1. Institute of Shock Physics, Imperial College London, London SW7 2AZ, UK. E-mail: c.jacobs10@imperial.ac.uk
2. Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK
3. Grantham Institute for Climate Change, Imperial College London, London SW7 2AZ, UK
4. Lamont–Doherty Earth Observatory, Columbia University, New York 10964, USA