Why Are Heat Waves Becoming Common In The UK? Know What Causes Them | EXPLAINED

UK Heatwave: The Met Office has issued a rare 'Amber Warning' that covers most of England and half of Wales. Exceptionally high temperatures are possible from July 17, lasting into early next week.

A heatwave is sweeping across the United Kingdom (UK) and continental Europe. On July 11, 2022, temperatures soared to 32 degrees Celsius in the UK. 

The Met Office, the national weather service of the UK, has issued a rare 'Amber Weather Warning' that covers most of England and half of Wales.

On July 11, the Met Office wrote that "exceptionally high temperatures" are possible from Sunday, July 17, lasting into early next week. 

What Is Amber Warning?

The Met Office issues weather warnings, through the National Severe Weather Warning Service, in order to warn of impacts caused by severe weather. The UK's official weather service provides warnings up to seven days ahead for rain, thunderstorms, wind, snow, lightning, ice, extreme heat and fog. The warnings are given three colours — yellow, amber or red — depending on a combination of both the impact the weather may have and the likelihood of those impacts occurring. 

Amber warning is used to represent an increased likelihood of impacts from severe weather, which could potentially disrupt one's plans. There is a possibility of road and rail closures, and power cuts, damage to property, travel delays and cancellations, and loss of water supplies, among other risks. Therefore, people must think about changing their plans and taking action to protect themselves and their property. 

What Is A UK Heatwave?

An extended period of hot weather relative to the expected conditions of the area at that time of the year, which may be accompanied by high humidity, is known as a heatwave. A UK heatwave threshold is said to be met when a location records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold. The threshold varies depending on the UK county. 

The revised thresholds use the 1991-2020 averaging period introduced in January 2022. The heatwave threshold daily maximum temperature could be 25 degrees Celsius, 26 degrees Celsius, 27 degrees Celsius, or 28 degrees Celsius, depending on the county.

Geographical differences result in climate differences across the UK. 

What Is Causing A Heatwave In The UK?

According to the Met Office, heatwaves are most common in summer when high pressure develops across an area, and can occur in the UK due to the location of the jet stream, which is usually to the north of the UK in the summer. 

The jet stream is a core of strong winds around five to seven miles above the Earth's surface, blowing from west to east, and causes changes in the wind and pressure at that level, affecting things nearer the surface, such as areas of high and low pressure. This helps shape the weather. 

Slower jet streams can allow high pressure to develop over the UK, resulting in persistent dry and settled weather. 

A system called the Azores High is responsible for the UK heatwave. The Azores High is a large, persistent atmospheric high-pressure centre that develops over the subtropical region of the eastern North Atlantic Ocean during the winter and spring seasons in the Northern Hemisphere, and moves westward during the summer and fall.

The Azores High usually sits off Spain, but has grown larger and pushed farther north. This has brought high temperatures to the UK, France and the Iberian Peninsula, an article published by The Guardian said.

The UK has become 0.9 degrees Celsius warmer in the past three decades.

Will It Get Hotter In The UK?

Annie Shuttleworth at the Met Office said that the UK will cool a little in the middle of the week, as cooler air pushes down from the north, according to the article. However, southern England will still have temperatures in the high 20s.

After this, the jet streams are expected to turn southerly, and this will bring hot air up from north Africa and the Sahara. Shuttleworth said that at the end of the week, temperatures will be close to 40 to 45 degrees Celsius across France and Spain. The UK will tap into some of the heat in the wake of a southerly wind.

In the month of July, the days are long and nights are short, as a result of which strong sunshine builds up high temperatures. Night-time lows are potentially above 20 degrees Celsius in central England and affect sleep. 

There is a strong chance of the hottest day of the year so far in the UK occurring this week, the article stated. The temperature may surpass the 32.7 degrees Celsius recorded at Heathrow on June 17. The all-time UK record, which is the 38.7 degrees Celsius recorded in Cambridge University Botanic Garden in July 2019, could be beaten.

Is Climate Change Responsible For The UK Heatwave?

In a UK series from 1884, Summer 2018 was the equal-second warmest summer for mean daily maximum temperature, shared with 1995. Research shows that climate change is making heat waves more likely.

The Met Office had conducted a scientific study into the Summer 2018 heatwave in the UK, and found that the likelihood of the UK experiencing a summer as hot or hotter than 2018 is a little over one in 10. 

Due to the higher concentration of carbon dioxide in the atmosphere, it is 30 times more likely for heat waves to occur now than before the industrial revolution, according to the study.  

As greenhouse gas concentrations increase, heatwaves of similar intensity are projected to become even more common and frequent, according to the Met Office. The heatwaves may occur as regularly as every other year by the 2050s. Since the pre-industrial period (1850-1990), the Earth's surface temperature has risen by one degrees Celsius. The UK temperatures have risen by a similar amount. 

According to the Guardian article, human-caused heating is making every heatwave more intense and more likely. Dr Friederiko Otto of Imperial College London said that when it comes to summer heat, climate change is a complete game changer and has already turned what would once have been called "exceptional heat into very frequent summer conditions". The fossil fuels burnt over the last decades have caused every heatwave experienced today to become hotter than before. 

Impact Of The Heat Waves 

Temperatures will soar above 40 degrees Celsius in western continental Europe. According to the article, Europe as a whole experienced its second warmest June on record, at about 1.6 degrees Celsius above average. The extreme temperatures were recorded from Spain to France to Italy.

Heatwaves could be a severe threat to public health because they may cause heatstroke and dehydration, which are the main risks to health, particularly affecting young children and elderly people. 

Dr Laurence Wainwright of the University of Oxford said that heatwaves can have a significant impact on mental health, and that there are "positive associations between daily high temperatures and suicide". 

Dr Michael Byrne of the University of St Andrews said that the current heatwave is a dangerous reminder of the accelerating impacts of global warming, and that London is expected to feel like Barcelona by 2050. He also said that the UK is braced for more frequent and severe heat waves over the coming years.

According to the Met Office, the adverse health effects for those vulnerable to heat include sunburn, heat exhaustion and other heat-related illnesses. 

During a heatwave, failure of heat-sensitive equipment may occur. Loss of electricity, water supplies and gas is also possible. 

There is a likelihood of some disruption to travel. This may result in heavy traffic and queues. 

Due to the heatwave, there is also an increased risk of water safety incidents.

The UK experienced heatwave conditions lasting 10 days in August 2003. The heatwave conditions resulted in 2,000 deaths.

A record maximum temperature of 38.5 degrees Celsius was recorded at Faversham in Kent in 2003. Similar conditions occurred in July 2006, breaking records and resulting in the warmest month on record in the UK. 

The 2003 maximum temperature record was broken at Cambridge University Botanic Garden in the summer of 2019.

Heatwave Plan

The UK Health Security Agency, in association with the Met Office and other partners, has created a heatwave plan to aid in the preparation and awareness before and during a spell of very hot weather. It recommends a series of steps to reduce the risks to health from prolonged exposure to severe heat for the National Health Service (NHS), local authorities, social care, and other public agencies; professionals working with people at risk; and individuals, local communities and voluntary groups. 

Human Influence Increasing Likelihood Of Temperatures Above 30 To 40 Degrees Celsius In The UK: Study

According to a 2019 study published in the Nature Communications journal, summers in the UK are getting warmer as European heatwaves are becoming more severe. The study showed that human influence is increasing the likelihood of temperatures above 30 to 40 degrees Celsius in the UK. 

The authors noted in the study that the "probability of recording 40°C, or above, in the UK is now rapidly accelerating and begins to rise clearly above the range of the natural climate".