Increased atmospheric ammonia over the world's major agricultural areas detected from space

This study provides evidence of substantial increases in atmospheric ammonia (NH₃) concentrations (14-year) over several of the worlds major agricultural regions, using recently available retrievals from the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. The main sources of atmospheric NH₃ are farming and animal husbandry involving reactive nitrogen ultimately derived from fertilizer use; rates of emission are also sensitive to climate change. Significant increasing trends are seen over the US (2.61% yr^-1), the European Union (EU) (1.83% yr^-1), and China (2.27% yr^-1). Over the EU, the trend results from decreased scavenging by acid aerosols. Over the US, the increase results from a combination of decreased chemical loss and increased soil temperatures. Over China, decreased chemical loss, increasing temperatures, and increased fertilizer use all play a role. Over South Asia, increased NH₃ emissions are masked by increased SO₂ and NO_x emissions, leading to increased aerosol loading and adverse health effects.