New study finds: Climate change caused extra potential evapotranspiration this July, exacerbating the effects of the already low rainfall conditions

A group of researchers from the WASITUS group in Maynooth University, supported by researchers at Met Éireann and Teagasc, have carried out a rapid attribution study on climate change impacts summer weather and how this may change in the future with further warming.

At the end of a summer where the United Nations Environment Program (UNEP) report said the world is on track to exceed 1.5°C of warming (UNEP, 2026) we summarise the extreme weather that affected Ireland and discuss its impact on agriculture and wider society. The UNEP “Limiting Overshoot” report highlights the worrying reality that current policies place the world in a position that exceeding global warming of 1.5°C is ‘unavoidable’. This striking message calls for urgent action in reducing our greenhouse gas emissions, but also acknowledges that we must adapt and prepare for worsening conditions as global temperatures continue to rise.

Focusing on Ireland, the Climate Change Advisory Council have voiced their concerns of the impact of climate change, including increased heat stress combined with prolonged winter rainfall, on agriculture. They cite the potential impacts on crop yields, fodder reserves and supplies, animal welfare, and animal waste, amongst other issues (CCAC, 2026).

This study sets out to further understand how climate change impacts summer weather and how this may change in the future with further warming.

Note: In this study Potential Evapotranspiration (PET) is analysed. PET is the amount of water which could be evaporated given sufficient water availability. In this analysis, PET is used to reflect the atmospheric drying capacity, independent of locally varying land surface conditions.

Key Messages

• Human-caused warming has already increased the likelihood of extreme July Potential Evapotranspiration (PET) by approximately 8-fold and the intensity by 7% in Ireland. As global temperatures increase, we expect the likelihood and intensity of future July PET events to further increase, with a nearly 6% increase in PET on present levels expected at 3°C of warming globally.
• Really dry Julys in terms of low precipitation levels, like those experienced this summer, are becoming rarer. However, when these exceptionally dry Julys do occur, they are expected to bring even less rainfall.
• The evidence indicates that it was the PET which exacerbated the effects of the low rainfall conditions and therefore exacerbated the drought conditions experienced across Ireland in July 2026. In general, drying in July is being driven by rising temperatures, which leads to more evaporation, rather than changes in precipitation.
• Maximum and minimum summer temperatures are following the expected trend and it is becoming not only more likely to have warm summers, as experienced this year, but future summers are also set to become warmer, not just during the day but also at night.
• Ireland’s agriculture sector is highly dependent on expected weather conditions. As global temperatures continue to rise, we expect soils to become increasingly dry during the warm summer months. What, historically, has been seen as unusually dry soil conditions will become increasingly common under further global warming, and it is important that farmers start to plan for such an eventuality rather than seeing the past summer as a one-off.

This rapid climate attribution study was carried out by researchers at Maynooth University supported by researchers at Met Éireann and Teagasc, under the umbrella of the WASITUS project. WASITUS aims to build an operational event attribution capability for Ireland in collaboration with the World Weather Attribution (WWA) team.

Quotes

Dr Claire Bergin, Researcher for the WASITUS project, ICARUS Climate Research Centre, Maynooth University, said: “While warmer summers may sound appealing to the majority, the added evaporative potential the high temperatures provide is a cause for concern for those who rely on the land for their living. We know Irish winters are getting wetter and, in turn, resulting in later season waterlogged fields. Then, when temperatures rise in the summer, these same fields are set to dry out if there’s any lack of rainfall, thus resulting in reduced grass yields.

The effects of climate change are no longer a future problem. We must reduce our reliance on fossil fuels now, so that our meteorological future resembles the conditions our society has grown accustomed to, and needs, to maintain a steady economy. ”

Paul Moore, Climatologist at Met Éireann, said: “Ireland has experienced its second consecutive warmest summer on record, and six of the ten warmest summers have now occurred since 2001. The stable climate of the recent past, under which our modern ecosystem evolved, no longer exists. We are now in a rapidly changing climate, both in Ireland and globally. In Ireland, this is evident from the increasing frequency of broken records along with an uptick in extreme weather events. As global temperatures continue to rise, due to the burning of fossil fuels, Ireland’s climate will continue to shift away from its recent baseline along with a continuing upward trend in the frequency and intensity of extreme weather events.

Adapting to a fixed change in Ireland’s climate, although extremely difficult, might at least be possible if the climate stabilised again. However, adapting to a continuously changing and warming climate becomes ever more challenging with every increment of warming. This highlights the urgency of transitioning to a carbon neutral economy”.

Dr Pádraig Flattery, Research Meteorologist at Met Éireann said: “The hot, dry weather of summer 2026 created conditions for wildfires to start and spread, drying out vegetation that had grown earlier in the year, providing fuel for fires. With plenty of this fuel available and little rainfall to relieve the dry conditions, the weather left many areas of the landscape vulnerable to fire for prolonged periods.”

Elodie Ruelle, Senior Research Officer at Teagasc said: “The prolonged dry conditions of summer 2026 significantly affected agriculture in the most impacted areas, with reduced grass growth forcing many livestock farmers to increase supplementary feeding and, in some cases, use winter fodder reserves. Dry conditions also affected crop performance across the tillage and horticultural sectors.

