Prof. Toumi was awarded his PhD from the University of Cambridge. He was then appointed a temporary lecturer in the Chemistry Department in Cambridge and a Fellow in Physical Chemistry at Christ's College. In 1994 he moved to the Physics Department at Imperial College as a Lecturer, promoted to Professor of Atmospheric Physics in 2005 and was Head of the Space and Atmospheric Physics Group (2014-2020). Since 2020 he has been the Co-director of the Grantham Institute - Climate Change and Environment.

Awards include 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. Significant services to the community were as Co-chair of Adaptation Services in the Climate KIC (2013-2015) and co-authoring and reviewed many international reports such as WMO Ozone Assessments, SPARC and IPCC Reports. He has served on the ESA mission advisory and the European Commission Climate Services Road Map groups.

He is advisor to the WMO Asia-Pacific Typhoon Collaborative Research Center and on the board for the Japan typhoon dropsonde program. Commercial interactions include being a founding director of OASIS LMF Ltd which is promoting open access catastrophe modelling for the insurance sector and others. He was Co-Investigator in the UK Centre for Greening Finance and Investment. Over his career his research has covered a wide range of topics in climate science, atmospheric chemistry and physics. He has supervised 36 PhD students and leads Europe's largest research group on tropical cyclones.