Man made contributions to Harvey's severity. Paving without zoning or planning. It's a major contributing factor, but 50 inches of rain is still unprecedented and would have inundated the region.

We know that the severity and impact of hurricanes on coastal cities is exacerbated by at least two factors: higher sea levels, caused primarily by the thermal expansion of seawater; and greater storm intensity, caused by higher sea temperatures and the ability of warm air to hold more water than cold air.

Before it reached the Gulf of Mexico, Harvey had been demoted from a tropical storm to a tropical wave. But as it reached the Gulf, where temperatures this month have been far above average, it was upgraded first to a tropical depression, then to a category one hurricane. It might have been expected to weaken as it approached the coast, as hurricanes churn the sea, bringing cooler waters to the surface. But the water it brought up from 100 metres and more was also unusually warm. By the time it reached land, Harvey had intensified to a category four hurricane.

The heat of an urban area and the pavement that has been laid willy-nilly in Houston conspired to aggravate the impact of all of that rain. The questions people need to ask themselves - are they willing to just build wherever, or will they move out of flood plains. Will they zone so runoff is better managed? Will communities work to move the poorest, most vulnerable, into safer areas without marginalizing them or simply rendering them homeless? Will media start addressing Climate Change as a real thing and keep up the pressure on local, state, and federal managers?