Solar controls of fire events during the past 600,000 years

Fires have accompanied terrestrial life from the beginning, yet with incomplete knowledge about feedback to paleoclimate and vegetation. Here, we have assessed how climate triggered the activity of vegetation fires in a 600,000 years continental record. We recorded benzene polycarboxylic acids as markers for burned organic carbon residues (BC) in sediments of Lake Van (Turkey), one of the oldest lacustrine archives currently available on Earth. Though fire and BC peaks were assumed to occur during dry climates, BC concentration and related fire temperatures were largest during periods of warm/humid climatic conditions. During humid periods, we recorded up to 45 mg BC per cm3 sediment (precipitation ∼ 800 mm/a), while BC amounts during dry climates were smaller by a factor of 10 (<5 mg BC per cm3 sediment, precipitation < 200 mm/a). Overall, BC concentration in Lake Van sediments paralleled that in other lake sediments. They all following orbital forcing, showing that fires events peak globally with a cyclicity of ∼100,000 years.