They're cool guys. I was giving one of them a lift from Lytton to Lillooet a couple years ago and he asked if I was "one of those rich American kids that comes up to Lillooet to buy weed"
Yes!
The following article lists 15 things we can do. We only have to do 7 of them to stabilize the amount of greenhouse gasses and hence the warming occurring. If we did more than 7 of the 15, we could begin to reduce atmospheric greenhouse levels.
http://www.sciencemag.org/cgi/content/abstract/305/5686/968
It is both, because the quality and supply of water suitable for drinking are both decreasing.
Recently, pilgrims were warned that they should not even bathe in the Ganges. That's a billion people right there.
Actually, the number of people in the world without access to clean or safe drinking water is at an all-time high, as is the number of people dying of dehydration (thirst).