This micro heatwave, and this summer, crystallise something I’ve been wondering about for a while. Global warming is measurably changing the geographical pattern of weather across the UK. 

This summer it’s been warmer and drier in the S abc E than the N and W. that’s normal. But it’s been warmer and drier compared to averages in the S and E than the N and W. And that’s not normal. Same with many / most of our recent summers, with the Northerly blocking aberration of 2018 being an exception.

Not just SE-NW but within the wider SE, the area South and East of the Chilterns has been significantly drier and sunnier vs average than the South Midlands and Thames Valley. Look at the June stats: actually drier than average in Kent and Essex. Yet for summer months overall it’s been getting slightly wetter, and duller, for the UK as a whole as well as England. Meanwhile in France they are into the third year in a row of severe summer drought across central and Northern regions and the 4th in 6 years. 

I think this is the climate change signal in action. The European continent is warming more rapidly than the ocean. Those areas most influenced by continental air masses are warming faster, and staying drier in summer, than those areas influenced by the Atlantic.   The longer term implications could be interesting. 

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I think we need to start talking about a changed climate rather than climate change.

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Given that it's only going to get worse I wouldn't use the word 'interesting'.  I won't say much more because we will end up with a climate change thread but the implications are troubling with likely water shortages linked to population growth and climate change and population growth accentuated by climate refugees.

Even more scary is that the rate of change will accelerate because we're not cutting GHG emissions at anything like the rate required.

If you think Covid has been scary just wait for the waves of climate change to just keep rolling in.

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Here’s an illustration: 

And this - last summer as a whole:

When you consider the norms are so much sunnier and drier in the South and East, these maps imply a much more marked regional divide.

The temperature stats are less marked than the sun and rain. More generally warming.

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The climate here is becoming much more maritime with cloudier, wetter summers and snowless winters. It is absolutely dire and has completely killed my interest in the weather - the 21st Century is the worst era for weather since modern recording began in the mid-19th Century.

It now takes exceptional synoptics to deliver better than average conditions in the summer such as in 2018. Pretty much everything else, even synoptics that would have given reasonable conditions in the past, gives poor weather due to fronts being further south so no longer just afftecting the Highlands. 2013 and 2018 have been the only drier than average summers since 2007. Only four Junes since then have managed average sunshine and the same for July. Staggeringly awful statistics. This run of summers is poor without precedent in at least the past 160 years.

Soon it will be 8 years since we had 10cm of lying snow, something that used to happen in the majority of years, even in previous relatively snowless eras like the 90s. There hasn't been any lying snow at all since February 2019 yet both Mays since then have recorded falling snow so it's nothing to do with the arctic not being cold enough and everything to do with relentless westerlies and an almost dearth of northerlies. On the rare occasion we get them there they are inexplicably 'bone dry' when they would have generated lots of showers in the past.

Autumn is a disgusting mild claggy mess year in year out with horrid double digit mins persisting well into October killing off any leaf colour. The majority of Octobers used to see frost but now this is seldom seen until November.  Convection has almost died off completely in spring and as a result there hasn't been a wetter than average spring since 2006.

It's beyond tedious as there is no variety and unpredictability any more. Other than 2018, it's just like living the same year over and over again on a loop. I can barely think of anything to distinguish 2015, 2016, 2017, 2019, 2020 from one another. Dire snowless winters and horrid wet summers. Sunshine markedly higher during the cold months due to relentless westerlies but at record low levels during the summer. Mean temperatures practically the same and unsettled but never particularly wet.  I call it the 'blandification' of the climate.

 

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I have mentioned a lot in the past about synoptic situations which used to bring a lot of rain to the SE of Scotland, but which no longer does so. Examples of this are southerly tracking lows which are more likely to miss us to our south nowadays than in the past, and stalling weather fronts which are now more likely than before to pile a lot of rain into the west of Scotland, without any of that rain ever quite managing to reach us here in the east of Scotland.

However, what has happened in the past few days is the perfect example of the opposite scenario happening where we have had some rain out of a synoptic setup which used to be much drier here in the past. It used to be that a build of high pressure to our south, would extend across quite a large part of the UK with any cloud and rain being confined to the far north and west of Scotland for a few days at least.

