Analysis: A climate attribution study has found that last month's mini-heatwave can be linked to human-influenced climate change
By Claire Bergin and Peter Thorne, Maynooth University
While the two day "mini-heatwave" of mid-July was a pleasant surprise for some, it posed the question if hot Irish days are worsening due to climate change. A new EPA/Met Éireann funded project WASITUS (Weather Attribution Science Irish operaTional User Service) aims to answer just such questions quickly and robustly to ensure better societal and policy responses to our rapidly changing climate.
Observational records maintained by Met Éireann show that overall temperatures in Ireland are increasing, and the latest IPCC report concluded that this was unequivocally due to human activities. In addition, we can now say for certain that the two-day "mini-heatwave" July 11th and 12th last was made more likely and more severe due to human activities.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
From RTÉ News, climate change made Europe's July heatwave up to 4C hotter
The higher than normal temperatures this spring and summer have already seen the public reach for lighter clothing and head to the beach on multiple occasions. On June 30th, highs of 29.6°C were registered in Roscommon. In contrast, the highest summertime temperature of last year was 26.6°C. For context, Ireland's all-time temperature record in June 1887 sits at 33.3°C, while the second highest temperature on record is 33.0°C which was seen in 2022.
In the days before the mid-July heatwave, Met Éireann forecasted that temperatures may exceed 27°C and it was possible that they would reach the low 30s on Saturday. This understandably sounded like a good excuse for ice-cream and a trip to the beach for many, but posed worrying thoughts in the minds of climate scientists.
In our first rapid attribution study, we sought to establish if we can link this "mini-heatwave" to human-influenced climate change. Following methods established by World Weather Attribution the 2-day heat was analysed to see if, and how, human-influenced climate change had altered the likelihood, and severity.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
From RTÉ Radio 1's Morning Ireland, how well prepared is Ireland for the effects of climate change?
The heatwave that happened in today's climate was compared with how it would have been expected to occur in a 1.3°C colder, pre-industrial climate, before humans started actively warming the planet. We also compared this to a potential future date, where the climate is a further 1.3°C warmer. This is something that, on current emissions trajectories, will be sadly reached at some point later this century and will be potentially experienced by many of our younger citizens.
By comparing these three cases, we can analyse if, and how, climate change is altering the regularity and intensity of these events. Focusing on the regularity of our mid-July "mini-heatwave", it was found that the high temperatures of over 27°C, experienced over these two days, would have been expected to occur once in every 14 years in a pre-industrial climate. Now, with 1.3°C of human-caused global warming, similar two-day high temperatures are expected to happen once in every 6 years. Worse, with a further 1.3°C of warming, the same event would occur once in every 2.5 years.
Interestingly, we found the temperature of the two-day "mini-heatwave" increased similarly to global warming in general. In pre-industrial times, the two-day event would be expected to be about 1.3°C cooler. In the future, we expect a similar event to be around 1.4°C warmer. These are maximum temperatures averaged across Ireland and they do vary based on location.
Paying particular attention to the high temperatures of July 12th, a 28°C+ temperature day would have been expected once in every 21 years in a 1.3°C cooler climate. However, in a 1.3°C warmer climate from now, we expect it will become a once in every three years event.
Yes, it's been hotter before but, in the Met Éireann gridded daily temperature record which starts in 1961, five of the eight hotter two-days streaks, and four of the five hotter single days, have occurred since 2000. That metaphor about frogs being slowly boiled in a pot and thinking how lovely it is? That’s quite literally us.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
From RTÉ Brainstorm, where did all the historical Irish weather data go?
While the media often portray heatwaves as good fun with pictures of beachgoers, the truth is that there are many negative impacts. Hotter, drier conditions lead to an increased risk of forest fire, negative heat related health impacts (particularly for those vulnerable members of society), animal health impacts and a potential increase in injuries and fatalities due to water-based accidents.
Understanding how our weather has changed, and is set to change further with increased global warming, can help us adapt and prepare for future hot weather events. We aim is to build an operational event attribution capability for Ireland. We will regularly undertake event attribution studies like this one within days or weeks of a noteworthy extreme climate event. The analysis, depending upon the type of the event being considered, will be carried out in collaboration with agencies such as Met Éireann, the EPA, OPW and the Marine Institute.
Analysis of past events of the last 10 to 20 years will also be carried out as part of the project to gain a better understanding of how our extreme weather events have changed over the last few decades and the role (or otherwise) of humans in loading the proverbial dice. We will also be undertaking outreach with impacted communities to understand the impact and utility of our work with a view to improving the usefulness of the studies to those who need them most.
Follow RTÉ Brainstorm on WhatsApp and Instagram for more stories and updates
Dr Claire Bergin is a postdoctoral researcher at the Irish Climate Analysis Research Units (ICARUS) at Maynooth University. She is studying climate attribution analysis as part of the EPA/Met Éireann-funded WASITUS project. Prof Peter Thorne is Professor in Physical Geography (Climate Change) and Director of the Irish Climate Analysis Research Units (ICARUS) climate research centre at Maynooth University.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
