An "ignition source" refers to something that can start a fire or cause an explosion. It could be a spark, flame, or hot surface that can ignite flammable materials. Full definition
If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate. (nature.com)
That could pose a fire hazard if the gasoline meets a hot ignition source. (automobilemag.com)
If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate. (realclimate.org)