Greenland has had its day in the Sun. Now it's back to the Arctic sea ice.
The Guardian has more for me to copypaste today:
Loss of Arctic sea ice '70% man-made'
Study finds only 30% of radical loss of summer sea ice is due to natural variability in Atlantic – and it will probably get worse
The radical decline in sea ice around the Arctic is at least 70% due to human-induced climate change, according to a new study, and may even be up to 95% down to humans – rather higher than scientists had previously thought.
The loss of ice around the Arctic has adverse effects on wildlife and also opens up new northern sea routes and opportunities to drill for oil and gas under the newly accessible sea bed.
The reduction has been accelerating since the 1990s and many scientists believe the Arctic may become ice-free in the summers later this century, possibly as early as the late 2020s.
"Since the 1970s, there's been a 40% decrease in the summer sea ice extent," said Jonny Day, a climate scientist at the National Centre for Atmospheric Science at the University of Reading, who led the latest study.
"We were trying to determine how much of this was due to natural variability and therefore imply what aspect is due to man-made climate change as well."
To test the ideas, Day carried out several computer-based simulations of how the climate around the Arctic might have fluctuated since 1979 without the input of greenhouse gases from human activity.
He found that a climate system called the Atlantic multi-decadal oscillation (AMO) was a dominant source of variability in ice extent. The AMO is a cycle of warming and cooling in the North Atlantic that repeats every 65 to 80 years – it has been in a warming phase since the mid-1970s.
Comparing the models with actual observations, Day was able to work out what contribution the natural systems had made to what researchers have observed from satellite data.
"We could only attribute as much as 30% [of the Arctic ice loss] to the AMO," he said. "Which implies that the rest is due to something else, and this is most likely going to be man-made global change."
Not too long ago there was another paper by Notz and Marotzke about the Arctic sea ice loss and the role of AGW. They focussed mainly on the influence of the PDO and AO (see Chris Reynolds' blog post on the paper and his PS on the AMO).
This possible connection between AGW/CO2 and Arctic sea ice loss reminds me a bit of the connection between smoking and lung cancer. It's pretty obvious from the data that one causes the other, but how to prove it? Well, we have more and more data coming in, and it seems more and more researchers are taking up the challenge to prove the connection.
We have a canary, we see it asphyxiating, we have a very strong suspicion it has to do with the coal mine. How long until we can be sure?