Friday, 11 December 2015

Did Climate Change (TM) Cause the UK Floods? [Pt. 2]

Here we go again. Another wet UK winter, another round of attempts by politicians and activist scientists to capitalise upon winter flooding to advance their global warming agenda - in the case of politicians, to justify their need to impose swingeing taxation upon homes and businesses in the pursuit of a low carbon economy. First off the blocks, Dame Julia Slingo of the Met Office who last time (Somerset flooding in winter 2013/14) said "all the evidence points to a link with climate change". This time, a little more caution, or should I say, a greater use of weasly words which allow for more wriggle room but which still manage to convey intact the essential message that global warming is wrecking our weather:
"It’s too early to say definitively whether climate change has made a contribution to the exceptional rainfall. . . . . However, just as with the stormy winter of two years ago, all the evidence from fundamental physics, and our understanding of our weather systems, suggests there may be a link between climate change and record-breaking winter rainfall. Last month, we published a paper showing that for the same weather pattern, an extended period of extreme UK winter rainfall is now seven times more likely than in a world without human emissions of greenhouse gases."
Cue Liz Truss, our Environment Secretary un-extraordinaire, who then joined the party by claiming that the pattern of winter flooding was what could be expected due to climate change. The Times Environment Editor Ben Webster begged to differ, as did Christopher Booker, among others. The point is, what caused the floods was our weather, and what drives our weather during such wet winter periods is depressions crossing/forming in the Atlantic, guided by the Jet Stream. To glibly state that 'fundamental physics' suggests there may be a link between heavy rainfall in winter and global warming is ridiculous; it's just more global warming propaganda from the Met Office Chief Scientist. There are a huge variety of factors at play in determining the weather of the British Isles and the changing patterns of that weather and if you want to get to the root of what may be the emergence of a new pattern, you have to examine those factors in detail.
What is virtually certain is that neither the Somerset flooding nor this year's Cumbrian floods are in any way 'unprecedented'. They are notable, they are unusual in the context of 'recent' weather; taken in combination with just two years separating them, they may even be suggestive of a change in the pattern of winter weather over the British Isles, be it temporary or more long term. Certainly, the rain which Storm Desmond dumped on Yorkshire, causing the waterfall over Malham Cove to flow for the first time in what may be hundreds of years, is a precipitation event worthy of note. But of course, what this means is that, long before cars, buses, planes and trains - and coal-fired power stations - were emitting vast amounts of fossil fuel CO2 into the atmosphere, it was raining just as heavily oop north as it is now. And England was probably cooler on average then, if the Central England temperature record is anything to go by. Which brings me to an interesting post by Paul Homewood.
We see from this that Lamb identified a period of increased storminess and elevated precipitation in Northern Europe at the close of the Medieval Warm Period and the beginning of the Little Ice Age. Indeed, Paul Homewood has another enlightening post which points to increased storminess actually during the Little Ice Age. It would appear to be the case that an enhanced temperature difference between mid-latitude air and much colder Arctic air during the LIA was the engine that energised sections of the Jet Stream causing more storms over the British Isles, in combination perhaps with a more southerly tracking (meridional - 'looping' as opposed to zonal - more straight) Jet Stream at that time. This is exactly the type of pattern that appears to be happening now and, in addition to causing very wet, mild, stormy winters, has also given us a notably very cold winter during 2009/10, the 2nd coldest December since 1659 in 2010 and the very cold Spring of 2013. So over the last 6 years, it hasn't all been wet and mild as far as winters go.
England has been cooling on average since about 2005 according to the CET record. The record warm year of 2014 has reversed that trend a little, but not erased it and even with the warm winter we have so far had, 2015 is looking unremarkable. Meanwhile, despite a very strong El Nino, the Pause in global warming continues at least in the two satellite datasets, the Arctic this winter continues to gain ice at a record rate, whilst Greenland remains decidedly frigid and the North Atlantic 'cold blob' actually grows. Growing Arctic sea ice and a colder Atlantic are indicative of the slowing in AMOC [Atlantic Meridional Overturning Circulation] and the downturn in AMO [Atlantic Multidecadal Oscillation], having recently peaked. These two major oceanic/climate indices, of course, are intimately linked.
With solar activity predicted to decline further in SC25, it is entirely feasible that the Northern Hemisphere at least may see a period of sustained cooling, especially if, as seems increasingly more probable, the actual transient climate response to CO2 is less than that which emerges from the climate model runs of CMIP5. With all this in mind, I am persuaded towards the heretical viewpoint that the climate of the British Isles is changing, but not because of CO2; rather, we are headed for a cooler, more turbulent period due to natural variability - entirely in keeping with past variations in the British climate. Who knows, by 2100 we may be growing grapes on Tyneside, but I personally doubt that!