OBSERVER: A wrap-up of Europe’s summer 2022 heatwave

OBSERVER: A wrap-up of Europe’s summer 2022 heatwave

OBSERVER: A wrap-up of Europe’s summer 2022 heatwave
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Thu, 22/09/2022 – 10:41

Data from the Copernicus Climate Change Service (C3S) show how unusually intense and widespread the heatwaves across Europe this summer have been. Together with prolonged dry periods, they have contributed to higher-than-average wildfire activity and severe droughts; and several countries have reported thousands of additional deaths.

What is a heatwave?

Perhaps surprisingly, there is no standard definition of a heatwave. The World Meteorological Organization suggests a heatwave is ‘statistically unusual hot weather persisting for a number of days and nights’, but countries adapt this guideline based on the impact on the local population. For example, high humidity and low wind speeds exacerbate heat stress on humans. In addition, the number of days a heatwave lasts, overnight temperatures and number of additional deaths are also important factors to consider. Therefore, although a heatwave is a meteorological event, human impacts are key.

An unusual year

The consequences of the heatwaves of 2022 have affected hundreds of millions of people, with implications for health and wellbeing, agriculture and food supplies, energy prices and demand, natural ecosystems, and river, air, rail and road transport.

Each episode has been striking; either because of the extreme temperatures reached locally, their duration, and/or unusually early occurrence in the season. Many local, national and regional temperature records were broken, or came close to being broken.

Exceptional events, but in line with the global trend

Although exceptional, these events were not unexpected. They are in line with the evidence presented in the latest IPCC Assessment Report, which indicates that the frequency and intensity of heatwaves continues to increase. These changes are attributed to human-induced climate change with high confidence and are expected to last, or maybe even amplify, as the climate warms globally.

May – southwestern Europe

The first signs of unusually warm weather in Europe appeared during May, when hotter-than-average air from the western Sahara moved northwards pushing the temperature up in waves in several areas of southwestern Europe, including Portugal, Spain, southern France and parts of western Italy.

At a national level, May 2022 temperatures set many new records, starting with France, where it was the warmest May since records began in 1900. It was the warmest May in 92 years of records for Portugal, and only May 1964 was warmer for Spain, in a data record starting in 1961, according to the analyses of the respective national meteorological services.

Many local records were also broken. The Spanish city of Seville reached 41°C, a first for the month, and Jaén experienced both its hottest day in May and the highest daily minimum temperature ever recorded in May in mainland Spain.

Portugal reported a heatwave in the first half of the month and a ‘heat burst’, an exceptional sudden rise in temperatures, later in the month. This relatively rare phenomenon was seen also in southern France in mid-May.

At a regional scale, the C3S ERA5 reanalysis, in a database going back to 1967, shows that in 2022 southwestern Europe [1] recorded the highest average May daily maximum temperatures, ahead of 2015, 2020 and 2017. The minimum daily average temperatures were also the highest; slightly higher than in May 2020 and 1999.

Averages of daily maximum and minimum surface air temperature anomalies for southwestern Europe[1] for the month of May from 1967[2] to 2022, relative to 1991–2020. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

Unusually warm temperatures continued into the early summer

Heatwaves continued to take place over several regions of Europe during June. These events left a mark on the monthly average temperatures: the month as a whole was, jointly with 2021, the second warmest June on record for Europe.

Southwestern Europe, including parts of Spain, Italy and France, continued to experience long spells of exceptionally high temperatures. Following the shorter period of unusually warm temperatures that peaked on 21 May, a longer episode of exceptionally high temperatures occurred four weeks later, peaking on 17 June. Average temperatures then fell rapidly in the region, although heatwave conditions developed further to the east and north.

Daily maximum temperatures in Spain, France, and Italy reached above 40°C, exacerbating the ongoing drought conditions in the Po river basin. Numerous June temperature records were broken across France and Spain.

Averages of daily maximum (red) and minimum (blue) temperatures during March to June 2022, for southwestern Europe. The temperatures are shown alongside the maximum and minimum for 2017, the warmest year on record for the region.

