Enhanced flood risk with 1.5 °C global warming in the Ganges-Brahmaputra-Meghna basin

Flood hazard is a global problem, but regions such as south Asia, where people's livelihoods are highly dependent on water resources, can be affected disproportionally. The 2017 monsoon flooding in the Ganges-Brahmaputra-Meghna (GBM) basin, with record river levels observed, resulted in ∼1200 deaths, and dramatic loss of crops and infrastructure. The recent Paris Agreement called for research into impacts avoided by stabilizing climate at 1.5 °C over 2 °C global warming above pre-industrial conditions. Climate model scenarios representing these warming levels were combined with a high-resolution flood hazard model over the GBM region. The simulations of 1.5 °C and 2 °C warming indicate an increase in extreme precipitation and corresponding flood hazard over the GBM basin compared to the current climate. So, for example, even with global warming limited to 1.5 °C, for extreme precipitation events such as the south Asian crisis in 2017 there is a detectable increase in the likelihood in flooding. The additional ∼0.6 °C warming needed to take us from current climate to 1.5 °C highlights the changed flood risk even with low levels of warming.