I don't know the cities he's talking about, but I do know about subsidence in San Jose along San Francisco Bay. Contrary to Lomborg's statement, it's a big deal and a serious problem, especially when combined with other potential flooding problems that usually exist because cities are normally located near rivers.
The other point Lomborg misses is that city subsidence is geographically limited. The only area that needs to be protected from relative sea level rise is a small stretch of shoreline. And cities are the most economically valuable land on the planet, so the cost of protecting them relative to their value constitutes the best possible scenario.
Sea level rise, even minor sea level rise, is a much bigger deal. Here in Santa Clara County, we're going to have to deal with it, and it's already costing taxpayers money. Flood projects for near-sea-level creeks are right now being designed to handle sea level rise, which is the only intelligent way to construct these long-term structures. Adaptation is already here, it's a significant problem, and the question is who should pay for the costs. Seems like greenhouse gas emissions would be a good place to look for a tax to pay for greenhouse gas costs.