Severe rapid indian monsoon weakening due to emissions from extreme Canadian wildfires

August 2023 was the driest Indian monsoon August in recorded history, the causes for this extended precipitation deficit in an otherwise typical monsoon remaining unclear. Given that monsoonal precipitation is highly sensitive to northern hemispheric aerosol abundances, here we investigate whether the smoke emitted by the unprecedented Canadian wildfires that occurred during the same season contributed to the monsoon anomaly. We conducted ensemble simulations with a state-of-the-art Earth System Model and a very similar precipitation anomaly during the Indian monsoon is observed when accounting for the Canadian fire smoke, as opposed to when not accounting for it. The mechanism proposed for this anomaly based on model findings is the generation of a pronounced low-level pressure anomaly over the Asian continent following smoke-related cooling, which led to weakened monsoonal winds and reduced moisture transport in the region, thus diminishing Indian monsoon precipitation. The modelled mechanism is supported by comparisons with radiosonde, reanalysis and satellite data that we performed. Wildfires are becoming more severe with climate change, and our study highlights the potential for large-scale wildfire events to impact crucial meteorological phenomena in regions very far away from the emission source.