The disappearance of Arctic sea ice has crossed a "tipping point" that could soon make ice-free summers a regular feature across most of the Arctic Ocean, says a British climate scientist who is setting up an early warning system for dangerous climate tipping points.

Tim Lenton at the University of Exeter has carried out a day-by-day assessment of Arctic ice-cover data collected since satellite observation began in 1979. He presented his hotly anticipated findings for the first time at the Planet Under Pressure conference in London on Monday.

Up until 2007, sea ice systematically fluctuated between extensive cover in winter and lower cover in summer. But since then, says Lenton, the difference between winter and summer ice cover has been a million square kilometres greater than it was before, as a result of unprecedented summer melting. This real-world data is in contrast to what models predict should have happened

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Tim studied Natural Sciences as an undergraduate at the University of Cambridge. Reading Jim Lovelock’s books on Gaia ignited his passion for studying the Earth as a whole system. This led to his PhD studies on what regulates the nutrient balance of the ocean and the oxygen content of the atmosphere, supervised by Professor Andrew Watson at Plymouth Marine Laboratory and later the University of East Anglia (UEA). After gaining his PhD, Tim worked at the Centre for Ecology and Hydrology, Edinburgh, where he built a simple coupled carbon cycle and climate model, and then coordinated the development of the GENIE family of Earth system models. In 2004 he returned to UEA and built up an Earth system modeling group, working on key events in the coupled evolution of life and the planet, including human-induced global change. He recently published a book on this with Andrew Watson called ‘Revolutions that made the Earth’ (OUP, 2011). Tim moved to the University of Exeter in 2011, where he and his group are focusing on understanding these past revolutions, on developing an evolutionary model of the marine ecosystem, and on early warning of climate tipping points. Tim works closely with Professor Nick Talbot on the overall environmental research strategy for the University.

Tim’s work identifying the tipping elements in the climate system won the Times Higher Education Award for Research Project of the Year 2008. He has also received a Philip Leverhulme Prize 2004, a European Geosciences Union Outstanding Young Scientist Award 2006, the British Association Charles Lyell Award Lecture 2006, and the Geological Society of London William Smith Fund 2008. Tim is a Fellow of the Linnean Society and a Fellow of the Geological Society.