On Tuesday 19 July, a temperature of 40.3°C was reached in Coningsby, Lincolnshire, breaking the previous high temperature record of 38.7 °C set in 2019. Local records have been broken at 46 stations across the country. Minimum temperatures were also very high, with 25.8°C while recorded at Kenley, Surrey, broke the previous record from 1990 at 1.9 °C.

Extreme Heat and Climate Change: Attribution Studies

The heat wave is very well predictedand the Met Office, UK Meteorological Office, issued an extraordinary high temperature warning long before the arrival of historical heat. The UK Health Safety Agency heat health alert level 4 has been issued for Monday and Tuesday. This warning level is used when a heat wave is so severe and/or prolonged that its effects extend beyond the health and social care system. At this rate, disease can occur in healthy and fit people, not only in high-risk groups.

Scientists from South Africa, Germany, France, Switzerland, New Zealand, Denmark, the United States and the United Kingdom collaborated to assess how much human-caused climate change is changing the likelihood and intensity of heat waves.

Using published peer-reviewed methods, we analyzed how human-caused climate change alters the probability and intensity of these heat waves in the red alert region (see Figure 1). To capture the duration of the event, as well as the temperature record, we looked at the maximum and average 2-day highs observed.

Main findings

The heatwave of 2022 is estimated to have drowned at least 13 people, bringing challenging conditions to the NHS with increased emergency calls and care services supporting the elderly and vulnerable under stress. death associated with extreme heat. The impact is uneven across demographics. Even in London, there is a high degree of inequality in temperature experienced, with certain, often poorer, neighborhoods lacking green space, shade and water that can be lifesavers during a heatwave.

While Europe is experiencing increasingly frequent heat waves in recent years, the heat recently observed in the UK is just as extreme which is also a rare event in today’s climate.

The average observed temperature over 2 days is estimated to have a return period of approx. 100 years in the current climate. For a maximum temperature of 1 day over the region shown in Figure 1, return time is estimated to be 1 in 1000 years in the current climate. Note that the temperature return period varies between different measurements and locations and is therefore highly uncertain.

In the three individual stations, 1 day highs are as rare as 1 in 500 years at St James Park in London, approximately 1 in 1000 years at Durham and only estimated to average once in 1500 years in the current climate of Cranwell, Lincolnshire.

The probability of observing such an event in a world with a temperature of 1.2°C is very low and statistically improbable in two of the three seasons analyzed.

Observational analysis suggests that the UK heatwave, as defined above, would have been about 4°C cooler in pre-industrial times.

To estimate how much of these observed changes were due to human-caused climate change, we combined climate models with observations. It is important to underline that all models systematically underestimate the observed trend. Therefore, the combined results are almost certainly too conservative..

Combining the results based on observational and model analysis, we find that, for both event definitions, man-made climate change makes the event at least 10 times more likely. In the model, the same event would have been about 2°C colder on a 1.2°C cooler world, which is a much smaller change in intensity than was observed.

This difference between the modeled and observed trend and variability is also makes it difficult to be confident in projecting future trends.

Heat wave risk

Heat waves during peak summer pose a major risk to human health and are potentially deadly.. This risk is exacerbated by climate change, but also by other factors such as population aging, urbanization, changes in social structure and level of readiness. The full impact is only known after a few weeks when the death toll has been analyzed. An effective heat contingency plan, coupled with accurate weather forecasts such as those issued before this heatwave, reduces impact and becomes even more important given the increasing risk.

World Weather Attribution