AirToob Lightning
Is our weather getting worse? Channel 4 documentary
Britain has had some extraordinary weather in 2012, varying from severe drought to record levels of rainfall, with flash floods across the country. This excellent Channel 4 documentary (from which my screenshots come) considers if extreme weather is to be expected occasionally, or whether it provides evidence of an increasing climate change problem - not just in Britain, but everywhere.

Judging by how often the documentary is being repeated on UK TV, it's a question that certainly interests people in the UK. If you click on any image, you may still be able to view it online if it interests you as well.

(The rather beautiful instrument seen above, by the way, is a Campbell-Stokes sunshine recorder, invented in 1853 and still in use today.)

This is some of what happened in Britain in 2012:

On January 3rd, severe storms with gusts of over 100 mph battered the coastline of much of the UK from Scotland to the south.

On February 5th, 4" of snow fell across southern England, with hundreds of flights cancelled.

4 weeks later there was a dramatic change in the weather. On March 26th, record-breaking heat baked Scotland, Aberdeen, with temperatures above 27°C (81°F).

Drought affected 35 million people across the country, in the driest Spring for 100 years.

Then, no sooner had the hosepipe ban been issued, when everything changed. On April 3rd snow warnings were issued across the country. In Scotland, temperatures plummeted by 27°C in just 2 days. The snow quickly melted, and on April 18th was replaced by torrential downpours across England and Wales.

By the end of the month the Met Office declared that it was the wettest April in a century, and the heavens remained open through the whole of May. By early summer the whole of Britain was saturated.

On June 22nd, a series of torrential thunderstorms funnelled into West Yorkshire's Hebden Bridge (which floods once every 5 years on average, but nothing like this). A month's worth of rainfall fell in 7 hours.

On July 9th, another cunim cloud, 10 miles high, towered over West Yorkshire. It burst at 1 pm. A month's worth of rain fell in just 3 hours.

And the extreme summer just went on and on. In July, a severe storm in Leicestershire produced hailstones the size of golfballs, and the rainfall continued into August. By the end of the summer, 4,000 homes across Britain had been devastated by floods. Saturated ground meant that even small amounts of rainfall caused flash floods.

On September 25th, a severe storm churned up plankton in the North Sea, swamping the Scottish town of Footdee in a thick layer of strange foam.

On October 11th, this flash flood was triggered in the Devonshire town of Clovelly when 2 weeks worth of rain fell in just 90 minutes.

Flooding doesn't just destroy homes, it takes lives. By far the deadliest place to be is trapped inside a car.

Training for flood survival and car rescue is not for the faint-hearted. Teesside Barrage at Stockton on Tees, a major facility for international "white water" events, is also used as a flood survival training centre. Four huge archimedes screws (each 13 metres or 45½ feet in diameter) lift water to create an artifical flood, pumping tons of water every second into the river. (BTW, there are plans to generate electricity by running these screws in reverse when the course is not being used.)

It only takes seconds for the weight of water to break the instructor's grip and sweep him away (a cubic metre of water weighs a ton). Avoiding lethal debris means keeping pointing downstream and trying to steer around what is coming.

Car rescue training starts inside a car anchored to the concrete bottom.

You need to get out through the window, and onto the roof...

"I'm on the roof, but there's not a lot to hold onto here..."

What has been causing Britain's extreme weather in 2012?

Part of the story is this:

The northernmost of 4 jet streams is responsible for delivering weather to Britain, and its position varies according to our seasons. In Spring 2012 the jet stream moved north of the UK, a position it normally takes in mid summer. This early move north brought us unusually high temperatures and drought.

And then in summer, something very different happened. The jet stream switched south, a position it usually takes during winter, bringing cold stormy weather to the British Isles. Even now, the behaviour of the jet stream remains a mystery(*).

*In January 2013, the BBC Weather Report featured a new development which has managed to link Sudden Stratospheric Warming with changes to the jet stream, and has allowed the Met Office to forecast weather events relating to jet stream movement much earlier than was previously possible.

Was 2012 just a freak year, or are these events part of a much bigger picture? Is our weather really changing?

What we saw in 2012 was certainly not a one-off. The past 15 years saw 8 of the warmest years on record, and some of the wettest years on record.

On July 28th 2005, a tornado ripped across Birmingham, spawned by severe thunderstorms, causing £40m of damage in 4 minutes.

Tornados by themselves are not enough to indicate that our weather is changing, but they are part of a series of extreme weather events that have plagued the UK in the last decade.

