> build flood control systems.

Water is only one problem. By 2070 some places might be uninhabitable according to this[1] study, due to heat.

> At WBTs [wet bulb temperature] above 35C, the high heat and humidity make it physically impossible for even the fittest human body to cool itself by sweating, with fatal consequences after six hours. For less fit people, the fatal WBT is below 35C. A WBT temperature of 35C – the combination of 46C heat and 50% humidity – was almost reached in Bandar Mahshahr in Iran in July 2015.

At some point it's going to cost big bucks. If the study holds water, the Gulf will either need to be evacuated or artificial habitation will need to be built.

[1]: https://www.theguardian.com/environment/2015/oct/26/extreme-...

Will still be a wakeup call. And I seriously doubt that flood control (and/or relocation) for all major costal cities will be cheaper than climate engineering.