A lot of people mix up the ozone hole and global warming, believing the hole is a major cause of the world's increasing average temperature, researchers said. (Agencies)
Scientists, on the other hand, have long attributed a small cooling effect to the ozone shortage in the hole. Now a new computer-modeling study suggests that the ozone hole might actually have a slight warming influence, but because of its effect on winds, not temperatures.
The new research suggests that shifting wind patterns caused by the ozone hole push clouds farther towards the South Pole, reducing the amount of radiation the clouds reflect and possibly causing warming rather than cooling.
"We were surprised this effect happened just by shifting the jet stream and the clouds," said lead author Kevin Grise, a climate scientist at Lamont-Doherty Earth Observatory of Columbia University in New York City.
Grise noted this small warming effect may be important for climatologists trying to predict the future of Southern Hemisphere climate.
In the 1980s, scientists discovered thinning of the ozone layer above Antarctica during the Southern Hemisphere's spring months. An actual consequence of the ozone hole is its odd effect on the Southern Hemisphere polar jet stream, the fast flowing air currents encircling the South Pole.
Despite the ozone hole only appearing during the spring months, throughout each subsequent summer the high-speed jet stream swings south toward the pole, researchers said.
"For some reason when you put an ozone hole in the Southern Hemisphere during springtime, you get this robust poleward shift in the jet stream during the following summer season," said Grise.
"People have been looking at this for 10 years and there's still no real answer of why this happens," said Grise.
Scientists wondered if the ozone hole's impacts on the jet stream would have any indirect effects on the cloud cover. Using computer models, they worked out how the clouds would react to changing winds.
"Because the jet stream shifts, the storm systems move along with it toward the pole. If the storm systems move, the cloud system is going to move with it," said Grise.
High- and mid-level clouds travelled with the shifting jet stream toward the South Pole and the Antarctic continent. Low-level cloud coverage dropped in their models throughout the Southern Ocean, the team discovered.
When the cloud cover moves pole ward, the amount of energy the clouds can reflect drops, which increases the amount of radiation reaching the ground, researchers said.
A lot of people mix up the ozone hole and global warming, believing the hole is a major cause of the world's increasing average temperature, researchers said.