It seemed there could not have been a better example of the phenomenon of global warming when the Larsen B shelf on the tip of the Antarctic Peninsula suddenly disintegrated last month.

It was a piece of ice about the size of Rhode Island - 3,250 square miles in surface area, 600 feet thick - 500 billion tons of it. Satellite pictures of the area disintegrating and separating from the Peninsula over a period of about a month were dramatic. Without any exception that I have been able to find, the news stories at the time blamed global warming, often citing a 2.5 ?C increase in average temperatures in the region, and often saying that increase was greater than for any other region in the Southern Hemisphere. Fear must have flashed into the mind of everyone watching. Are we going to be able to survive the terrible wounds we humans have inflicted on our environment? A better question might be whether we're going to be able to survive our own ability to exaggerate and scare the pants off each other.

The Larsen B break-up was not the harbinger of a global warming catastrophe that it appears to be.

First, it was not the surprise that news reports implied it was - huge cracks in the shelf were noted as long ago as 1994, and the break-up itself was predicted by the British Antarctic Survey in 1998.

Second, it may not be true that the Antarctic, as a whole, is getting warmer, and there is no evidence at all that it is warming to an extent that is out of step with that occurring globally. Despite all the hype about it, that amounts to a warming of about 0.5?C since the late 19th Century. Third, there is no evidence to indicate a decline in overall Antarctic sea ice extent.

Fourth, the break-up may have been an event occurring either as a perfectly natural part of the Antarctic environment or, even, as a response to a period of global warming that occurred 20,000 years ago . depending on whose explanation you happen to be reading.

It is harder to be precise about the Antarctic than it is about other regions of the earth, because climate records for that region are pretty thin, going back for 50 years or less. It is also a region where temperatures vary greatly quite naturally from year to year.

There certainly have been what seem to be unusual climate changes in the central and southern parts of the west coast of the Antarctic Peninsula. But sizeable though the Peninsula is, it is still a very small part of the massive continent of Antarctica. It juts out towards the southern tip of South America, some of it beyond the Antarctic Circle. Larsen B was an ice shelf. That means it was formed by the activity of a glacier which pushed out beyond the coast of its supporting land mass, spreading over and floating on the sea. Although it seems dramatic, tidal forces, water erosion and sunlight from above eventually weaken ice shelves and break them off. That is a natural process. Larsen B was one of five ice shelves in the area that are being affected by the localised climate change.

A position paper published this year by the British Antarctic Survey, which has been monitoring weather in the area for the last 50 years, has this to say about warming trends: "Few Antarctic stations have climate records extending back longer than 40 years so it is difficult to say whether temperature changes in Antarctica reflect those in the global record, which shows an overall warming trend of about 0.5?C between the late 19th Century and the present.

"Antarctic temperature records are characterised by a very high level of inter-annual variability that makes the determination of trends from short records problematical. Over much of Antarctica, warming trends are very small and there has even been a small cooling in recent years at the South Pole.

"The extent of winter sea ice around Antarctica is thought to be a very sensitive indicator of climatic change but it has only been possible to observe this since suitable instruments were deployed on satellites in the early 1970s. Like the temperature records, the sea ice record exhibits a great deal of inter-annual variability.

"In recent years, reducing sea ice extent in some regions has been balanced by increasing extent in others and there is no evidence for a decline in overall Antarctic sea ice extent."

On the subject of the Antarctic Peninsula, the Survey's position paper goes on to say: "Climate records from this region extend back 50 years and, over this period, annual mean temperatures have risen by about 2?C - a far larger rise than seen elsewhere in the Southern Hemisphere. Although climate model predictions do indicate an enhanced response to future global warming in some parts of the Polar regions, the Antarctic Peninsula is not one of these areas.

"The lack of a clear modelled association between Peninsula warming and global warming means that it is premature to attribute warming in the Peninsula to an enhanced 'greenhouse' effect."

The position paper makes it clear that the greenhouse effect cannot be ruled out as a cause for enhanced warming in some parts of the Antarctic, but it does also point out that climate models that can predict global changes reasonably well, cannot reproduce the warming effect in the Peninsula.

"Changes have also occurred in the upper atmosphere over Antarctica," the report continues. "Measurements made over the Antarctic Peninsula and the Falkland Islands show that the level of peak electron concentration in the ionospheric F-region (at about 300 kilometres altitude) has fallen by about 8 kilometres over 38 years. Unlike the surface temperature trends, these changes can be attributed to increased greenhouse gas concentrations with some level of confidence. While the lower atmosphere warms in response to increasing concentrations of greenhouse gases, the upper atmosphere cools. Theoretical studies indicate that the observed fall in the height of the F-region is compatible with expected temperature changes in the thermosphere.

"...We know that the climate of the region is highly sensitive," the position paper says, "as a result of complex interactions between atmosphere, oceans and sea-ice, and studying it can tell us much about polar climate processes. Recent research also shows that the climate of this region is strongly influenced by climate variations in the subtropical and tropical South Pacific, such as those associated with El Ni?o - Southern Oscillation (ENSO). While such "teleconnections" are responsible for much of the short-term variability in climate seen in this region, their role in driving longer-term (decadal to century scale) change remains to be clarified."

That is an interesting and perhaps significant fact. It does now seem likely that we are about to experience another strong El Ni?o warming of the Pacific Ocean, bringing weaker than normal easterly winds, lower pressure over the eastern tropical Pacific and higher than normal pressure over Indonesia and northern Australia. The Antarctic Peninsula is on the side of the continent closest to South America and the Pacific Ocean-Drake Passage passes between it, on one side, and Tierra del Fuego and the Falklands on the other.

In a general sense, the warming that is being experienced in Antarctica is on the Pacific side of the continent, the cooling on the farther side.

The jet streams over the eastern Pacific Ocean are stronger than normal during warm episodes. Extratropical storms and frontal systems are known to follow paths that are significantly different from the normal, resulting in persistent temperature and precipitation anomalies in many regions. It may be that El Ni?o has a more pervasive effect than was first suspected.

Whatever the truth of that, it does seem certain that the Larsen B ice shelf collapse does not mean the End is Nigh. So relax already.