Night-time temperatures that made summer 2025 the warmest on record were 40 times more likely due to human-caused climate change, a first-of-its kind study from Met Éireann and Maynooth University shows.
Wednesday, September 24th
The first high-temperature seasonal climate change attribution study for Ireland was carried out under the umbrella of the WASITUS project and sought to find out more about how the record-breaking mean temperature of 16.19°C for summer 2025 (June, July, August) came to be.
Key findings:
- Both maximum and minimum average summer temperatures have warmed by 1°C due to climate change, compared to 1.3°C (a pre-industrial climate).
- Overall, average minimum temperatures experienced in 2025 are now a 1-in-15 year occurrence and have become 40 times more likely than in a pre-industrial climate (a climate 1.3°C cooler than that experienced in 2025) when they may have been expected to occur once every 600 years.
- Average summer minimum temperatures, similar to those of summer 2025, are expected to happen 1-in-10 years in a 1.5°C warmer than pre-industrial climate, 1-in-5 years in a 2.0°C warmer climate, and 1-in-2 years in a 3.0°C warmer climate.
- While the average maximum summer temperatures of 2025 were not as extreme, they are now 9 times more likely in comparison to a pre-industrial climate. Similar summer maximum temperatures are expected to happen every 1-in-4 years in a 1.5°C warmer than pre-industrial climate, 1-in-3 years in a 2.0°C warmer climate, and 1-in-1-to-2 years in a 3.0°C warmer climate.
What is the impact of higher temperatures on other aspects of our climate?
- Climate change has increased the frequency and intensity of extreme weather events. As temperature increase, heat extremes are likely to be warmer and more frequent.
- Climate change is adding fuel to storms due to warmer waters and more moisture in the atmosphere.
- Irish rainfall patterns are expected to change, with an increase in both dry periods and heavy rainfall events.
- There is high confidence that maximum rainfall rates will increase due to a warmer atmosphere carrying more moisture.
- The impacts to Ireland’s population, infrastructure, economy, and agriculture at varying degrees of global warming are explored further as part of Met Éireann’s TRANSLATE Programme.
Summer 2025 was provisionally the warmest summer on record nationally with a mean temperature of 16.19°C, breaking the previous record of 16.11°C set in 1995. Human-caused climate change made the warm summer days nine times more likely, and the warm summer nights 40 times more likely. As climate change continues to drive global temperatures upwards, similarly warm summers are set to become more likely and average temperatures are set to increase yet further.
Figure 1: Top 10 warmest summers on record for Ireland, showing the anomaly (°C) with respect to Ireland’s LTA.
The warm temperatures of summer 2025 were caused by a number of factors including a combination of dry soils following a dry spring, the influence of multiple European heat domes throughout the summer, and continuous marine heatwaves in Irish waters. While day-time temperatures were not as warm as previous record-breaking summers in 1976 and 1995, high night-time temperatures pushed the temperature average up to break the warmest summer record. Most Met Éireann observing stations recorded their highest mean minimum temperature for summer on record.
Paul Moore, Climatologist at Met Éireann, said:
“The overall meteorological setup for Ireland during summer 2025 saw high pressure to the south and low pressure to the north leading to winds mostly between southerly and westerly. This is a fairly typical setup for Ireland in summer and led to near average sunshine and rainfall. The two previous warmest summers on record for Ireland, 1995 and 1976, were not typical at all. Both those summers were dominated by high pressure and were very dry and sunny by comparison. This means we have reached a point where the background warming due to climate change can transform an otherwise average season into a record warm season.”
Dr. Pádraig Flattery, Senior Climatologist at Met Éireann, said:
“This study reveals the influence of climate change on Irish temperatures, particularly summer night-time minima. It shows that what would have been expected only once in 600 years in a pre-industrial climate is on course to become commonplace if global warming continues at current or higher rates. This is a stark reminder of the urgent need to reduce greenhouse gas emissions to net zero in order to avoid the worst impacts of climate change, while also ensuring that Ireland adapts to the changed climate we are already experiencing.”
Dr Claire Bergin, Researcher for the WASITUS project, ICARUS Climate Research Centre, Maynooth University, said:
“We have known for years that society’s reliance on fossil fuels has been leading to a warming climate. Now, as we produce the first Irish-based seasonal high temperature attribution analysis we know for certain that Ireland is seeing a direct effect of global climate change. The average summer maximum temperatures experienced this year have become 9 times more likely and nearly 1°C warmer due to climate change. The record high night-time temperatures, defined in our report as average summer minimum temperatures, have become 40 times more likely due to climate change. The regularity of increased summer heat is only set to increase in the future with increased global warming.
“The high temperatures experienced this summer are set to become more regular and warmer. Most houses in Ireland are not built with these rising temperatures in mind so preparing and adapting houses now will be important for the increasing regularity of future warm summers. In particular, for those warm summer nights which are set to become more regular.”
About the WASITUS project
WASITUS is a 4-year project co-funded by the Environmental Protection Agency (EPA) and Met Éireann and undertaken by the ICARUS Climate Research Centre at Maynooth University in collaboration with the World Weather Attribution (WWA) team until 2029. WASITUS works on real-time national events that arise during the lifetime of the project as well as retrospective analysis of selected historical events. The aim is to build a picture of how climate change is impacting the extreme weather and climate events that have profound implications for society and the economy.
The WASITUS project has set out to build towards an operational event attribution capability for Ireland in collaboration with the WWA team led by Prof. Fredi Otto at Imperial College London. The aim of event attribution analysis is to identify if, and how, human-influenced climate change alters the likelihood and severity of noteworthy extreme weather events. This is carried out by comparing weather observations with climate models using various statistical techniques. When not working on Irish events WASITUS contributes to WWA global event analyses.
About this study
Summer 2025, defined as the months June, July and August, was the warmest summer on record for Ireland, according to Met Éireann’s Island of Ireland Temperature Series, with records dating back to 1900. Periods of hot weather are becoming warmer, longer and more regular due to human-caused climate change. To quantify the effect of human-caused warming on extreme heat, scientists analysed climate data. This analysis involves comparing how similar events have changed between a 1.3°C cooler climate (or pre-industrial climate), today’s climate, and a future, +0.2°C, +0.7°C and +1.7°C warmer climate. The current analysis looked at the average summer maximum and minimum temperatures for Ireland.
The full study can be found at: https://mural.maynoothuniversity.ie/id/eprint/20572/.
For further details on the climate attribution study, the WASITUS project, Ireland’s warmest summer on record, or any other related matters, please contact media@met.ie.