July 13, 2024

I, Science

The science magazine of Imperial College

Just what caused us to fall back into the bitter cold of midwinter when spring was meant to be on the horizon?

The mild February weather was marked by Woodland Trust reports that spring was showing signs earlier than in previous years. Yet, the month ended and spring officially started on the 1st March amid one of the coldest and snowiest weeks recorded in the UK in years. The Beast from the East swamped across the country bringing in a bitter cold weather front from Siberia and Scandinavia that affected all of Britain, from the Scottish northeast all the way down to the south westerly tips of Cornwall and further west to Northern Ireland. To make things worse, damage was exacerbated by the arrival of Storm Emma from the Southwest, which met the icy blast head on.

Brits love a chat about the weather, and the extreme conditions have been widely covered in the media as the snow provoked devastating chaos across the UK causing deaths, water and gas shortages, and closures of roads, schools and hospitals as the Met Office issued several red alerts. And while media coverage included an Animals Footprints Quiz and extended to discuss the financial damage caused by the snow, which has continued to affect the northern areas of the country, perhaps unsurprisingly, very little has been said this about the atmospheric science behind all the havoc of last week.

But the very unusual meteorological indicators are worth noting, as reported at the BBC by the UK Weather Forecast Channel. The British climate is normally temperate oceanic, with four marked seasons. Generally mild temperatures and distributed rainfall which are influenced by masses of air called jet streams hitting us from southwest towards the northeast across the Atlantic ocean. Our climate is also affected by the North Atlantic Drift ocean current, which carries warm waters from Florida towards Europe. Additionally, unstable weather conditions called Atlantic depressions form on the Atlantic and travel east towards Britain carrying warm and moist air.

Storm Emma, an area of low pressure formed over the Atlantic, arrived from the west running moisture northwards into the UK and combined with the unusually strong mass of dry and cold air, known as the Beast from the East, which was travelling southwards to cause heavy snowfall. The unusual combination granted the Met Office to warn of the possibility of freezing rain occurring, which is rare in the UK. This occurs when falling snow, ice, sleet or hail passes through a warm layer of air on the way down to the ground, melting into liquid water droplets. If these droplets then meet a layer of sub-zero air above the ground, they become super cooled and freeze.

To add the chaos, the disruptive weather hitting the UK also affected marine wildlife causing masses of sea creatures to wash up from the North Sea onto the English coastline. Speaking to The Guardian, Bex Lynam, from the Yorkshire Wildlife Trust explained that “there was a 3°C drop in sea temperature last week which will have caused animals to hunker down and reduce their activity levels. This makes them vulnerable to rough seas – they became dislodged by large waves and washed ashore when the rough weather kicked in.”

While spring is being delayed in the UK by the unusually cold temperatures, climate scientists are pointing to the unprecedented warming of the Arctic Circle seen in recent weeks, with the North Pole and northern Greenland reported to be up to 22°C (40F) warmer than usual. Also, new research published in Nature indicating that spring is arriving in the Arctic 16 days earlier than it did a decade ago. And scientists are linking the two events.

Speaking to the BBC4 Inside Science programme and podcast, earth scientist Professor Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research in Germany explained there has been a breakout in the North Pole. ‘Usually the cold Arctic air is fenced in the so called Polar Vortex and this vortex seems to be weakening in the recent decades, and more and more often it virtually breaks down in the stratosphere and even reverses slightly, which is associated with this very cold air moving over the Eurasian continent while it is extremely warm over the Arctic ocean.’

We should certainly be alarmed, but can we say these changes are down to climate change? While conservative meteorologists commenting on the weather this last week seemed to agree that no individual weather episode can be linked to climate change until it becomes a pattern, climate scientist reporting on the warming of the Arctic were more assertive of the effects of global warming in weakening the Polar Vortex. Perhaps it is as the Guardian Editorial said on the weekend: ‘It is human nature to worry more about 2 cm of snow falling in our backyard today than all the oceans of the world rising by 10 times as much over the next century’.

Marcela Leite is studying for an MSc in Science Communication at Imperial College London

Banner Images: Oxford in the snow, Flickr