Is that the rumble of recession I can hear over the distant horizon?

'There is a feeling that if things start to turn down, the world economy might flip round rather fast'

It is like the rumble of distant thunder. A slight change in the temperature; a drop in the barometric pressure; and a noise, so faint that you are not sure you have heard it at all. There is something out there that doesn't feel quite right, and it is the rumble of recession.

It is like the rumble of distant thunder. A slight change in the temperature; a drop in the barometric pressure; and a noise, so faint that you are not sure you have heard it at all. There is something out there that doesn't feel quite right, and it is the rumble of recession.

The R-word, recession, has not been much in evidence of late. We had a little scare last year, when the economy slowed for a few months, but then things picked up again. For many people the memory is faint indeed. Nearly a quarter of our workforce has never experienced recession, and I am not at all sure they will encounter its cool embrace in the immediate future.

Rationally, the odds are probably against recession - the economy actually shrinking for six months or more - in the next year or so. A slow-down, sure: to some extent that seems to be happening now. But actual recession? Things are cantering on pretty nicely in almost all the developed world, and experience tells us that at times like this the sheer momentum of the world economy takes a while to slow down.

You look at the normal warning signs. A rise in inflation? Well, yes it has come up a bit, but inflation is still amazingly low by the standards of the past 30 years. An oil crisis? Well, yes, but oil is still cheaper in money terms than it was in the early 1980s and far cheaper in real terms. Some kind of balance-of-payments crisis? Again, there are certainly serious imbalances in the sense that the US is having to attract enormous amounts of capital to hold the dollar up, while continental Europe is seeing equally vast amounts of capital flood abroad, hence the weakness of the euro. But if Europeans are happy to go on investing in the US - and they seem to prefer that to their own countries - then the imbalance can continue a long while.

As for Britain, the astounding thing is the way we seem to be managing to go on growing pretty fast without much sign of strain in the job market or uplift in inflation. The balance of payments is not too bad; the Government is in surplus; sterling is strong. And yet... and yet there is that faint rumble. What can one really hear?

The starting point is that most of the world economy has been growing strongly for somewhere between six and nine years. There are bits that have not, such as Japan, but there are special factors to explain that. Look back and downturns seem to come about every eight to nine years: here in Britain in the late 1960s, the middle 1970s, the early 1980s and the early 1990s. That of itself means nothing, except that we ought to be listening hard now for sounds of distress.

Here are five signals of concern.

One obvious one is the impact of the oil price rise. The last two led to recessions, so might this? In very round terms its impact on demand is about half as big as the previous shocks, so while it is a blow it is not an utterly shattering one. It is also hitting a world where the prices of other items are stable, so the knock-on effect is smaller too. In money terms the price of crude oil is still lower than it was 20 years ago (the reason for the doubling of the petrol price is taxation). On the Continent the rise of the oil price has been compounded by the fall of the euro - it has been a double whammy for them - and inflation in the eurozone is worrying the European Central Bank. Inflation is also cutting the real wages of workers, so the next wage round looks edgy.

But the rise in the oil price does not help, and while you could sketch a chain-reaction triggering a more serious downturn, I can't see it leading to recession unless something else happens - like the price going to $45 a barrel this winter, which at the moment does not appear likely.

The next obvious sign of strain is in the capital markets. It was easy to predict in this column that there would be an internet crash. That has now happened: money for loss-making electronic retailers, for example, seems to have dried up. Now the fall-out in the form of company collapses is feeding through. Another European e-retailer, Boxman, went under this week. More important, even where companies can struggle on, they are cutting back their marketing spend. The print media is seeing sharp falls in advertising revenue, for marketing by new economy companies has been a very significant contributor to its revenues.

Third, a lot of big high-technology companies, particularly in the US, are warning about profits: Dell, Intel, Apple, Lucent and Motorola have seen their share prices savaged as a result. Suddenly people are pondering whether the market for PCs has reached saturation, rather like that for televisions. Once two-thirds of the homes have one, demand comes from a replacement market, not a new market. As for companies, all you need is for them to decide to replace their PC every four years instead of every three (as many are now doing), and demand falls there too.

So far this is not a catastrophe: these companies are doing fine - just not as fine as people had previously thought. Expectations had become so overly optimistic that even normality disappoints, and that is worrying, for it suggests that, if things do head down, the impact on the investment community will be disproportionately large. When investors run scared, confidence in the wider economy becomes more fragile.

Fourth, people are just starting to worry about the level of bad debts in the banks. In previous booms banks over-lent to property companies and piled up loans that could not be serviced. This time it presumably won't be property companies, for while banks managed to make that mistake three times in the last 30 years, surely they cannot make it a fourth. But maybe there are other vulnerable areas: telecommunications companies, for example, that have borrowed for the mobile phone licences, or perhaps conventional retailers that no longer need as much floor space as they have at the moment.

And finally, not so much a single, simple murmur of concern, but rather a feeling that if things start to turn down, the world economy might flip round rather fast. The lack of savings in the US is sustainable while asset prices hold up, but this year Wall Street may end down. If confidence starts to unravel, tensions that don't seem to matter in the good times suddenly matter very much.

For the moment, the weather is still fine. Enjoy it. The next change in the climate may merely be a bracing shower rather than a deluge. I think at the moment a shower is the more likely. But you can get very wet in a shower if there is no shelter and you don't have an umbrella.