What is tending to happen now though is that these builds of high pressure are further south than before, but with more intense effects that now result in the far SE of England being guaranteed some really temperatures at some point during even the poorest of summers overall. Because these builds of high pressure are further south though, this is allowing Atlantic weather systems coming around the top of that to come further south than before and because of that, we are now getting rain from those systems which once used to be more confined to the far north and west of Scotland.

Indeed, the rainfall which we got from yesterday's warm front was probably a good example of that but to me, this is probably why we don't get that typical spell of good weather in most summers which last for up to a week or even a fortnight, as we used to.

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It is amazing how easily we seem to be getting these ultra hot days. Something above 35°C used to be an archievement that only the best summers/heat waves earned, and now it's almost becoming a yearly occurrence. I'm sure someone said earlier today that it used to be on the national news when it happened?

I am now convinced that we will hit 40°C sometime in the very near future (maybe sometime this decade). If isolated days can produce 37/38°C now, then surely a more prolonged spell, like that of August 2003, will see 40°C recorded.

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Very good for wine production in the SE.

 

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It's an exaggeration of trends which have been going on for decades - the magnitude of the events is increasing. There's a reason Dungeness (inaccurately) advetises itself as the UK's only desert, for example!

It's also long been the case that some of the warmest temperatures are found in the far SE too (some people scorn Brogdale, but it's ideally situated. A warm airmass travelling over the Downs sinks and bam, you have really strong heat). The Downs also cause the break-up of many a rain cloud, rain "fizzling out" before it gets here is by no means unusual.

That said, it does raise an eyebrow to see how quickly things warm up in the right conditions these days!

(The same can work in reverse, of course... just two years ago, it reached -14C here, the coldest place in the UK by several degrees. Again, proximity to the continental landmass was key).

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It has been my perception that at Baldock in North Hertfordshire, it has been unusually warm, dry and windy for 2019 and 20. The graphics above seem to bear this out for the warm and dry parts but has it really been unusually windy?

The dividing line between the conditions North/South of the Chiltern hills is really fascinating. Baldock lies in a bowl on the northern edge of the chalk scarp which forms the Chilterns and is consequently sheltered from some of the worst weather but we have had persistent northerly and easterly winds for what seems like an eternity.

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Bringing this back to the top now July maps are in, as they reinforce the perception for this summer:

As I just commented in the July temp thread, we've just had the worst (vs averages) month of 2020 so far for central England and the UK as a whole, yet for the far South and SE it's been average at worst, a little warmer, drier and sunnier than average in some spots. The Chiltern and ridgeway dividing line is there for rain and sunshine, and the more classic Bristol to the Wash line for temperature.

This is not just a 2020 and 2019 fluke. Last year I ran the stats for JJA rainfall, temp and sunshine from 1970 to present for the met office NW and SE regions and charted the difference between the two over time. I can't work out how to post the charts, but suffice to say the gaps increase clearly over time. The trend lines show the following:

Temp: gap increased from 1.8 to 2.1C in favour of SE

Rainfall: gap increased from 80mm to 140mm in "favour" of NW (i.e. NW used to be 80mm wetter across the summer, now 140mm wetter!)

Sunshine: gap increased from 95hrs to 135hrs in favour of SE

The numbers show that meteorological inequality is demonstrably increasing, year on year.

 

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A little while ago I did an exercise using the Met Office 5km gridded data to calculate the JJA "Summer Index" for every square in the UK from 1961-2016 and in particular the change in index over the period

The "Summer Index" used Kevin's formula for Manchester data

10 x [(mean max of summer) +(total sunshine)/67 - (rain days/8)]

Nearly every location has increased apart from the blue areas shown as overall rising temperatures have more than offset slight overall increases in rainfall

But the SE has been the big winner with areas around N Kent and S Essex being in the gold medal position and a general decrease in change going from SE to NW as this thread has been discussing

 

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What I find interesting on the above is the grey blob covering East Yorkshire and northern Lincolnshire and the dark blob over Hull. I wonder if there is a more specific reason for the low sunshine percentage there compared to nearby.

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Speaking from the point of view of my area, it is hard to disagree there Richard.

