Leading climate experts discovered that human-driven climate change increased the intensity of extreme storm deluges contributing to disastrous floods in the UK and Ireland from October last year to March by roughly 20%. These findings were revealed by a “quick attribution analysis” conducted by researchers associated with the World Weather Attribution (WWA), a collective that counts Met Éireann among its constituents. They underscored the ripple effects of the flooding during that timeframe which implications spanned across public health, food production and escalated living costs.
In the latter part of the previous year and earlier this year, the UK and Ireland underwent an especially stormy season. Approximately 13 to 14 severe storms battered these nations, and 11 of these were labelled by the Western Europe Storm Naming Group. The christening of Storm Kathleen in April marked only the second instance an ‘K’ was utilised in the sequential naming system since the formation of the group in 2015.
The storms most destructive in Ireland and the UK were Babet, Ciarán, Henk, and Isha. They resulted in catastrophic flooding, causing least 13 fatalities and wreaking havoc on homes and infrastructure. In addition, they were responsible for power failures, travel suspensions, and the destruction of crops and livestock.
To measure human-induced climate change’s influence on these strong winds and heavy rainstorms, scientists examined weather information and climate models. They compared how these types of weather phenomena have evolved between our contemporary climate – now approximately 1.2 degrees warmer globally – and the cooler climate of a pre-industrial era.
From October to March, typically the height of the storm season, the scientists focused their attention. They applied the storm severity index (SSI) to pinpoint the most turbulent days. This measurement assesses the intensity of wind and the size of the impacted region. For these specific days, they studied wind velocity and rainfall amounts.
The researchers also reviewed the total rainfall from October to March, given the effects on farming and agricultural lands from both major storms and less severe weather systems. This period was identified as the second wettest in the UK and third wettest for Ireland.
Rainfall from storms is intensifying and becoming more frequently observed in many parts of the world due to global warming. Comparatively, in this region during pre-industrial time – before humans began burning fuels such as oil, gas, and coal – they argue that storms of the intensity seen in the 2023-2024 season would have been experienced only once every 50 years.
In the existing climate, which is experiencing a rise of 1.2 degrees, researchers have discovered that heavy storm rainfall is becoming more frequent, expected approximately once every five years. Moreover, climate change is causing a surge by approximately 20% in the rainfall intensity during these storms. The aftermath of Storm Babet in Midleton highlights the damage caused.
The data suggests that if global warming hits a 2-degree mark, projected to happen in the 2040s or 2050s unless we drastically reduce emissions, storm rainfall intensity will rise by an additional 4%, with a forecasted recurrence of once every three years. This study was released on Wednesday.
Climate change also plays a significant role in altering rainfall patterns during autumn and winter, impacting agricultural practices. In an environment with lower, pre-industrial temperatures, we experienced heavy rainfall seasons like the one observed between last October and March just once in 80 years. These wet periods are now four times more frequent in the current climate, predicted to happen once every 20 years.
According to the research, climate change is linked to an approximate increase of 15% in overall rainfall. If the planet’s temperature rises by 2 degrees, it could lead to frequent intense rainfalls causing massive agricultural damage, occurring every 13 years.
Despite a slight reduction in wind speeds during storms, other studies reveal varied results. Some report small decreases or increases in storm winds with warming. Thus, there’s a vital need for continuing research to understand these patterns.
Although storm predictions are quite accurate in this part of Europe, significant damage was seen across Ireland and the UK last year with Storms Babet, Ciarán, and Debi striking in quick succession.
This research was undertaken by a team of 22 researchers, incorporating scientists from academic institutions and meteorological services in Ireland, the Netherlands, and the UK.
Ciara Ryan, a climatologist at Met Éireann, indicated that this is the second investigation into the correlation between storm-related rainfall in Ireland and the changing climate. The study reveals a distinct rise in the probability and severity of these events, owing to human-driven climate change.
Throughout the recent autumn-winter season, the consequences of heavy and sustained downpours on our society, land, and specifically the farming and agricultural sectors, have been noticeably severe, causing waterlogged soils with negligible time to dry and become suitable for use. She emphasised that the knowledge gained from these studies is crucial in strategising for the future, assisting adaptation and mitigation methods for a climate that is already showing changes.
So, what exactly is attribution science?
A comparatively new field, attribution science delves into differentiating the contribution of climate change from natural weather fluctuations and climate variation.
This science can provide an in-depth understanding of the link between extreme weather and climate change, giving us a clearer picture of which specific emissions have the most detrimental impacts and hence, aiding in forming climate solutions.
Attribution is the process of establishing the causes behind the observed modifications in climate, known as “climate forcings”. These may either be natural, such as alterations in solar cycle, volcanic eruptions or La Niña, or human-caused like greenhouse gas emissions, deforestation, or aerosols.
The World Weather Attribution is a global consortium comprised of leading meteorologists and climatologists. Their objective is to examine and disseminate information about the likely impact of climate change on extraordinary weather events, including storms, exceptional rainfall, heatwaves, and droughts.
Advancements in climate modelling technology, and accessibility to high-performance supercomputers, enable quick and precise attribution analysis of enormous data sets.
Finally, Met Éireann recommends that forecasts for Ireland should account for a likely rise in rainfall and storm surges.