WHAT CAUSED THE HEAT WAVE?
The heatwave was triggered by high pressure building over Europe in recent days, causing warm air to move northward from Europe over the UK.
“At this time of year, southerly winds will always lead to above-average temperatures,” said Peter Inness, a meteorologist at the University of Reading.
“Air from continental Europe, the Mediterranean and even North Africa is brought into the UK.”
“The eastward passage of the North Atlantic weather fronts and lows are currently being blocked by the high pressure over Europe,” added University of Reading climatologist Len Shaffrey.
WAS IT RELATED TO THE US HEAT WAVE?
The recent hot weather in the US was caused by a high pressure dome building up across much of the country, trapping summer heat.
This has far reaching effects.
“Heat wave conditions in the US Midwest and East Coast have strengthened the jet stream,” explained environmental scientist Kate Sambrook of the University of Leeds.
‘Resulting thunderstorms occurring on the mainland have helped the jet stream meander and move towards the north of the UK.
“As a result of this change, warm air has been drawn from Europe causing the high temperatures we are experiencing this week.”
The hot weather in the US had been caused by a high pressure dome building up across much of the country, trapping summer heat.
HOW LONG WILL THE HEAT LAST?
“Although there is some uncertainty in the forecast, it looks like it will get colder on Friday as the high pressure over Europe slowly moves eastward,” said Dr Shaffrey.
“This will allow the weather fronts to move over the UK, bringing cooler air and possibly some rain,” Professor Shaffrey added.
HOW HOT CAN IT?
Forecasters are forecasting high temperatures reaching 100°F (38°C) in central and eastern England on Thursday.
Although different forecasts anticipate slightly different details, “the general message of all the forecasts is the same,” said Dr. Inness.
“It will be hot, with high temperatures persisting through overnight periods, and there is a risk of some UK thunderstorms.”
These will continue through Wednesday.
“If conditions continue, we are likely to experience the warmest July on record,” said Dr. Sambrook.
“However, the outcome is uncertain as conditions are expected to change early next week.”
Oxford University climatologist Karsten Haustein added that “there is a 40% to 50% chance that this will be the warmest July on record.”
The final estimate depends on which observational data set is used, he noted.
While he agreed that next week’s weather will determine July’s place in the record books, Dr. Inness noted that 2019 brought us the warmest June known since the year 1880.
“In fact, 9 of the 10 warmest Junes on record in the world have occurred since the year 2000,” he said.
In Europe, he noted, this June was also the warmest on record, reaching almost a degree Celsius above the previous number one in 2003.
“Normally, weather records are not broken by such wide margins; a few tenths of a degree would be more likely.”
The current conditions may turn out to be record breaking, but they are also part of a recent trend towards hotter summers in the UK.
‘2018 was the hottest set [year] on record with the highest temperature measured at around 35C, similar to temperatures expected this week,’ said University of Leeds climatologist Declan Finney.
The probability of experiencing such hot summers has risen from less than 10 percent in the 1980s to 25 percent today, he added.
IS CLIMATE CHANGE PRODUCING HEAT WAVES?
“The fact that so many recent years have seen very high summer temperatures both globally and across Europe is very much in line with what we expect from human-caused global warming,” Dr Inness said.
“Changes in the intensity and likelihood of extreme weather is how climate change manifests itself,” said environmental scientist Friederike Otto of the University of Oxford.
That doesn’t mean all extreme events are more intense because of it, but many are. For example, each heat wave that occurs in Europe today is more likely and more intense due to human-induced climate change.
However, local factors also play a role, as each extreme weather event is influenced by location, season, intensity, and duration.
The current heat wave is not the only notable indicator of climate change, experts point out, as ongoing droughts, such as those experienced in many parts of Germany, are also in line with scientific predictions.
Research into the 2003 European heat wave suggested at the time that human activity had more than doubled the risk of such hot summers – and that annual heat waves like the ones we are experiencing now could become commonplace by mid-century.
“It has been estimated that some 35,000 people died as a result of the European heat wave in 2003, so this is not a trivial problem,” said Dr Inness.
“With further climate change, there could be a 50/50 chance of future hot summers,” agreed Dr. Finney.
“That’s similar to saying that a normal summer in the future will be as hot as our hottest summers to date,” he added.