Eye on the storm: The Met Office on a mission

It's a beautiful day in Devon, and the glass walls of the building sparkle against the blue sky. A curving path leads to a light, airy atrium. The building bristles with eco-credentials – the concrete floors, under a sleek layer of slate, keep workers cool without air conditioning, while water from the pond outside is used to flush the toilets. Green, clean and light, this office feels friendly, open, transparent.

It's difficult to believe that anything mysterious could happen in this office on the outskirts of Exeter, but the information gathered, analysed and extrapolated here is so sensitive that it has the power to crash stock markets, shape warfare and shed light on the future of mankind. You may think of the Met Office as home to some friendly – if sometimes hapless – weather forecasters, but that would be a mistake.

Under the floor is a bomb-proof bunker. This is not paranoia. The reason for its presence lies in the past, present and future of the Meteorological Office. Founded in 1854 by Admiral Robert Fitzroy, its original purpose was to protect merchant ships from storms, but its remit has grown. It was on the advice of a Met Office employee that the D-Day landings were launched in 1944. By the end of the Second World War, 90 per cent of Met Office staff were in uniform. It advised the Falklands Task Force in 1982.

The Met Office is owned by the Ministry of Defence, and the data gathered and analysed in this building influence the lives and deaths of troops stationed in Iraq and Afghanistan. Many of the office workers here now are engaged in work that falls under the Official Secrets Act. "We're responsible for planning deployment across the world," says Dave Britton, media spokesman.

The Met Office's forecasters don't simply dole out advice from the comfort of these bright offices, built four years ago when they moved from Bracknell, outside London. They're also out on the front with the military men and women who rely on their know-how. "The Mobile Met Unit consists of 50 reserve officers of the RAF," Britton says. "It's made up of forecasters and technical staff who are integrated into the military, wherever the troops are. It's dangerous work."

Climate change is affecting military operations overseas. "The MoD is interested in climate predictions because it's interested in security," says Dr Vicky Pope, head of climate change at the Met Office Hadley Centre for Climate Research. "It invests in equipment that has to last a long time, so it needs to understand how climate is going to affect that. Recently, helicopters weren't able to take off in Iran because of an change in air pressure."

But even in the more innocuous departments of the Met Office, storm clouds are gathering. The weather forecasting operations centre is an open-plan office packed with constantly updated satellite images on row upon row of computer screens. Our day-to-day forecasts are generated here, and it's where this summer's extreme weather was first spotted and plotted.

The question a lot of people are asking after last month's flash flooding is: did the Met Office give us enough warning? In April, it said this summer would be warmer and drier than ever, but what it didn't make clear enough was that this was a global, not national, prediction. The Met Office's chief forecaster, Ewen McCallum, admits that "it ought to have been made clearer".

Brian Golding is the head of forecasting research. "The problem we have is that even a very short-range forecast always has some uncertainties, and if you go further ahead, that uncertainty grows," he says. "The Environment Agency, which has to warn people to evacuate, doesn't want to give out false alarms."

A vast, bomb-proof hall in the basement houses a supercomputer, a 20-ton monster. Without it, the Met Office couldn't cope with the torrent of incoming data. Even with it, accurately predicting the weather is a struggle in a world where historic patterns are being disrupted and people are demanding more warning.

Today, the Met Office's forecasts for 24 hours ahead are right about six times out of seven, and three-day forecasts are as accurate as one-day forecasts were 20 years ago. In future, it hopes to offer town-by-town forecasts, but the technology isn't cheap.

A £120m computer upgrade is scheduled for 2009, but even that may not provide enough power. "We need the upgrade to be able to do town-by-town forecasting operationally," Golding says. "We believe we can just about do it with what we're expecting to get in 2009, but it's touch and go." Pope anticipates that the upgrade also won't be powerful enough for the climate change research that needs to be done.

In Europe, the Met Office is one of the "big three", with Météo-France and Deutsche Wetterdienst. An independent review found: "It is beyond dispute that the Met Office occupies a position at the pinnacle of world climate science."

Some meteorologists want one service for the European Union, with each country having a national hub to focus on local weather. Golding isn't keen: "There is nothing like a bit of competition to drive people to produce in the research business."

Sharing information is a sensitive business. Last year, the cost of America's orange juice soared when cold weather and then hurricanes hit the citrus farming states; the average price of a gallon of juice was 14 per cent higher in 2006 than in previous years. If stock investors knew of that in advance, shares could soar or plummet. The weatherman would be a powerful ally.

Inevitably, it is wealthy countries such as the UK that lead the way in climate-change research. Meanwhile, developing countries stand to lose the most. To this end, the Met Office's Hadley Centre has developed a regional climate model – Providing Regional Climates for Impacts Studies, or Precis for short – that can be run on a PC and be used by developing countries to collate their own climate data.

On the way back to the atrium, the meteorologists tell me about their enthusiasm for their jobs. "All I ever wanted to do as a kid was to forecast the weather," admits Keith Groves, programme manager for forecasting. The Met Office staff are a dedicated bunch, but then they need to be; the office is manned at all times, all year, every year.

Once you know what goes on here, it starts to feel like something out of a James Bond film. Stealthy satellites, weather radar and Argo, a system of floats that lie beneath the surface of the oceans, rising every 10 days and taking measurements as they go, are impressively hi-tech.

I ask if there's one rule the meteorologists here live by, Official Secrets Act or not. There is: never tell anyone what you do for a living. "I'm lambasted about the weather every day," Britton says. "All I get is, 'I'm going on holiday; what's the weather going to be like?' If anyone asks, I just say I work for the government."

Siân Lloyd on how the information gets from satellites to TV screens

Interview by Rob Sharp

I got my first job as a weather presenter in the early 1990s because I have a good memory; you have to work without an autocue.

For a year, I got day release from ITV to study with the Met Office. I took a specialist course for broadcast meteorologists. It came as a shock, reading weather charts, taking on board chemical equations and theoretical physics, almost to university level. I'm proud of the qualification I got.

But that is nothing like the advanced tuition the people here have taken. We've got some of the best number-crunchers in the world. It saddens me when computers take over and the personal element is lost.

Without a doubt, the forecasters at the Met Office are the best at what they do. It's an honour to work with them. People don't pay them enough respect. Even with the floods, the focus has been on giving more money to the Environment Agency, but there's a case for backing the Met Office, too. In a world of climate change, we need more computing power to predict where these floods are going to be.

I've never been approached as often as this summer – and it's the time I decided to get an open-topped car! The weather can be a matter of life of death, and now it's making news. Fifteen years ago, that wasn't the case.

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