For the second time in less than one month, a widespread and intense heatwave impacted Europe, with many new maximum and minimum temperature records, disruption to transport and infrastructure and stress on people's health and the environment.
Belgium, Germany, Luxembourg and the Netherlands saw new national temperature records, as temperatures passed the 40° Celsius mark at the peak of the heatwave on 25 July. In France, Paris recorded its hottest day on record, with a provisional temperature of 42.6 °C at 1632, an unprecedented value since the beginning of measurements. The United Kingdom saw its hottest July day on record.
National meteorological and hydrological services have issued heat alerts - including the top-level red alert - and, in some areas, fire warnings to minimize the risk to life and the environment.
The heatwave was caused by warm air coming up from North Africa and Spain. According to forecasts, the atmospheric flow will transport the heat towards Greenland, resulting in high temperatures and consequently enhanced melting. Persistent high melt and runoff the last few weeks but season total running just below 2012 record high loss, according to climate scientists with the Danish Meteorological Institute. This will also impact Arctic sea ice, which where the loss of ice extent through the first half of July matched loss rates observed in 2012, the year which had the lowest September sea ice extent in the satellite record, according to the US National Snow and Ice Data Center.
The July heatwave follows an unusually early and exceptionally intense heatwave in June, which set new temperature records in Europe and ensured that the month of June was the hottest on record for the continent, with the average temperature of 2° Celsius above normal.
June was also the warmest June on record globally, with severe wildfires in the Arctic.
Climate change and heatwaves
“Such intense and widespread heatwaves carry the signature of man-made climate change. This is consistent with the scientific finding showing evidence of more frequent, drawn out and intense heat events as greenhouse gas concentrations lead to a rise in global temperatures,” according to Johannes Cullmann, Director of WMO’s Climate and Water Department.
“WMO expects that 2019 will be in the five top warmest years on record, and that 2015-2019 is to be the warmest of any equivalent five-year period on record,” he said. WMO will submit a five year report on the state of the climate 2015-2019 to the UN Climate Action Summit in September.
Many scientific studies have been conducted on the links between climate change and heatwaves.
"Every heatwave occurring in Europe today is made more likely and more intense by human-induced climate change," said a study published by scientists at World Weather Attribution on the Human contribution to record-breaking June 2019 heatwave in France.
"The observations show a very large increase in the temperature of these heatwaves. Currently such an event is estimated to occur with a return period of 30 years, but similarly frequent heatwaves would have likely been about 4 ºC cooler a century ago. In other words, a heatwave that intense is occurring at least 10 times more frequently today than a century ago," it said.
In its Fifth Assessment Report (2014), the Intergovernmental Panel on Climate Change said that “it is very likely that human influence has contributed to the observed global scale changes in the frequency and intensity of daily temperature extremes since the mid-20th century. It is likely that human influence has more than doubled the probability of occurrence of heat waves in some locations.”
In its 2018 report on Global Warming of 1.5°C, the IPCC said that climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5 °C and increase further with 2 °C.
Limiting warming to 1.5 °C rather than 2 °C could result in 420 million fewer people being exposed to severe heatwaves, it said.
Between 2000 and 2016, the number of people exposed to heatwaves was estimated to have increased by around 125 million persons, as the average length of individual heatwaves was 0.37 days longer, compared to the period between 1986 and 2008, according to the World Health Organization.
Many countries have issued national climate assessments and scenarios which underline the close connection between climate change and heat.
For instance, the UK State of the Climate report showed an increase in higher maximum temperatures and longer warm spells. The hottest day of the year for the most recent decade (2008-2017) has increased by 0.8°C above the 1961-1990 average. Warm spells have also more than doubled in length – increasing from 5.3 days in 1961-90 to over 13 days in the most recent decade (2008-2017).
The summer of 2018 was the joint warmest on record for the UK as a whole and the hottest ever for England. The Met Office research showed that human-induced climate change made the 2018 record-breaking UK summer temperatures about 30 times more likely than it would have been naturally. By 2050 these are expected to happen every other year.
