Climate-induced variations in global wildfire danger from 1979 to 2013

Abstract

Climate strongly influences global wildfire activity, and recent wildfire surges may signal fire weather-induced pyrogeographic shifts. Here we use three daily global climate data sets and three fire danger indices to develop a simple annual metric of fire weather season length, and map spatio-temporal trends from 1979 to 2013. We show that fire weather seasons have lengthened across 29.6 million km 2 (25.3%) of the Earth's vegetated surface, resulting in an 18.7% increase in global mean fire weather season length. We also show a doubling (108.1% increase) of global burnable area affected by long fire weather seasons (41.0 s above the historical mean) and an increased global frequency of long fire weather seasons across 62.4 million km 2 (53.4%) during the second half of the study period. If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate.

Impact of anthropogenic climate change on wildfire across western US forests

“…S7 A and B) hastened increases in fire-season fuel aridity, consistent with observed increases in the number of consecutive dry days across the region (10). Natural climate variability, including a shift toward the cold phase of the interdecadal Pacific Oscillation (35), was likely the dominant driver of observed regional precipitation trends (36) (Fig.…”

“…Observational studies have shown that fire growth preferentially occurs during high fire danger periods (52,53). We also calculate the fire weather season length for the four daily fire danger indices following previous studies (10).…”

“…Increased fire activity across western US forests has coincided with climatic conditions more conducive to wildfire (2)(3)(4)8). The strong interannual correlation between forest fire activity and fire-season fuel aridity, as well as observed increases in vapor pressure deficit (VPD) (9), fire danger indices (10), and climatic water deficit (CWD) (11) over the past several decades, present a compelling argument that climate change has contributed to the recent increases in fire activity. Previous studies have implicated anthropogenic climate change (ACC) as a contributor to observed and projected increases in fire activity globally and in the western United States (12)(13)(14)(15)(16)(17)(18)(19), yet no studies have quantified the degree to which ACC has contributed to observed increases in fire activity in western US forests.…”

Spatio-Temporal Linkages between Declining Arctic Sea-Ice Extent and Increasing Wildfire Activity in the Western United States

“…They found that, beginning in the mid-1980s, the onset of MLCs-which reduce fire activity by bringing cooler temperatures and precipitation-occurred later, the frequency of MLCs significantly decreased, and these changes were coincident with greater wildfire activity. Similarly, Jolly et al [40] found that fire-weather season length and annual area burned were positively related on a global scale, while Spracklen et al [41] found the combination of May-October mean temperature and fuel moisture conditions accounted for 24%-57% of interannual variability in area burned in the western U.S.…”

“…Mean area burned from 1999 to 2015 (1,846,667 ha) was 2.5 times greater than during 1980-1998 (737,167 ha), and all regions experienced similar inflection dates for increased fire activity. The increase in area burned is related to an increase in fire-season length [38][39][40] where fire season begins earlier and ends later. In the Northern Rockies, Knapp and Soulé [39] examined trends during 1900-2004 in the onset and frequency of major mid-latitude cyclones (MLC) during the latter half of summer, which coincides with peak fire season.…”