Sunday 26 May 2019

Praying for rain could become the norm amid global warming

The Beast from the East and record temperatures in Ireland may share some common ground, writes John Sweeney

Marie Louise de Jong, Marleen Wester, David Faber and Judith van Driel of The Dudok Quartet Amsterdam at Bantry House, Co Cork. They are performing in St Brendan’s Church at 8pm on Tuesday at the West Cork Chamber Music Festival. Photo: Michael Mac Sweeney
Marie Louise de Jong, Marleen Wester, David Faber and Judith van Driel of The Dudok Quartet Amsterdam at Bantry House, Co Cork. They are performing in St Brendan’s Church at 8pm on Tuesday at the West Cork Chamber Music Festival. Photo: Michael Mac Sweeney

John Sweeney

On July 2, 1887, the following circular was issued by the Church of Ireland Bishop of Meath: "Rev and Dear Brother, The long drought threatens to become a national calamity. Agreeably to the apostolic precept, that 'in all things by prayer and supplication, with thanksgiving, our requests should be declared to God', our Church sanctions public prayers for such changes of weather as may be most conducive to human comfort and prosperity. I therefore authorise you, under the present circumstances, to use the prayer for rain."

In a country where we mostly pray for the rain to stop, this exhortation to pray for drought relief seems to be the only such occurrence over the past three centuries. Droughts in Ireland do not figure prominently in our consciousness.

However, recent work by my colleague Conor Murphy and his team at Maynooth University has demonstrated that, historically, they were much more of a feature of the Irish climate than has been the case over the past 40 years. Indeed, the weather chart for the end of June 1887 is almost identical to that of the end of June 2018. Then, as now, the drought was most severe in the east of the country and led to widespread crop failures and water supply problems. Health concerns were more prominent as the public sewers lacked enough water to flush waste through them.

In an equally severe event in 1893, a suggestion was made to explode dynamite above the city of Dublin to generate rainfall - not a good idea perhaps, but not too far removed from what cloud seeding practices around the world tend to be based on.

Shannon Airport's 32C last Thursday brings long-standing records into range. The highest recorded temperature in Ireland was 33.3C in Kilkenny on June 26 in the midst of the aforementioned drought of 1887.

The highest value of the 20th century was 32.5C in Boora, Co Offaly, on June 29, 1976, again a year marked by drought.

It is a bit puzzling that the highest temperature extremes in Ireland tend to occur at the end of June and not later in the summer. Part of the answer lies in the sea. The sea surface temperatures and the temperatures inland are quite similar in June, around 13.5C. Air flowing from the sea is therefore not subjected to the same uplift and instability that it experiences by July, when the land has warmed up.

Indeed, how many holidays have been ruined by the rains of July, when continental Europe heats up and sucks Atlantic air across Ireland in a gigantic sea breeze-type system some climatologists refer to as the European monsoon? Of course it doesn't happen every year, but August tends to be the wettest of the three summer months, especially in eastern Ireland.

The anticyclone which brought the extremes of temperature has begun to drift north and more modest temperatures are likely to prevail in coming days. But the jetstream is still weakly wandering through the high Arctic and conditions remain suitable for further anticyclonic development in the vicinity of Ireland.

Some research now links increased anticyclonic blocking to the rapid warming of the Arctic as the sea ice retreats and the temperature difference between high and low latitudes diminishes.

The driving force for the jetstream is thus weakened and, as it meanders, it facilitates more extreme events of all kinds.

The Beast from the East and the events of June 2018 may therefore have some common ground.

What is clear, though, is that as the world warms extreme events are likely to become more common, even in Ireland.

It seems inevitable that air coming from areas that are 0.5-1C warmer than 30 years ago, and entering an Ireland that is everywhere more than 0.5C warmer than 30 years ago, will challenge long established temperature records. Kilkenny's record high of 1887 will not last too much longer.

Meanwhile, the summer of 2018 continues to remind us how dependent we are on a continuation of the status quo in our water supply and agricultural systems.

Increased vulnerability to climate shocks exists in both categories as urban and rural land use intensification increases. June 2018 yielded 3.8mm of rain in the Phoenix Park in Dublin. Six hours in Malin Head in August last year generated 63mm.

Irish climate is now clearly producing exceptional events. It's something we have to get used to and part of the price we pay for not pulling our weight in tackling climate change.

Oh, and by the way, the Bishop of Meath's prayers were answered. The drought finally broke - in November.

John Sweeney is emeritus professor, Irish Climate Analysis and Research UnitS (Icarus) at Maynooth University

Sunday Independent

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