KIRUNA, Sweden (Reuters) - Cold weather this winter is thinning the ozone layer over the Arctic, part of a worsening trend which will expose Europeans to skin cancer and other diseases, top scientists warned Saturday.

Scientists said spells of very cold weather over the Arctic circle and northern Europe in December and early January had reduced the ozone layer, which shields the earth from the sun's harmful radiation, and may create a new hole in it.

``We're experiencing ozone losses in the Arctic because of the cold winter,'' Neil Harris, head of the European Ozone Research Coordinating Unit, told Reuters.

``It's too early to say whether an ozone hole will appear. It will all depend on how cold it gets here in coming weeks. But if things stay cold it's on the cards.''

``This study is very important for all Europeans because, to avoid the increased ultraviolet radiation caused by ozone decline impairing our health and well-being, it's vital to understand what is happening in our atmosphere,'' Busquin told Reuters at the Kiruna space research site, about 150 km north of the Arctic circle.

``The loss of ozone could lead to a rise in skin cancer in Europe in coming years.''

Over half of the five to seven percent increase in skin cancer each year in Europe was caused by thinning of the ozone, said Paul Simon, director of the Belgian Institute of Space Aeronomy.

The ozone layer has had large holes eaten out of it -- such as in Antarctica -- by compounds released by chlorofluorocarbons (CFCs) and halons used in refrigerators, causing skin cancer, affecting the eye and weakening the immune system, as well as the air quality and the environment.

Harris said he expected authorities in Europe to issue warnings about skin cancer as early as March because of the low ozone levels in the Arctic and the worrying levels in central Europe.

Scientists, including several from NASA in the United States, will next week look at the concern Europeans have about the possibility of an Arctic ozone hole and the long-term ozone decline over Europe, which has been particularly severe during the cold winters of the last decade.

The development of a hole usually follows a period of unusually low temperatures coupled with high levels of pollutants in the stratosphere, which destroy the ozone layer.

``We are losing something like three percent of ozone per decade in the northern hemisphere,'' said Jacques Pommereau, director of research at France's Center National de la Recherche Scientifique (CNRS).

``I don't see an improvement in the ozone until 2015.''

Busquin said the EU and NASA funded project was important to understand the ozone decline, its impact on the health and well-being of Europe's population and what action is needed.

Scientists said they would know in weeks whether a hole in the ozone layer was being formed over the northern hemisphere, but they did not expect one to be as large as the one discovered in Antarctica in the mid-1980s.

They will analyze the ozone and other atmospheric gases using satellites, aircraft, large and long-duration balloons. The findings will be presented in March.