The world has lots of water, lots of desert, too much carbon dioxide, far too many people who do not have enough to eat and insufficient clean water. What follows is a possible solution.
I have posted my idea here
http://www.halfbakery.com/idea/Water_20transportation#1287975564
To save the above website from being slashdotted, here is my idea plus a few edits.
Deliver water and electricity anywhere on the planet cheaply
In Iceland they have built a vast hydroelectric system.
http://en.wikipedia.org/wiki/K%C3%A1rahnj%C3%BAkavirkjun
They are using the electricity to smelt aluminium. I propose a different plan, that they use the electricity to smelt hydrogen from the sea.
The three beautiful attributes of hydrogen are, it can be used to lift things, make electricity and it is one of the two elements that make up water.
Why not combine all three attributes of hydrogen to improve the planet and undo some of the harm, our species appears to be doing.
Put the hydrogen in a vast balloon, attach a motor driven propeller and a hydrogen compressor, both driven by the hydrogen in the balloon, navigate it automatically using GPS.
Fly the balloon into the jet stream using the compressor to control the height of the balloon, use the jet stream to transport the balloon encased hydrogen most of the way, to where water is required on the planet. When the hydrogen is as close to where it is wanted as you can get it, using the oxygen hydrogen reaction, start compressing the hydrogen and the balloon will sink.
In one cubic mile of uncompressed hydrogen, there is potentially 744316795 gallons of water, which is enough water to fill over a thousand Olympic swimming pools.
Water is very heavy so would be expensive to transport about, simple just transport the hydrogen 'coz the oxygen is already there!
Once we can get the water to the dry areas of the planet and grow oil palm plantations there, we can stop the absolute scandal of chopping down jungle in Indonesia to plant oil palm plantations and in so doing - destroy the orangutans environment.
Imagine a plentiful supply of water in the middle of Australia or in the Sahara.
More water in dry areas means more plants means less carbon dioxide in the atmosphere.
If the water is stored at the top of mountains then hydroelectricity could be made when the water is needed at the bottom of the mountains.
The electricity generated when the hydrogen and oxygen are combined in a fuel cell, could be used to create fertilizer and if there were any juice left over, you could always smelt aluminium with it :)
The price of scrap aluminium is very cheap, the planet has little need of smelted aluminium.
Little Iceland, needs an economic lifeline so as to pay off its debts.