we are unable to demonstrate a statistically significant change in surface temperatures because of the difficulty in defining a statistical model that would describe the normal behaviour of surface temperatures
This seems to be based on work by someone called Doug Keenan, who argues that the Met Office admits that claims of significant temperature rise is untenable. Doug Keenan argues that significance means that the temperature rise could not be reasonably attributed to natural random variation. He then seems to argue that significance can only be determined using a statistical model. Furthermore, he suggests that there is a statistical model (driftless ARIMA(3,1,0)) that would allow us to conclude that the surface temperature could indeed be simply some random natural variation. Furthermore, he suggests that the Met Office have admitted that their statistical model is inadequate.
Well, here is the Met Office’s response and I don’t think it is quite saying what Doug Keenan or Andrew Montford are claiming. I also don’t think it’s all that complicated, so I don’t see why someone with a science degree and who runs a science blog, can’t get this. Essentially – as I understand it – the Met Office’s statistical models is indeed, in some sense, inadequate. This, however, does not mean that there is a statistical model that is adequate. It means that there are no statistical models that are adequate.
Why is this? Well, statistical models are used to determine the properties of a dataset. For example: what is the trend?, what is the uncertainty on the trend? However, they cannot – by themselves – tell you why a dataset has those properties. For that you need to use the appropriate physics or chemistry. So, for the surface temperature dataset, we can ask the question are the temperatures higher today then they were in 1880? The answer, using a statistical model, is yes. However, if we want an answer to the question why are the temperatures higher today than they were in 1880, then there is no statistical model that – alone – can answer this question. You need to consider the physical processes that could drive this warming. The answer is that a dominant factor is anthropogenic forcings that are due to increased atmospheric greenhouse gas concentrations; a direct consequence of our own emissions.
So, Andrew, I really do think you can get this. It’s not that tricky. I appreciate that it may be embarrassing to have to admit that you’ve misunderstood something so simple. The alternative, however, is that some may think that you’re explicitly trying to mislead people, and that – I assume – is not your intent. Of course, in the interest of true skepticism, I’m happy to be convinced that I’m wrong or have misunderstood something.