Via http://www.metoffice.gov.uk/research/news/2016/national-flood-resilience...

Including:

The Met Office based these on recently recorded extreme events, and added substantial but plausible  additional uplift s,   of    between 20% and 30% for each  of the six standard climatological regions  of England and Wales, determined  from  modelling and analysis of monthly rainfall records for these regions. 

 

Role of climate change in past extreme rainfall and flooding events

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The Met Office, through its National Climate Information Centre (NCIC), and the Environment Agency hold detailed observational records of meteorological variables and river flows. These have been combined with other measurements, such as sea level rise, and with published evidence to make an assessment of the influence of climate change on past events.

The observational record of monthly accumulations since 1910 [1] suggests some detectable changes in the rainfall distribution across the UK and across seasons, particularly in the northern and western parts of the UK. However the attribution of those changes to climate change continues to be challenging because of the large natural variability of the UK’s climate [2,3].

• Although the last 50 years has shown a trend of increasing winter rainfall, in the longer context of the last 100 years values being observed now are close to those in the e arly part of the 20th century (figure 1, upper panel).

• However, the observational record up to 2014 shows that 7 of the 10 wettest years in the UK have occurred since 1998 [4] . The cluster of flood events through the early years of the 21st century, and the duration of recent runoff and recharge patterns are near to the extreme range of historical variability over the past 100 years [4].

• Extreme rainfall is often related to very intense events occurring on daily or even hourly timescales. Observations on these timescales are much more limited, and comprehensive UK daily rainfall records are currently only available back to 1960. These show a clear signal of more heavy daily rain events in the most recent decade. This is consistent with the thermodynamic effects of climate change; increases in rainfall intensity have been documented world- wide and are recognised as being one of the most detectable signals of climate change in rainfall characteristics [5].