A Critical Look At The Media Claim That 40°C Summer Days Have Become Much More Likely Because Of Climate Change

Here’s the media hype:

Many parts of England are expecting their first heatwave of the year this week, as the Met Office warns that hotter summers are on the way.

In July 2022, people in the UK were caught off guard. The country experienced its first recorded temperature above 40°C on 19 July, when the mercury climbed to a high of 40.3°C at Coningsby in Lincolnshire.

There’s still a “remember where you were when” quality to the baking hot air that day. But summer 2022’s intense heatwave should not be dismissed as an isolated occurrence, according to a new report from the Met Office.

Due to climate change, there is now a 50-50 chance of seeing another 40°C day in the next 12 years, scientists at the national weather and climate service say.

"The chance of exceeding 40°C has been rapidly increasing, and it is now over 20 times more likely than it was in the 1960s,” says Dr Gillian Kay, senior scientist at the Met Office and lead author of the report published in the journal Weather.

So let’s take a look at this study to see what it really says.

But just before doing so, note what the Met Office media release says about this study:

New study highlights how UK heatwaves could become longer and hotter due to escalating climate trends.

Met Office scientists have published a new study detailing the increasing likelihood of extreme temperatures in the UK, revealing that the chance of exceeding 40°C in the UK is accelerating at pace.

‘Rapidly increasing chance of record UK summer temperatures’, published in Weather journal, underscores the need for people and organisations to prepare for even higher heat extremes in the near future. In July 2022, the UK experienced its first recorded temperature above 40°C, when Coningsby in Lincolnshire reached 40.3°C. This unprecedented temperature formed part of Europe's warmest summer on record. There were significant impacts, including wildfires, disruptions to transport and power systems, and increased mortality.

40C days are becoming more likely due to ‘escalating climate trends’. That’s a curious turn of phrase. But Dr Gillian Kay, a senior scientist, clarifies the issue (apparently):

Dr Gillian Kay, Senior Scientist at the Met Office, and lead author explains: "The chance of exceeding 40°C has been rapidly increasing, and it is now over 20 times more likely than it was in the 1960s. Because our climate continues to warm, we can expect the chance to keep rising. We estimate a 50-50 chance of seeing a 40°C day again in the next 12 years. We also found that temperatures several degrees higher than we saw in July 2022 are possible in today’s climate.”

So, it’s a warming climate that is responsible, aka imminent Thermageddon supercharged by your gas boiler and your car. Few people - and even fewer journalists - will look any further than this. But this Substack is fuelled by Heineken when it comes to extreme weather/heatwave studies - it reaches the parts other media cannot reach.

Dr Gillian Kay is the lead author of that Met Office study:

So, she oughta know wot she’s talkin’ about, right? Wrong.

The first thing to note is that prior to 2022, when 40C or above was recorded at several UK weather stations in SE England (at RAF jet runways or other non-ideally located stations for all of one or two minutes probably), another Met Office study found that the chance of exceeding 40C in the UK was very low. This was only in 2020, two years before the extremely unlikely happened!

The possibility of exceeding 40°C in the UK was mooted a few years ago, using a multimodel analysis (Christidis et al., 2020). A low probability was estimated for the 2020s, with a return time of 100–300 years, although this is likely to be conservative given that models have been reported to underestimate trends in summer extreme temperatures in northwest Europe (e.g. Patterson, 2023; Vautard et al., 2023). Now this threshold has been surpassed, the question arises of when we should expect a repeat – could this happen again in the climate of today and in upcoming years?

But magically, now that the extremely unlikely (once in every 100-300 years) has actually happened, the chances of it happening again are once in every 24 years! Wow. Did the world change that much in just 5 years, or did ‘the science’ change?

Turns out that the science hasn’t changed and the world hasn’t really changed. All that’s happened is that the authors adopted a methodology first described in 2017 and, crucially, they validated their approach using the ‘fact’ that 40C+ had been observed at several Met Office weather stations in 2022; hence they estimated the ‘new’ return period of 40C+ in the ‘stationary climate’ of 2023 to be 1 in 24 years, not 1 in several centuries! Cute.

There are a few approaches available for estimating current chances of exceeding a threshold. Using observational data alone, making a well-characterised estimate via statistical methods is possible. However, it relies not only on the observations being a good sample of the underlying climate but also that we understand the structure of the underlying climate and can represent it in the statistical model. The UNSEEN (UNprecedented Simulated Extremes using ENsembles, Thompson et al., 2017) approach is not bounded by these assumptions, but instead uses physically based modelling that can capture a wide range of plausible climate outcomes in a changing climate, including those that have not occurred in our more limited observational sample.

Let’s not forget that, using statistical methods trained on observations only, World Weather Attribution found that the observations recorded at two weather stations during the 2022 heatwave were basically statistically impossible! As I pointed out at the time:

Statistical Analysis - Temperatures at 2 Stations were so Extreme they were Impossible!

But now that the impossible (or extremely unlikely) has happened, climate ‘scientists’ can recalibrate their ‘science’ using the new improved observational dataset and basically tell us that sizzling hot 40C+ heatwaves have got much more likely and are coming our way unless we ditch the car and the gas boiler and don’t use electricity unless we’re told to.

