Sherlock Holmes At The Met Office: I Found The 'Fingerprints Of Climate Change' On Our Hot June
Curry & Johnstone: It's the NAO stupid!
This is just getting silly now. I’ve already written about how the Met Office has been hyping the allegedly ‘hottest June in the UK’.
They’re doubling down on their narrative now and have performed a ‘rapid attribution study’ apparently which demonstrates that the warm June (temperatures never exceeded 32.2C anywhere and most of the time they were in the 20s to high 20s) has the grubby fingerprints of climate change all over it.
They don’t link to the study, probably because they are too embarrassed to do so. But the clue that the paper it’s written on is probably worth no more than your average toilet roll is here:
Paul Davies, Met Office Climate Extremes Principal Fellow and Chief Meteorologist, explains: “We found that the chance of observing a June beating the previous joint 1940/1976 record of 14.9°C has at least doubled since the 1940s. Alongside natural variability, the background warming of the Earth’s atmosphere due to human induced climate change has driven up the possibility of reaching record high temperatures.
“Using our UKCP18 climate projections, we can also see that there is a difference in the frequency of these sort of extremes depending on the emissions scenario we follow in the future.
By the 2050s the chance of surpassing the previous record of 14.9°C could be as high as around 50%, or every other year.
It only covers the period from 1940 and their assessment included natural variability, but they conveniently neglect to inform us what contribution natural variability actually played in the observed record of June temperatures. Then they pull out the climate modelling white rabbit from their magic hat to inform us that this one isolated 2023 instance of June surpassing the previous warm records of 1940 and 1976 could occur every other year by 2050! No shit Sherlock. That’s bloody amazing detective work.
I’m guessing the ‘natural variability’ which they seem reluctant to emphasise beyond a brief mention is the Atlantic Multidecadal Oscillation (which peaked positive in the 1940s and has done the same in the first two decades of the 21st century) and the related North Atlantic Oscillation. These two modes of internal climate variability have a huge impact on the climate of northern Europe, especially the British Isles. Now as it happens, Judith Curry has a very informative post on her Climate etc. blog which explains in some detail the role of the NAO in the exceptionally warm North Atlantic temperatures recorded from April onwards into June this year. It’s a joy to behold such sanity and scientific rationality in a world gone global warming nuts. Judith and her co-author identify a very anomalous negative NAO as being responsible for the observed warmth in the North Atlantic and they elucidate the physical mechanisms behind that warming, related to that negative NAO.
The atmospheric circulation in June in the north Atlantic was highly anomalous, which manifested particularly in the surface winds and sea level atmospheric pressure:
On the left, you have the average June pattern, that which we would normally expect to see, with high pressure (the Azores high) dominating the mid Atlantic and low pressure further north, impacting Greenland, Iceland and the British Isles. The second panel shows the actual pressures and surface winds and the final panel shows the June anomalies in the region, which are huge compared to the normal climatology. A band of high pressure dominates all of the north Atlantic stretching from Canada to the British Isles (which incidentally was probably instrumental in the Canadian wildfires and the subsequent drifting of the smoke down the highly populated eastern seaboard of the United States). This climatological surface pressure anomaly was linked to a highly negative June North Atlantic Oscillation index, which as Judith points out, resulted in truly extraordinary north Atlantic warming.
An extreme negative NAO index in June was preceded by moderately negative anomalies in both March and April (Table 1), which led to repeated monthly warming of the North Atlantic Arc and extreme cumulative effects by late June. The Arc warming observed from February to June (+0.85°C) exceeds the total net Atlantic warming of the past century.
