An annual increase in the rate of accumulation of carbon dioxide (CO₂) of more than 2 ppm was observed at the AGAGE station at Mace Head, Ireland during 2002-2003, in close agreement with a similar increase in the growth rate of CO₂ reported from measurements at the Mauna Loa Observatory, Hawaii. This increase is unexpected, as it did not occur in a major El Niño period, and although CO₂ emissions from global fossil fuel increased by more than the recent trend in 2002 and 2003, the additional increase (estimated from data in the BP Statistical Review of World Energy to be about 0.4 GtC in 2003, mainly due to increased coal consumption) is not sufficient to account for the anomaly. Sustained increases in the growth of CO₂ above the historical average annual trend are significant, and would imply a positive feedback on global warming thereby accelerating climate change.

Moreover, at Mace Head simultaneous in situ measurements of CO, CH₄, H₂, O₃, and CH₃Cl also exhibit similar trends in their annual rates of increase as with CO₂ in 1998-99 and 2002-03, both periods with intense global fires. These perturbations demonstrate a causal relationship between large-scale biomass burning events and the interannual variability of these gases, and imply that the recent increase in the rate of accumulation of CO₂ is a hemispheric wide phenomenon related to large-scale biomass burning rather than a change in ocean exchange.

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Article: A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to large-scale biomass burning events? P.G. Simmonds, A.J. Manning, R.G. Derwent, P. Ciais, M. Ramonet, V. Kazan and D. Ryall (2005). Atmospheric Environment 39: 2513-2517 (doi: 10.1016/j.atmosenv.2005.02.018).