centuries.

However, given the importance of the planetary temperature and the historic record – in terms of it setting the parameters for so much public policy – knowing how the measurements are taken is of more than idle interest. And I see no reason to take published figures on trust, any more so than one accepts any official pronouncements.

Being good little Muppets, though, we are not supposed to ask awkward questions. Our role is, unquestioningly, to imbibe the wisdom of our masters and betters. After all, the "science is settled" so there is no need to question anything. Our role is simply to believe what we are told.

In that context, we now have handed down to us the latest ex cathedra pronouncements from the magisterium of the state broadcaster, which proudly instructs us that: "The past seven years have been the hottest on record, according to new data from the EU's satellite system".

This has been relayed by the dutiful Guardian, with a similar headline, prefaced by the obligatory "Climate crisis" descriptor.

So far, few other legacy media organisations have retailed the report, although Sky News is on the case with: "Last seven years were warmest on record 'by a clear margin', say EU scientists".

Evidently seeking to outdo the BBC, it also tells us, "The latest data from the European Union's Copernicus service shows 'signs of another nail in the planetary coffin'", not forgetting to add its standards link: "Why you can trust Sky News".

It's too much to expect much technical detail from popular media reports, and all we get from the BBC is that: "the Copernicus data comes (sic) from a constellation of Sentinel satellites that monitor the Earth from orbit, as well as measurements taken at ground level.

This is just as well we are told this, as the "record" goes back to 1850 and, unless readers know different, the EU wasn't around in 1850. As for the satellite systems, the EU relies for its temperature data on the Sentinel-3, with the first launch on 25 February 2016.

As far as I can ascertain, though (following the trail is not easy), the Sentinel-2 series is optimised for sea temperature measurements. This constellation is thus due to be augmented by the Sentinel-8 system, which will be optimised for land-surface temperature measurements. The projected launch date for this system is not until 2029.

In the interim, it seems that land surface temperature (LST) are estimated from Top-of-Atmosphere brightness temperatures, derived from infrared spectral channels using the Meteosat Second Generation, GOES and MTSAT/Himawari constellations of geostationary satellites.

Nevertheless, regardless of the satellite systems used, it stands to reason that the EU's data set is relatively recent (and incomplete) which no doubt explains why the record must be supplemented by measurements taken at ground level – lots of them.

Since we're not supposed to ask questions – much less awkward questions – we should not even be thinking about comparability issues. Thus, it must be a matter of supreme irrelevance that satellites measure surface temperatures, while the ground stations measure air temperatures.

There have been many studies – such as this, pointing out the differences. In summary, not only are the two influences by different factors, but ground temperatures tend to be more extreme than their air temperature equivalents.

The satellite data – as ESA admits - are also subject to their own specific limitations, which affect the accuracy.

According to the space agency, the accuracy of Sentinel data is limited to 1ºK. The best performance is at night when differential surface heating is absent". The data from top-of-the-atmosphere proxies are likely to be even less accurate, although I have no specifics on this.

Now, if one was encouraged to ask questions, one might look closely at the statement made by Mauro Facchini, the head of Earth observation for the European Commission. As retailed by the Guardian, he says: "The 2021 analysis is a reminder of the continued increase in global temperatures and the urgent necessity to act", with the Copernicus data showing 21 of the 22 hottest years having come since the year 2000.

Firstly, one might ask how Copernicus can reach back to the year 2000, to provide useable temperature data, and how it can be compared with historic data which are collected on a completely different basis, with different biases and errors.

Most of all, though, if one was allowed the luxury of open questioning, one might ask how it is that we are being told that the global temperature is 1.2ºC above pre-industrial levels, when the accuracy of the system is probably limited to whole figures.

Of course, if the science wasn't so settled, and anyone asking questions wasn't immediately dismissed as a "denier", then I am sure we could ask our masters and better to reach down and explain the details to us mere mortals. And, doubtless, there is a very simple answer, which our gifted climate scientists could provide.

As it is, they seem to be struggling to convince us that, with the claim that 2021 ranks as only the fifth hottest year on record, we still have a climate "emergency".

For this, we have the BBC's Justin Rowlatt, proudly described as their "climate editor" – although I bet he doesn't actually edit the climate. If he could, perhaps we wouldn't have to cut our emissions, and could abandon "net zero".

Rowlatt tells us "it would be easy to dismiss the latest global temperature figure as a non-event", but these annual temperature updates, he says, measure out the pace of change in our world. "The increments may be tiny", he adds, "a fraction of a degree", but the direction of travel is inescapable.

And therein lies the problem. It is hard enough accepting that it is even possible to measure the global temperature, or that representing the planetary temperature by a single annual figure has any meaning – especially when the Guardian now talks about heating.

But, when Rowlatt talks so glibly of fractions of a degree, someone needs to explain to us mere plebs how it is that a system which has so many inbuilt errors and biases, that one is even able to speak reliably in terms of single degrees, much less than fractions of a degree.

However, as long as the science is "settled", this is something that quite obviously we don't need to know. It's getting hotter, even when it's getting cooler. That's all we need to know.

Also published on Turbulent Times.

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