Wednesday, 30 December 2015

More on the 'Unprecedented' Rainfall Causing UK Floooding

In response to me linking to my latest blog post on Twitter, BBC weatherman and meteorologist Simon King pointed me to this graph of UK annual rainfall  since 1910 which shows a significant increase in trend since 1980 - a point which he made when being interviewed on BBC FiveLive apparently.
uk
Aside from the fact that the UK series is very much shorter than the EWP which goes back to 1766, there is indeed a marked positive trend in UK annual rainfall, starting around 1973, and exceeding that of 1910. Here is the corresponding graph for England:
england
And for Wales:
wales
Though the same trend exists, it is not very pronounced. It is more pronounced for Northern Ireland:
northern_ireland
It is a lot more pronounced for Scotland:
scotland
Thus, it would appear that the overall increase in annual UK precipitation from 1973 is due in large measure to an increase in rainfall in Scotland, with a lesser contribution from Northern Ireland and only very minor contributions from England and Wales.
Cumbria, Lancashire and Yorkshire are of course in England and the Environment Agency is of course responsible only for flood defences in England. So pointing out that rainfall in the UK has increased significantly, when much of that increase has been in Scotland and Northern Ireland, is not that relevant, particularly when the flooding in England has provoked sharp criticism of England's freshwater flood preparedness measures as managed (badly, it seems) by the Environment Agency. It is even more irrelevant in that even the UK annual rainfall data shows there has been no really significant increase in Winter precipitation since 1910, the issue at present being winter rainfall causing flooding.
uk1
2014 again stands out but there is very little overall increase in trend since 1910. Given the fact that winter 2015/16 still has 2 more months to go, it may or may not turn out out to be a particularly wet winter overall.
The lesson here (if there is one) is, don't listen to BBC Radio FiveLive if you want all the facts about current severe flooding and what may be contributing to it.

Monday, 28 December 2015

Flooding in the NW - Is December's Rainfall 'Unprecedented'?

Unprecedented flooding, unprecedented river levels, even - according to Liz Truss, unprecedented rainfall. I thought I would take a look at the HadUKP data to see if the hype from the politicians matches up to reality. Short answer: not really.

Firstly, let's take a look at the December graph for England and Wales, which goes back to 1766 (2015 data is obviously not in yet as there are a few days to go).


What is obvious is that for the first 100 years after 1766, England and Wales were relatively dry for this month. Thereafter, it got quite a lot wetter in general. In 1876, the record for December rainfall was set. Since then, no December has ever been wetter. 2015 looks unlikely to beat the 1876 record of 194mm - it is 120mm as of Dec 26th.



We would need very heavy rainfall widely across England and Wales over the next few days for this record to tumble. But regardless of whether it does or not, it can be seen that, from the beginning of the 20th Century, there has been no clear upward trend in December rainfall in England and Wales. Indeed, if we look at the decade centred on 1910, we can see that this actually had the wettest run of Decembers in the entire period.

So, what about December rainfall in the North West?


Again, no overall increase discernible since about 1910. It is noticeable that from about 1907 to 1920, Decembers in this region were consistently very wet, hence the peak in the decadal average. It has been quite wet in the NW in December since 1980 - though not consistently so - and the record was set in the early 80's, which also might be broken by this year's very wet December. But 'unprecedented'? Hardly. The NW records only go back to 1873. If 2015 rainfall exceeds the early 80's record, it will only be 'unprecedented' within the last nearly 150 years and even then, a fairly isolated extreme occurrence.

Finally, let's look at winter rainfall in general, firstly in the NW:


Once again, we don't see much evidence of a definite trend throughout the last 100 years. The record wet winter for this region occurred about 1992. Will 2015 be wetter overall? Jan and Feb are yet to come. Watch this space. What about winter precipitation in England and Wales as a whole?


It's the same story really. No clear increasing trend in winter precipitation since the very wet period centred around 1910. 2014 stands out as a clear record though, but very wet winters would have to continue for a good few years yet for meteorologists to point to a trend and then for climatologists and politicians to tell us that that trend is anthropogenic in origin.

So, the data (inconvenient as it may be) doesn't match up to the climate change rhetoric being spouted by politicians looking for an excuse for a woeful lack of flood preparedness, plus the hype by green activists and their insistence upon bandying around their favourite term 'unprecedented'.

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!