This is an extract from the March edition of Temperature Check, The Journal’s monthly climate newsletter. Sign up to receive Temperature Check to your email inbox for free in the box at the end of this article.
It has been a hell of a week at the North and South poles.
They haven’t quite turned into fire and brimstone just yet, but both the Arctic and Antarctic recorded major temperature jumps in recent days that are well above what’s expected at this time of year.
In Antarctica, temperatures at the Concordia Research Station on Dome C, one of the continent’s tallest summits, were not ten, not twenty, not thirty, but forty degrees above average for March, rising from around -50 to just -11 Celsius.
While it’s too early to know for certain whether climate change is the cause, scientists say the event was extreme and unexpected.
Let’s walk through why it happened and what it means.
The basic science behind the heatwaves is the same at the two poles – warm, moist air travelled to the regions from other parts of the globe.
Speaking to The Journal for Temperature Check, lead scientist at Berkeley Earth Dr Robert Rohde explained that the heatwave in the Arctic was what’s called an advection event.
“It’s when you have warm air from lower latitudes being pushed up into the Arctic by wind patterns,” he said. “It’s large-scale circulation blowing relatively warm air up into the Arctic, in this case, doing so around the North Atlantic.”
In Antarctica, the warm air came south in an “atmospheric river”, which is a “band of warm, moisture-saturated air in the atmosphere travelling towards Antarctica”.
So how exactly does this affect temperatures at the poles?
Professor Peter Thorne at Maynooth University has a useful analogy for explaining how warm air at the poles can increase temperatures.
If you think about how much heat it takes to melt your freezer and how much heat it takes to boil the kettle – that is, to change ice to water or to change water to water vapour – the process that happens with warm air at the poles is the reverse.
“There’s a heat output when you change from water vapour to water and from water to ice, so there’s been a huge amount of energy released by the phase changes of water over Antarctica in particular,” Thorne explained.
For the Arctic, the pattern of warm air in itself is not unusual, though it reached particularly high temperatures this week. It’s a “large example of a fairly common kind of disturbance”, Dr Rohde said.
Down south, however, it’s a different story. This was an entirely unexpected event for Antarctica that caught researchers by surprise.
“What happened in the Antarctic was much more surprising and unusual,” Dr Rohde said.
“Usually, the air is sort of middling in humidity – sometimes it gets very full of moisture, you get rain in places.
“In this event, you had a lot of moisture from oceans north of Antarctica being pulled through the air and coming ashore in a part of east Antarctica and dumping a lot of moisture into the air above Antarctica.
“Because it was warm, moist air, a lot of that heat was transferred to the surface. You had this moisture transferring warmth to the surface, and doing it very effectively – to a degree we’ve never seen before in the Antarctic.”
At Dome C, one of Antarctica’s tallest summits, he described the record-beating nature of the temperature as “astonishingly large”.
With a temperature around 40 degrees Celsius higher than usual, it beat the previous record for March by more than 20 degrees Celsius.
Meanwhile, Professor Peter Thorne noted that though the event in the Arctic “may not be as noteworthy or as unusual” as the event in Antarctica, it could signify the start of a longer period of unseasonable weather.
There may be a lower area covered by ice in the Arctic by the end of the summer this year – “but of course, we’ve got six months of weather to happen between now and then that might either put a stop to a melt or accelerate the melt”.
“The Arctic has been warm for weeks and weeks and weeks, unseasonably warm. So it’s possible that we will see a significant story unfold later in the summer – possible, but far from certain.”
“Seemingly, we have not seen this in the 60-odd years that we have on record in Antarctica, so it’s highly unusual,” said Professor Thorne.
“But whether that’s climate change is unclear.
“If we now get increasing numbers of those types of events in Antarctica, then we would very rapidly come to the view that it must be climate change.
“But a single extraordinary event like that? We can’t pin its occurrence, at least, on climate change.”
Dr Robert Rohde is on the same page.
“I don’t think there are very many people in the scientific community who are prepared to say this is definitely climate change, because, particularly in the Antarctic, we’ve seen this one time, and one time does not make for very good statistics,” he said.
“I think we need to have a better understanding of what just happened because it was very surprising.
“An analogy I’ve made before is to say that sometimes there are rare weather events that until you’ve seen them, you don’t expect them. If you were sitting in a coastal city and you had never seen a hurricane before – you might go 50 years without ever seeing a hurricane – and suddenly, a hurricane comes ashore, it changes your perceptions about what’s possible.”
Overall, it’s well-documented that human influence on the climate is unsettling global weather patterns, pushing up average temperatures, and increasing the likelihood, frequency and severity of extreme weather events.
Closer to home – separate to the polar events – Ireland has faced particularly warm weather this week, with Met Éireann recording temperatures of up to 18.5 degrees yesterday.
A single warm spell may or may not be due to climate change – but overall, we know that average temperatures in Ireland are rising at all times of the year compared to the past.
“The shoulder seasons, spring and autumn, are always variable,” said Thorne, but the Intergovernmental Panel on Climate Change is “very, very clear” that abnormal weather can occur at any time of year.
He said the weather this week is a “significant departure from the seasonal expectation”.
“Heatwaves have been made both more frequent and more severe due to human influence.
“Although there were heatwaves in the past, we should be making the connection here that some component of this current heat wave is driven by us and that we might expect to see increasingly more of these and more severe heatwaves as we move forward.”
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