Washington: Sediment cores from a small
Arctic lake in Canada stretching back 200,000 years show
unprecedented gains in global warming since 1950, indicating
human activity is the likely cause, a study said.
"The past few decades have been unique in the past
200,000 years in terms of the changes we see in the biology
and chemistry recorded in the cores," University of Colorado
glaciologist Yarrow Axford said in the study by Canadian
and US researchers.
"We see clear evidence for warming in one of the most
remote places on Earth at a time when the Arctic should be
cooling because of natural processes," added the chief author
of the study published yesterday in the Proceedings of the
National Academy of Sciences.
For thousands of years, environmental changes in a remote
lake on Canada's Baffin Island closely matched natural,
cyclical climate changes such as those caused by the Earth's
periodic wobble as it swings around the sun, the researchers
said.
However, lake sediment cores dating from 1950 show that
expected climate cooling was overridden by human activity like
greenhouse gas emissions, the study said.
Researchers were able to reconstruct the local climate
over the past 200,000 years by analysing algae, insect fossils
and geochemical traces in sediment cores extracted from the
100-acre lake.
Bureau Report
First Published: Tuesday, October 20, 2009, 08:19