Just how heavy could the rains become?
On a very wet day we can expect 1-2 inches of rain to fall in the UK, perhaps double that in extreme conditions. But as Harvey, Irma and other storms have shown, in warmer climes prolonged rainfall can be many times heavier. So in a warming world, just how heavy could rain become?
I think the only safe answer here is “lots”. The planetary weather system is extremely complex, meaning that it has many variables, many of which are currently unknown. Simple projections linked to how much water the atmosphere can hold by temperature are a reasonable starting point, but other variables (such as the ratio of sea to land, composition of atmosphere, salination of sea etc) all act as modifiers to that projection, making it incredibly difficult to say how accurate those projections will ultimately turn out to be.
In short, we know that weather events are going to be more extreme and that extreme weather events are likely to increase in frequency, and our best guess at putting a number to this is a 7%-ish (where “ish” represents the unknowns) increase in both.
I remember standing in the doorway of the British Council building in Dar es Salaam during a rainstorm, and noting that I could not make out anything of the building opposite, about four yards away. Several tonnes of water seemed to fall for 10 or 15 minutes (and yet the streets were dry a few minutes later).
I cannot imagine how much more rain could fill that air space, unless one were literally under water. My guess would be that more water in the clouds would simply mean a longer rain shower, rather than denser water fall. How long such “showers” could last before the area became uninhabitable is anyone’s guess.
Francis Blake, London N17
Storm Desmond deposited some 340mm of rain on Honister Pass in Cumbria in 24 hours, on 5 December 2015. The problem wasn’t the intensity of the rain, as much as the duration. Mabllechidris
I’m afraid it’s going to get biblical – as in Noah and his ark.
Jackie Howard, Manchester