Karl is an atmospheric chemist and physicist who studies the often subtle interactions between land surfaces and the atmosphere. One of his primary interests is emissions, chemistry and uptake of particles and gases, such as volatile organic compounds, which can affect local air quality and climate. In 2010, he led a research team that found plants can absorb far more air pollutants than previously thought. Karl also studies urban/regional air quality and the impact of land-use changes, such as suburban development and the expansion of agroforests, on the atmosphere. He works in NCAR’s Atmospheric Chemistry Division.