Tag: HadUK

Effect of UHI This Summer

As I wrote a couple of days ago, there is a big discrepancy between the Met Office’s HadUK dataset, which shows this summer as being 0.4C hotter than 1976, and its own CET series, which shows the two summers as tied.

A busy street in London with pedestrians walking, featuring the iconic Big Ben clock tower and the Houses of Parliament in the background.

From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

Table showing Central England temperatures from 1659 to 2025, organized by seasons and years, including ranks for winter, spring, summer, and autumn temperatures.
https://www.metoffice.gov.uk/hadobs/hadcet/data/meantemp_ranked_seasonal.txt

As I wrote a couple of days ago, there is a big discrepancy between the Met Office’s HadUK dataset, which shows this summer as being 0.4C hotter than 1976, and its own CET series, which shows the two summers as tied.

One of the major differences between the two datasets is that CET is based on rural stations, unlike HadUK. It is therefore worth looking at the Min and Max temperatures:

A table comparing summer temperatures for the years 1976 and 2025 across three categories: Mean, Max, and Min, with data from HadUK Midland and CET.

Both datasets show 1976 as being hotter in terms of daily max temperatures, though the gap is smaller on HadUK.

But the biggest difference between the two sets is on minimum temperatures, which accounts for about two-thirds of the difference in mean temperatures.

This begs the question of how much UHI has contributed to HadUK temperatures this summer. We know that many of the sites used by the Met Office are urban, that the UHI effect has increased in recent decades and that the Met Office do not adjust for it.

While we all have our theories, it is plainly not our job to prove or disprove anything. The massive discrepancy between CET and HadUK must now be explained by the Met Office themselves.

It is, of course, a much wider issue than a single comparison with 1976. The whole HadUK dataset is contaminated with spurious UHI warming, which cannot simply be waved away.

Finally, have a look at this little puzzler, which compares CET with Heathrow:

A table comparing summer temperatures recorded at Heathrow and the CET for the years 1976 and 2025, showing mean, maximum, and minimum temperatures along with the differences.

What I want to draw your attention to is the relative figures for Minimum temperatures. The comparison with 1976 is virtually identical between CET and Heathrow, both about 0.7C lower in 1976.

Heathrow is 0.74C warmer this summer, which is much less than the 1.49C listed for HadUK.

We regularly rightly call out the heat spikes during the day at Heathrow, but at night the heat there quickly dissipates, unlike in urban areas.

This is strong evidence that HadUK minimum temperatures are inflated by UHI effect.

Hottest Summer?

The Met Office have been widely mocked and accused of gaslighting for declaring that the UK has just had the hottest summer on record, which they say was a whopping 0.4C hotter than 1976.

A stylized map of the United Kingdom on a fiery background, symbolizing extreme heat or climate change.

From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

The Met Office have been widely mocked and accused of gaslighting for declaring that the UK has just had the hottest summer on record, which they say was a whopping 0.4C hotter than 1976.

At first sight, this claim is absurd. The heatwaves in 1976 were far more severe and longer lasting than this summer, which frankly never got out of the ordinary. Taking daily max temperatures on CET, in 1976 there were nine days above 30C, with a highest of 33.1C. Despite repeated claims of “four heatwaves” this year, only two days topped 30C this summer, with the highest being just 30.7C

Now the Met Office’s claim however has been contradicted by their own Central England Temperature series, which still shows 1976 as the hottest, albeit tied with this summer.

This is not a regional anomaly, as the Met Office’s figures, part of the HadUK dataset, also show the Midlands region as hotter than 1976, and by an even bigger margin of 0.5C. The Midlands covers almost exactly the same geographical area as the CET.

Map of the United Kingdom showing different regions marked in varying shades of green, indicating temperature data or climate zones.

Below is a chart of recent hot summers, comparing HadUK with CET. What stands out is how much 1976 has been marked down on HadUK; the same is also true of 1995 and 2003, both of which are similar on CET to 2006 and 2022, but are much lower on HadUK:

A graph comparing mean temperatures of seven recent hot summers in the Midlands region, highlighting differences between HadUK and CET datasets.

If we compare summer temperatures since 1884 for both datasets, we see that for most of the record CET has run about 0.6C higher – ignore the absolute numbers, they show that the idea of an “average temperature” across a region is not a scientific concept; it is the trends that matter.

But then around twenty years ago, that gap dropped to about 0.2C. In short, since around 2006, HadUK Midland temperatures have run 0.4C hot compared to CET.

There is no logical reason why this should be so.

A graph showing summer mean temperatures in the CET less HadUK Midland region from 1880 to 2020, with temperature changes illustrated in orange bars against a white background.

The CET is carefully constructed  and based on rural stations. HadUK, however, is largely made up of junk stations, so poorly sited that that temperatures recorded may be as much as five degrees too high. We have had this discussion many times.

But on top of this, many of the Met Office sites are also in heavily urbanised areas.

In short, the Met Office’s UK dataset is not fit for purpose and only has propaganda value. If, as the graphs suggest, UK temperatures are being overstated by 0.4C, the whole of the Met Office’s narrative is destroyed.