Will UK Floods Get Worse?–Part II

By Paul Homewood

 

 

According to the UK’s Climate Risk Assessment Report ,recently published :-

But the main risk is that global warming will cause flooding that could cost up to £12 billion every year because of heavy rainfall in the winter and rising sea levels, affecting up to 3.6 million people by 2050.

We have already seen that there seems to be very little trend in national rainfall levels, (see here). But, as some readers have pointed out, even monthly statistics can cover up high daily totals that can sometimes lead to flash floods.

As well as providing rainfall data, the UK Met Office summarise the number of days with rainfall over 1.0mm, “raindays”, and these are available by region, so we can calculate the average rainfall per rainday. It is highly likely that an increasing number of “high rainfall days” would boost this average, so what does the data tell us?

 

 

 

About the only thing that stands out is the heavy rainfall experienced in the summer of 2007, mainly in Yorkshire and the Midlands. Was this year a one off? Certainly there is nothing in the trend to suggest otherwise.

It is also worth pointing out that, nationally, the 1960’s and 1970’s were relatively dry, compared to previous years and this pattern appears to apply to all regions. The data seems to suggest that lower annual rainfall correlates with lower rainfall per rainday, (in other words, low rainfall has more to with less heavy rain falling, rather than less days of rain). It is not unreasonable to suppose that, in the decades leading up to 1961, rainfall per rainday would have been marginally higher than the 1960’s and 1970’s. (Rainday data is only available since 1961).

There is no evidence either from these figures or the total rainfall data that climatic factors have been increasing the incidence or severity of floods in the UK. The past, of course, is no guarantee of what the future will bring. But it seems a pretty good place to start.

 

P.S. Regional rainfall data will posted up tomorrow.