Sat Oct 1st, 2005 at 05:24:22 PM EST
From the BBC World News: Arctic Ice "Disappearing Quickly"
The area covered by sea ice in the Arctic has shrunk for a fourth consecutive year, according to new data released by US scientists.
They say that this month sees the lowest extent of ice cover for more than a century.(...)
"It's still a controversial issue, and there's always going to be some uncertainty because the climate system does have a lot of natural variability, especially in the Arctic," says Mark Serreze, of the National Snow and Ice Data Center (NSIDC), Boulder, Colorado.
"But I think the evidence is growing very, very strong that part of what we're seeing now is the increased greenhouse effect. If you asked me, I'd bet the mortgage that that's just what's happening."
We aren't sure what it all means...but here is some information to chew on:
"What we're seeing is a process in which we start to lose ice cover during the summer," he said, "so areas which formerly had ice are now open water, which is dark.
"These dark areas absorb a lot of the Sun's energy, much more than the ice; and what happens then is that the oceans start to warm up, and it becomes very difficult for ice to form during the following autumn and winter.
"It looks like this is exactly what we're seeing - a positive feedback effect, a 'tipping-point'."
The idea behind tipping-points is that at some stage the rate of global warming would accelerate, as rising temperatures break down natural restraints or trigger environmental changes which release further amounts of greenhouse gases.
Possible tipping-points include
-the disappearance of sea ice leading to greater absorption of solar radiation
-a switch from forests being net absorbers of carbon dioxide to net producers
-melting permafrost, releasing trapped methane
tipping points...sounds ominous...can anyone out there say more about this?