HISTORICAL BIOMASS BURNING - LATE-19TH-CENTURY PIONEER AGRICULTURE REVOLUTION IN NORTHERN-HEMISPHERE ICE CORE DATA AND ITS ATMOSPHERIC INTERPRETATION

Ice core data from Yukon and Greenland spanning from similar to 1750 t o 1950 indicate that between similar to 1850 and less than or equal to 1910 a clear atmospheric signal exists of an episodic biomass burning event that is referred to as the Pioneer Agriculture Revolution, This is best seen in NH4+ ion and particulate concentrations 4 but also in some limited black carbon concentration data, where for all three qua ntities maximum levels reach about 3 times the prerevolution backgroun d concentrations. Tree cellulose delta(13)C data and some early, contr oversial, French, air CO2 data, occurring within the same time interva l, are interpreted as providing other independent evidence for the sam e, mainly North American, late 19th century biomass burning event, Som e hitherto problematic northern hemisphere ice core derived CO2 concen tration data may now be interpreted as containing a biomass burn signa l, and these data are compared, especially as to the time of occurrenc e, with all the other results, A global carbon cycle model simulation of atmospheric CO2 mixing ratios using a maximum input of 3 Gt(C)/yr a t northern midlatitudes produces ''anomalous'' CO2 levels close to som e of the ice core carbon dioxide values, However, other values in this data set do not reasonably represent fully mixed atmospheric values. This suggests that these values might be transients but still ''tracer s'' for biomass burning, Nevertheless, it appears possible that interh emispheric CO2 gradients of similar magnitude to the present one could have existed briefly late last century.