• The effects of climate change are becoming more evident, through unprecedented disintegrating ice caps, oceans becoming more acidic, more frequent and intense floods and longer droughts. But how do we know if a specific extreme weather event is due to climate change? ‘Event Attribution’ is the term for how scientists work out what percentage, if any, climate change is responsible for the frequency and scale of extreme events such as the 2020 Australian wildfires, the 2021 Canterbury floods and 2021 Pacific Northwest heatwave that killed an estimated billion marine animals and over 500 people, Cyclone Gabrielle in Aotearoa in February 2023, and the 2025 Los Angels fires.
  
• If we understand how likely an event occurs because of climate change versus natural fluctuations such as El Niño—we can better plan to mitigate future climate costs.
• Insurance underwriters use these tools to help calculate the cost of insurance, or to decline your insurance; for example if you live in an area at risk from rising sea levels.
• Like to know more about specific events? See World Weather Attribution.

For too long, weather’s randomness has kept events such as these from being blamed squarely on climate change… Now, we can specify increased chances for specific events. This extends to forecasts: we can identify the places that are more likely to see wildfires, mudslides and fish die-offs. Such calculations dent both climate denial and a false sense of security. They take away the argument that ‘extreme weather happens anyway, so we don’t need to worry about it’. Extreme weather happens—and these metrics pinpoint what is becoming more likely, by how much and why… Such evidence is also useful for legal proceedings when citizens call corporations or governments to account for their role in climate change. – Richard A. Betts