Farm Ireland

Wednesday 16 January 2019

Last 10 years have been wettest since records began more than 300 years ago

Farmers in floods of water. Photo: Ray Ryan.
Farmers in floods of water. Photo: Ray Ryan.
Paul Melia

Paul Melia

THE years between 2006 to 2015 made up the wettest decade in more than 300 years, with average rainfall across the 10-year period almost double that experienced since 1711.

And a new record of Irish rainfall patterns says the continuous rise in annual and winter precipitation is consistent with human-induced climate change, linking the changes in our climatic system with the flooding of 2015/2016 and stormy winters over recent years.

Using UK and Irish data, senior geography lecturer at Maynooth University Dr Conor Murphy and colleagues found that average rainfall between 2006 and 2015 was 1,990mm per year.

This compares with an average across the three centuries of 1,080mm, and just 940mm between 1740 and 1749, the driest decade on record.

The record is based on historic observations and scientific measurements taken every month between 1711 and 2016, and while noting that confidence in the data prior to 1790 is “low”, earlier records present “compelling evidence” of “exceptionally” dry and wet winters.

“The most recent decade was our wettest on record, and when we look at the long-term context, we see a continuous rise in annual and winter rainfall,” Dr Murphy said.

“This is consistent with expectations of human driven climate change.

“The fact that we have such a long rainfall record for Ireland is thanks to the meticulous work of weather enthusiasts and meteorologists from the Ireland and the UK over hundreds of years. The record draws on the very earliest rainfall observations made in this region, together with weather diaries compiled during the 1700s.”

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Reference is made to a report in 1733 about “primroses and violets blooming at Christmas,” the paper says.

A 305-year continuous monthly rainfall series for the island of Ireland (1711-2016)provides the country with one of the longest, quality-assured rainfall records anywhere in the world.

While the rainfall record recorded over the past decade is among the most significant findings, the data also reveals that over the long-term, winters are getting wetter and summers drier.

It finds that the driest winter on record is that of 1783-4, which coincided with the eruption of the Laki volcano in Iceland, which emitted millions of tonnes of sulphur dioxide into the air, creating what was called the ‘Laki haze’.

“This gave much of Europe an extremely hot summer, followed by a dry and severe winter,” Dr Murphy said, adding that changes in rainfall have resulted in severe impacts here.

“Recent wet weather has had significant effects on Ireland; winter 2015/16 saw extensive flooding across Ireland, while winter 2013/14 was the stormiest on record. These winters, which not only took place during our wettest decade, are also the first and second wettest individual winters on record.”

The UK Met Office stitched historic data together in 1979, with a report on the exercise found during a refurbishment of Met Éireann, and that record was merged with another dataset compiling weather in Ireland between 1850 and the present.

“We can not only see how rainfall has changed in Ireland, but also look at what was going on in the wider world to influence it,” Dr Murphy said.

The dataset can also be used to track changes in rainfall, while helping to stress-test infrastructure such as flood defences and water systems, he added.

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