ABC News Online, Posted Wed Sep 17, 2008 3:01pm AEST
Updated Wed Sep 17, 2008 3:21pm AEST
- Audio: Scientists fear ice-free Arctic summer within decades (The World Today)
There are new warnings that the Arctic will be free of ice in summer in the space of a generation.
With summer drawing to a close in the Northern Hemisphere, it is clear that the melt this year has not been quite as dramatic as it was in 2007.
But scientists say it would be a big mistake to assume that global warming is on the wane. Instead, they argue, the cooler summertime temperatures should have halted the thaw by a much greater degree.
Walt Meier, a research scientist at the National Snow and Ice Data Centre in Colorado in the United States says this year's melt is "the second lowest on record and far lower than any other previous year, except for 2007."
He says there is no comfort for climate change sceptics who might argue that because of the smaller ice melt, we should not be panicking.
"It's a little bit higher than last year, but I would resist any temptation to call it a recovery," he said.
"We did have a little bit of a cooler summer this year, the conditions weren't quite as favourable to melt, which makes it actually in some ways remarkable that we went as low as we did, given that we would expect more of a rebound from last year.
"But the ice was so much thinner, that we still lost a lot of ice to summer. The long-term trend is still downward and actually has been accelerating over the past few years and this year really is simply reinforcing that.
"And so we're still on a long-term track towards an ice free summer in the Arctic Ocean at some point in the future," he added.
But he says it is difficult to speculate on when that might happen.
"It's really hard to give any kind of definitive answer on that, because a lot does depend on whether you have a cool summer or two, or whether you have a really warm summer. It could accelerate things," he said.
"The consensus seems to be among sea ice scientists in the order of 2030, so in the next 20, 25 years, seems to be a reasonable estimate.
"There have been some that have suggested earlier, as early as within five years. That's a little bit extreme I would say. I would disagree with that but it's not impossible, it's not a crazy idea by any stretch.
"Regardless of exactly when it happens, it's looking clearer and clearer, and this year again only reinforces it, that at some point in the not too distant future, we're going to have conditions where the ice, the sea ice in the Arctic Ocean melts completely during the summer. We'll have a blue Arctic Ocean so to speak."
He says the implications for the climate are severe and will not just be restricted to the Arctic.
"When you are removing the ice cap, you're really changing your energy balance. You're going to warm up the Arctic a lot more than it normally would because the sea ice reflects a lot of the solar energy and doesn't absorb it - whereas the ocean absorbs almost all of the incoming solar radiation during the summer, solar energy," he said.
"And so that's going to be adding a lot more energy to the Arctic region and going to heat things up even more than what you would normally get, so it's kind of amplifying the greenhouse gas effect in the Arctic.
"But the effects are going to be felt much more widely than that, because the climate is a completely inter-connected system. The Arctic and the connection between the Arctic, and the lower latitudes and the cold Arctic and the warmer lower latitudes help set up ocean and wind circulations and essentially the weather pattern - things like the jet stream and so forth and storm system tracks that you see, those are going to be changing.
"At the very least, over the Northern Hemisphere, throughout North America and Europe and Asia and that's going to have a pretty big impact on people's lives down the road, as people have to adjust to changing weather patterns.
"There may be changes in for example, what you may be able to plant and when you may be able to plant certain crops and so forth."
However, Mr Meier says the effects of climate change from the Antarctic melt may have a delayed impact on Australia.
"The Antarctic is quite a bit different than the Arctic in terms of its general environment. The Antarctic always has an extreme ice melt, it loses most of the ice cover, the sea ice cover during the summer time, the summer melt," he said.
"So we have seen some increasing trends in the Antarctic, in contrast to the Arctic. But these trends are a fair bit smaller than the Arctic and are not as significant in terms of any climate change signal, because essentially the climate change signal is being delayed in the Antarctic because the Antarctic is such an isolated place.
"It's a continent on the bottom of the world surrounded by ocean and you get very strong ocean currents and very strong winds that circle the Antarctic, that kind of act as a wall to prevent any kind of interaction, or most of the interaction between the Antarctic and the lower latitudes towards the equator.
"And so you don't have that interplay between the lower latitudes and the poles that you do in the Arctic, so we expect that the response would be slower and that you might actually see some increasing trends for a time.
"Eventually that will turn around as the warming temperatures eventually penetrate that wall, but it hasn't happened yet, but it probably will before too long.
"We have seen some areas of the Antarctic that have shown some considerable warming, most notable the Antarctic Peninsula where we've seen a lot of warming in terms of the temperatures, and we've also seen some pretty dramatic decreases in sea ice in the western side of the Antarctic Peninsula.
"Though it's a more complicated, more mixed picture in the Antarctic, it doesn't offset what we're seeing in the Arctic.
"The Arctic signal is a very strong powerful signal with very big climate impacts, whereas the Antarctic is a smaller signal with at least for the time being, smaller impact," he added.
Based on a report by Simon Santow for The World Today, September 17