Why Did The Met Office Predict A Dry Winter?
“All the evidence suggests there is a link to climate change”, says Julia Slingo. There is a slight problem though – the Met Office report she quotes , “The Recent Storms and Floods in the UK”, says no such thing at all.
What it does say is that recent weather events are linked to “major perturbations to the Pacific and North Atlantic jet streams driven, in part, by persistent rainfall over Indonesia and the tropical West Pacific.”
The report speculates that this may all be connected to warmer waters in the Tropical West Pacific, without explaining what has, in turn, caused this.
I will leave this matter in the capable hands others, but the report itself concludes “In terms of the storms and floods of winter 2013/2014, it is not possible, yet, to give a definitive answer on whether climate change has been a contributor or not”
I would, though, leave the question – as these waters have been warmer for the last decade, a fact the report acknowledges, why have we not seen this particular jet stream phenomenon before?
(In passing, it is worth noting that there is no attempt to blame “melting Arctic ice”. Does this mean that theory is now in the garbage can?)
But what I am more interested in, as far as this post is concerned, is the question of how unusual this winter’s weather has been. The report points to how wet it has been in the last two months, but as even Slingo herself admits, it has not been unprecedented.
According to Met Office data, there have been eight other 2-month periods in England, which have been wetter since 1910, than the last two months total of 274mm. (The different England & Wales dataset, which dates to 1766, also shows that there were five years, prior to 1910, that also had higher 2-month totals : 1771, 1811, 1822, 1852 and 1877).
|Oct – Nov|
|Nov – Dec|
|Dec – Jan|
Note also that in 1914/15, 1929/30 and 2000/01, the high levels of rainfall extended over three months, not just two.
We sometimes get hung up about measuring rainfall in “seasonal blocks”, such as December to February. The reality, in the UK at least, is that the wettest months of the year are October through January. It seems logical, therefore, to use these four months when looking at trends, etc.
Over this full four month period, by far the wettest year was 1929/30. This latest period ranks only fourth, certainly exceptionally wet, but hardly “biblical”, as David Cameron has described it.
Equally relevant is the fact that the 10-year trend is, if anything, lower than much of the first half of the 20thC, and shows no sign of increasing. (Although, it is higher than the relatively dry interlude of the 1960’s and 70’s). If global warming really was leading to wetter winters, why have we not seen any sign of this yet?
The report also addresses the issue of storms, but accepts that this winter has been no stormier than 1993. (It certainly would not compare, either, with 1991, the year of the Burns Day Storm, the first of 12 severe gales to hit the country in the space of 6 weeks).
It is also worth noting that the UK Climate Projections Report , issued in 2012, finds that:
Severe windstorms around the UK have become more frequent in the past few decades, although not above that seen in the 1920s.
Whereas it is not our purpose here to discuss detailed links between the NAO and storminess, it will be immediately apparent that the two stormiest periods in Figure 1.14, in the 1920s and 1990s, coincide with decades of sustained positive NAO index, whereas the least stormy decade, the 1960s, is a time when the smoothed NAO index was most negative.
There continues to be little evidence that the recent increase in storminess over the UK is related to man-made climate change.
It is all very well for the Met Office to claim that they know the reason for the recent wet and stormy weather, but it is clear they knew no such thing last November, when they forecast the likely probability of a dry winter. Certainly, the factors in the Pacific, that they now blame, were in play at the time. (If they were not, then they are just “weather”, and cannot be claimed to be linked to “climate change”).
None of this gives us much confidence in the Met Office’s ability to forecast more than a few days out. But it must surely also cast doubt on the worth of the latest report, which seems to be a rushed attempt to explain recent bad weather.