Emitting a mighty belch, nature has grounded us. Our busy plans, large and small, our vaunted technologies, our governments and economies have all been made to seem rather puny beside that quaint and old-fashioned thing from the geography text-books, a volcano. Beyond the misery for some and the inconvenience for many, this moment of cold turkey for a society hooked on aviation offers a brief moment of reflection while we wait for the aeroplanes to fly once more.
Bang on cue, a report from Engineering the Future, an apparently respectable working party set up by the Engineering and Physical Sciences Research Council, has revealed that "virtual water" embedded in the products we import is having a disastrous effect upon the most drought-stricken countries in the world. "We must take account of how our water footprint is impacting on the rest of the world," says one of theauthors, Professor Roger Falconer.
Water footprint, virtual and embedded water: if you sense already that these phrases contain new reasons for us all to feel bad about the way we live, you are right. The idea behind measuring virtual water is that the water which a UK consumer sees every day is a mere three per cent of actual usage.
Embedded in every product is the water which has been used to grow its ingredients and produce it. If the report is to be believed, the embedded water in a pint of beer is 130 pints. A cup of coffee costs 140 litres of virtual water, the making of a T-shirt over 2,000 litres. A kilogram of steak runs in a 15,000 litres, 10 times the amount needed to grow a kilogram of wheat. Two-thirds of the embedded water which we use as consumers is from imported goods.
In the relaxed, pre-volcano world of the past, these figures would be laughed out of court. If a virtuous British environmentalist sipping a cup of Fairtrade coffee in his Greenpeace T-shirt is committing some sort of eco-crime, then truly, it would have been thought, we are all as guilty as each other and there is nothing much to be done about it.
It is useful, though, to be reminded of the power of nature. None of the uncertainties surrounding climate change apply to water. We know that a billion people right now have no access to clean drinking water. We know that Western consumers demand vegetables, fruit and flowers from countries, like Kenya, where water is scarce. The government's chief scientist, Professor John Beddington, has said that the global demand for water will have increased by 30 per cent over the next two decades. With a 50 per cent increase in energy demand and a similar increase in the need for food, the result, according to Professor Beddington, will be a perfect storm of crisis.
Around the world, the use of desalination plants, which are heavy on energy, is on the increase. Where there is access to fossil water, a non-renewable resource which has been sealed in aquifers deep below the earth's surface for thousands of years, modern technology is extracting it.
At this moment of pause, is it not at least worth asking whether it is entirely responsible for Britain, a country where it rains for much of the year, where inhabitants are profligate with water, where conservation is still a minor priority, should be cheerfully importing goods which make dry, impoverished countries even drier? How much more serious does the situation have to become before businesses are obliged to look at their supply chain and consider how water is used, and from where?
Of course, there are economic arguments – the Kenyan economy is dependent on the roses, sugar-snap peas and beans that would normally be arriving at Britain's airports – but human activity is susceptible to change. All the short-term political arguments in the world cannot alter the fact that we are being rather too relaxed about the earth's most important resource.
Reports are issued, technological breakthroughs announced, but in the end, as events in Iceland have shown, nature will follow its course. It may be sensible for those in the privileged West to consider a little more self-reliance, and possibly even self-restraint.