If global warming truly becomes a problem then human populations may be forced to build underground where it is safe. This would also protect us from solar flares and solar radiation. Building vertical Tunnel habitats straight down instead skyscrapers makes a lot of sense.

For instance there is no way to crash an aircraft into a building, which goes straight down into the ground like the middle eastern Arab international terrorists did in 9/11. Once a vertical Tunnel was built straight down the walls could be fused together using laser molecular realignment technologies. This would make the walls stronger than steel by using the forces of molecular bonding to hold the wall in place while it was being built.

In doing this we would not have to make buildings, which goes straight up and we could connect the walls and the floors of the building laterally into the dirt and therefore it would be much stronger and cheaper to build. People could live in these underground vertical Tunnel habitats and then simply use an elevator to get up to the surface of the planet where they could catch transportation to the rest of the city.

As land and real estate prices get too expensive the buildings get higher and more dangerous. However, if we build downwards we have miles and miles to go before we ever run out to of the earth's crust to build into. Please consider this in 2006.