The heat persisted through the summer

Europe continued to experience unusually warm temperatures in July, with an intense and prolonged heatwave that started in Spain and Portugal before spreading further north and east, towards France, the United Kingdom, central Europe and Scandinavia. Dry conditions also continued throughout July, exacerbated by the heat. As a result, some countries saw record high temperatures and recorded their driest July ever.

In mid-July, an area of high pressure settled over western Europe. Combined with hot air flow from North Africa ahead of a trough moving northeastwards from west of Portugal, this led to more heatwaves which affected the majority of western Europe.

Temperatures reached more than 40°C for at least one day in Spain, France and the United Kingdom. In particular, the UK saw a national daily maximum temperature record of 40.3°C, set at Coningsby in Lincolnshire on 19 July – the first time the country had ever recorded a temperature of over 40°C. The observation network data indicate that the previous UK temperature record of 38.7°C (recorded in July 2019) was met or exceeded at 46 stations across the country.

Longevity and extremes

In general, western Europe saw a larger number of days with temperatures above 35°C and 40°C than a typical July. While the heatwave daily temperatures were extreme, in some regions reaching local and national records, it was mainly the duration of the period with daily maximum temperatures between 35°C and 40°C that characterised July; particularly in southwestern Europe.

The number of days above 30°C was also well above average, but, as with the number of days above 35°C, generally not record-breaking. The low number of days above 35°C in southeastern Europe is also noteworthy, again indicating that the heat mainly affected the southwest.

July 2022 was the warmest on record in southwestern Europe in terms of average maximum temperatures. Average minimum temperatures were also among the top three warmest Julys.

Animation showing a heatwave over the west of Europe in the middle of July. ERA5 daily mean temperature anomalies over Europe in July are indicated relative to the daily average for the period 1991–2020, showing warmer-than-average (red) and colder­-than-average (blue) conditions. Source: C3S/ECMWF.

High temperatures continue into August

As the summer drew to a close, temperatures for August were higher than average across most of Europe. The far east of the continent saw the most-above-average temperatures, but southwestern regions were still much warmer than average.

Temperatures were also generally high in the western regions, but lower than the extremes experienced earlier in the summer, or in August 2003 and 2021.

C3S support

More detail about surface air temperatures across Europe and the rest of the world can be found in the C3S monthly Climate Bulletins. Monthly, seasonal, and yearly data are freely available in the C3S Climate Data Store (CDS). Find out more about C3S reanalyses and ERA5 in the reanalysis Q&A.

Working with key climate-sensitive sectors, C3S has developed applications, based on quality-assured and freely accessible data, to support public and private sectors in their climate-sensitive decisions. For example, due to artificial infrastructure and human activities, urban areas are often significantly warmer than their rural surroundings. These higher temperatures can negatively impact human health. Using C3S ERA5 climate reanalysis data on air temperature, specific humidity, relative humidity and wind speed, the demonstrator application set up by VITO reports on urban heat island intensity for 100 European cities from 2008 to 2017 at a high spatial resolution of 100 metres.

The application shows locations at risk of urban heat stress and enables users to visualise the spatial distribution of cool spots in a city. This information can be used by urban planners, for example, to develop a network of accessible cool spots that are promoted during heatwaves. It can also support the implementation of local adaptations, such as the requirement for green roofs in building codes.

The impact on the population of hot, and cold, weather, can be visualised using another application – the Thermal Assessment Tool. This will support public health and urban planning managers, climate change researchers, and other stakeholders to visualise past and future climate trends and make appropriate decisions.

*C3S is implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission.

Notes

[1] The southwestern Europe region used to calculate the anomaly timeseries is defined as land bounded by longitudes 25°W and 15°E and latitudes 36°N and 45°N, excluding the region bounded by longitudes 0 to 12E and latitudes 36 to 38N.

[2] For the time series shown and discussed in this article, C3S relied on the period 1967–1978 of the final release of the ERA5 dataset back extension. This is the period for which the back extension is the most reliable over the regions considered.

Thu, 22/09/2022 – 12:00

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