Wildfire responses to abrupt climate change in North America
Fire is the most ubiquitous form of landscape disturbance, and has important effects on climate through the global carbon cycle and changing atmospheric chemistry. There has been a significant increase in large-scale wildfires in all regions of the world during the past decade. This has triggered an interest in knowing how fire has changed in the past, and particularly how fire regimes respond to periods of major warming.
The end of the Younger Dryas, about 11,700 years ago, was an interval when the temperature of Greenland warmed by over 5°C in less than a few decades. Marlon et al. used 35 records of charcoal accumulation in lake sediments from sites across North America to see whether fire regimes across the continent showed any response to such rapid warming.
They also examined the changes during the major cooling at the beginning of the Younger Dryas, ca 12,900 years ago - because a team of scientists led by an isotope geochemist at Berkeley had suggested that a large comet exploded over North America then, triggering widespread fires as well as the cooling. Marlon et al. found no evidence for continental-scale fires. They did find clear changes in biomass burning and fire frequency whenever climate changed abruptly, but most particularly when temperatures increased at the end of the Younger Dryas cold phase.
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