France has also reported an increase in the frequency and intensity of heatwaves over the past 30 years, according to Météo-France, in an observation echoed elsewhere in Europe.
Swiss climate change scenarios warn that if greenhouse gas emissions continue to increase, by the middle of this century, average summer temperatures may be up to 4.5 °C higher than now.
“The increases in the highest temperatures are even more pronounced than for the average seasonal temperatures. By 2060, the hottest days in an average summer could be up to 5.5 °C higher than they are today. This is explained in part by the fact that less water will be evaporating and cooling the ground because there will be less moisture in the soil,” says the Swiss report.
“The regions of Europe that surround the Mediterranean Sea, including Switzerland, are affected by some of the most severe increases in temperature extremes worldwide. This trend has been apparent even over recent decades and is very likely to continue into the future,” it says.
The new absolute record of 42.6°C for Paris was recorded on 25 July at the centennial weather station in Paris-Monsouris, and broke the previous record dating back to 28 July 1947 with 40.4 °C. This temperature is typical of the average July temperature in Bagdad, Iraq. The night of 24/25 July was also exceptionally hot, with minimal temperatures above 25°C and even 28.3°C in a downtown Paris weather station. What is striking is the margin with which the records were beaten. Lille recorded 41.4°C, that’s nearly 4°C above the previous record. France set a new national temperature record of 46°C during the last heatwave on 28 June.
It was only the second time Méteo France has ever issued red level warnings for a heatwave in France. The first time was during June's heatwave when several departments in the south were put on red alert. But it is unprecedented for Paris and the north of the country to be on a red alert for a heatwave.
Météo France said, "all of us are threatened, even healthy people." It adds: "The danger is greater for seniors, people with chronic illness or mental health issues, people who take regular medication and people who are isolated." Those who work outside are told to take care and watch out for the signs of heatstroke.
The German Weather Service, Deutscher Wetterdienst, described 25 July as A day which will make weather history. Germany set a new national temperature record (provisional figure) of 42.6°C in Lingen, near the Dutch border, defeating the old record by 2.3 °C. There were 25 weather stations above 40 °C. The previous national temperature record was 40.3°C (5 July 2015).
The Netherlands broke a 75-year-old heat record (set in Aug 1944) with a temperature of 40.7°C at Gilye Rijen. Belgium also set a new national record of 41.8°C. Luxembourg set a new national record of 40.8°C.
Temperatures in the United Kingdom reached 38.1 Celsius in southern England, setting a new record for the highest July temperature recorded in the UK. The new record was set in Cambridge at 15:37 this afternoon, beating the previous record of 36.7°C set in Heathrow in 2015, according to the Met Office.
Météo-France is warning that the heatwave will accentuate the drought because it has not rained in many parts of the country since the end of the last heatwave at the start of July. A number of places have set new records for the lowest amount of rainfall since records started, including 0.2 mm at Orly airport, 1 mm in Lille. Thousands of hectares were burned by wildfires in northern France, where it is very unusual to see wildfires. In Normandie alone, a total 1500 hectares burnt yesterday with 28 different fires. This region never experienced such a situation before.
Spain’s national meteorological service, AEMET, is also forecasting temperatures of above 40°C and AEMET is warning of extreme fire risk in large parts of the country because of a combination of heat, wind and lightning. A fire raged in central Portugal at the start of the week.
National meteorological and hydrological services in Europe work closely with national and local authorities on heat-health action plans to protect lives. These heat-health early warning systems have activated civil protection efforts across the region.
Heat events kill thousands of people every year and often trigger secondary events such as wildfires and failures to electrical grids.
Urbanization compounds the problem. Heatstroke, dehydration, cardiovascular and other temperature-related diseases are major health risks.
During the ongoing heatwave, public transport was disrupted and authorities in many cities imposed limits on private cars to try to keep pollution in check.