The poles really are poles apart
2008-05-02 22:10
Washington - The Arctic and Antarctica are poles apart when it comes to the effects of human-fuelled climate change, scientists said on Friday: in the north, it is melting sea ice, but in the south, it powers winds that chill
things down.
The North and South poles are both subject to solar
radiation and rising levels of climate-warming greenhouse
gases, the researchers said in a telephone briefing. But
Antarctica is also affected by an ozone hole hovering high
above it during the austral summer.
"All the evidence points toward human-made effects playing
a major role in the changes that we see at both poles and
evidence that contradicts this is very hard to find," said
Jennifer Francis, an atmospheric scientist at Rutgers
University in New Jersey.
An examination of many previous studies about polar
climate, to be published May 6 in the journal Eos, "further
depletes the arsenal of those who insist that human-caused
climate change is nothing to worry about," Francis said in a
telephone briefing.
In the Arctic, Francis and co-authors of the research said,
warming spurred by human-generated carbon dioxide emissions has
combined with natural climate variations to create a "perfect
Arctic storm" that caused a dramatic disappearance of sea ice
last year, a trend likely to continue.
'New state'
"Natural climate variability and global warming were
actually working together and they've sent the Arctic into a
new state for the climate that has much less sea ice," said
James Overland, an oceanographer at the US National Oceanic
and Atmospheric Administration. "There's very little chance for
the climate to return to the conditions of 20 years ago."
In Antarctica, the ozone hole adds a new factor to an
already complicated set of weather patterns, according to
Gareth Marshall of the British Antarctic Survey.
The changes in air pressure that go along with depleted
stratospheric ozone are responsible for an increase in the
westerly winds that whip around the Southern Ocean, at
latitudes a bit north of most of Antarctica.
These winds isolate much of the southern continent from
some of the impact of global warming, Marshall said. The
exception is the Antarctic Peninsula, which reaches northward
toward South America. There, the effects of warming have been
dramatic, he said, because the winds that protect the rest of
Antarctica do not insulate the peninsula.
The stratospheric ozone hole, caused by the ozone-depleting
release of chemicals found in refrigerants and hair sprays, is
likely to fully recover by 2070 as less of these chemicals are
in use, as a result of international agreements.
The ozone layer shields Earth from harmful solar radiation,
but its recovery is likely to open the way for warming in
central Antarctica, the scientists said.