How freezing winters are indicative of climate change

The sudden bitter temperature drop this winter is a result of climate change and not fuel or evidence for the climate naysayers – the science behind how that works.

When climate change is addressed, the often-used buzzword ‘global warming’ seemingly associates it solely with heat. Articles and media packages are often illustrated with facts, figures and stats from summers - I’m talking mass heat waves, record-breaking heats and Glasgow buildings melting.

However, although it may not be the type of extreme weather typically associated with climate change, the extreme cold snaps experienced in Europe, America and China over the start of December and the ‘beast of the east’ of March 2018 are also symptoms of global warming. Perhaps counterintuitively, global warming doesn’t necessarily mean that our winters will become milder. Climate science instead suggests that we may experience more varied seasons and fewer but more extreme spells of cold over the winter – cold snaps. Seem familiar? Let’s discuss the science behind it.

Naturally, we should experience different winters - due to a phenomenon known as arctic oscillation. To break weather and this concept down, air moves around the world from areas where it is denser (high pressure) to areas where it is less dense (lower pressure). Arctic Oscillation is known as the movement of the air between the North pole and the south. If there is high-pressure air in the polar regions, the arctic air is pushed southward – giving us a colder and wetter winter . If there is high pressure in the south, the warmer air pushes northward, keeping the arctic air at the poles and resulting in a milder winter.

Tracking and understanding this natural cycle enables meteorologists to predict the upcoming weather and its natural variation from year to year, as well as allowing our weather forecasters and Siri to lovingly spell out whether we will be needing to wear our flip-flops or winter-coats. Importantly, the Gulf stream (a horizontal strong band of wind high-up in the atmosphere) is also responsible for keeping the coldest air away from the south. Cold snaps are becoming more extreme to a level non-associated with natural variation caused by arctic oscillation because this jet stream is becoming weaker. As it does, it allows sudden strong releases of cold air from the artic that would usually be kept at bay.

Representation of how a wavy polar vortex can affect the jet stream and induce cold-snaps. Created on Biorender.com by Hannah Dodd-Vastiau

This weakening can directly be linked back to climate change as increasing temperatures cause more ice and glacier melt, which leads to the cooling of the arctic ocean and an altered Atlantic current. This current determines the strength of the gulf-stream – which is currently at its weakest state in 1000 years as stated by Levke Ceasar from the University of Bremen.

A warmer climate also disrupts the polar vortex, a massive swirling vortex of low-pressure and cold air at the poles. Warmer Air in the atmosphere causes this vortex to wave and weaken, which also goes on to disrupt and weaken the gulf stream – again causing us to all cling to our hot water bottles when arctic air is released to the south.

The bottom line, these harsh and sudden cold spells are evidence of climate change and should serve as a further warning of unreliable and extreme weather to come with our current climate trajectory.

Image by Sean Gentle from Pixabay