Neil Hall/EPA vía Shutterstock
LONDON — At the point where the River Thames empties into the North Sea, Boris Johnson wanted to build an airport on an artificial island.
It was 2009, and Mr. Johnson was newly in office as London mayor. To study the airport idea, he tried to enlist a leading scientist, Prof. David King, except Professor King had recently warned about rising water levels on the Thames. Hardly ideal conditions for an airport, he told the mayor, balking at the project while instead offering to look into other uses for the waterway.
So the professor was taken aback when Mr.