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Is recent flooding and heavy rainfall unusual?

I've written at length about the excessive rainfall the UK has experienced, particularly last year but also since the late 1990's; six out of the years from 1998 to 2012 are in the top ten wettest on record, based on Met Office rainfall data which began in 1910.

There are various theories as to why our summers have been so wet, and why the jet stream has been further south than normal.

It's worth remembering as exceptional as the last few years have seemed, climate history shows us that flooding in the UK has always been normal.

This point is highlighted in research which was carried out by Durham University following the serious summer floods in 2007 and highlighted on the website this week.

The research is five years old, but it rings very true today, and the prediction made in 2008 of increased flooding and heavy rainfall in subsequent years has proved to be all too correct.

The author Professor Stuart Lane looked back at rainfall patterns starting in the mid 1700's.

He concluded that our climate has always fluctuated between very wet and very dry periods, some of which lasted for a few decades.

Crucially the period from the early 1960's to the late 1990's saw far fewer river flooding episodes compared with before the 1960's and after the 1990's.

Ominously, he points out that because more than three quarters of our flood records started during the 1960's, when there were far fewer river flooding episodes, we have underestimated the frequency of flooding.

And this has a knock on effect as to how much flood plain development local authorities will allow.

It's a vicious circle as more flood plain development is likely to make any future flooding even worse.

The article on the Durham University website can be found

UK weather outlook:

The heavy snow that brought disruption to parts of the UK on Friday has melted rapidly as a result of milder air and rainfall.

The next 48 hours will be dominated by a very common January weather pattern, with a powerful jet stream bringing rain or showers to all areas, accompanied by strong to gale force winds.

There's uncertainty about Friday's weather though, with an Atlantic depression expected to bring rain to parts of the UK.

Just how far north the rain will come is open to question, but with colder air pushing southwards as it clears away, some of it could turn to snow.

2012 Global temperatures:

Provisional Met Office figures show that 2012 was the 9th warmest on record, 0.45C above the 1961-1990 average. This is very close to their prediction for 2012 which was for a global temperature 0.48C above the 1961-1990 average.

According to the UAH satellite temperature measure, 2012 was also the 9th warmest on record.

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Amounts of snow across some parts of our region are the deepest since December 2010, with 21 cms being reported at Pateley Bridge in Nidderdale at midday, and a notable 18 cms in the middle of Sheffield at Weston park.

Waddington in Lincolnshire is reporting 14 cms of snow.

There are some big contrasts though, with only 2cms reported at Church Fenton in the Vale of York.

The snow, on Friday and last night, was forecast well in advance and first signalled at the beginning of last week.

Further snowfall is likely on the North York moors tonight, but for many it should become dry, with the main hazard being that of widespread ice.

Patchy rain, sleet and snow in coastal areas tomorrow will push inland to affect some areas, but further snowfall amounts will be small.

A change to milder weather will come at the weekend, with rain, preceded by some snow; the last week of January looks much milder with rain at times.

The thaw, when it comes could be rapid and with the ground already saturated from last year's excessive rainfall, flooding is likely to be a concern.

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Many parts of Yorkshire and Lincolnshire had their first snowfall of the winter yesterday, with coastal areas suffering the largest falls with around 10cms (4 ins) of fresh snow being reported by yesterday evening.

Temperatures could easily reach -10C (14F) in rural locations where there's snow cover during the next couple of nights.

But by the end of the week and into the weekend, things will become much more interesting, as weather fronts make the first of what could be two attempts to bring less cold air in from the Atlantic, with a risk of snow and disruption to travel.

As is always the case in these situations there's a lot of uncertainty about how fast the less cold air moves north-eastwards.

Experience suggests that computer models are often too quick to replace cold continental air.

Current indications are that the first Atlantic weather front will push across our area through Friday night and into Saturday as a weakening feature, bringing some increasingly light snow.

The next more active weather front will bring heavier snow on Sunday, which will eventually turn to rain as less cold air spreads eastwards.

But to highlight the uncertainty, some solutions are quicker with the snow and bring it across Yorkshire and Lincolnshire on Friday, with others slower.

There's bound to be changes to the timing of these systems as we get nearer the event, but there's clearly a risk of disruptive snow as we head into the weekend.

Next week looks very unsettled, and although the air will be somewhat less cold, temperatures are still likely to below average, with rain at times which could easily turn to snow in places, especially over the hills.

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A new global temperature forecast published by the Met Office, through to 2017, has scaled back projections of the amount of warming they expect compared with previous estimates.

The new projection can be seen below with on the Met Office website.

In the 12 years to 2011, 11 out of 12 forecasts were too high - and although all projections were within the stated margin of error, none were colder than expected.

One of their most high profile forecasts came in late 2009, coinciding with the Copenhagen climate conference.

It stated that half the years between 2010 and 2015 would be hotter than the hottest year on record, which I wrote about on my blog.

This already appears wide of the mark.

The latest projection seems to address this error with a prediction to 2017 in which temperatures rise 20% less than previously estimated.

In November 2009 I wrote about this levelling off in global temperatures, using research available at the time on the Met Office website.

In it, the Met Office explained that the levelling off of global temperatures that we were experiencing can be expected at time periods of a decade or less, because of the computer models internal climate variability.

But intriguingly, the research ruled out zero trends for time periods of 15 years or more.

The new projection, if correct, would mean there will have been little additional warming for two decades despite rising greenhouse gases.

It's bound to raise questions about the robustness and reliability of computer simulations that governments around the world are using in order to determine policies aimed at combating global warming.

The Met Office says natural cycles have caused the recent slowdown in warming, including perhaps changes in the suns activity, and ocean currents.

And mainstream climate scientists, who are in a majority, say that when the natural cooling factors change again, temperatures will be driven up further by greenhouse gases.

But climate sceptics, who have long argued that natural processes are either underestimated, or not properly understood, will not be surprised at this scaling back of expected warming.

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UPDATE at 1pm on Mon 7th Jan

2012 was provisionally 3rd wettest on record according to the England & Wales rainfall series which started in 1766, behind 1872 and 1786. December was also the wettest since 1978 in the same dataset.

ENDS

2012 averaged across the UK was the second wettest on record in data which stretches back to 1910, falling short of a new record by only 6.6mm.

In total 1330.7mm fell last year, compared with the average of 1154mm.

A new record has been set across England and Wales with 1205mm of rain.

And locally new records have been set for Yorkshire, with 1230.8mm (136% of average) and Lincolnshire with 841.3mm (135% of average).

It's been a remarkable run of wet years in the UK since 1998; 6 years are now in the top 10 wettest - 1998, 1999, 2000, 2002, 2008 & 2012.

Even more striking are figures based on the much longer England and Wales rainfall data series, first started in 1766.

2012 is provisionally in the top 4 wettest in 246 years (the other years being 2000, 1872 & 1786).

Also of significance is that 2012 is the only year in this 246 year data set in which 2 calendar months set new records for rainfall: April and June.

2012 has certainly been a remarkable year which has seen the jet stream too far south for long periods of time.

But weather patterns are very different as we head into early 2013. The jet stream has re-positioned itself further north, with high pressure building across the country.

This means an emphasis on much drier weather across the UK as whole in the next few days, which will come as a huge relief to many, although rain is expected early next week.

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