Environment

Q&A: What is causing these severe snow warnings?

A climate scientist at Maynooth university explains what is likely to happen in coming days

Commuters walking in the snow on London Bridge, as temperatures take a dive. Photograph: Steve Parsons/PA Wire

Peter Thorne
Mon Feb 26 2018 - 16:20

Met Éireann has warned of a "very serious weather event" this week predicting a level of snowfall not seen in years.

There is a likelihood of red weather warnings in places due to a combination of freezing cold and strong winds but what is causing the “beast from the east” and will it live up to its name?

Will it be as bad as predicted?

It will certainly be a high impact event. There are so many predictions out there, the key is to use and refer to trusted sources. In this case, recourse should be made to Met Éireann. It is also important to note that snow impacts can be very local. Especially sea-effect snow which we shall likely experience in the next few days. These snow showers set up aligned with the wind in bands so if the wind does not shift, snow can fall across a narrow line for a prolonged period. Just because you may miss the snow does not mean its not impactful even a few kilometres north or south of you.

Any danger of a repeat of 1947, when a months-long blizzard caused many deaths?

No. The 1947 winter event, started much earlier in the winter season. As people will have felt over the weekend the sun is now getting higher in the sky and feels warm even when the air is cold. The returning sun will win out much more quickly than was the case in the 1947 event which started in January. Meteorological spring starts on Thursday, not that it will feel like it.

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How much of it is linked to climate change?

The event has been caused by a major event in the stratosphere high up over the Arctic (50km high) that may have been made more likely by the fact that the Arctic is warming faster than the tropics. But that is very much a maybe, not definitive. On the flip side, the fact we are in a warmer world means the event is less cold than it would have been without climate change.

Is this a sign of the future? Or just bad luck?

Overall, the warming climate has made such events less impactful. But the scientific jury remains out at this time whether they are being made more or less likely.

Is there any link between this and what happens in the summer – El Nino, etc?

There is a slight increased chance of this when the El Nino phenomenon is in the La Nina state (the cool phase), which it is now. Such La Nina states increase the chances of an unusually cold late winter or early spring over northwest Europe.

How often do we get snow?

There have been many worse winters in the past, but not in the last 30 years. Met Éireann have a good compendium of historical events available at www.met.ie.

In modern times, snow is synonymous with Christmas. Christmas cards, songs and scenes from the Victorian period, notably in Charles Dickens’s novels, all portray snow falling at Christmas, as Met Éireann pointed out in a pamphlet in 2012.

The origins of a White Christmas may, it said, originally have come from the ‘Little Ice Age’ that occurred during the period 1550-1850. In Ireland, snow occurs most frequently in the months from December to March.

Countrywide snow fell on 17 Christmas days, at a least one of our Synoptic stations, since 1961 (1961, 1962, 1964, 1966, 1970, 1980, 1984, 1990, 1993, 1995, 1998, 1999, 2000, 2001, 2004, 2009 and 2010).

There were nine Christmas days (1964, 1970, 1980, 1993, 1995, 1999, 2004, 2009 and 2010) with snow lying on the ground at 9am in the morning, during this period. The maximum depth of snow ever recorded on Christmas day was 27cm at Casement Aerodrome in 2010.

Are there different types of snow? Does dry snow make it more difficult for motorists?

Yes, the Inuit have hundreds of words for different types of snow. Typical snow we get is very big and fluffy with high moisture content. These events will tend to disrupt power, damage trees etc. Drier, smaller snow flakes are more of a nuisance but less likely to stick. Given the changing sources of snow, over the week we may get a mix of snow types starting with dry type and changing over to our more typical fare (better for making snowballs/snowmen at least). Regardless, drivers should drive with due caution.

Why is it colder when the wind comes from the East at this time of year?

Our typical weather comes from the west. During the summer the Atlantic stores a lot of heat that it gives back up over winter. Europe and Asia cool down much more quickly. So, right now Europe is frigid and the Atlantic warm. Switching the winds around brings in this much colder weather.

How much damage can this do? Does it kill first grass permanently? Does it damage soil if it lasts?

It will do little lasting damage, although it may significantly affect winter crops and delay the onset of the growing season.

There have warnings about wind chill. Why is it dangerous?

Wind chill, caused by the passing flow of lower temperature air, can lead to hypothermia, and, ultimately death. Particularly at risk are the homeless, the young and the elderly. Keep an eye on those most vulnerable. Met Éireann has said it could potentially take temperatures as low as minus 9 degrees.

How dangerous is it to animals?

Animals can suffer just like humans. Pets should be kept in overnight and farm animals housed appropriately.

Advice for homeowners?

Keep the house warm enough to avoid freezing. Leave several taps dripping (no need for more than drips) to try to avoid pipes freezing and bursting.

Peter Thorne is Professor in Physical Geography (Climate Change) at NUI Maynooth and Director of the Irish Climate Analysis and Research Unit group (Icarus)

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