A gloomy outlook?

Russell Layberry looked out of the window. "It was so quiet, no bird song, no cars, nothing. The water looked chest-deep in the village and waist-deep in everyone's houses. It was bizarre."

He sat down on the settee and played the guitar, floating around the lounge. Outside his neighbours went past in a kayak and called out "morning". Russell chuckled: "I thought they were delivering the papers."

Russell is the most westerly-based of our staff, living in a village near Burford. He's an energy efficiency specialist, and he was our first - and hardest-hit - flood victim. His car and kitchen were a write-off.

"But the worst thing is the damage to our personal stuff, like 5,000-odd photographs. A neighbouring farmer lost 1,000 pheasants because they wouldn't come out of their hutches in the dark. There's a lot of old folk who remember 1947 and they think it was worse than that. Most people blame it on building on flood plains and the like."

So, we are all agreed that it has been wet. But has this summer been unusually wet?

My first stop is Hang Gao, the observer for Oxford University's Radcliffe Meteorological Station.

The station has the longest series of temperature and rainfall records for any site in Britain, continuously from 1815 and irregularly from 1767.

Perhaps surprisingly, Hang says this is only the 23rd wettest July, with 110 mm of rain. This is, however, nearly double the long-term average, and the worst since 1968.

The wettest was 1834, when 183.4mm of rain fell - an absurd coincidence of numbers.

On that dramatic Friday, July 20, only 34 millimetres of rain fell in Oxford, compared to the astonishing 120-plus millimetres recorded at Brize Norton, emphasising how much rainfall can vary across the county.

More weather records jump from the monthly summaries that Hang posts publicly outside the department.

Remember that glorious April? The average temperature was 11 degrees centigrade, a whopping three degrees above the long-term average, equalling the historical high of 1943. It was the third-driest, too.

Things started to go downhill in May - there was 135mm of rain and it was the third-wettest since 1767. In June, wind stood out - the average of 9.9 knots being the seventh-highest since 1881.

Returning along the corridor, I felt a bit sheepish as I picked up the report from Hang's native China - 650 dead in their latest flooding and more than 100m affected.

We are clearly not alone in enduring extreme weather. Nor are we anything like the worst affected. But Hang's statistics confirmed that this summer has definitely been unusual.

But what has been the cause?

The Jet Stream is the 'buzz phrase' which has rushed out of meteorological textbooks and into the pubs of Oxfordshire and Gloucestershire.

It is a band of fast-moving air a few hundred kilometres wide which travels around the northern hemisphere at about 36,000 feet. In a 'normal' summer, it directs our rain-bearing Atlantic depressions north of the UK, across Scandinavia. And in the UK, we get high-pressure systems that bring warm, settled conditions.

But this summer the Jet Stream has moved south, over us. The weather has been worsened by the heatwave currently over much of Europe, which is reacting with the depressions to generate storms and cloudbursts.

Why, then, has the Jet Stream shifted south - and how likely is it do so in the future?

Readers may have seen various explanations and predictions in the media, but the reality is that the scientists really don't know - yet.

Let us, however, take a step back.

The weather does seem to have been, for want of a better word, 'funny' for quite a while. The Radcliffe Meteorological records show that since 2000, 80 of the 90 months have been above their long-term temperature average.

And while our summer may have been wet and horrible, it has been warmer than usual.

Time for a climate scientist's expertise, I think.

Dr Mark New is a deputy program leader in the UK's Tyndall Centre for Climate Change Research and director of Oxford's Masters in Water Science, Policy and Management.

His experience of the recent flooding was unsettling.

"We were driving back from Ireland on Sunday at 4am. Diverted through Burford we came across the tragic sight of rabbits being trapped between the flooded fields and the traffic. It was carnage."

Mark believes there is no longer any 'natural' weather, because we are now altering the climate.

The tricky bit is we can't say by how much for any particular weather event, and our ability to quantify the effect decreases the smaller the scale.

"For global average temperature it is quite easy to attribute a large part of the change over the last 100 years to greenhouse gas increases.

"Temperature is directly linked to the way increasing carbon dioxide in the atmosphere changes the heat content.

