Guidance for Met Éireann forecasters on how to inform people about the impact of the climate crisis detailed a “run of very wet months” and how rainfall in both February and March was almost fifty percent more than expected.
An advisory for staff said that record high sea surface temperatures over the Atlantic had lasted for over a year and were making the atmosphere both “warmer but also moister”.
It said this was linked to increases in extreme weather events such as storms and intense rainfall.
The guidance described how 2023 had been the third wettest year on record with 20 percent more rain compared to the long-term average in the period between 1981 and 2010.
This had only continued into the New Year with rainfall levels in February 49 percent above average and in March 46 percent over what was considered the norm.
Met Éireann staff were told that a “southerly displaced jet stream”, which the country had seen multiple times since last summer, brought low pressure systems to Ireland and more rainfall especially in the South and the East.
“Ireland is now warmer, and wetter compared to previous decades and years,” said the guidance document.
It explained how a warmer atmosphere carried more moisture, around 7 percent for each degree of warming, which would inevitably lead to a greater intensity of “heavy rainfall events”.
The document also said the growing season for crops and plants was increasing because of the warming climate.
Met Éireann data showed the growing season over the decades now lasted on average fourteen days more in Belmullet, County Mayo, and an extra sixteen days at both the Valentia Observatory in Co Kerry and the Phoenix Park in Dublin.
Another briefing on the number of storms that were hitting Irish shores said that since the practice of “storm naming” had begun, there were an average of eight named storms in each season.
However, by the time of Storm Kathleen in early April, it was the eleventh of the season although, conversely, there were only four during the storm season between September 2022 and spring of 2023.
The guidance document said that overall, last year had been “the warmest year on record by a large margin, and one of the wettest years on record”.
“It was the warmest year on record at 21 out of 25 [weather] stations (record lengths between 10 and 83 years),” said the briefing.
“Eighteen stations had their highest mean maximum temperature on record and twenty-four stations had their highest mean minimum temperature on record.”
Another document on the context of climate change said it was still unclear exactly how the frequency and intensity of storms hitting Ireland would evolve.
It said: “There is, however, high confidence that maximum rainfall rates will increase as a result of a warmer atmosphere carrying more moisture.”
Rising sea levels were also expected to increase storm surge and coastal flooding risks, according to the records, which were released under FOI.
One update for staff said there was a particular danger from so-called “compound events” where heavy rainfall arrived at the same time as high tides.
In internal discussions, Met Éireann staff also wrote about how the record high temperatures of 2023 had been somewhat unexpected and that this year had been anticipated to be warmer due to the El Nino weather system.
An email from one meteorologist said: “In Ireland, we should be preparing for both warmer summers and winters as this is what the climate projections in [our systems] are showing going forward as mean temperatures globally continue to increase due to human caused climate change.
“This will not necessarily be a linear or steady increase, especially here in Ireland, with our climate being dependent on other factors such as the position on the jet stream and Atlantic SSTs [sea surface temperatures].”
In a statement, a spokesperson for Met Éireann said their role was to monitor, analyse, and predict Ireland’s weather and climate for the public and stakeholders.
They said: “All the climate information, services and content provided by Met Éireann is based on the objective scientific analysis of Ireland’s climate and broader global climate information.
“An important part of our role is to communicate information to all audiences, in terms of current weather and climate and also broader historical and future insights to help inform immediate and longer-term policies and decisions.”