Earlier quoted context omitted.
James Lovelock, the inventor of Electron Capture Detector, which he used to discover CFC's, and the person behind the Gaia theory, predicts that only Canada, Northern Europe and Siberia will be habitable in the later part of this century. www.rollingstone.com/politics/news/james-lovelock-the-prophet-20071101
Yes but its more than just habitability. Soil condition/quality as well as availability of water, etc. is important for farming.
Very true - there will be a limit to what size of a population can be sustained by farming within those northern areas. Whatever that number is, it's probably not 9 billion people