We Irish people are notorious for discussing the weather. In many parts of the world, especially the tropics, the weather remains the same for long periods of time. Not so in Ireland: since we live on the edge of the Atlantic, the weather is changing all the time. However, March 2013 was the coldest March in Ireland since records began more than 70 years ago. The biting wind from the east added two or three degrees Celsius wind-chill factor to already low temperatures.
Farmers were very badly hit. Because of the low temperatures, there was very little growth and farmers had to keep their animals in sheds for two to three weeks more than they normally would. The situation is exacerbated by the poor summer of 2012 which resulted in few farmers having sufficient silage or hay to feed to their animals during the winter of 2012/2013. Now they have to buy expensive fodder to feed their animals.
During March I was often asked, ‘How can you continually claim that global warming and climate change is happening when northern Europe has experienced one of the coldest Marches in decades?’ The first thing to say is that the weather experience for one year does not constitute a change in the climate. Secondly, many forget that March 2012 was one of the hottest months of March since records began, while March 2011 was an average month in terms of temperature.
Most people think that global warming will lead to higher temperatures everywhere. Scientists are now beginning to challenge this assumption, especially as far as northern Europe is concerned. They are wondering whether the recent cold spell is linked to changes in the jet stream, which is a current of high winds blowing 10 kilometres up in the atmosphere. The jet stream separates cold winds coming from the Arctic from the warmer winds which emanate from the tropics. Normally, by the month of March, the jet stream moves northwards bringing warmer air from the sub-tropics. This is why the usual March weather in Ireland is wet, windy and mild.
Scientists are researching whether the cold weather we experienced on March 2013 and in the winter of 2010, is due to the fact that the melting of Arctic sea ice, pushes the jet stream further north and weakens it.
During the past 30 years the percentage of sea ice in the Arctic has fallen by 40%. During late 2012 and early 2013, the extent of sea ice was near or below average levels throughout most of the Arctic.[1] For scientists such as James Overland of NOAA’s Pacific Marine Environmental Laboratory, the question is not “if there will be nearly ice-free summers (in the Arctic) but when.” The growing consensus is that it will happen before 2050.[2]
Professor John Sweeney from the Geography Department of NUI Maynooth, recently called attention to some research which links the fairly dramatic drop in Arctic sea-ice to the movement of the jet stream. “The link is that as we warm up the Arctic, the light ice surface which reflects heat is replaced by dark sea surface which absorbs more heat, the jet stream is being displaced because it doesn’t have to blow so hard to displace the cold.”[3]
In 2013 the jet stream behaved very differently. Instead of keeping the cold at bay, scientists point out that it was weak. The image they use is the contrast between a fast-flowing river and one that meanders slowly. As the jet stream loses its momentum, strong easterly winds from the Arctic begin to dominate the weather in much of northern Europe including Ireland. So, each summer, as more and more of the Arctic sea ice melts, the jet stream seems to lose even more energy. As a result the cold weather which northern Europe experienced in March 2013 and in the winter of 2010 might become a much more regular feature of winter weather systems in Ireland. Because of these changes Professor John Sweeney could not rule out bitterly cold weather becoming a feature of the Irish winter. Because of such a counter-intuitive outcome, Sweeney believes that we should stop using the term global warming when what is at stake is climate change. In some situations, such as the Arctic and Antarctic, climate change will mean that temperatures will increase. In temperate climates such as Ireland, it might mean colder winters.
[1] http://nsidc.org/arcticseaicenews/
[2] “Arctic Nearly Free of Summer Sea Ice During First Half of 21st Century, Experts Predict,” April 12, 2013, http://www.sciencedaily.com/releases/2013/04/130412142848.htm?utm_source=rss1.0&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29
[3] Paula Melia, “Chilling changes take icy grip on our climate,” The Irish Independent, April 10, 2013, pages 18-19.