Our institute has prepared an atlas of the world's snow and ice resources, which describes all the ice on the earth and even offers a map of the world without ice. It is, however, a model, not a forecast. Yet there are forecasts warning that if the global warming seen at the end of the 20th century continues for several decades, a lot of ice in the Artic Ocean will melt.

There is, however, a subtle but important qualification: if Artic ice should melt, the sea level will not change because the volume of water created by melting ice is equal to the volume of water that ice displaces when floating. The danger is different: warming could lead to the melting of huge island and continental glaciers.

The biggest of them cover the Antarctic, where 90% of the world's ice is accumulated, and Greenland. The melting of this ice could lead to a catastrophe. But is there any reason to panic? The temperature rise of 3-6 degrees Celsius over the next century promised by pessimists could not have a significant influence on the Antarctic, where the average temperature is less than 40 degrees below zero.

The processes ongoing in the permafrost are even more complicated than those in the ice. All the winters of the last decade were more or less abnormal. Because of that, the permafrost in areas just beyond the Artic began receding and melting.

The period of warming was tangible, but now it may be drawing to a close. Most natural processes on the earth are cyclical, having a shorter or longer rhythm. Yet no matter how these sinusoids look, a temperature rise is inevitably followed by a decline, and vice versa.

Studies of the ice core retrieved by Russia's Vostok Antarctic station show that this is what has been happening on earth for at least the last 400,000 years. Today, scientists say that the melting of the permafrost has stalled, which has been proved by data obtained by meteorological stations along Russia's Artic coast.

We are now studying the influence of the atmosphere and snow cover on permafrost in space and time. In the permafrost zones, a layer melts in the summer, when the temperature rises above zero. However, in the winter this layer freezes again.

This is a normal process: what melts, freezes. Yet if a winter is abnormally warm, this seasonal melted layer may not freeze back. Then the so-called "talik," a layer with a temperature of around zero, is formed. This is a very unpleasant thing for buildings and pipelines.

It seems that the permafrost should be melting if the temperature is rising. However, many areas are witnessing the opposite. The average annual temperature is getting higher, but the permafrost remains and has even started to spread. Why? An important factor is the snow cover. Global warming reduces it, therefore making the heat insulator for the permafrost thinner. Then even weak frosts are enough to freeze the ground deeper below the surface.

In many places, the frozen ground is 500-800 meters deep. Even if the highest warming forecast comes true and the temperature rises by 3-6 degrees, no more than 20 meters of frozen ground will melt. Some people are afraid that the melting permafrost will pollute the air with methane. However, frozen water takes up only 15% of the 20-meter layer, and the amount of gases dissolved there is insignificant. So we are unlikely to receive such unpleasant surprises from the permafrost within the next hundred years.

Today, scientists fear not so much global warming as changes in atmospheric circulation. In recent years, the so-called western shift has dominated, which means that air masses have been moving from the west eastwards. There has been little mention of the so-called meridian masses, moving from the south to the north and back. Now, however, the meridian shift has become more frequent.

If it goes south, it causes a spell of cold weather; if it goes north, it brings warm air masses with a lot of precipitation in the winter. This results in thaws and snow drifts on plains and in heavy snowfalls, avalanches and mudflows in the mountains. Meridian processes have been gaining in frequency lately, which promises different weather anomalies: unusually high and low temperatures, heavy rains and snowfalls and longer droughts, which in turn may lead to natural calamities.

Nikolai Osokin is a glaciologist at the Institute of Geography, the Russian Academy of Sciences.

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