Prof. Toumi was awarded his PhD from the University of Cambridge on stratospheric ozone under the supervision of Prof. John Pyle, FRS. He was then appointed a temporary lecturer in the Chemistry Department in Cambridge and a Fellow in Physical Chemistry at Christ's College Cambridge. In 1994 he moved to the Physics Department at Imperial College as a Lecturer. He was promoted to Professor of Atmospheric Physics in 2005 and Head of the Space and Atmospheric Physics Group from 2014-2020. Since 2020 he is Co-director of the Grantham Institute (Climate Change and Environment).
He was awarded the Phillip Leverhulme Prize for "scholars of outstanding distinction" (2002), a Merit Award by Imperial College for outstanding achievement in research (2004), a Royal Society Industry Fellowship (2006-2010) and a NERC Knowledge Exchange Fellowship (2009-2012) on adaptation in the energy sector. He was Co-chair of Adaptation Services in the Climate KIC (2013-2015). He has co-authored and reviewed many international reports such as WMO Ozone Assessments, SPARC and IPCC Reports. He has served on the ESA mission advisory group and the European Commission Climate Services Road Map group. He was a founding director of OASIS LMF Ltd which is promoting open access catastrophe modelling for the insurance sector and others. OASIS was also the basis of a large Europe wide Climate KIC and later H2020 projects he co-led. He is advising the Bank of England on physical impacts of climate change on the financial sector. He has published extensively covering a wide range of topics in climate science including graduating 33 PhD students. He currently leads the largest research group on tropical cyclones in Europe.