Thursday 20 June 2019

Ireland may need radical thinking on climate change

Mallow Street, Limerick was closed when a tree fell from the Peoples Park during storm Darwin. Photo: Sean Curtin
Mallow Street, Limerick was closed when a tree fell from the Peoples Park during storm Darwin. Photo: Sean Curtin

John Sweeney

Ireland's moist and equable climate is a function of its location amid the mid latitude westerly wind belt and as an island bathed by the North Atlantic Drift.

Yet while the Atlantic dominates Irish climate, it acts on a rather unusual island topography of coastal uplands and an interior plain.

Many aspects of Irish climate therefore show a contrast between an exposed maritime fringe and a sheltered interior.

The main drivers, though, of the dramatic day-to-day weather changes Irish people are accustomed to result from often rapid changes in airflows between tropical, polar, oceanic and continental origins.

Overall, however, oceanic influences prevail. The moderating influence of the North Atlantic Drift provides Ireland with one of the most equable climates.

It takes around a year to deliver water from Florida to the Kerry coastline at around 10C in February and 16C in August. Mean January temperatures are a mild 7C along the south-west coast, falling to less than 4C in inland parts of Ulster.

The sea is cooler than the land in summer, however, and with a mean July temperature of 16.4C, Shannon Airport is almost 2C warmer than the northern tip of the island at Malin Head.

Oceanic influences discourage extremes in both seasons. The warmest summer of the last century was 1995 when 30.8C was recorded in Kilkenny, while 1962/3 was the coldest winter.

More recently, many readers will remember vividly the cold snap of 2010/11 when temperatures in the border counties dipped below -17C. Such extremes of heat and cold are, however, unexceptional in a wider European context.

The interaction between the topography and Atlantic airflows produces a classic west to east decline in rainfall with some parts of the western mountains receiving over 3,000mm annually while sheltered areas of the east coast only get around 750mm.

Despite our perception, it only rains 6.5pc of the time in eastern parts of Ireland, though rain may fall on 150 days of the year, and up to 225 days in the west.

Snow seldom lingers on the ground. Based on the past 50 years the chance of snow on the ground on a Christmas morning is about one in five.

Ireland has warmed by about 0.8C since the early 1900s. Climate modellers at Maynooth University and Met Eireann expect a further warming of about 1.5C to occur over the next 40 years.

Future rainfall changes are more uncertain, though winter increases and summer decreases are projected by most models, most likely with heavier, more intense downfalls. This has serious implications for flood occurrences in winter and also for water supply in some parts in summer.

The changing climate also has significant implications for agriculture, biodiversity, tourism, forestry and energy demand, and vulnerability in these sectors are being examined in a number of research projects.

A concern is the possibility of more storms, especially in conjunction with a rising sea level.

Last winter was the stormiest on record for this part of the eastern Atlantic. The events are still etched in many people's memory, particularly the January/February period with its hurricane-force winds and 25-metre waves.

Whether the warmer Atlantic will make destructive winter storms a more recurrent feature, or whether the storm tracks will migrate north is one of the great unanswered research questions of Irish climate at the moment.

A recent sequence of extreme seasons: cold winters, warm summers, cold springs, wet autumns, stormy winters though have heightened concerns that Ireland's climate is increasingly responding to global greenhouse gas loading of the atmosphere, particularly related to a less reliable westerly airflow in the high atmosphere.

If this turns out to be the case, radical new thinking on how to adapt to Ireland's changing climate will be required in many key areas.

Professor John Sweeney is a lecturer at the Geography Department of NUI Maynooth

Irish Independent

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