There were large interannual variations in burned area in the boreal region (ranging between 3.0 and 23.6 ¿ 106 ha yr-1) for the period of 1992 and 1995--2003 which resulted in corresponding variations in total carbon and carbon monoxide emissions. We estimated a range of carbon emissions based on different assumptions on the depth of burning because of uncertainties associated with the burning of surface-layer organic matter commonly found in boreal forest and peatlands, and average total carbon emissions were 106--209 Tg yr-1 and CO emissions were 33--77 Tg CO yr-1. Burning of ground-layer organic matter contributed between 46 and 72% of all emissions in a given year. CO residuals calculated from surface mixing ratios in the high Northern Hemisphere (HNH) region were correlated to seasonal boreal fire emissions in 8 out of 10 years. On an interannual basis, variations in area burned explained 49% of the variations in HNH CO, while variations in boreal fire emissions explained 85%, supporting the hypotheses that variations in fuels and fire severity are important in estimating emissions. Average annual HNH CO increased by an average of 7.1 ppb yr-1 between 2000 and 2003 during a period when boreal fire emissions were 26 to 68 Tg CO-1 higher than during the early to mid-1990s, indicating that recent increases in boreal fires are influencing atmospheric CO in the Northern Hemisphere.