PNNL

Abstract

Understanding how atmospheric aerosol particles are initially formed is a major challenge in climate change assessment. Although new particle formation (NPF) mechanisms have been elucidated at specific sites, such mechanisms in most regions of the world remain a mystery because of lack of ability to simulate critical NPF processes. Here, we synthesized molecular-level experiments to develop unprecedented comprehensive representations of 11 NPF mechanisms and the complex chemical transformation of precursor gases in a fully coupled global climate model. Despite remaining uncertainties, combined simulations and observations suggest that previously neglected or underrepresented mechanisms involving organics, amines, iodine oxoacids, and HNO3 most likely dominate NPF in regions possessing high concentrations of aerosols or large aerosol radiative forcing. The mechanisms and impacts of NPF vary greatly with region and altitude, indicating that comprehensive simulation of NPF mechanisms is essential for accurate estimation and source attribution of aerosol climate forcing.