Saturday, March 1, 2014

New paper shows fire activity at end of 20th century was low in comparison to past 2000 years

A new paper under review for Climate of the Past reconstructs fire activity of the Northern Hemisphere over the past 2000 years, and finds fire activity was very low toward the end of the 20th century in comparison to the past. The authors find the greatest fire acitivity and droughts occurred from 1000–1300 AD and 1500–1700 AD, but show that fire activity at the end of the record in 2000 was unusually low.
Three proxies of fire activity all show very low levels at the end of the 20th century. 

Clim. Past Discuss., 10, 809-857, 2014

P. Zennaro1,2, N. Kehrwald1, J. R. McConnell3, S. Schüpbach1,4, O. Maselli3, J. Marlon5, P. Vallelonga6,7, D. Leuenberger4, R. Zangrando2, A. Spolaor1, M. Borrotti1,8, E. Barbaro1, A. Gambaro1,2, and C. Barbante1,2,9
1Ca'Foscari University of Venice, Department of Environmental Science, Informatics and Statistics, Santa Marta – Dorsoduro 2137, 30123 Venice, Italy
2Institute for the Dynamics of Environmental Processes, IDPA-CNR, Dorsoduro 2137, 30123 Venice, Italy
3Desert Research Institute, Department of Hydrologic Sciences, 2215 Raggio Parkway, Reno, NV 89512, USA
4Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
5Yale School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, CT 06511, USA
6Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Ø 2100 Copenhagen, Denmark
7Department of Imaging and Applied Physics, Curtin University, Kent St, Bentley, WA 6102, Australia
8European Centre for Living Technology, San Marco 2940, 30124 Venice, Italy
9Centro B. Segre, Accademia Nazionale dei Lincei, 00165 Rome, Italy

Abstract. Biomass burning is a major source of greenhouse gases and influences regional to global climate. Pre-industrial fire-history records from black carbon, charcoal and other proxies provide baseline estimates of biomass burning at local to global scales, but there remains a need for broad-scale fire proxies that span millennia in order to understand the role of fire in the carbon cycle and climate system. We use the specific biomarker levoglucosan, and multi-source black carbon and ammonium concentrations to reconstruct fire activity from the North Greenland Eemian (NEEM) ice cores (77.49° N; 51.2° W, 2480 m a.s.l.) over the past 2000 years. Increases in boreal fire activity (1000–1300 CE and 1500–1700 CE) over multi-decadal timescales coincide with the most extensive central and northern Asian droughts of the past two millennia. The NEEM biomass burning tracers coincide with temperature changes throughout much of the past 2000 years except for during the extreme droughts, when precipitation changes are the dominant factor. Many of these multi-annual droughts are caused by monsoon failures, thus suggesting a connection between low and high latitude climate processes. North America is a primary source of biomass burning aerosols due to its relative proximity to the NEEM camp. During major fire events, however, isotopic analyses of dust, back-trajectories and links with levoglucosan peaks and regional drought reconstructions suggest that Siberia is also an important source of pyrogenic aerosols to Greenland.

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