December 2010 was Britain's coldest ever.

In 2003, UK temperatures hit a record 38°C (100°F). This intense heatwave killed more than 2,000 people.

In fact, extreme weather events have occurred throughout the last century, and much earlier than that...

Over nine hundred years ago, in 1091, a medieval version of Mary-le-Bow Church in London (immortalised in the nursery rhyme Oranges and Lemons - a Cockney is traditionally defined as someone born within the sound of Bow Bells) was destroyed by the first recorded tornado in British history, approaching via the site of the modern London Eye and ripping the church tower to shreds - more than 600 homes were destroyed and London Bridge was damaged.

The deadliest natural disaster ever to hit our shores was in 1703, when a destructive hurrican ripped across southern England, killing 8,000 people. It became known as The Great Storm, the first properly documented weather disaster in British history.

We have always had violent and erratic weather events, but have they become more frequent?

Less than 70 years after The Great Storm, the collection of reliable weather data had begun. In 1772 scientists started to record the daily temperature of central England.

The Campbell-Stokes sunshine recorder was invented in 1853, marking the start of systematic weather observations from around the world. As well as using instruments dating from Victorian times, data is now gathered from satellites and weather balloons, and analysed using supercomputers.

Scientists can see that the world has warmed by about three-quarters of a degree in the last 100 years, with an even greater increase of one degree for Britain in the same period. One degree may not sound much, but it's enough to change our weather. As temperatures across the world rise, so does the level of moisture in the atmosphere, with more heat, and more energy in the system.

The atmosphere has 4% more moisture now than it had in the 1970's, and with more moisture, there is much more likelihood of severe weather events.

The increase in world temperature, climate scientists agree, is caused by greenhouse gases.

By drilling nearly a kilometre deep into the Antarctic ice sheet, we can measure levels of carbon dioxide and other gases that were present in our atmosphere over the last 800,000 years. They show that CO2 levels have fluctuated over thousands of years, however it always remained below 300 parts per million. 100 years ago it was 280 parts per million. Today, we are just crossing a threshold of 400 parts per million. Most scientific institutions conclude that man-made CO2, following the industrial revolution, is the culprit for global warming. Most scientists agree that global warming is having a dramatic effect on our weather, leading to more and more severe weather events.

The warmth contains lots of energy, and it's the energy from the warmer ocean and land that is driving our extreme weather.

Scientists at the Met Office have calculated that the chances of 2003-style heatwaves in the UK have approximately doubled. Ironically, we might also get colder, harsher winters in the UK, because of the effect on the Gulf Stream. If melting polar ice causes the Gulf Stream to weaken, then some calculations show that temperatures in Britain in winter might fall by 5 degrees, heading for more like a Scandinavian climate.

These predictions, scientists emphasise, are by no means a certainty - much work still needs to be done.

It isn't just Britain...

When we look at the whole world, we begin to realise that recently extreme weather has touched every corner of the globe...

America's recent weather events are well known, but in Italy in Winter 2012 we saw extreme snowfalls occurring in places that had never seen snow in living memory.

In 2010, the hottest summer on record affected many parts of the world. In Russia alone, 50,000 deaths were directly attributed to the sweltering heat.

In 2011, severe flooding caused havoc across the globe, from Australia to Thailand, and in the same year America's worst tornado season in living memory claimed 500 lives.

In 2012, Superstorm Sandy was fuelled by near record ocean temperatures, something people living on the USA's East Coast will not soon forget.

After watching this sobering documentary, I reflected that it is easy to understimate the effect of a few degrees rise in temperature. It doesn't take much energy to raise (say) a litre of water by a couple of degrees (an average person could generate this much energy on a stationary bike pedalling for around 20 seconds), and it doesn't give up much heat when it cools again. But the world's oceans contain about 1.3 billion cubic kilometers of water, and each cubic kilometer contains a trillion (1,000,000,000,000) litres of water. Even if a tiny fraction of the ocean warms by a few degrees, the energy involved is beyond imagining.

The other thing that struck me is the complexity and importance of the three-dimensional system of currents in the ocean, and how drastic can be the effects of an alteration in their behaviour.

Unfortunately, if decision-making people continue to ignore the science (which seems to happen for political, religious or corporate profit reasons, among others), we won't have to imagine the effects of global warming as the years go by - they will be all too obvious, and it will be too late to do much about them.

If you're interested in this kind of stuff, you might also like...

[The Secret Life of Waves]
[My environment and technology web page]