Why is it so hot in the UK and around the world?

As Britain comes to the end of its second month of extreme heat, many British people are enjoying another week of basking in the never-ending sunshine.

However, as the heatwave continues the Met Office has issued a health warning urging people to stay out of the sun and a hosepipe ban has been brought into force.

Worldwide, soaring temperatures are taking a far more serious toll. Deadly wildfires have torn through Greece and Sweden and a record 41.1C has been recorded in Japan, where after claiming 65 lives, the heatwave has been declared a natural disaster.

More than 22,000 people have also been taken to hospital, with heat stroke, nearly half of them elderly.

As the UK heads towards record temperatures and the world continues to heat up, many have started to question what is behind this spate of hot weather, and how it fits into our understanding of climate change.

1. What is causing the current phase of hot and dry weather in the UK?

   While hot weather during summer – even a British summer – is perfectly normal, it tends to be broken up by occasional rainfall.

   Currently, a high-pressure weather system situated over the UK is steering storms that normally find their way to the UK northwards to Iceland.

2. Is climate change to blame?

   Luck plays a role in determining the weather and the current heatwave is no exception.

   “We have always had heatwaves and we always will. With the UK being in the mid latitudes we get a variety of different weather types, and the natural variability of our weather is the stuff of legend,” said Grahame Madge, a spokesman from the Met Office.

   “What we can say is that with a background of climate change, we know that the planet has warmed by around 1C since pre-industrial times, and we know that if you add that heat to the system it is very likely heatwaves will be more extreme.”

   Mr Madge said it was too soon to say for sure how big an impact man-made climate change has had, but Met Office scientists would soon be able to work it out exactly once they have collected the necessary data.

   Professor Len Shaffrey, a climate scientist at the University of Reading, added that one way to think about this link is in terms of probability.

   "Global temperatures are increasing due to climate change," he said. "The global rise in temperatures means the probability that an extreme heatwave will occur is also increasing."

3. What other factors are contributing to the heatwave?

   “The current hot and dry spell in the UK is partly due a combination of North Atlantic Ocean temperatures, climate change and the weather,” said Professor Shaffrey.

   Temperatures in the North Atlantic can influence weather in the UK because they affect the strength and direction of the jet stream.

   Warmer ocean waters of the kind seen this summer have pushed the jet stream further north and influenced the high pressure system that has led to heatwaves across the UK and Europe.

   Meanwhile, far away in the tropical Pacific Ocean temperatures tend to swing between a warm phase known as El Nino and a cooler phase known as La Nina.

   Although the region was in the grip of La Nina since October, its effects began to weaken around April and had almost vanished by June, just as the current hot spell began.

4. How hot is the UK compared to historical heatwaves?

   Professor Shaffrey predicted that if current weather patterns continue the summer could turn out as hot and dry as the extreme heatwave that struck Britain in 1976.

   Then, the country hit its hottest average summer temperature on record – with a temperature of 32C or more recorded for 15 consecutive days.

   Heatwaves of similar magnitudes have struck Britain sporadically, but Professor Shaffrey said the biggest concern is that they are likely to be more common in the coming years.

   “Recent studies have assessed that climate change has increased the probability of extremes such as the 2017 European 'Lucifer' heatwave by a factor of at least four,” he said.

5. Is a similar phenomenon taking place around the world?

   Vast swathes of the northern hemisphere in particular have experienced prolonged heatwaves in recent months and the results have often been deadly.

   Temperatures in the Algerian city of Ouargla hit 51.3C at the beginning of July, setting the record for the highest reliably recorded temperature on the continent of Africa.

   Meanwhile, the wildfires that struck north of the Arctic circle were a reminder that it is not only warmer regions feeling the effects of this global heatwave.

   While it is difficult to attribute these events to wider phenomena while they are still happening, experts predict that as in the UK climate change and related factors like a weakening jet stream are the likely culprits behind them.