Session: Benchmarking & cross-cutting Group 1 (Isotope modelling, COMPARE)
Author: Sandy P. Harrison / firstname.lastname@example.org / University of Reading
Co-author: Patrick J. Bartlein, University of Oregon;
Victor Brovkin, MPI Meteorology, Hamburg;
Sander Houweling, Utrecht University;
Silvia Kloster, MPI Meteorology, Hamburg;
I. Colin Prentice, Imperial College London;
The recent observational record is too short to estimate the strength of fire-related carbon-cycle feedbacks unequivocally; model-based estimates are contradictory. Sedimentary charcoal records provide regional and global time series of biomass burning and show that fire has responded sensitively to climate variations over the past two millennia. Thus, they could provide an alternative constraint on this feedback. We use a single-box model of the land biosphere to quantify the biomass-burning feedback, using charcoal data from the Global Charcoal Database and the Mann et al. global palaeotemperature reconstruction for the pre-industrial Common Era. Charcoal increases with global mean temperature, and varies coherently with the stable carbon isotope composition of methane in ice cores. We estimate a centennial-scale feedback strength of 2.9 ± 1.1 ppm K–1 land temperature for pre-industrial biomass burning, with uncertainty dominated by the absolute value of the carbon flux. Satellite-based estimates of biomass burning emissions for 2000–2014 yield a feedback strength of 6.5 ± 3.4 ppm K–1 land temperature, with uncertainty dominated by the slope of the global emissions-temperature relationship. The modern relationship mainly reflects tropical deforestation and peat fires. Comparison with a consensus model estimate of the total land climate-carbon cycle feedback (13.1 ± 6.4 ppm K–1) suggests most of the contemporary climate-carbon cycle feedback is linked to anthropogenic burning.