Variation of lightning-ignited wildfire patterns under climate change
Study key findings & significance
- "Hot lightning" strikes (those lasting much longer than average — from approximately 40 milliseconds to nearly a third of a second) are capable of transferring more heat to flammable things like trees, shrubs or grass.
- Observations of satellite data show that about 90% of US wildfires between 1992 and 2018 started because of these hot lightning strikes.
- A study of the rate of such lightning strikes over the years combined with computer simulations showed that a higher frequency of these lightning strikes was associated with the atmosphere warming.
Further, climate models indicate that hot lightning strikes may increase from three per second to four strikes per second in the coming years.
Lightning is the main precursor of natural wildfires and Long-Continuing-Current (LCC) lightning flashes are proposed to be the main igniters of lightning-ignited wildfires (LIW). Previous studies predict a change of the global occurrence rate and spatial pattern of total lightning. Nevertheless, the sensitivity of lightning-ignited wildfire occurrence to climate change is uncertain. Here, we investigate space-based measurements of LCC lightning associated with lightning ignitions and present LCC lightning projections under the Representative Concentration Pathway RCP6.0 for the 2090s by applying a recent LCC lightning parameterization based on the updraft strength in thunderstorms. We find a 41% global increase of the LCC lightning flash rate. Increases are largest in South America, the western coast of North America, Central America, Australia, Southern and Eastern Asia, and Europe, while only regional variations are found in northern polar forests, where fire risk can affect permafrost soil carbon release. These results show that lightning schemes including LCC lightning are needed to project the occurrence of lightning-ignited wildfires under climate change.