Six Degrees by Mark Lynas Harper, HK$148 We have until 2015 to cut back greenhouse-gas emissions if we are to avoid 'dangerous' levels of warming, Mark Lynas believes. Even if we do so, owing to the thermal time lag of the planet, temperatures will probably rise, he estimates, but within a 'safe corridor' of up to two degrees Celsius. One of many books about climate change, Six Degrees distinguishes itself by presenting a degree-by-degree guide to Earth's future. If the world heats up by one degree, for instance, we stand to lose fresh water from a third of its surface; if temperatures rise four degrees that's it for China's agriculture; a planet six degrees warmer ... who knows? Climate models almost all shy from simulating six degrees of warming by 2100, Lynas points out, although that doesn't preclude him offering a warning that stops short only of humanity's extinction. Unlike the book's cover, which shows Big Ben being swallowed by a tidal wave, the work does not use shock tactics to shake the reader. It doesn't need to. Demonstrating soberly how he came up with his conclusions - by trawling through thousands of scientific papers and entering the data into a spreadsheet - Lynas succeeds in raising the temperature on an already hot topic.