WYorksWeather

Ironically though, that's actually quite a mild pattern for the UK, with the +10C isotherm in - a long way above average if the ECM is right. Some cooler weather to get through first though from Saturday through Monday:

I was just using those as examples of how forecasters can portray things differently. You're right that wording is difficult. For what its worth, I'm very convinced around the issue of climate change, I'm just not sure it is necessarily something that is easy for every weather forecaster to talk about. Meteorology and climatology seem similar but there are quite a lot of distinctions - if you make rash comments it can actually reduce trust. What is needed are more high quality science and data journalists, and good science communicators. Not all weather forecasters are necessarily suited to doing that sort of work. For example, there was a statement made shortly after the event by Al Gore to the effect that Hurricane Katrina was caused or at least worsened by climate change. The effect of climate change on hurricanes is quite nuanced and still somewhat contested, and that sort of unsubstantiated statement can actually backfire. Especially since much less was known about that specific issue 15 years ago. If he had spoken about heatwaves, well that's much safer ground. I also think that most weather forecasters do a good job when talking about extreme conditions, for example like last July. I remember a lot of forecasters remarking that this was not just another heatwave, urging people to be careful, and warning of very significant impacts and that the situation was unprecedented.

Yep, in fact from a CC perspective the noticeable thing is more that our annual CET is running equal to 2022 despite very poor synoptics through that core summer holiday period. It's just that a lot of the bad days have been slightly less cool than they would otherwise have been, and when the synoptics have come together we've managed to run up the CET quite high, and there's also been an absence of any notably colder than average spells.

There is a difference between opinions and facts. Everyone is entitled to their own opinions and value judgements, but what nobody is entitled to do is to expect to say things that are flat out wrong, and expect nobody to say anything in response. 'All the seasonal models predicted a hot summer and its been nothing but cold' is a statement of fact, not an opinion, and it happens to be an incorrect one.

Hi all, I thought I'd start this post (which may turn into a series) to have a look at some historic climate changes over time. This is partly inspired by a recent discussion I had in another thread on the Paleocene-Eocene. For each epoch I look at, I'll try to explain what the impacts were regionally and globally, what caused the change (if known) and what lessons can be learned if any. If this does turn into a series, I'll probably tackle different climate epochs in reverse chronological order. I thought about starting with the 20th century, but that's probably been largely done to death in the historic weather section, so I thought it better to move beyond that. Absent any requests, if I do turn this into a series (mostly dependent on interest), my next post will probably be on the Medieval Warm Period, followed by the Holocene Climate Optimum. Happy to discuss any issues raised in the comments. What was the Little Ice Age? In the words of the IPCC (AR6): In English, it's most likely the coldest period of global temperatures in the last 2,000 years, as shown in the PAGES2k climate reconstruction. The time frame that we are interested in is bounded by the black vertical lines I've added to the chart: As shown, the global impact is relatively modest, and not significantly different from zero. However, the effects are much more noticeable if you look at smaller geographies, such as the 2010 reconstruction of extratropical Northern Hemisphere temperatures (from 30 degrees N to 90 degrees N) by Ljungqvist below. Temperatures were likely more than half a degree below 1961-1990: In short, much of the variation is smoothed out on a global scale, but it does seem reasonable to suppose based on available evidence that there were very substantial changes in much of the Northern Hemisphere, at a minimum. Selected notable climate or climate-related events Expansion of glaciers in much of the Alps Some of the UK's coldest documented winters (including the legendary 1683-4 winter) Swedish army marched across the ice to Denmark in 1658 (The March Across the Belts) Widespread crop failures in Iceland Abandonment of Norse colonies in Greenland Harsh winters in New World colonies Causes Causes of the Little Ice Age are still fairly disputed - there are potentially a number of factors which may have acted together. I've listed a few causes, in rough order of how commonly they are cited as a major factor: Volcanic activity Lower solar activity Orbital changes Internal climate variability Reduced human population Summary The Little Ice Age was significantly cooler than the mid to late 20th century across large parts of the Northern Hemisphere, but the impact on a global scale was smaller or possibly even zero. Since this is still relatively modern (compared to climatic variations in the more distant past), we can learn a lot about how societies reacted to the changes. It has also lived on in our cultural memory! I'll end with an illustration of the Thames Frost Fair in the winter of 1683-84, and one of the famous prints you could have bought on the River Thames (held by the Museum of London, and this one bought by King Charles II!): If you've got this far, thanks for reading.

