Global temperature change potential of nitrogen use in agriculture: A 50-year assessment.

Nitrogen (N) use in agriculture substantially alters global N cycle with the short- and long-term effects on global warming and climate change. It increases emission of nitrous oxide, which contributes 6.2%, while carbon dioxide and methane contribute 76% and 16%, respectively of the global warming. However, N causes cooling due to emission of NO, which alters concentrations of tropospheric ozone and methane. NO and NH also form aerosols with considerable cooling effects. We studied global temperature change potential (GTP) of N use in agriculture. The GTP due to NO was 396.67 and 1168.32 Tg COe on a 20-year (GTP) and 439.94 and 1295.78 Tg COe on 100-year scale (GTP) during years 1961 and 2010, respectively. Cooling effects due to N use were 92.14 and 271.39 Tg COe (GTP) and 15.21 and 44.80 Tg COe (GTP) during 1961 and 2010, respectively. Net GTP was 369.44 and 1088.15 Tg COe and net GTP was 429.17 and 1264.06 Tg COe during 1961 and 2010, respectively. Thus net GTP is lower by 6.9% and GTP by 2.4% compared to the GTP considering NO emission alone. The study shows that both warming and cooling effects should be considered to estimate the GTP of N use.