Tim Lenton is a Professor at the University of Exeter. His research focuses on understanding the behaviour of the Earth as a whole system, especially through the development and use of Earth system models. After gaining a BA in Natural Sciences at Cambridge University, he investigated what regulates the nutrient balance of the ocean and the oxygen content of the atmosphere as a PhD student of Andrew Watson. He also worked closely with James Lovelock developing the Gaia theory and trying to reconcile it with evolutionary theory. Moving to the Centre for Ecology and Hydrology in Edinburgh, he focused on understanding the feedbacks between the carbon cycle and the Earth's climate. Having returned to the University of East Anglia in 2004, his work identifying climate tipping points won the Times Higher Education Award for Research Projects of the Year 2008. He holds a number of other awards and fellowships. Andrew Watson holds a Royal Society Research Professorship at the University of East Anglia. His career has spanned planetary and atmospheric sciences, oceanography, and climate, giving him a strong interest in the evolution of the Earth system as a whole. After obtaining a BSc in physics from Imperial College, he investigated the history of oxygen in Earth's atmosphere as a PhD student of James Lovelock. He worked on NASA's Pioneer Venus space mission at the University of Michigan. Returning to England and the marine research laboratories in Plymouth, he developed a new method of tracing large scale water movements. He became a professor at the University of East Anglia in 1996, was elected a Fellow of the Royal Society in 2003, and became a Royal Society Research Professor in 2009. He holds a number of other fellowships and awards.