If so, how do fires and associated climate change ascribed to human activity differ from natural biomass burning?
The links between biomass burning and increased agriculture (and therefore increased GHGs including carbon dioxide and methane) and the prolongation of interglacial climate are only valid if measured increases in burning demonstrate a quantifiable relationship with increased temperature. In addition, lake cores contain necessary palynological evidence for human-induced fires such as the anthropological pollen index, pollen indicators of slash-and-burn cultivation, the presence of fire-tolerant species suggesting frequent fire activity, and changes in the arboreal pollen influx. The multi-proxy nature of ice and lake cores presents the perfect material to investigate the linkages between early agricultural activity and climate change as temperature, palynologic evidence, and levoglucosan are measured from the same depth and time within the surrounding matrix.
This understanding of the role of biomass burning and agriculture in climate-fire feedbacks has important implications for the future. Deforestation fires significantly contribute to the atmospheric carbon dioxide concentration which creates a positive feedback loop as the associated warming increases extreme fire weather. Currently, deforestation fires for agriculture supply up to ~19% of the total modern increases in radiative forcing. Discriminating past natural from anthropogenic fire regimes has the potential to quantify human impacts on the climate system for thousands of years as well as to provide essential insight into the role of atmospheric aerosols under a warming climate.