To focus on the language issue - yes, agree that there is a question about what descriptors you use for temperatures. The problem is that some words that are used are relative to time of year or season. For example, a maximum temperature in the mid to high teens might be described as 'cool' in July, but 'exceptionally mild' in November! I think the best weather forecasters are generally able to make the distinction - with phrasings like these. In July: "Whilst it might still feel pleasant enough under sunny skies, temperatures will be struggling in the mid to high teens, which will give it something of an autumnal feel, with temperatures more typical of September than July." In November: "The sun is quite low in the sky and so it will still feel quite chilly near any exposed coasts, but with temperatures in the mid to high teens, it will be exceptionally mild for the time of year"

I think taking the period overall you may be right. Again I make no judgement at this stage regarding the length of the cold spell - it's too soon. The most I'd be prepared to say is that it's warm up until Wednesday, bit of a N/S battleground through Friday, then cooler than average for most from Friday through Sunday and possibly quite cold further north. Agree though that at your location you're likely to be closer to average than most of us. Beyond Sunday is still FI I think. GFS ensembles are out and it is a massive outlier once it goes into FI, but the broad pattern through Sunday is reasonably well supported:

Not really qualified to talk RE: those outputs, but I will flag up the National Hurricane Center forecasts. Yellow X in the Gulf of Mexico can probably be ignored - only 20% chance of formation and probably not likely to head our way. However, the red X is likely to form in the next few days: As a general rule, we've been seeing a lot of these tropical storms / hurricanes tossed out to sea as they approach the U.S. East Coast, which normally then sends them extratropical and heading E or NE towards Europe, leading to direct or indirect effects on our prevailing weather patterns - the cause of our heatwave in September and then more recently Storm Agnes. I wouldn't rule out further effects from this one in a week or so if it does get tossed in our general direction.

Yeah it is important to take the OP runs with a pinch of salt - as I've been pointing out over the past few days the operational runs have been close to the bottom of the ensemble packs lately. However, tonight it does seem that the 12z runs are mostly singing from the same hymn sheet (pending ECM), and so it does look like there'll be a period of cooler weather. I also think given the tropical features at this time of year, anything beyond T+120 is iffy, and beyond T+168 is FI. Strictly for fun only.

Yep, does look like the models have finally settled on quite a substantial cold spell. I know I was previously sceptical of the idea (mea culpa). To be fair to myself - the models were fairly equivocal about the progression - some failing to push the cold front through at all, or quickly replacing it with milder air. ECM isn't out yet, but here's UK Met, GFS and GEM at T+72 and T+120: By T+120, all three models drawn down some sort of northerly airflow. Beyond that, some variation in the length of the cold spell, but all models keep the cooler air in place at least up to T+168, but after that the GFS keeps it cool right out to T+240. The GEM also stays relatively cool, but by T+240 looks to be setting up another warm southerly, though perhaps mild is a better descriptor by the time we get to the latter stages of October. A lot to happen before now and I wouldn't put too much stock beyond T+168 or even T+120 - I think the consensus is warm until Wednesday, bit of a battleground until Friday but then cold wins out and most likely stays in place through the weekend, which is probably as far as we can reasonably look with confidence. Will be interesting to see if ECM follows the same broad pattern out to T+120/168. If so, I think we can call it a cold spell!

GEFS 12z ensemble charts for London, Sheffield, Newcastle and the Cairngorms: Generally looks like a fair amount of rain spikes (though not a total washout). Snow more likely than not on the Cairngorms, but zero snow risk on the other charts. Broadly, further north is generally closer to seasonal averages. Overall it looks like the prevailing pattern is very warm further south out to the end of the run, but as you move northwards probably closer to average. In the Cairngorms, maybe a touch below average. Still a fair bit of uncertainty as there are some runs that still aren't interested in the cold push, and some that make more of it. Of course, it will still feel much cooler than it has of late for most of us, as even long-term average conditions will be cooler by comparison.

