Why do you think climate change will kill a billion people over the next century? Not saying you're wrong, just bewildered that you are able to make any kind of prediction on this at all.
I've been hearing nearly all my life that coastal areas like Bangladesh, Mumbai, Kolkata, orissa etc are at a severe risk of drowning due to rising sea levels.
I've experienced first hand water scarcity in many parts of the country, but more prominently near the Deccan plateau due to rainfall failures and lakes, rivers drying up as a consequence of exploitation leading to crop failures.
Their 1 billion number doesn't seem too far off though if we take into account not many hospitable places have measures controlling resource usage and exploitation.