Bubbles Reveal Biggest Rise
In CO2 For 800,000 Years
By Steve Connor
05 September, 2006
The rapid rise in greenhouse
gases over the past century is unprecedented in at least 800,000 years,
according to a study of the oldest Antarctic ice core which highlights
the reality of climate change.
Air bubbles trapped in ice
for hundreds of thousands of years have revealed that humans are changing
the composition of the atmosphere in a manner that has no known natural
Scientists at the British
Antarctic Survey (BAS) in Cambridge have found there have been eight
cycles of atmospheric change in the past 800,000 years when carbon dioxide
and methane have risen to peak levels.
Each time, the world also
experienced the relatively high temperatures associated with warm, inter-glacial
periods, which were almost certainly linked with levels of carbon dioxide
and possibly methane in the atmosphere.
However, existing levels
of carbon dioxide and methane are far higher than anything seen during
these earlier warm periods, said Eric Wolff of the BAS.
"Ice cores reveal the
Earth's natural climate rhythm over the last 800,000 years. When carbon
dioxide changed there was always an accompanying climate change,"
Dr Wolff said. "Over the past 200 years, human activity has increased
carbon dioxide to well outside the natural range and we have no analogue
for what will happen next.
"We have a no-analogue
situation. We don't have anything in the past that we can measure directly,"
The ice core was drilled
from a thick area of ice on Antarctica known as Dome C. The core is
nearly 3.2km long and reaches to a depth where air bubbles became trapped
in ice that formed 800,000 years ago.
"It's from those air
bubbles that we know for sure that carbon dioxide has increased by about
35 per cent in the past 200 years. Before that 200 years, which is when
man's been influencing the atmosphere, it was pretty steady to within
5 per cent," Dr Wolff said.
The core shows that carbon
dioxide was always between 180 parts per million (ppm) and 300 ppm during
the 800,000 years. However, now it is 380 ppm. Methane was never higher
than 750 parts per billion (ppb) in this timescale, but now it stands
at 1,780 ppb.
But the rate of change is
even more dramatic, with increases in carbon dioxide never exceeding
30 ppm in 1,000 years -- and yet now carbon dioxide has risen by 30
ppm in the last 17 years.
"The rate of change
is probably the most scary thing because it means that the Earth systems
can't cope with it," Dr Wolff told the British Association meeting
at the University of East Anglia in Norwich.
"On such a crowded planet,
we have little capacity to adapt to changes that are much faster than
anything in human experience."
© 2006 Independent News
and Media Limited