Outdoor burning generates CO

The atmospheric trace gas, carbon monoxide, has important effects on methane and on ozone, and is important both in atmospheric chemistry and for its indirect influence on climate. Little is known about the abundance and sources of CO prior to the industrial age, or about the importance of anthropogenic activities on its budget. Wang et al. (p. 1663, published online 2 December; see the Perspective by Prentice) present a 650-year-long record of CO atmospheric concentration and isotopic composition, using samples from Antarctic ice cores, in order to begin to reconstruct past CO variability and its causes. The concentration of CO decreased by about ~ 25%, from the mid-1300s to the 1600s, and then recovered completely by the late 1800s. Large variations in the degree of biomass burning in the Southern Hemisphere are likely to have been primarily responsible for the observed changes.

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