Impacts of Global Warming on Severe Drought in Northern Taiwan: A Future Projection Based on the Year 2021

In 2021, Taiwan experienced its most severe drought in 56 years, resulting in substantial crop losses, estimated to be approximately NT$1.65 billion due to insufficient water in reservoirs. This study employed the pseudo-global-warming method to project changes in seasonal rainfall during future droughts in northern Taiwan using a high-resolution (1 km) regional mesoscale model. The simulation was based on the severe drought event of 2021 and employed the Weather Research and Forecasting model driven by the global High-Resolution Atmospheric Model under the Representative Concentration Pathway 8.5 scenario for the mid-21st century (2040–2059). The modelling projections revealed significant variations in seasonal rainfall in northern Taiwan, exhibiting a pattern described as “dry season gets drier, wet season gets wetter.” Notably, a more than 40% decrease (increase) in spring (Mei-yu season) rainfall was observed. During the dry season, rainfall intensity was expected to decrease significantly due to a reduction in heavy rain and an increase in light rain (±5%) in the rainfall intensity range, whereas the opposite trend was anticipated for the wet season. These findings indicate that changes in rainfall due to global warming will worsen drought conditions in northern Taiwan if a severe drought reoccurs, particularly affecting major reservoir watersheds such as the Feitsui Reservoir, which was projected to experience 13% annual and 50% spring rainfall reductions.