Multi-factor assessment of future climate hazards to apple production across Switzerland’s growing regions

Abstract Apple production is likely to face increased climate hazards in the future resulting from climate change. The magnitude and relative importance of different climate hazards remain unclear, especially when considering multiple emissions scenarios. Here, we perform a multi-factor climate hazard assessment for apple-growing regions in Switzerland that considers summer heat, summer drought, spring frost, and insufficient winter chill as sources of climate hazard. We use fine-scale climate and hydrological data from the CH2018 project to develop a composite index that distinguishes between “potential” and “effective” hazard, where the latter accounts for the vulnerability of apple-growing systems to each hazard. Our results identify summer heat and spring frost as the main drivers of climate hazard across Swiss apple-growing regions, with heat hazard expected to significantly increase throughout the century and frost hazard to decrease. Whether heat will become the dominant source of hazard in the mid-term (2045–2074) and long-term (2070–2099) depends on the emissions trajectory followed and the region considered. Staying under the moderate-emissions scenario (RCP 4.5) rather than a high-emissions pathway (RCP 8.5) would prevent close to half of Swiss apple production from exposure to high climate hazard by the end of the century.