Earth is melting down like a nuclear reactor. At current rates of warming, Arctic sea ice will melt away by 2030. According to the UN's environmental program, countries' current greenhouse gas emissions pledges for the year 2020 would put them on par with current global levels, not enough to prevent the planet warming by at least 2C by the end of the century. Nasa climate scientist James Hansen has described such a rise as “a prescription for disaster”, leading to an increase of droughts, floods and other forms of extreme weather. Some estimates project a rise upwards of 6C by 2100.