Managing variable weather is at the core of farming, but higher evapotranspiration, increased variability and more frequent extremes will place additional pressure on Irish agriculture. Greater flexibility, together with the ability to recognise emerging pressures and adapt management early, will be increasingly important in preparing farms for conditions ranging from too dry to too wet.”

Click on this link to read Summer Round up Report:

Notes to Editor

For more information:
David Kinch
MKC Communications
david@mkc.ie
086-2322439

About the WASITUS project

The WASITUS project aims to build towards an operational event attribution capability for Ireland in collaboration with the World Weather Attribution (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.

The WASITUS project is funded by the Environmental Protection Agency (EPA) and Met Éireann and executed by the ICARUS Climate Research Centre at Maynooth University in collaboration with the WWA team. For individual events we work with additional parties such as the OPW and Marine Institute. The project works on real-time events but is also compiling a catalogue of analyses for significant events over the past two decades. When not working on Irish events we contribute to WWA global event analyses.

About Maynooth University

One of four constituent universities of the National University of Ireland, Maynooth University is in the top 90 global Times Higher Education Young University Rankings.

On 16 June 2027, Maynooth University will celebrate its 30th birthday, having been formally established as an autonomous university in 1997. Yet, it traces its origins to the foundation of the Royal College of St. Patrick in 1795, drawing inspiration from a heritage that includes over 200 years of education and scholarship.

Maynooth University is one of Ireland’s fastest growing universities with more than 17,000 students, including over 2,500 postgraduates.

About this study

Background

Most of western Europe, including Ireland, was dominated by high pressure during summer 2026. The North Atlantic jet stream was weak and displaced to the north of Ireland through most of the season. Intense high-pressure systems amplified through the upper and lower levels of the troposphere, known as heat domes, extended north over Ireland on several occasions during the summer months bringing prolonged periods of hot weather. The hot, sunny and dry conditions that resulted were always most intense in the midlands, south and east, while the northwest was cooler and cloudier overall.

The first period of exceptionally hot weather for Ireland during summer 2026 came in the final third of June. A hot air mass moved north over the country and brought exceptionally high daytime and nighttime temperatures, along with high humidity. July saw the Azores high pressure system extend over Ireland for most of the month. It was an exceptionally dry month with an extended hot period that built over the country under the dominant high-pressure conditions. This resulted in one of the hottest, driest and sunniest months on record for Ireland. August saw high pressure close by for most of the month, however, it was less dominant compared to July as low pressure passed close to, or over, the country at times. Another hot air mass moved north over the country during the second week of the month which brought a relatively short, but intense, hot spell.

Methods

To fully understand the extreme nature of weather in Ireland in summer 2026, we investigate a number of different meteorological variables.

Given that the previous warmest summer record was only broken in 2025, and a full study was undertaken at the time (Bergin et al., 2025), we revisit the analysis with observation based data only. In addition, rainfall levels from October to March give a good indication of the growing conditions across the country, as the rainfall over winter and spring, 2025 to 2026, had been previously analysed (Bergin et al., 2025, Bergin et al., 2026), we restrict the analysis herein to observation based data.

• Tx3month – three-month average daily maximum temperature for June, July and August, spatially averaged over Ireland
• Tn3month – three-month average daily minimum temperature for June, July and August, spatially averaged over Ireland
• Precip – 6month – six month averaged daily rainfall for October to March, inclusive, spatially averaged over Ireland

In addition, a full drought study was carried out by analysing precipitation levels, or lack there of, and potential evapotranspiration (PET) for the month of July, when the largest effects of the drought were felt. Following the methods used in Kew et al. (2026), PET is calculated using the Hargreaves formula (Hargreaves and Samani, 1982; Hargreaves and Samani, 1985). By analysing both precipitation levels and PET we may ascertain whether the drought was directly linked to the lack of precipitation, or due to the warm temperatures causing evaporation of moisture in soils and plants.

• Precip – July – averaged daily rainfall for July, spatially averaged over Ireland
• PET – July – averaged daily PET for July, spatially averaged over Ireland

The methods for observational and model analysis, and for model evaluation and synthesis, follow the World Weather Attribution Protocol, described in Philip et al., (2020), with supporting details found in van Oldenborgh et al., (2021), Ciavarella et al., (2021) and WWA, 2021.

Full study

To be distributed with this release.

Graphics

(a)

Claire Bergin, ICARUS Climate Research Centre, Maynooth University, Maynooth, Ireland

Lionel Swan, ICARUS Climate Research Centre, Maynooth University, Maynooth, Ireland

Pádraig Flattery, Met Éireann, Glasnevin, Dublin 9, Ireland

Seánie Griffin, Met Éireann, Glasnevin, Dublin 9, Ireland

Chang Liu, Met Éireann, Glasnevin, Dublin 9, Ireland

Paul Moore, Met Éireann, Glasnevin, Dublin 9, Ireland

Elodie Ruelle, Teagasc, Moorepark, Fermoy, Ireland

Review authors

Peter Thorne, ICARUS Climate Research Centre, Maynooth University, Maynooth, Ireland