The likelihood of super storms such as Storm Desmond happening again has increased by 25% because of climate change, research has indicated.
Desmond hit Ireland and Britain in early December 2015, an extratropical cyclone that brought strong rainfall and enough rainfall to break the 24- and 48-hour British rainfall records, with a number of British and Irish rivers recording highest-ever peak discharges.
A study by researchers, including one from the Irish Climate Analysis and Research Unit in the Department of Geography at Maynooth University suggests that “the severity of the storm may be a harbinger of expected changes to regional hydroclimate as global temperatures continue to rise”.
Those behind the study, which also involved researchers at Liverpool’s John Moore University and the National Oceanography Centre in Southampton, explored the amount of water vapour transported by atmospheric rivers (AR), the intensity of which depends on wind speed and atmospheric moisture water content. It found that Storm Desmond was accompanied by an AR “of severity unprecedented since at least 1979, on account of both high atmospheric humidity and high wind speeds”.
According to the research, Storm Desmond occurred during the warmest year globally since observations began, in a December that was the warmest on record for Britain. It also points out a number of aspects of the storm’s “unusualness”, including that “Desmond’s AR was most remarkable for its 24-hour intensity, rather than the total moisture flux over its lifetime.
It does acknowledge some caveats regarding its findings, but concludes that “we interpret that long-term North Atlantic warming may have increased the chance of an AR as severe as in Storm Desmond. This conclusion may help provide a tangible, easily communicated example for wider dissemination, of the impacts from climate change on North Atlantic hydroclimatic extremes”.
We conclude that, given exactly the same dynamical conditions associated with Desmond, the likelihood of such an intense AR has already increased by 25% due to long-term climate change,” said researchers.
Research published last year by the Irish Centre for HighEnd Computing at NUI Galway, indicated significant projected decreases in mean annual, spring and summer rainfall amounts by the middle of this century, but increases in rainfall in autumn and winter.
That research, entitled ‘Impacts of climate change on midtwentyfirstcentury rainfall in Ireland: a highresolution regional climate model ensemble approach’ and published in the International Journal of Climatology, said: “The projected decreases are largest for summer, with reductions ranging from 0 to 13% and from 3 to 20% for the mediumtolow and high emission scenarios, respectively. The frequencies of heavy precipitation events show notable increases of approximately 20% during the winter and autumn months.”