CO2: Humans to blame
2006-09-05 12:55
Norwich - Air from the oldest ice
core confirms human activity has increased the greenhouse gas
carbon dioxide (CO2) in the atmosphere to levels not seen for
hundreds of thousands of years, scientists said on Monday.
Bubbles of air in the 800 000-year-old ice, drilled in the
Antarctic, show levels of CO2 changing with the climate. But the
present levels are out of the previous range.
"It is from air bubbles that we know for sure that carbon
dioxide has increased by about 35% in the last 200
years," said Dr Eric Wolff of the British Antarctic Survey and the leader of the science team for the 10-nation European
Project for Ice Coring in Antarctica.
"Before the last 200 years, which man has been influencing,
it was pretty steady," he added.
The natural level of CO2 over most of the past 800 000 years
has been 180-300 parts per million by volume (ppmv) of air. But
today it is at 380 ppmv.
"The most scary thing is that carbon dioxide today is not
just out of the range of what happened in the last 650 000 years but already up 100% out of the range," Wolff said.
CO2 was close to 280 ppmv from 1000 AD until 1800 and then
it accelerated towards its present concentration. Wolff added
that measurements of carbon isotopes showed the extra CO2 coming
from a fossil source, due to increased human activity.
The ice core record showed it used to take about 1 000 years
for a CO2 increase of 30 ppmv. It has risen by that much in the
last 17 years alone.
"We really are in a situation where something is happening
that we don't have any analogue for in our records. It is an
experiment that we don't know the result of," he added.
Professor Peter Smith, of the University of Nottingham in
England, said the study showed more needed to be done.
"There is an urgent need to find innovative technologies to
reduce the impact we are having on our climate," he told the
science conference.