Climate and Megafires

When large fires occur, it is common to try and attribute them to extreme climate conditions (e.g., worst drought on record). However, extreme climate is not always a necessary factor for large events, though a climate “minimum” is needed to produce sufficient conditions for large fire growth. A natural question is “How extreme does the climate need to be for certain fire events to occur?” Climate conditions and departures from normal effectively establish the background potential such that other factors (e.g., human and short-term weather) can facilitate fire size. This study focuses on deriving climate thresholds for megafires by examining quantitative indices of relevant climate variables (e.g., drought indices, fuel moisture) in relation to megafires. The study objective is to determine climate conditions that are associated with large fires, including megafires. To do this, climate thresholds are examined for varying fire size classifications. The determined thresholds are further examined with future climate predictions in order to assess frequency changes during this century.