You have more fires; they creep farther north; they burn in these soils which have a lot of C02 and methane that can be exposed directly at the moment of the fire and then decades after. That contributes again to global warming; you have again more fire.

Sander Veraverbeke of Vrije Universiteit Amsterdam

• States that changes in climate and fire regimes are transforming the boreal forest, the world’s largest biome
• States that boreal North America recently experienced two years with large burned area: 2014 in the Northwest Territories and 2015 in Alaska
• Uses climate, lightning, fire and vegetation data sets to assess the mechanisms contributing to large fire years
• Finds that lightning ignitions have increased since 1975, and that the 2014 and 2015 events coincided with a record number of lightning ignitions and exceptionally high levels of burning near the northern treeline
• Finds that lightning-caused fires have risen 2 to 5 percent a year for the last four decades
• Finds that lightning ignition explained more than 55% of the interannual variability in burned area, and was correlated with temperature and precipitation, which are projected to increase by mid-century
• The analysis shows that lightning drives interannual and long-term ignition and burned area dynamics in boreal North America, and implies future ignition increases may increase carbon loss while accelerating the northward expansion of boreal forest