Indirect long-term global radiative cooling from NOx emissions

Anthropogenic emissions of short-lived, chemically reactive gases, such as NOx 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, CH4 and the HFCs. This study uses the characteristics of the natural modes of the tropospheric chemical system to decompose the greenhouse effect of N Ox and CO emissions into (i) short-lived modes involving predominantly trop ospheric O-3 and (ii) the long-lived mode involving a global coupled CH4-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 CH4 and O-3-we find that most types of anthropogenic NOx emiss ions lead to a negative radiative forcing and an overall cooling of the ear th.