Snow on the Acropolis does not herald a new Ice Age.
Klassekampen, 26 February 2021
It's like clockwork: as soon as it freezes somewhere – like -27.5 degrees Celsius in Hemsedal, Norway recently – the climate skeptics wake up from their hibernation. In this case, it was none other than the vice-speaker of parliament, Morten Wold, who in a Facebook post put the strong frost forward as proof that global warming isn't that bad. A fallacy, of course, because no serious climate scientist has already referred winter to the history books. It isn't surprising either that it's cold in a ski resort, like Hemsedal.
And still: it was also cold in other, less common places. In Texas, where everything is said to be bigger anyway, temperatures dropped almost to 20 degrees below zero. Gas pipes froze and water pipes burst. Power plants were unprepared for the low temperatures, causing outages across the state. As a result, millions of Texans were left without electricity, water and heat. Dozens of people lost their lives, directly from the cold or from carbon monoxide poisoning after desperate efforts to keep warm.
In Europe it wasn't much warmer: huge amounts of snow were falling from the sky in Spain, the Acropolis looked like an arctic ruin in Athens, and people were skating with glee on the canals in Amsterdam for the first time in a decade. If you didn't know better, you would think that a new ice age had arrived.
But this week we saw the other extreme: people were already having a picnic in the sun in the Netherlands, records were broken with temperatures above 20 degrees in northern Germany, and the snow melted quickly after the mercury quickly rose to 25 degrees in Texas. It has even started to thaw in Hemsedal in the meantime. What's going on here? Has the weather gone crazy? How is it possible that it's extremely cold at first, but dozens of degrees warmer straight after?
We have to look to the Arctic for a possible explanation. While cold weather prevailed in Europe and the US, it was unusually warm in the Arctic. In fact, arctic sea ice has become so thin that last week a commercial ship was able to complete the Northeast passage – a first for this time of year. Ironically, this was an LNG tanker that sailed from China to the Yamal Peninsula to collect natural gas, thus only accelerating the melting of the sea ice. And it's going so quick already: there is hardly any sea ice to be found north of Spitsbergen while it should have been there this time of winter.
The loss of millions of square kilometers of sea ice is one of the main reasons why the Arctic is warming more than twice as fast as the rest of the world. Sea ice reflects most sunlight, while the open ocean mainly absorbs sunlight and warms up as a result. Due to more open water and a warmer ocean, temperatures are rising higher than before.
These kinds of outbreaks of cold arctic air are not new
When the Arctic gets warmer, this decreases the temperature difference with the tropics. This temperature difference is one of the drivers behind the jet stream, the strong wind high up in the atmosphere, at the cruise altitude of aircraft. When the jet stream is strong, and maintains a relatively straight west-east pattern, cold arctic air remains trapped in the polar region. This was the case a year ago when it was particularly cold in the Arctic while we had a mild winter in Europe.
The idea is that if the temperature difference between the tropics and the polar region diminishes due to climate change, we will get a weaker jet stream that will wobble from north to south in a wave-like motion. If this happens, there can be "outbreaks" of cold air to the south, like in Texas. On the other side of that wave movement, a lot of warm air is blown to the North and temperatures rise to much higher levels than usual. When such a weather system moves to the east, you can experience a sudden transition from extremely cold to extremely warm weather.
However, not all scientists are convinced that a warmer polar region leads to more extreme winter weather. A study in Nature Climate Change last year showed that climate models and measurements do not provide an unambiguous answer about the underlying cause.
The thing is, these kind of outbreaks of cold arctic air are not new – they have always happened. Ten years ago, a winter storm also led to power outages in Texas. In 1989 there was even an outbreak of cold arctic air almost identical in size and strength to the one that happened this month. Because these kinds of situations do not occur often, people are poorly prepared for them. This leads to disastrous consequences which of course make the news. But this rarity also makes it difficult to find out whether this weather phenomenon is increasing. There is simply too much statistical noise.
In other words, more time and more research is needed to determine whether climate change has caused this winter's extreme weather. It is possible, but it can also be the randomness of the weather. In any case, it is clear that cold winter weather is not a thing of the past, even in a warmer world. Also in Hemsedal.
This text originally appeared in Klassekampen on 26 February 2021