Temperatures in the UK exceeded 40 degrees Celsius (104 degrees Fahrenheit) for the first time on Tuesday, making it the country’s hottest day on record.
Prior to 2019, the UK had only seen a city exceed 37.8 degrees Celsius (100 degrees Fahrenheit) one time in August 2003.
Since then, it has happened four times in four years. So what was before thought of as impossible, or maybe a one-in-100-year heat event, is now happening almost annually.
Stephen Belcher, the UK Met Office’s chief scientist, and Professor Paul Davies, the Met Office’s chief meteorologist, said there are three things that are making these conditions possible.
The first is a so-called “wavenumber 5 pattern,” Belcher, Davies and the Met Office said in a blog post on Tuesday. The wavenumber 5 pattern describes “the difference in surface temperature from their average values.” It shows that there is a wave-like pattern around the Northern Hemisphere with five regions of high-pressure, they explained, adding that these are the places likely to experience heat waves. The wavenumber 5 pattern also explains why it’s possible to have concurrent heat waves around the world, Met Office scientists said.
The Met Office says climate change, the second factor, also plays a role. Belcher and Davies wrote in the blog post that temperatures in the UK are “unprecedented in recorded history.”
“In a climate unaffected by human influence, climate modelling shows that it is virtually impossible for temperatures in the UK to reach 40°C,” the Met Office said in the blog.
Belcher and Davies said climate change is mostly driven by the accumulation of greenhouse gases in the atmosphere. Hotter conditions are a result of these gases combining with atmospheric circulation patterns — like the wavenumber 5 pattern, according to the Met Office.
The third factor that is contributing to the extreme heat is environmental and soil conditions, Belcher and Davies said.
“It has been a dry year over many parts of England. When the sun shines on the ground, dry soils cannot release energy through evaporation of moisture, which means that more of the sun’s energy goes into heating the air, further amplifying the temperatures in the UK,” the blog said, adding that climate scientists call this the soil moisture feedback.
“These three elements have come together in the UK: the global wavenumber 5 pattern driving high temperatures, in the presence of an already warmed climate due to climate change, further enhanced by the soil moisture feedback,” the Met Office added.
The consequences: The UK is woefully unprepared for the impacts of the climate crisis. It struggles to manage floods when they occur. In the heat, the nation buckles.
So many fires ignited in London on Tuesday that the city’s fire brigade declared a “major incident” and were stretched beyond their capacity. At least four people have drowned as people flocked to beaches, rivers and lakes just to try to get cool. Even a runway at an airport on London’s outskirts had to be closed off as it melted in the heat.
CNN’s Brandon Miller contributed reporting to this post.