A hole that developed in the Earth's protective ozone layer over the Arctic this year was the largest ever recorded in the Northern Hemisphere and spread over parts of northern Russia, Greenland and Norway, the journal Nature reports.

For the first time, the hole was comparable to one that appears regularly over the Antarctic, researchers found.

The ozone layer in the upper stratosphere provides a shield against UV radiation from the sun that can cause skin cancer and cataracts.

Authors of the report, released today, show that the hole opened over northern Russia, parts of Greenland, and Norway in March, subjecting people there to high levels of the UV radiation.

As reported by The Guardian, the researchers found that the unsually large hole was not due to man-made causes, rather to unusually strong wind patterns at high altitudes and intense cold.

Holes in the ozone layer at both poles increase in size annually, The Guardian notes, but says the huge hole in the Arctic could become an annual event.