Climate change impacts on spatial and seasonal meteorological drought characteristics for the island of Ireland

Understanding how climate change is likely to impact on meteorological droughts is key to informing adaptation planning. For Ireland, little research has examined how droughts are likely to change in future. Here we examine changes in the monthly climate water balance, aridity index and changes in magnitude, frequency and duration of droughts using standardized drought indices for the island of Ireland derived from bias-adjusted CORDEX simulations for the 2080s (2070-2099), forced with a high (RCP8.5) and moderate (RCP4.5) emissions pathway. Findings highlight that increases in potential evapotranspiration, driven by increasing temperature, together with changing seasonal rainfall patterns increase aridity in summer with water deficits extending into spring months, especially in the east and midlands by the end of the century. Increases in drought frequency and magnitude are also evident, with greatest increases for RCP8.5. Critically, increases are considerably greater for the standardized precipitation evapotranspiration index (SPEI) than for the standardized precipitation index (SPI), emphasizing the importance of using metrics that capture potential evapotranspiration in monitoring and assessing future drought risk. Summer and spring show the greatest increase in drought magnitude and frequency, most marked in the east of the island. By contrast, multiseasonal droughts, assessed using 6-month accumulation periods show more modest changes in magnitude and duration. The resultant impacts of climate change on drought for Ireland would require considerable adaptation given the vulnerabilities exposed by the 2018 drought.