I find this idea simply breathtakingly silly:
Here is why I find this silly (oh... where to begin)
1st off, there is no reason to build these things because the global warming myth is just that... a myth. The world has already begun cooling down as it has cycled from hot to cool for millions and millions of years.
Secondly, Who would want to live on these huge ships with virtually no way of getting on/off? Keep in mind that these things are supposed to just float around in the ocean's currents. There are no engines to propel these things and if there was, imagine the power it would need just to keep it stationary. This power requirement alone would defeat the entire purpose of reducing the carbon footprint that these things are supposed to reduce. If these things are not powered in some way, won't they eventually crash land against land? what then? Perhaps it will be anchored to the sea bottom... but won't this destroy the ecology underneath this huge thing?
Thirdly, Has anyone actually rode out a hurricane in the the ocean? I thought those global warming scare mongers keep saying there will be more hurricanes and other natural extreme weather. If this is the case, they are in for a real rough ride, no matter how big these things are, they will be affected by rough seas. I hope they will pack enough barf bags.
Fourthly, How many people can survive in one of these things? Will there be mandatory birth control to maintain a certain population level? Who gets to decide who can have kids and who cannot? Not only that, it seems that everyone will be given a job to perform, much like a kibutz. While there is nothing wrong with this form of socialism when practiced by a willing but small community, it becomes overbearing and too controlling over people's lives when there are more than just a small community. For instance, on one of these ships, someone has an aptitude to be a dentist, yet there are already too many dentists, thus that person becomes the garbage collector.
And lastly (and there are so many other points) these things will never, ever get built even if everyone agrees it is the only thing that will save mankind. Why? Because there are environmental whackos who will argue that it will irreparably damage the echo system , cause extinction of (fill in the lifeform here) and pollute the air by having so many humans concentrated in a confined space. Jeez, we cannot even drill a small hole in a barren wasteland in Alaska to make us more energy independent. where will this thing get built? Keep in mind that these whacko's philosophy is 'BANANA': Build absolutely Nothing Any Where Near Anything.
Thus, it will be Whacko Vs. Whacko debating how and where these things should be built. the rest of us will be watching and laughing our asses off as if we are reading Spy Vs. Spy comic strips where the black spy is always at odd with the white spy found in Mad Magazine.