Just found the TORRO site which is good for this stuff: The Tornado and Storm Research Organisation (TORRO) WWW.TORRO.ORG.UK TORRO is a privately-supported research body specialising in severe convective weather in Britain and Ireland From there, looks like the latest 26C is the 13th October. If you allow rounded 26C, then the 18th. Looking further ahead the latest 25C is the 18th (unrounded) or 19th (rounded). Latest 21.1C (70F in old money) is 13th November, set last year. And latest 20C is 23rd November. Will be interesting to see if we can get any 'warmest day so late in the year' records. Looks like we'll fall just short this time.

Yeah as a bit of a pedant myself, that sort of mistake is slightly annoying. You should write in to the BBC and get a correction made

Yeah I guess it depends on the wording. Most likely though based on those stats they said early October but actually meant mid-October, or were quoting some sort of wider figure like an average for the South of England, which would probably be lower. In any case, we can broadly say most areas except north of Newcastle saw temperatures about 5C above average for the time of year. That's a good benchmark, because it means that an equivalent spell of weather in summer would qualify as a heatwave.

I think they often quote the monthly average, which skews it a bit at the start of a month, particularly in Autumn and Spring. In most places in the UK the mean is dropping by about 1C per week on average from mid-September to mid-November. Looking at Heathrow, average high for October is 15.8C, so probably rounding up to 17C is justified. Couldn't find Southend on the Met Office climate averages - closest was Shoeburyness. Average is 15.3C, so probably fairer to say between 16C and 17C there. Any greenhouses at Southend for the heat to reflect off?

I think the more recent warming trend is something like 0.2C per decade, so it's actually closer to 0.2-0.3C. Factor in an adjustment for land warming faster than ocean, and you probably arrive at a figure closer to 0.4C. Anyway, we have the rest of October to look at before we consider the annual! All in all I think we can probably say that outcomes above 14C and below 11C are unlikely, but that frankly doesn't tell us much! I think we need more clarity from the models about whether this cold spell will come off - in the last few days we've seen GFS getting the -5C isotherm in next week, and ECM has some bonkers ensemble members in the other direction, including one earlier today that got the +18C isotherm in on the 22nd! Hopefully we'll have a better idea of the road ahead by early next week.

As I was discussing on the autumn thread - I don't think we've seen anything like the upper limit of what is possible for surface temperatures given the record breaking 850s we've had in September and October. In any case, to get this back to models, looking at the very short range spot maxima for tomorrow, there's general agreement on the 23-25C range being the spot maximum. Given most of the models were slightly under today, I'd say 25C is likely, possibly even 26C in an isolated spot.

I think one of the reasons this has snuck up on us is that it has been subtle this year rather than dramatic. Even the poor spells of weather in the summer are not as bad as they could have been. Obviously it's not much comfort if like you like warm summer weather, but a poor spell of weather being 18C and rainy instead of 16C and rainy makes quite a big contribution. Same thing in September - even the wetter and cooler interludes later in the month had as much to do with the record-breaking CET as the initial heatwave, simply because they were cooler, but not enough to really collapse the CET.

I'd go a bit further than that to be honest. One of the things is that we're not seeing the full range of what the current climate can do - whereas further back we have a relatively stable temperature trend, so older records are 1 in 100 year events. A lot of recent records have been set under less-than-perfect conditions. Last year's 40C was prevented from going even higher, as the very highest 850s began to clear to the east just after lunchtime, or it might even have reached 42C or 43C as was projected by some models. Makes you wonder what could be achieved with a 1 in 100 year event in each month in 2023, so my speculation below. If we look at intervals of 5C that haven't been achieved in a given month, then I think 20C in December and January is a no-brainer possibility. 25C in November and February probably a stretch since it's quite a jump and those records are quite recent. A 30C March is probably beyond the range of possibility for now, but certainly April and October are possible. This is in fact a record-breaking 850hPa flow, so there's no reason why better surface conditions wouldn't have smashed the record. Even with fairly poor surface conditions (wet ground, lots of high cloud, poorly directed surface wind) we've got to 25C today. Moving on to the extended summer period, 35C in May is only an advance of just over 2C on a 70-year old record, so that should be doable. 40C in September would be bonkers and probably not doable at the moment, same in June I think. 40C in August is probably doable. Not saying any of these will happen in the next year or two, but given the trajectory we're on, I'd be surprised if we don't see at least a couple of these by 2030, and most of them by 2050.

