We already create urban "heat islands" that cause afternoon rainstorms in places like Atlanta, so I do no think these towers do anything that has not been done already. They seem to be a brilliant idea that should have been stumbled upon decades ago!
The thermal updrafts now feed into thunderstorm cells and all of that energy essentially goes to waste, but with this technology constructed in the right locations perhaps the benefit would be two fold: Energy from the uplifting air, and essentially being able to control (or at least influence) the local weather in the area around the tower. I'm not climatologist but it seems like a little multidisciplinary collaboration could really pay off in big ways (i.e. where droughts seems to never end and where excessive rain/flooding is a problem).
If it is possible to build a tower and funnel hot air upwards, couldn't we also build a giant cone to take advantage of cold air falling? -- I guess this must get into pressure gradients and all sorts of other science... so I'll stop typing now.
"How many other brilliant concepts are just waiting for an untrained eye to look at them differently?"