Uncertain Climate Effects of Anthropogenic Reactive Nitrogen

Our results emphasize what is clear from previous literature—that a range of models are needed to quantify the climate effects of anthropogenic Nr, including uncertainty. Future research is clearly needed on this important topic, both to better define and narrow the uncertainties on the climate effects given here and (as discussed in ref. 1) to quantify climate effects for processes for which estimates do not yet exist (for example, aerosol–cloud interactions due to Nr emissions). Crucially, a natural way forward to reduce uncertainties involves continuous improvement of key processes in the models based on thorough evaluations against a range of observations.