UPDATED: Comedy headline: 'Proof' humans cause global warming
"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.
"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."
Mr Axford is the chief author of the study published 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.
Just for interest, here is a section from Ms Axford's personal web page:
Why study the Arctic?
The Arctic is changing rapidly today. And ongoing changes in the arctic cryosphere (ice and snow) and hydrosphere (water) have important ramifications for global climate. Understanding how the arctic environment has changed in the past may shed light on both the future of the Arctic, and the future of the wider world.
My dissertation research focused on the climate histories of Iceland and Baffin Island. The economies and natural environments of Iceland and Nunavut are potentially very vulnerable to future climate change. It is important to understand the nature, rate, and magnitude of past paleoenvironmental changes in these regions in order to help constrain future risks. Paleoenvironmental records from the warm early Holocene provide glimpses of what the environments of Iceland and Nunavut might look like in a future greenhouse world. (source)
No agenda there, clearly.
Read it here.
UPDATE 1: Anthony Watts posts on this here, and links the decline to DDT use.
UPDATE 2: And this from the BBC, for all you who think tree-rings tell the whole story:
The intensity of cosmic rays also correlates better with the changes in tree growth than any other climatological factor, such as varying levels of temperature or precipitation over the years.
"The correlation between growth and cosmic rays was moderately high, but the correlation with the climatological variables was barely visible."