The persistent nature of the storms that have been repeatedly hitting the UK is due to processes as far flung as Indonesia and the North Pacific, also involving the polar vortex, these have caused the jet stream configuration that has steered storms to the UK, and intensification of the Jet that has been part of the intensity and frequency of the storms. For the details, those interested should read page 13 onwards. However that is but part of the equation, we're seeing 'natural' processes modified by anthropogenic global warming processes (similar to the droughts plaguing Australia). As Dr Slingo states:
"There is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly rain events."
As detailed in the Met Office report the intensification of rainfall has been observed.
Furthermore, where there are sufficiently long records of hourly rainfall data, it has been shown that rain rates potentially increase with temperature at rates that exceed the simple thermodynamic Clausius-Clapeyron relationship (6-7% increase in humidity for 10C rise in temperature) between temperature and humidity17 (Figure 23). This can be understood through the dynamic amplification of rain-bearing systems, where the induced circulation drives greater convergence of moisture into the system and hence heavier rainfall.So the increase of heavy rainfall is proceeding at a rate that is greater than the most elementary physics might lead one to suppose.
The Thames is currently flooding and is due to continue rising for at least the next 24 hours, despite little rain being forecast. This means that by the time the next storm comes in (Tuesday) the Thames will still be rising. The Met Office report cites measurement of flow at Kingston Upon Thames, which has records from 1883 to present. Daily flows this winter have not exceeded the peak flows measured at times throughout that period. But the greatest number of consecutive days of flow over 275m^3/second was at 39 days up to 31/1/14, this is substantially higher than any other such period in the 131 year record.
The reason for this is the extreme amount of rainfall experienced this winter over the south of England, below is figure 3 of the report. The red horizontal line shows how far above previous years the rainfall has been during January.
Figure 2 shows the regions of the UK that have experienced twice the average amount of rainfall (darkest blue).
And figure 1 of the Met Office report shows a count of the number of stations reporting wind speeds over 60 knots (69mph), an indicator of the unusual frequency of the storms.
Are we really to believe that this is just ordinary weather variation, and that human caused global warming has no role in what is happening? My suspicions have been building for some time, this Met Office report just firms up those suspicions into opinion. The UK is now firmly in the Age Of Consequences, with Arctic sea ice loss linked to the cold winters of 2009/10 and 2012/13 (which I've blogged on), and the Post 2007 Summer Pattern leading to wet summers in the UK (which I've also blogged on).
It might be wondered by some why I avoid taking on climate change denialists, some might even suspect that as a former sceptic of climate change maybe I don't want to rock their boat.... The primary reason why I don't bother with the denialists is this: We have a real and ongoing process, there are two theories about it (well a theory and a vague hand-waving bag of bollocks).
1) Humans are causing climate change, the prime mover being emissions of Carbon Dioxide.
2) The Sun / Unphysical relaxation from the Little Ice Age / Unphysical 'natural' random walks of the climate system / "What warming/climate change?" / ...enter your own poorly considered balderdash here.
In the case of theory 1 the process will continue and intensify as we emit more and more CO2.
In the case of 2 the process won't continue because there is no ongoing forcing to drive it.
Those backing 2 are doomed. They have already lost the scientific argument, and as the weather shows the early signs of climate change the argument for public perception is being lost, bit by bit. Rapidly consigning the denialists to the same wacko paddock as Young Earth Creationtists, Spiritualists, "Aliens abducted me!", "It's a Jewish conspiracy!" and all the other people that most of us make polite excuses to move away from when we encounter them socially.
The denialists are digging their own hole, deeper and deeper, they won't disappear completely (like the nutcases I list above), but more and more they'll disappear from public view, In short they are irrelevant. Public opinion is more swayed by experience than by any amount of technical argument, and the weather that people experience is changing.