As I mentioned recently in the thread we had on the great summer of 1995, for me summers in the past 22 years at least in my part of the world have become worse, not better. Of the entire period going back to 2000, the only years which have produced good or even decent summers here have been 2003, 2006, 2013, 2014 and of course 2018. The period from 1989 to and including 1997 saw generally much better summers in those 9 years than we have seen in the vast majority of years going all the way back to 1998.

Perhaps when the AMO returns to a negative phase (it has been in a mostly positive phase since the mid-late 1990s I believe), it will perhaps help to even things out. However, the predictions that some made back in 1995 about summers like we saw that year becoming the norm have been well wide of the mark thus far, for most areas.

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Your last sentence is very important and shows how generalisations about the future of climate based on "Western Europe" or even the UK as a whole can be misleading when it comes to regional climates.

In my view what we are seeing across the UK is absolutely in line with climate change projections, but unfortunately that means that in some places the weather actually gets more rubbish.

The attached from the Met Office contains all the projection maps for 2020-39 and every 20 year period up to 2099, and it's quite stark.

https://www.metoffice.gov.uk/research/approach/collaboration/ukcp/land-projection-maps

Particularly for 2020-39 for the JJA season:

• Temperature, 50th percentile 1-2C warming across SE England, less than 1C over the rest f the UK and in the 10th percentile cooling over Scotland.


• Rainfall: drier in the South and SW, wetter in the far North and Scotland

So if you're in Scotland and it's not really warmed since 1995 and has got wetter (and duller, but they don't seem to model that), that would be consistent with the projections.

The only difference with recent months is the more SW bias of drier weather in the projections vs actuals, but I don't know what a longer term trend would look like.

 

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I remember that in the climate forum for a few years prior to its closure early last year, there was a thread which someone had opened discussing the Atlantic Multidecadal Oscillation (AMO) and the positive and negative phases it goes through. IIRC, this thread was started in response to a video that TWO's own Gavin Partridge did on his own website a few years back looking at the past behaviour of the AMO and what it is likely to do in the future.

At the moment the AMO, as far as I am aware, is in a positive phase and it has been in this state for much of the time since the mid-late 1990s. I recall it being said by someone in a piece I read a while ago that when the AMO returns to a negative phase, it could actually improve the chances of the UK getting generally better summers than tends to be the case during positive phases. I have to admit that I know virtually nothing about the AMO myself and had no knowledge or awareness of it until a few years back, but if there is indeed any connection between the phase it happens to be in and the types of weather that the UK (or parts of the UK) receive at various time of the year, I would suggest that summers in this part of the world have become wetter and duller during the current positive phase of the AMO than was the case for a while beforehand.

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Interesting thread. The changes we have seen in the UK are part of larger scale changes and they are linked to circulation changes. Below is the change of summer (JJA) 500 hpa heights over the last 25 years (1995-2019) compared to the previous 25 years (1970-1994). Pressure has risen near Greenland and has fallen west of the UK, which partly explains the much warmer summers in Europe (biggest changes in eastern Europe, where the change is ~2C!). There is also the potential link to the big sea ice losses in the Arctic.

 

Pretty much the same story over here Richard, although we are always more prone to that accursed 'maritime' influence than you would be. 

A quick summary of the climate trends of this Island:

1. Mean temps have risen since the 1961-1990 average (which in itself, is based on an unusually cold period of the 20th century) by about 0.7c, but this is more down to the sharper rise in mean minima than mean maxima, of which the latter has only risen about 0.3c.


2. No indication that there has been an increase in summer heat or heatwaves. It's actually a struggle to break previously held heat records in this season.


3.  The severity and frequency of autumn winter storminess had declined markedly with heat records more likely to easier broken during these seasons. 


4. Extreme rainfall events becoming a little more likely in recent times during Autumn and winter seasons, but no real trend in spring and summer. 


5. Regardless of these slight changes, the climate still remains as bland and dreary as can possibly be found anywhere on this planet. 

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I was told many years ago that Kent, SE Essex, and to some extent Sussex, had a climate that was influenced to a good degree by the proximity to the continent.  So if the French climate has become hotter and drier (which it has) then it is not surprising that this has affected the far SE of England.

P.S. This is certainly an interesting thread.

