Indirect long‐term global radiative cooling from NO x Emissions

Anthropogenic emissions of short‐lived, chemically reactive gases, such as NO x and CO, are known to influence climate by altering the chemistry of the global troposphere and thereby the abundance of the greenhouse gases O 3 , CH 4 and the HFCs. This study uses the characteristics of the natural modes of the tropospheric chemical system to decompose the greenhouse effect of NO x and CO emissions into (i) short‐lived modes involving predominantly tropospheric O 3 and (ii) the long‐lived mode involving a global coupled CH 4 ‐CO‐O 3 perturbation. Combining these two classes of greenhouse perturbations—large, short‐lived, regional O 3 increases and smaller, long‐lived, global decreases in CH 4 and O 3 —we find that most types of anthropogenic NO x emissions lead to a negative radiative forcing and an overall cooling of the earth.