ScienceAlert: Scientists warn that unless greenhouse gas emissions are significantly and rapidly reduced by 2020, by at least 25 per cent below 1990 levels, global warming and climate change will become irreversible and uncontrollable. As a consequence, large areas of the planet may be unable to sustain their present population or become uninhabitable. Massive population movements will be caused by an increasingly severe climate producing flooding, draughts and crop failures, compounded by hunger and …