<P> Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land - use change (Banuri et al., 1996, pp. 93--94). The actual calculation of net emissions is very complex, and is affected by how carbon sinks are allocated between regions and the dynamics of the climate system . </P> <P> Non-OECD countries accounted for 42% of cumulative energy - related CO emissions between 1890 and 2007 . Over this time period, the US accounted for 28% of emissions; the EU, 23%; Russia, 11%; China, 9%; other OECD countries, 5%; Japan, 4%; India, 3%; and the rest of the world, 18% . </P> <P> Between 1970 and 2004, global growth in annual CO emissions was driven by North America, Asia, and the Middle East . The sharp acceleration in CO emissions since 2000 to more than a 3% increase per year (more than 2 ppm per year) from 1.1% per year during the 1990s is attributable to the lapse of formerly declining trends in carbon intensity of both developing and developed nations . China was responsible for most of global growth in emissions during this period . Localised plummeting emissions associated with the collapse of the Soviet Union have been followed by slow emissions growth in this region due to more efficient energy use, made necessary by the increasing proportion of it that is exported . In comparison, methane has not increased appreciably, and N O by 0.25% y . </P> <P> Using different base years for measuring emissions has an effect on estimates of national contributions to global warming . This can be calculated by dividing a country's highest contribution to global warming starting from a particular base year, by that country's minimum contribution to global warming starting from a particular base year . Choosing between different base years of 1750, 1900, 1950, and 1990 has a significant effect for most countries . Within the G8 group of countries, it is most significant for the UK, France and Germany . These countries have a long history of CO emissions (see the section on Cumulative and historical emissions). </P>

Which one of the following greenhouse gases is the largest concentration in the atmosphere