The authors did not find agreement in directional trends in fire activity for over 50% of terrestrial lands globally by 2039. Longer projections to the end of the century suggest that fire probabilities will increase in the mid- to high-latitudes and decrease in the tropics. They suggest that although future temperature is expected to rise across the globe, future fire activity seems to be driven by moisture availability in many areas.

Fire was common historically with mean fire return intervals of about four years until about 1860 with the arrival of European settlers and the removal of Native Americans who deliberately set fires for hunting and agricultural use.

Also, the authors suggest that long periods of drought may not be necessary to dry fuels enough to burn in the naturally arid climate of the Great Basin so that fires were actually more common in wet years than dry years when fuels were more abundant.

The authors found that globally, changes in temperature and precipitation may result in a rearrangement of fire probabilities where fire activity will increase in some areas and decrease in others under climate change.

The authors predicted an increase in fire occurrence, frequency, and size by midcentury in the Greater Yellowstone ecosystem due to projected increases in average spring and summer temperatures. They suggest that a shift toward a novel fire-climate-vegetation relationship as the increase in fire frequency becomes incompatible with the persistence of the current vegetation in the region.

The authors reconstruction of past fire activity suggests that until the late 18th century fire was driven mostly by climate. Specifically, they found that variation in global precipitation had the strongest influence on global fire activity. Post Industrial Revolution, anthropogenic activities had a stronger influence on global fire trends. Finally, predictions in future warming due to climate change suggest an imminent shift to temperature-driven global fire activity over the next century.

Charcoal records showed that regional synchroneity of fire frequency occurred historically due to fluctuations in climate where moister climate conditions resulted in fuel build up followed by drier conditions which resulted in regional fire years.

The authors found significant increases in the fire severity across all global climate model scenarios by the end of the century likely due to the role temperature plays in fire occurrence and severity. Global fire severity was expected to increases the greatest in the Northern Hemisphere by as much as three times the baseline Cumulative Severity Rating. They also found that fire season length was expected to increase across all regions where the fire season is not already year round.

The authors found that the Keetch-Byram Drought Index (KBDI) is expected to increase, driven primarily by increasing temperature across the Southwest, Rocky Mountains, northern Great Plains, Southeast, and Pacific coast, thereby increasing future fire potential across most of the continental U.S. The fire season is also projected to increase in length, potentially by several months in some regions.

Despite issues with pseudoreplication and the limited sample size, the authors found that post-fire conditions moved toward range of natural variation conditions after intense burning. Small trees and fire-susceptible understory trees were preferentially killed by fire and forest floor woody debris was within desired conditions. The sites had adequate regeneration of seedlings with no evidence of any landscape conversion to a non-forest vegetation type.

The authors found strong relationships between synchronized fire activity and summer drought in the year of the fire across all regions. Fire activity declined significantly during the late 16th century during a period of anomalously low temperature, referred to as the Little Ice Age.