The devastating floods along Victoria's Great Ocean Road, where cars and caravans were swept away, have sparked a crucial question: is climate change to blame? While it's challenging for climate scientists to distinguish between natural weather patterns and climate change impacts, one thing is certain: extreme rainfall events are becoming more frequent and intense.
A warmer atmosphere, caused by increased greenhouse gas emissions, can hold more moisture, leading to heavier rainfall. This is evident in observations worldwide, with daily rainfall events averaging 8-9% more rain than pre-industrial times. For short, intense rainfall, the increase is even higher, up to 20%.
However, this increase is primarily seen in extreme events, while regular rainfall may decrease in some areas. This is due to the warmer atmosphere's dual effect: it can hold more moisture for heavier rain but also make it harder for rain to form in the first place.
Despite little change in annual rainfall figures in many parts of Australia, the increase in extreme events means more frequent and intense floods, including flash floods. While floods are complex and influenced by landscape dryness, the most extreme flood events are getting bigger, posing a growing risk to life and infrastructure.
The impacts of climate change are evident worldwide, with major flooding in various Australian states and other countries. Yet, it remains challenging to attribute individual rain events to climate change due to the many factors at play, including moisture, ocean temperatures, weather patterns, and climate drivers like El Niño and La Niña.
Despite the complexities, one thing is clear: the world is warming, and our most severe rainfall events are becoming more intense. As Dr. Wasko says, "If the rarest events increase, the risk to life increases as well." Communities are already feeling the impacts, and the challenge is to adapt and mitigate these risks.
