Storylines of Future Drought in the Face of Uncertain Rainfall
Projections: a New Zealand Case Study
Abstract
Robust increases in temperatures will occur globally across the
twenty-first century; however, for some regions, sign changes in
rainfall remain uncertain. Navigating this uncertainty is crucial in
addressing drought-related challenges faced by climate-exposed sectors.
New Zealand represents these challenges, exhibiting significant model
uncertainty in warm-season rainfall change. Here, we examine how
temperature-driven increases in potential evapotranspiration interact
with contrasting storylines of future rainfall to explore drought
outcomes for New Zealand. In our drying storyline, we find that
increasing temperatures accompanied by less rainfall bring forward the
onset of drought several months and delay its termination. In the
wetting storyline, increases in rainfall partly offset the
temperature-induced drying effect, leading to minor reductions in soil
moisture. Examining extreme years, the average hydrological year in the
future becomes comparable to the driest years of the current climate,
while the worst future events exhibit unprecedented drought severity.