"At the other end of the scale, it is difficult to tease out the human influence on any one local event. The heatwave in 2003 was a lot easier to attribute because it was a temperature extreme and covered a large area. With rainfall extremes there are many stages between increased carbon dioxide, increased heat, and how much rain falls during a particular event."

So it is impossible to say for sure that climate change caused these extreme rains.

But why do we get more extremes in general?

"Because there is more energy in the atmosphere. The climate system is being heated up. With temperature, the average is increasing, and the spread around this average is probably also increasing. What was an unusual temperature 20 years ago is much more frequent now.

"Rainfall is more complicated. One aspect is that higher temperatures increase evaporation rates, and faster cycling of water interacts with a more energetic atmospheric system to produce more intense rainfall. This is theoretical reasoning, but there is evidence from the climate models that this will happen."

There has been some debate about the extent to which our wet summer and extreme rainfall events could have been predicted - 'seasonal forecasting' to use the jargon.

Mark explains that the key to successful seasonal forecasting is having one or a few factors that strongly control the weather, yet change slowly themselves.

In the tropics, sea surface temperatures vary slowly and strongly control rainfall.

"El Nino is the classic example. Once it has started it will not suddenly switch off, and you can make predictions."

But in the mid-latitudes in which the UK is found such relationships are more ephemeral.

We have a chaotic atmosphere with no single factor 'in charge', so our seasonal forecasts cannot be as robust.

If not the weather, then, what about the predictability, or otherwise, of the flood?

This depends upon knowing how much rain we had, the state of our catchment area (soil moisture, river flow, etc), and how well we can model its response to a given input of rain.

But our Thames catchment is complex, with several rivers interacting.

And while the Environment Agency has a good model to gauge its response, a problem in predicting flood surges and peaks may well have been the difficulty of monitoring the state of the catchment.

Financially it may be too expensive to get absolutely all the real-time data we need to make the most accurate predictions possible.

We may, instead, need to work with imperfect information, and settle for some probabilistic forecasting, a bit like we now experience with weather forecasts - "a 30 per cent chance of rain today" - etc.

If we cannot predict the Thames, can we tame it, even a little?

Over to Dr Mark New again.

"Changing river courses is very difficult - and risky. Their existing path will have evolved in tune with their historical flow and associated energy.

"If you force this flow elsewhere you put the river into disequilibrium. If flood protection is then breached, you may have a very much worse situation. Like the Mississippi."

So, if we cannot predict or tame the Thames, how should we prepare ourselves for these extremes?

Sensibly sited on the floor above Russell Layberry and his Lower Carbon Futures colleagues is our UK Climate Impacts Programme, an acknowledged world-leader in climate risk management.

UKCIP colleagues tell me the key to being prepared is to think about your 'thresholds of vulnerability', and to identify what weather patterns would break these.

For the record, the 'big four' headline weather patterns they have for a climate-changed future are: wetter, milder winters; warmer, drier summers; more extreme events (at any time of the year); and increasing sea levels.

Clearly, thresholds of vulnerability will vary from individual to individual. It follows, therefore, that what each of us does to prepare for extreme weather will also vary.

But, in general, it is clear that everybody has to be more conscious of where we build, how we build and how we refurbish.

In urban areas we've been putting in 'hard landscaping' without the corresponding drainage requirements.

Why? We know very well what drainage is required. But we choose not to act on this knowledge.

Many people have a list of ten things they can do to save energy.

I wonder whether we should all now have a list of the ten things we can do to prepare ourselves for the worst?

UKCIP say that it's not so straightforward, because much of this list would need to be at community and institutional levels, dealing with things such as infrastructure design, building regulations, road construction.

But there are things that individuals can do.

Sign up for the Environment Agency's flood-alert system, for instance. Keep those sandbags, too. If you are renovating, fit wider guttering, put plug sockets higher up the wall and have rugs rather than fitted carpets.

Oh, and do not pave over all the front garden.

• For more information about Oxfordshire ClimateXChange, contact Jo Hamilton 01865 275856, jo.hamilton@ouce.ox.ac.uk, or www.climatex.org