James is a marine geologist and is currently Head of the Department of Earth and Environmental Sciences. After a degree at the University of Oxford and a Postgraduate Certificate in Education at the University of Bristol, he completed a PhD on the Quaternary stratigraphy and palaeoenvironments of the Celtic Sea, Isles of Scilly and West Cornwall at the University of Cambridge. This research was undertaken in the laboratories of the Sub-department of Quaternary Research including the Godwin Laboratory led by Professor Sir Nicholas Shackleton FRS. He was then elected to a Research Fellowship at Girton College, University of Cambridge, but after a year was appointed to a Lectureship at Bangor University in the School of Ocean Sciences in 1985, being awarded a Personal Chair in 2005. He moved his research group to the Penryn Campus at the University of Exeter in February 2017.

James was President of the Quaternary Research Association (2008-2011) and Chair of the NERC Radiocarbon Facility Steering Committee (2007-2011). He was Editor of the Journal of Quaternary Science (2000-2004) and was awarded a Royal Society-Leverhulme Trust Senior Research Fellowship in  2008-2009. He was elected a Fellow of the Learned Society of Wales in 2014, was Director of the Climate Change Consortium of Wales between 2011 and 2016, and received the ScD degree from the University of Cambridge in 2023.