Here’s how anomalous NAO actually was, in June particularly, but across the whole period Mar-Jun:
Caution advised though, because this data only goes back to 1980. I’m pretty sure that we must have seen equally ‘anomalous’ spring and summer NAO indices prior to 1980. But there’s your explanation for the warm north Atlantic and here are the basic physical mechanisms explained as to why the north Atlantic was so warm:
Atmospheric anomalies associated with the NAO are primary drivers of Arc SST perturbations over short (monthly to seasonal) time periods. Figure 5 illustrates monthly anomalies of net shortwave (solar) surface heat flux, turbulent (latent/evaporative plus sensible) heat flux, total heat flux, and SST tendencies. Negative NAO anomalies correspond to negative subtropical SLP anomalies and weak trade winds to the south, including the MDR. Weak trades warm the underlying sea surface primarily by hindering evaporative cooling, but affect tropical SSTs through several complementary mechanisms, simultaneously favoring warming through reductions in stratocumulus cloudiness, Saharan dust advection, upper-ocean mixing and coastal upwelling off NW Africa. Overall, the turbulent flux associated with weak winds has dominated over the shortwave flux in warming the Atlantic.
Weak surface winds greatly hinder cooling via evaporation. Combine this with the increase in solar UV radiation due to persistent high pressure and clear skies and you get very significant sea surface warming. This explains most of the observed north Atlantic warming. It also helps explain why June in the UK was particularly warm and sunny (not blisteringly hot), from start to almost the finish, and thus why (perhaps) the UK in June was the warmest overall it’s been since 1884. ‘Climate change’ might have played a minor supporting role but it was the NAO which really did it, not your car, your washing machine, or your ice-cube making fridge freezer.
Judith and co-author sum up nicely:
The extreme North Atlantic conditions that developed in recent months are likely due to a combination of dynamical factors, including stochastic weather anomalies, regional positive feedbacks and global-scale changes. The high rate of recent Arc warming is particularly noticeable due to the extreme SST anomalies it produced; however comparable warming over periods of ~4 to 6 months occurred previously in late winter to spring seasons of 1983, 1987, 1989 and 2010 (Figure 2), which preceded a wide range of late summer hurricane anomalies.
The dominant cause of the warm SSTs is dynamical (atmospheric circulations) that modify surface wind speeds (evaporation; apparently the largest factor) and clouds (solar radiation).
El Nino also might also have played a part:
Another contributor to the remarkable spring changes in the North Atlantic may be the broader tropical warming involving the transition to El Niño conditions. Surface warming in the tropics typically leads to quasi-uniform elevation of tropospheric temperatures and geopotential heights throughout the tropical belt from ~20°N to 20°S. Spring increases in 250 hPa geopotential heights (Z250) over the tropics were accompanied by declines immediately poleward over the subtropical NE Pacific and North Atlantic, while SLP anomalies dropped steeply in a coherent tropical zone from the central Pacific to the eastern Atlantic.
So what’s all this got to do with the Little Ice Age I hear you ask? OK, you didn’t ask, but I’ll tell you anyway, because I think it’s important, because as we noted previously, the second warmest June in the long running CET series occurred during the coldest part of the Little Ice Age in the northern hemisphere and much warmer Junes than 2023 were also recorded in the first half of the 19th century. I think that’s significant and I think it has a lot to do with north Atlantic internal variability and even El Nino/La Nina conditions in the tropical Pacific. But I’m not going into that now, because this post is long enough already and was intended primarily to illustrate how global warming obsessed idiots at the Met Office are ignoring meteorology and weaponising the British weather in order to further the government’s political agenda.
“Using our UKCP18 climate projections"
So, more Xbox climate science.
Jolly good, carry on!
Back in in the last decade, they'd hint at climate but ultimately we'd get the ocean, the Jetstream or some other excuse for x weather. Now with the rapid attribution bs they can workout fail blame a fart on climate change - and somehow keep a straight face. It was much harder to push this a decade ago as it was the decade before that. This was to be expected as with each year that goes by the ratio of activists to 'scientists' increases and we end up with a brainwashed legion of over privileged middle class activist numpties ideologically aligned with XR and JSO who have no morals whatsoever (beyond telling you what wonderful people they are as they jet round the planet telling poor Africans to burn shite - because you know noble savages need whitey civilising the natives).