Much has been written over the past number of weeks in relation to the possibility of Ireland facing one of the coldest winters on record, with crippling blizzards predicted to inflict an icy misery across the country for much of an extended winter season. Such apocalyptic predictions it must be stressed have originated from the same British tabloids and sensationalist weather forecasters who annually predict ‘Britain’s Coldest Winter in Centuries Ahead’, which very frequently materialise into nothing more than typical British winters with a covering of snow across the Scottish Highlands, or across the Lake District. However, could 2019/20 be the year when such predictions, though not quite as sensationalist, do in fact materialise? Indeed will 2019/20 be a record-breaking winter in terms of low temperatures and snowfall? Or rather will we experience average conditions, bringing an end to what has been an extraordinary year in Irish meteorology. Here’s my reasoning why I believe winter 2019/20 may in fact be a colder than average winter, not just across Ireland, but indeed across much of Western Europe.
Jet stream variations
In the age of global climate change, where globally temperatures have increased on average at about one degree Celsius since the dawning of the industrial age, or rather some 0.6 degrees Celsius since the start of the last century, it seems to be somewhat paradoxical to talk of the possibilities of Irish winters becoming ever more unpredictable and in some cases potentially even colder than normal. Climate change has proven to occur in non-liner trends, meaning that while globally temperatures have increased at a rate of 0.6 degrees Celsius, over the Arctic this warming has been in the range of 2-3 degrees Celsius. This general distortion of the temperature gradient between the mid latitudes and higher latitudes has caused a weakening of the jet stream, which causes the jet stream to meander and buckle leading to prolonged spells of stationary weather patterns, such as we experienced during this summer’s heatwave. These findings have been pioneered by the work of Dr Jennifer Francis, who believes that the extreme weather conditions experienced across Europe over the past number of decades is testament to the slowing and meandering of the jet stream, caused by a weakening of temperature gradients which drive the jet stream eastwards across the Atlantic. With such patterns increasing it’s logical to at least consider that the risks of colder spells of weather would increase as opposed to our average climatic conditions.
Atlantic multidecadal oscillation
Did you know that the Atlantic Ocean itself enters into a multidecadal warming and cooling cycle, whereby the weather patterns over the Atlantic and surrounding areas are altered considerably? Such decadal oscillations have had considerable effects on our observed weather patterns over the past century, with each phase of the cycle typically lasting between 20-25 years. One theory as to why Ireland experienced such mild winters during the nineties and noughties was due to the AMOs positive phase, which results in the increased flow of westerly winds, warmer temperatures across much of western Europe, and a considerable reduction in European snowfall. However, a recent paper published in 2017 by Dr Elanor Frajka-Williams suggests that we may be entering into a negative phase of the AMO, resulting in an increase in the number of colder than average European winters. Early signs for this coming winter suggest that Sea Surface Temperatures (SST,s) across the Atlantic are consistent with the onset of a negative AMO, with colder than average SSTs observed across the sub-polar Atlantic, warmer than average temperatures across the sub-tropical Atlantic, and cooler than average conditions being found across the tropical Atlantic.
The final observation that I will mention refers to perhaps the least understood of all the potential reasons as to why winter 2019/20 will be colder than average. In fact the origins of the last observed factor in my 2019/20 winter forecast originates some 150 million kilometres away from the island of Ireland, in a place where the average temperature is some 5’400 degrees warmer than that of our own! I am of course referring to the sun. The sun too enters periods of activity, defined by low and high activity. These fluctuations between high and low activity are called solar cycles, and typically last around 11 years in duration. During periods of particularly low activity, known as solar minimums, it’s been observed that Europe experiences particularly cold winters, with the last observed minimum coinciding with the exceptionally cold winter of 2009/2010. Perhaps the most notable sequence of particularly cold winters in Europe occurred during what has become known as ‘the little ice age’, a period when solar activity remained exceptionally low from around 1600-1850, coinciding with severe European winters in which many of Europe’s sea ports froze over, with ice fairs being held on the river Shannon and other Irish rivers rather frequently in winter. As we look ahead to winter 2019/20 it’s certainly worth noting that our current solar cycle is expected to reach its minimum at some point over the coming months and persist through a considerable portion of 2020.
We’ve now looked at some of the major parameters, which typically influence our seasonal meteorological conditions, not just in Ireland, but rather in much of western Europe. We’ve observed how considerable natural variations can interact with the anthropogenic changes associated with climate change, influencing our weather in ways that we previously considered unimaginable. These changes in our annual atmospheric patterns are often dominated by natural forcing events such as the AMO and Solar Cycles which stamp their individual authority over the daily conditions that we observe here on the earth’s surface. But taking each of the observed parameters into account, I personally feel that winter 2019/20 will be a colder than average winter across the country, with lower than average rainfall totals, but with observed increases in seasonal snowfall amounts, particularly along eastern and northern coastal areas, along with many central areas of Ulster and Leinster.