Projection of future climate change and precipitation extremes over the Canadian Lake Erie and Lake Ontario basins under global warming

This study assesses projected changes in precipitation, temperature, and precipitation extremes over the Canadian Lake Erie Basin (CLEB) and Canadian Lake Ontario Basin (CLOB) under four global warming levels (1.5 °C, 2.0 °C, 3.0 °C, and 4.0 °C above pre-industrial). An ensemble of eight CMIP6 global climate models, downscaled and bias-corrected using the Multivariate Bias Correction method against the 10-km CaSR-v2.1 dataset, was analyzed under SSP245 and SSP585 scenarios. Relative to the 1980–2010 baseline, annual precipitation is projected to increase by 4.8–12.7% in the CLEB and 2.9%–10.4% in the CLOB across the four warming levels. Spring exhibits the largest seasonal increase (up to 28.6% in CLEB and 26.6% in CLOB at 4 °C). Mean annual temperature increases range from 0.83 to 3.17 °C in CLEB and from 2.07 to 4.49 °C in CLOB across the four GWLs, with winter warming exceeding 5 °C at the highest warming level. Extreme precipitation increases more rapidly than mean precipitation, with R99p and R95p exhibiting the largest relative changes, and PRCPTOT projected to rise by approximately 69 mm under 2 °C warming. Consecutive dry days increase more notably in CLEB, indicating elevated drought risk, whereas CLOB exhibits stronger increases in precipitation intensity (Rx1day, Rx5day), implying heightened flood and erosion risks. These basin-specific projections provide quantitative evidence to support adaptive water management and Environment and Climate Change Canada’s Freshwater Action Plan under future climate change.