New estimates for emissions of nitrous oxide

Nitrous oxide (N(2)O) is one of the natural components of the Earth's atmosphere. Its concentrations have been increasing for the last two centuries and have increased more rapidly during the last 50 years. Recent studies indicate that the increasing emissions and concentrations are largely associated with agricultural activities. In this paper we give an overview of sources of nitrous oxide, the atmospheric N(2)O budget, options for control of N(2)O from agriculture and some scenarios for future emissions and their consequences for atmospheric concentrations. We present new estimates for N(2)O from agriculture for a number of European countries, calculated following the revised IPCC Guidelines methodology. Our new estimates are in most cases higher than the emissions as reported by the countries in their 1998 national emission inventories. We also present estimates for global emissions for two scenarios. In our Base ("business-as-usual") Scenario global emissions increase from 11 Tg N in 1850 to 21.7 Tg N in 2020. In a Reduction Scenario assuming implementation of emission control, total emissions are 16.8 Tg N by 2020. This implies that in the Reduction Scenario total anthropogenic emissions are reduced by about 40% relative to the Base Scenario, and 20 25% relative to the 2000 level. Most of this reduction is realized in agriculture. However, the reductions may not be sufficient to avoid a further increase in atmospheric N(2)O.