When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth
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Breaking, NYT: Scientists Warn of Inexorably Rising Oceans as Antarctic Ice Melts
by Justin Gillis and Kenneth Chang, The New York Times, May 12, 2014
The
collapse of large parts of the ice sheet in West Antarctica appears to
have begun and is almost certainly unstoppable, with global warming
accelerating the pace of the disintegration, two groups of scientists
reported Monday.
The
finding, which had been feared by some scientists for decades, means
that a rise in global sea level of at least 10 feet may now be
inevitable. The rise may continue to be relatively slow for at least the
next century or so, the scientists said, but sometime after that it
will probably speed up so sharply as to become a crisis.
“This
is really happening,” said Thomas P. Wagner, who runs NASA’s programs
on polar ice and helped oversee some of the research. “There’s nothing
to stop it now. But you are still limited by the physics of how fast the
ice can flow.”
Two
papers scheduled for publication this week, in the journals Science and
Geophysical Research Letters, attempt to make sense of an accelerated
flow of glaciers seen in parts of West Antarctica in recent decades.
Various measurements have
captured the West Antarctic ice sheet changing very rapidly in the
region where it flows into the Amundsen Sea.Credit
Landsat
In this graphic, the red
regions are areas where temperatures have increased the most during the
last 50 years, particularly in West Antarctica, The dark blue regions
have had a lesser degree of warming. Temperature changes are measured in
degrees Celsius [per decade].Credit
NASA/GSFC Scientific Visualization Studio.
Both
papers conclude that warm water upwelling from the ocean depths has
most likely triggered an inherent instability that makes the West
Antarctic ice sheet vulnerable to a slow-motion collapse. And one paper
concludes that factors some scientists had hoped might counteract such a
collapse will not do so.
The
new finding appears to be the fulfillment of a prediction made in 1978
by an eminent glaciologist, John H. Mercer of the Ohio State University.
He outlined the uniquely vulnerable nature of the West Antarctic ice
sheet and warned that the rapid human release of greenhouse gases posed
“a threat of disaster.” He was assailed at the time, but in recent years
scientists have been watching with growing concern as events have
unfolded in much the way Dr. Mercer predicted. (He died in 1987.)
Scientists
said the ice sheet was not melting because of warmer air temperatures,
but rather because of the relatively warm water, which is naturally
occurring, from the ocean depths. That water is being pulled upward and
toward the ice sheet by intensification of the winds around Antarctica.
West Antarctic Glacier Ice Flows and Elevation ChangeVideo by NASA.gov
Most
scientists in the field see a connection between the stronger winds and
human-caused global warming, but they say other factors are likely at
work, too. Natural variability of climate may be one of them. Another
may be the ozone hole over Antarctica, caused by an entirely different
environmental problem, the human release of ozone-destroying gases.
The
basic problem is that much of the West Antarctic ice sheet sits below
sea level in a kind of bowl-shaped depression the earth. As Dr. Mercer
outlined in 1978, once the part of the ice sheet sitting on the rim of
the bowl melts and the ice retreats into deeper water, it becomes
unstable and highly vulnerable to further melting.
Richard
B. Alley, a climate scientist at Pennsylvania State University who was
not involved in the new research but has studied the polar ice sheets
for decades, said he found the new papers compelling. Though he has long
feared the possibility of ice-sheet collapse, when he learned of the
new findings, “it shook me a little bit,” Dr. Alley said.
He
added that while a large rise of the sea may now be inevitable from
West Antarctica, continued release of greenhouse gases will almost
certainly make the situation worse. The heat-trapping gases could
destabilize other parts of Antarctica as well as the Greenland ice
sheet, causing enough sea-level rise that many of the world’s coastal
cities would eventually have to be abandoned.
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