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I couldn’t see your attachment before but now I can. That map is truly stark, particularly for Kent and Essex. I’ve bought some land for a vineyard in the Downs south of Canterbury and this definitely validates the location choice. 

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There are two changing influences on the North Atlantic jet stream that are having opposite effects, but taken together may partly explain what is going on regarding increased summer rainfall in NW England and SW Scotland and reduced summer rainfall and higher temperatures in SE England:
1) Poleward expansion of Hadley cell ie tendency for Azores High to extend slightly further North than previously
2) Arctic amplification(*) causing the Jet Stream in the North Atlantic to be further South than previously in summer
I posted several weeks ago that 4 out of the last 5 Junes feature in the top 20 wettest Junes in the NW England rainfall series [length of record = 148 yrs]
It is possible that (1) + (2) taken together are causing summer low pressure systems to follow a narrowed path, providing other factors align - ie there will still be occasional variations from this such as June & July 2018.
* Arctic amplification is a term used referring to the fact that the arctic is warming faster than the rest of the world

I think this is indeed exactly what has been posited in some research papers - not so much the point about the jet going South (because that varies by longitude, it's been further North in other regions) but more that the subtropical highs are expanding North but the Northern edge of the polar front is not, so the Ferrel cell itself is becoming narrower.

The trends imply as much. It may not be the case that the NW / Scotland is getting more zonal weather than before, but just that it's getting the same as before, is too far from the Azores high to benefit from expansion, and the increased moisture content in the air through higher SSTs is enough to boost rainfall and cloudiness.

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Funny you should mention the Hadley Cell, I was just thinking of that as I read through this thread from the start. 

Last month caught my attention with respect to that. There was predominantly very low atmospheric angular momentum due to a developing La Nina event, which usually corresponds to more rainfall than usual right down into France (with temps varying around the average).

Yet, the southern reach of anomalously wet weather was southern Wales eastward and it was actually drier than usual in the far south (I saw about half the usual rainfall here).

An outcome that fits the notion of Hadley Cell expansion well.

 

Your suggestion regarding Arctic amplification, I'm less sure about. Arctic amplification is likely weakening the polar jet stream (on average, across the weeks and months), but that doesn't necessarily mean it moves southward. In fact, as amount of cold air the Arctic can support reduces, there ought to be an overall northward shift as the colder 'pool' shrinks in spatial coverage.

This, I believe, is where the North Atlantic sea surface temperatures are taking the wheel to steer things the other way. The central North Atlantic has been persistently cooler than its surroundings, often by several °C, for nearly all of the the past 5 years. This is likely to do with freshwater influx from Greenland ice melt interfering with the Atlantic Meridional Overturning Circulation (AMOC), of which the surface component is the Gulf Stream. 

This has shifted the warm/cool boundary southward in the North Atlantic.

 

The outlook for the next decade is likely to be one largely decided by the Hadley Cell expansion and Arctic amplification competing with that. There are striking possible outcomes of the battle - the southward-shifted North Atlantic polar jet may become more restricted to over the ocean, leading to an increased incidence of troughs west of Europe working in tandem with highs over Europe to bring high-end heatwaves.

Perhaps, the rapidly developed, yet intense hot spells of 2019 & 2020 are demonstrations of that starting to become a feature already.

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Just to illustrate the fact that we are at the edge of a significantly warmer continent, below shows the change in JJA 2m Temperature 1995-2019 minus 1970-1994.

  

The change in climate in the UK from 1961 to 2016 can be seen by looking at these trend maps for Annual Mean Temperature, Annual Rainfall and Annual Sunshine hours as total trends for the 56 years in the range

For Temperature and Rainfall there is quite clearly a change to warmer, drier conditions in the SE quarter of the UK to less warm(er) and wetter conditions moving west and north. This is within an overall increase in both temperature and rainfall in the UK as a whole

The trend for sunshine hours is much more confusing however. It would appear that the biggest gainers are the Midlands and North East of the UK presumably folkowing the trend for less heavy industry in those areas.

I am puzzled about the big increase in East Kent/South Essex whilst parts of the mid South od England in Hampshire, Dorset and Devon have shown a decrease. Anyone know why this should be

 

clickable maps below

 

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