Thomas has been Executive Director of SEI Oxford, MunichRe Foundation Chair in social vulnerability with the United Nations University Institute for Environment and Human Security, Reader in the Environmental Change Institute, University of Oxford, founding director of the UK Climate Impacts Programme, expert advisor to the UK House of Commons, and chair of the International Geographical Union’s Task Force on Vulnerability.

He is a leading expert on climate vulnerability and natural hazards, adaptation and food security, drawing upon 30 years of professional work.

He has contributed to all four of the assessments of the Intergovernmental Panel on Climate Change, and is Review Editor for the fifth assessment now underway.  He has contributed to many EC research projects, at present coordinating ClimateCost with Paull Watkiss and a major role in Mediation (with Paul and Sukaina Bharwani).

Through the Global Climate Adaptation Partnership he leads mainstreaming climate adaptation in the African Development Bank and a consortium organising to gear up the Adaptation Academy (led by Mohamed Hamza); both efforts involve collaborative projects with SEI Oxford.

He is author of over 100 journal articles, book chapters and technical papers.