The authors don’t need no stinkin’ empirical data (observations) to generate their fantasy heatwaves either:

Daily maximum air temperatures (T_max) for the summer season (June–July–August, JJA), 1960–2023, are used in this study (92 days × 64 years). Model ensemble data are taken from the Met Office Decadal Prediction System, version 3 (Dunstone et al., 2016) (hereafter referred to simply as ‘the model’). It has a spatial grid resolution of ~60km over the UK, and ‘60km grid’ is used to refer to the model grid resolution elsewhere in this article. The model is initialised each 1 May and runs for 11 months, making the summer season months 2–4 of the forecast. The ensemble comprises 40 members, giving 40 times as many samples as in the observations, assuming independence of the ensemble members: 2560 against 64 summers of data.

But they do need observations in order to test their model and to do this, they transform the observations - ending 2022, the year of the 40C heatwave - to a ‘stationary’ 2023 climate.

In the like-with-like comparisons made in fidelity testing the model against the observations, and in the examination of the dynamics of extreme high UK temperatures, the observational dataset is transformed, like the model ensemble, to a stationary 2023 climate (Figure 1b).

The UNSEEN method relies on good model performance such that the model ensemble members are statistically consistent with the observations and can be used interchangeably. Therefore, fidelity testing is necessary to establish whether the model ensemble is suitable for use in this application.

Because we are concerned with understanding the tails of the distribution of daily data, model performance is assessed using Extreme Value Analysis methods, following Kent et al. (2022). Using the stationary 2023 Tx1d datasets, a generalised extreme value (GEV) distribution is fitted to the observational dataset (64 data points) with maximum likelihood estimation of the location, scale and shape parameters that describe the distribution.

Unlike WWA, who only had data prior to 2022 and who therefore concluded that some of the present observations were so unlikely as to be statistically impossible, these authors, when doing their GEV analysis with 2022 data included, found that the likelihood of 40C+ had increased from ‘extremely unlikely’ to once in every 24 years. Well knock me down with a feather! I didn’t see that coming! The new observational record including 2022 also conveniently allowed them to validate their fantasy model data (no doubt generated by the Met Office using the absurd RCP8.5 high end GHG emissions scenario).

Game, set and match for climate crisis hysteria? Not quite. Because the reason why the UK and western Europe is experiencing such extreme temperatures during summer is not, as Dr Gillian Kay and the parroting media would have us believe, solely, or even mainly down to increasing background surface temperature (climate change). Dr Kay’s study points this out, but she appears to have ‘forgotten’ about it when briefing the press - or perhaps the press ‘forgot’ to quote her in full (it does happen).

Western Europe is recognised as a global hotspot of increasing heatwaves (e.g. Kornhuber et al., 2024) and dynamical processes are thought to contribute to enhanced observed trends in this region (Rousi et al., 2022; Vautard et al., 2023). With the climate model ensemble, we can examine the dynamics of a larger sample of UK hot extremes and compare the model circulation patterns with the observations.

The unprecedented hot conditions in the UK on 19 July 2022 were part of a larger pattern of extremely high temperatures over western Europe, with southerly flow advecting very warm air from continental Europe across the UK (Kendon et al., 2023).

The pattern of anomalously high daily T_max across northern and western Europe is replicated in monthly mean air temperature composite anomalies for those months in which the highest UK temperatures occur (Figures 5d,e). The wider spatial pattern thus also has a longer temporal signature. Atmospheric circulation anomalies on monthly (Figures 5f,g) and seasonal (not shown) timescales show that persistent high pressure dominates northern Europe. The pattern projects onto the Summer North Atlantic Oscillation (SNAO), the positive phase of which is related to high temperatures and low rainfall in the UK (Folland et al., 2009; Dunstone et al., 2023). Anticyclonic conditions are associated with processes that allow warm air to build over Europe: increased shortwave radiation, subsidence and, if persistent, soil moisture deficits arising from reduced rainfall – as occurred in summer 2022 (Schumacher et al., 2024) – could then intensify heating via land surface-atmosphere feedbacks (Seneviratne et al., 2006; Miralles et al., 2014). The relative importance of adiabatic compression, diabatic heating and horizontal transport in generating heat waves over the British Isles has been investigated (Zschenderlein et al., 2019; Schielicke and Pfahl, 2022) and may vary from event to event, but on the very hottest days, including the 40°C event in July 2022, horizontal advection from the warmer continent may be the dominant process (Mayer and Wirth, 2025). Daily winds are not available from the model, but the pattern of daily MSLP (Figures 5h,i) indicates that on days of exceptionally high temperatures in the UK, anomalous southeasterlies advect hot air masses from continental Europe over the UK. This picture is consistent with other studies (Herrera-Lormendez et al., 2023; Patterson, 2023; Vautard et al., 2023) that find that exceptionally hot days over western Europe are marked by flow with a southerly component.

There you have it, straight from the horse’s mouth. The same study which the media, the UK Met Office and even the study’s lead author are promoting as an increased likelihood of 40C killer heatwaves because of climate change does not in fact point the finger of blame at climate change, but at anomalous atmospheric circulation. In particular, during the 2022 heatwave, when 40C was recorded at several UK weather stations, the dominant process which contributed to those extraordinary high temperatures was hot air being drawn up from southern continental Europe.

Caught. Red handed. The Media spreading misinformation about climate change and extreme weather. They should be facing prison - according to the EU and the UN.