Ireland's Weather: Changing Climes
The horrible summers of 2007 and 2008 are insufficient as yet to say that climate change is upon us. But global warming is incontrovertibe, say meteorologists, and climate change will happen. By Malachy Browne
Ireland has had a miserable summer for the second consecutive year, with some of the wettest summer weather in recent decades. In June 2008, above normal rainfall was recorded almost everywhere in the country, and the south and south east of the country recorded twice the normal June rainfall. Last year, 2007, was worse. It was the wettest Irish summer for at least nine years, the wettest for 50 years in parts of Leinster.
Typically, June is usually the driest month for many southern parts of Ireland and less rain falls in eastern parts of Ireland than in the west. So these statistics buck the meteorological record.
However climatologists at Met Éireann say there is no objective explanation for the recent weather. “I think we're well within the limits of normal fluctuations”, says Liam Keegan, Head of Climatology and Observations at Met Éireann. “People have got themselves to thinking that we get good summers, and really, bad summers in Ireland are not unheard of.”
Liam Keegan says it's not possible to say yet if climate change has impacted on Ireland. “It's not impossible that our weather is already being influenced by climate change,” he says. “But there's random [weather] that goes on all the time. What we're seeing at the moment could well be random variations in weather that we have always got. The signal isn't large enough yet to say it's abnormal”.
However, Liam Keegan says that the evidence on global warming is incontrovertible. “You can unequivocally say that Ireland is warmer than it has ever been. You can draw that graph”. Although 1945 was the warmest year of the last 100 years, 10 of the 15 warmest years occurred since 1990 and the last decade has been the warmest.
Currently, average temperatures are around 8°C in the winter and 18 to 20°C in summer, up 0.7°C on 100 years ago. Much of this warming occurred since 1980. Community Climate Change Consortium for Ireland (C4I) is a research group studying climate change. It says that Ireland's average temperature will increase further, by 1°C to 1.5°C in the years 2021 to 2060 compared with 1961 to 2000.
While wider climate change patterns are as yet “inconclusive”, both Liam Keegan and C4I say that Ireland's climate will change as a result of global warming. “The warming of the atmosphere will bring about in a complex way a whole series of changes,” Liam Keegan says.
Indeed, one prediction is for Ireland to have drier summers, rather than the wet summers of late. And this is particularly true of the east. “Overall there won't be any great change [in total rainfall] over all the country, but there will tend to be less rain in the east in the summer, and more rain in the west”, says Liam Keegan.
Tido Semmler, a climatologist with C4I, predicts an increase in “heavy rainfall events” resulting from a warmer climate. Warmer air is more moisture laden, he says. “With increased temperature, the probability of heavy rainfall events is larger,” he says.
Other predictions include a four-fold increase in the number of “extra-tropical cyclones” with wind speeds of at least 66 knots (76 miles per hour). These are the remnants of severe Atlantic hurricanes which “can be very destructive, with severe winds or heavy rainfall”, according to C4I. Tido Semmler says that Ireland currently sees one or two “extra-tropical cyclones” annually, and four to six may be experienced annually in coming decades, on average.
Sea levels are expected to rise by 25 to 44cm around Irish coasts due to glacial melting. Couple the expected rise in sea levels with more storms and C4I predicts a significant increase in ‘extreme surge events', with water heights of over 1m, particularly in winter. “The vulnerability to flooding is clear,” a C4I report says.
Liam Keegan says an greater number of tornadoes has also been recorded. “It could be just that the country is more populated and everyone has a mobile phone with a camera in it,” he says. “But there is a suspicion that we're seeing more [tornados]. It wouldn't be inconsistent with a warmer climate; there's a bit more energy around in general”.
Ecological consequences will also arise, and C4I says “the impact on agriculture will be substantial”. There will be fewer frost days, a lengthening of the growing season and “a tendency for pests and diseases (e.g. Bluetongue) in southern parts of continental Europe to move northwards towards Ireland.” Bluetongue is an insect-borne viral disease of sheep and cattle.
Liam Keegan says there is also the possibility that mosquitoes that exist in warmer climates will move north to Ireland, and eastern areas might experience “water stress” in drier summers. Research conducted by Peter Wyse Jackson, Director of the National Botanic Gardens says that 20 per cent, or 170 plant species native to Ireland are threatened by climate change (see panel above). He says that potato growing may become economically unviable in Ireland – mud may be too wet to plant potatoes in spring and irrigation may be required if summers are drier.
However, doomsday speculation that the Gulf Stream could stop or slow arising from melted ice caps has been dispelled, says Liam Keegan. “Melting of sea ice doesn't matter,” he says, “because it doesn't affect the salinity of the water.” But if ice sitting atop Greenland melts, or if Siberia's big freshwater rivers melt and pour into the Arctic Ocean, this could reduce the salinity of the extreme North Atlantic. “No one can say definitely,” says Liam Keegan, “there is a mechanism going on there, but nobody is seriously suggesting that it is going to stop.”
Botanical effects of climate change
According to Peter Wyse Jackson, Director of the National Botanic Gardens continued global warming will adversly impact on Irish plant species. Flowering plants may be out of synch with pollinators, the balance of habitats may be disturbed and some plants may ‘out-compete' with other plants.
There could likely be a 20 per cent loss in the native Irish flora – 170 native Irish plants are threatened by climate change. Some exist on the southern limit of their range in Ireland, some exist in coastal habitats vulnerable to storm surges, and plants in higher areas might be forced out due to the creep of species from lower areas upward. There is also the potential for invasive species and pests to arrive.
Giant rhubarb (left) is spreading rapidly in rural bog lands and will impact on other species
Loveage, a wild herb used for culinary purposes on the north coast of Ireland may disappear
Wild asparagus which grows on sand dunes, and the crucifer, sea kale – a relative of cabbage which used to be grown in gardens may also be lost to climate change
Alpine meadow grass, a remnant of the last ice age, which is already down to a tiny population, grows only atop Benbulben and Mt Brandon. This may be forced out due to competition from other species
Potato growing may become economically unviable if climate predictions are correct. Mud may be too wet to plant the crop in Spring, and drier Summers may require expensive irrigation systems to be put in place
How Irish weather works
Ireland's weather is determined by its location at the north-western edge of Europe. The Atlantic, the Gulf Stream, continental Europe and latitudinal location all play a part. Ireland experiences a mild maritime climate by virtue of its proximity to Atlantic waters - water warms and cools more slowly than land, acting as insulation in winter and a coolant in summer.
Ireland's Atlantic waters are warmed by the Gulf Stream, the flow of water north east from the Gulf of Mexico, and this is particularly important. Warmer Atlantic waters create considerably different atmospheric conditions than Canada's eastern seaboard which is fed by the much cooler Labrador Current.
To the east, Europe's huge continental land mass experiences varying degrees of ‘continentality', or extremes of weather. The influence of these extremes is felt in Ireland with southern or easterly weather – generally, dry warm spells in summer and cold spells in winter. Easterly spells also tend to be hazy, especially in summer, when dust, pollution and pollen drift across from Europe.
Ireland's weather is also affected by its position in the mid-northern latitudes. Atlantic weather is typified by successive waves of depressions – weather systems centred on areas of low pressure. Depressions are generally ‘wrapped' in weather fronts generating rain and strong winds. In the middle latitudes, Ireland lies very near the main track of these sweeping weather patterns.