Not quite to the same extent, but some backing here from ECM. Attempts to push the cold through on Wednesday and Thursday, but fails to completely clear the warm air south of the Midlands: Above-average 850s return more widely on Friday: After that, ECM does look to push the cold air through, but at that point we're heading out of the reliable timeframe, and previous cold pushes have been downgraded, so I'll reserve judgement for now.

The anomaly to September was 1.61. Here's a few scenarios: October CET / October anomaly / Year-to-date anomaly / Nov + Dec average anomaly needed to exceed record (assuming record is exactly 1.68) 10.5 / 0.0 / 1.45 / 2.9 11.0 / 0.5 / 1.50 / 2.6 11.5 / 1.0 / 1.55 / 2.4 12.0 / 1.5 / 1.60 / 2.1 12.5 / 2.0 / 1.65 / 1.9 13.0 / 2.5 / 1.70 / 1.6 13.5 / 3.0 / 1.75 / 1.4 Overall, I'd say based on that it's odds-on favourite to be the warmest CET year if we get a 13.X October, less than 50% but still fairly likely with a 12.X, unlikely with an 11.X or lower.

Ah sorry - classic poor wording from me. My point is that if you don't agree with a) and b), there'd be no reason to support a transition to EVs. Putting myself in the position of someone who has that view, well then there are no CO2-related benefits to EVs over ICEs, so there'd be no reason to change, except on pure cost grounds. I'm not necessarily saying that if you agree with a) and b), you must support a transition to EVs. And I agree that EVs are only a small part of the solution. But I really don't see any alternative to having them as part of the solution. Public transport and active travel may replace cars or partially replace cars for some people, but clearly not for everyone, and the only feasible way to get a zero-tailpipe-emission car at the moment is an EV. Hydrogen cars are pretty much a bust - either you use fossil-derived hydrogen which has no benefit, or you pay three to four times the cost of existing fuels for green hydrogen, which will make an EV look cheap!

It's highly unlikely the effects will be as dramatic as the Paleocene-Eocene. Below are the IPCC Representative Concentration Pathways (RCPs). The RCP 8.5 scenario is the only one that gets close to Paleocene-Eocene levels, and is considered by most to be highly unlikely, as it's essentially a return to very high emission ways and very big population increases. Think a population of 15 billion powered almost entirely by coal. The only way it could happen absent that would be very high positive carbon cycle feedbacks. In other words, releases from wetlands, melting permafrost, etc. Best to put that scenario to one side, and focus on RCP 4.5. In short, by the relatively near term around 2050, you're looking at levels somewhere around 500ppm in RCP 4.5, maybe closer to 600ppm by 2100. In terms of the climate of the Paleocene-Eocene - you're talking absolutely extraordinary changes. Fossil evidence indicates that about 55 million years ago there were sub-tropical conditions in the Arctic - think palm trees and crocodiles. Highly, highly unlikely to happen today. Global temperatures were probably something like 5-8C above pre-industrial. By contrast, RCP 4.5 would put us on track for 3C by the end of the century.

Yeah was just about to post the equivalent chart but from TheWeatherOutlook - you've saved me the bother. All in all that's an extremely warm chart - the mean at this time of year is around 5C, dropping to 3-4C by the end of the run. Looks well above average to the 14th, then on balance average to slightly above thereafter. It is cooler further north relative to average - more of a dip into negative anomaly territory if you look at places like Newcastle. Crazy model runs - ECM However, there is one other thing worth pointing out - this from the ECM (my exclamation mark for emphasis): I checked other locations and it wouldn't even be London only - it gets the 15C isotherm in around the 22nd as far north as York. Frankly, utterly extraordinary that such a thing is even being modelled on an ensemble run. If you believe that the model runs are a faithful representation of reality, that means there is a version of UK weather patterns in a possible future where we get the 18C isotherm into the London area on the 22nd October. Just utterly bonkers. Of course, highly unlikely to verify.

I'm not entirely sure what you're asking. Do you mean whether it's likely we'll see concentrations get that high, or why they got that high so long ago and what the result of that was, or whether a similar process could happen today? If you can give me a clearer idea of what you want to know, I'll do my best to answer.