Why Ireland’s Rainfall Was So Much Heavier Last Winter, As Scientists Warn We Face ‘Wetter, Damper And Mouldier Future’

Rainfall in Ireland during the past autumn and winter storms was made about 20pc heavier by climate change.

Analysis of the downpours and flooding that hit towns, farms and businesses between October and March shows they were more intense and caused more damage because of the distorting effects of raised global temperatures.

The study was carried out by an international team of climate scientists in the World Weather Attribution (WWA) group, including Met Éireann staff.

They looked at Ireland and the UK in late 2023 and early this year when both countries experienced a “very active storm season”, with 14 named storms.

Storms Babet, Ciarán, Henk and Isha were some of the most damaging, leading to severe floods, damage to homes and infrastructure, power outages, travel cancellations and loss of crops and livestock.

At least 13 deaths were attributed to incidents in storm conditions in the two countries.

Met Éireann climatologist Ciara Ryan was one of the 22 experts involved in the study and stressed the importance of the research.

Flooding in Clonakilty, Co Cork, during Storm Babet. Photo Andy Gibson

“This is the second attribution study looking at rainfall associated with storm events in Ireland this season and once again, we see an increase in the likelihood and intensity of the rainfall events as a result of human-­induced climate change,” she said.

“Over the recent autumn-winter period, we have witnessed the impact that heavy or prolonged rainfall has had on our communities, our land and the farming and agricultural sector, waterlogging the soils with virtually no time for them to dry out and become usable.

“The insights that we gain from studies like this are important to help us plan for the future, to support adaptation and mitigation strategies for an already changing climate.”

WWA members work to examine extreme weather events and the role climate change may have played in them.

It has long been understood that warmer air and sea temperatures cause more dense cloud formation, with subsequent rain falling much heavier, faster and more destructively.

However, it is only in recent years that scientists have been able to provide fast analysis of recent events that can take account of the role of climate change. They do it by comparing rainfall events in a pre-warming world – the period prior to 1900 before fossil-fuel burning escalated – with events in a world that is now on average at least 1.2C warmer.

“For this region, in the pre-­industrial climate, rainfall from storms as intense as the 2023-24 season occurred about once every 50 years,” they said.

“However, in today’s climate, with 1.2C of warming, similarly intense storm rainfall is expected to occur more often, about once every five years.

“Climate change has also increased the amount of rainfall of these storms, making them about 20pc more intense.”

Sarah Kew, of the Royal Netherlands Meteorological Institute, warned that the trend would continue.

“Ireland and the UK face a wetter, damper and mouldier future due to climate change,” she said.

In a shorter time scale, however, the signs are of some good weather ahead, with long-range weather forecasting models indicating a warm summer with temperatures up to 1C higher than average.

However, Met Éireann warned that while seasonal models for June, July and August indicate temperatures running between half a degree and one degree above traditional averages, rainfall will prove close to normal, with some areas at times receiving more than average.

The best chance of extended dry spells consistent with traditional summer holiday weather is most likely July and August.

“June [is expected to] have a higher likelihood of wetter than average conditions, while July and August have the higher potential for drier spells at times,” the forecaster said.

“The sea surface temperatures around Irish coasts and over the Atlantic are expected to continue above average during June-August, trending one-fifth of a degree to one degree higher than normal generally, with the highest anomalies expected to the south of Ireland and in the Irish Sea.”

The more immediate future is mixed, with cloudy, showery conditions expected to extend to most areas from today, lasting into the weekend.

However, despite the showers, it will prove drier than normal for the time of year, with many areas warmer than average for late May.

Next weekend offers mixed ­weather, with Friday set to prove largely dry but cloudy whereas Saturday is forecast to be wet and overcast with a band of persistent rain spreading across the country.

An improvement is expected for Sunday and into next week.

However, hopes of a glorious June bank holiday weekend are likely to be dashed, with showers expected for ­almost the entire weekend.

(Source – Irish Independent – Environment – Caroline O Doherty & Ralph Riegel – 22/05/2024)

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