Unger joined Yale University as an Assistant Professor at the School of Forestry & Environmental Studies, where she was part of the Yale Himalaya Initiative.[6][7] Here she studied the role of aviation in climate change on global temperature.[8] She created a global-scale model that could evaluate the impact of reducing the levels sulphur in jet fuel on air quality.[8] Unger has studied the role of ozone and aerosols on the Earth's radiation balance, and the feedback between air quality and climate change.[9] Unger used the Yale University supercomputer to study the impact of the volatile organic compounds released during wildfires.[10] She calculated the concentration of aerosol particles and methane release during the Pliocene, and compared it to those released during the pre-industrial era.[11] She has argued that to achieve the Paris Agreement temperature targets wealthy countries will have to reduce carbon dioxide emissions from energy-use.[12]