The succinct part of this is simple.
So what's it all about - and why weren't the flood defences up to the job? Actually, it's surprisingly simple. A lot of rain fell. More rain than has ever fallen anywhere in the UK before in a 24-hour period.
A warmer climate allows the atmosphere to hold more water. When that water falls, it falls faster and for longer. Also there is a huge El Nino building in the Pacific. This has muted the Atlantic hurricane season, but the warm evaporating water has to go somewhere. This year it was us. Another year it will be somewhere else.
I was working in Turin at the time of the Po valley flooding in 2000. I drove to Milan to take the plane home and I drove through rain which I had never seen before. It was more like driving through a swimming pool than through rain, at times at least 4 inches was sitting on the road.
When I got back on the Sunday, I could not get back on the Autostrada and had to divert which took me 4 hours. It was not until Monday that I found out why. The massive 6 lane Autostrada bridge had gone 100m South and all other bridges within 100km were also out of action. In Turin itself there were brown street lamps where the muddy water had entered the glass. The Fiat building where they used to do the foundry work in the 1930's had been lifted off it's foundations and there was devastation all over the place. When I drove up the valley the next weekend to head for Sweden, it looked like the path of a hurricane had gone up the valley, train embankments washed out, Autostrada washed out.
I've read articles since which try to explain it all away and say it's river banks and not global warming. However the reality at the time, when everyone didn't realise the cost of mitigating global warming and so were not trying to deny it, was that it usually rained to 1,500m and snowed above. This whole weekend it had rained up to 3,000m and had brought down massive landslides and, much more damaging, rock slides. These rock slides were carried down by the raging river and destroyed everything in it's path. Retaining walls for flood barriers, houses, bridge founds, everything. Some of the rocks were 5m across, I saw them trying to move them when I drove North through the valley.
Whilst it's good to talk about land stabilisation and ecology, we are going to have to go much, much further than that. Right now the environment is more like 15,000 years ago and in the next 50 years is going to be more like 800,000 years ago. To deal with this we are going to have to do the same review of the water infrastructure that the Victorians did, but with an eye to the current situation. For instance we're going to have to re-do the Thames Barrier within 100 years. It simply won't cope with the rising sea levels and increased storms. When it does go, the old scenes of London flooding I remember will be a fond memory, because when it does go the resulting flood is going to be catastrophic.
It took humans 2,000 years to tame the river Rhone and it was only achieved by the implementation of cascaded barriers designed to deal with the flood conditions. Something similar is going to have to be done for the watersheds of the UK and it is NOT going to be cheap.
The world was told, in the 1990's, that the cost of avoiding climate change was going to be incredibly expensive and that every decade we did not do it, the cost would become higher. However the world was also told that the cost of NOT avoiding climate change would be paid in lives, lost land, lost countries and devastation on a scale the human race had never been seen before.
So we chose not to avoid. What we see now are the first warming up sounds of the orchestra. When we are in full symphony it will be incredible to see. But nobody will be enjoying it much....