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ironically, as the tech elite have begun
to deride MySpace s seizure-inducing
page designs and promiscuous friend
seekers, Facebook s clean user inter-
face and focus on real friends faces an
onslaught of new users and pointless
applications where tattooed zombies
buy drinks for your top friends.
However this all plays out, it s
clear that these sites are not going
to go away. In 2004, VCs bemoaned
any further investment in social-
networking companies, and pundits
argued that social-networking sites
would not endure as stand-alone
destinations. Today, they are some
of the biggest sites on the Web, and
we have an entire industry of wid-
get and tool providers building
on top of the social-
tem. There are niche
sites for moms, dogs,
pagans, and bodybuild-
ers. Ten years ago I
moved to Silicon Val-
ley to work at Netscape.
Today, Netscape cofounder Marc
Andreessen has a startup called Ning,
which helps people---what else---cre-
ate their own social-networking sites.
So what advice do I have for deal-
ing with the friend spam and keep-
ing on top of all these new ser vices?
Every once in a while, tur n o your
computer and go hang out with your
Entrepreneur Jonathan Abrams is founder and
CEO of the events-sharing service Socializr.
Determining how fast ice sheets are
melting is critical to future policy
decisions, says Richard Alley.
Are the Greenland and Antarctic
ice sheets our friends, which will
moderate sea-level rise over the next
century as polar snowfall increases?
Or are they ticking bombs, soon to
unleash oods on the world s coasts?
The uncomfortable fact is that while
the ice is looking less and less friendly
(see "Measuring the Polar Meltdown,"
p. 54), we re really not sure. The
United States has joined almost 200
other countries in seeking "stabili-
zation of greenhouse gas concentra-
tions in the atmosphere at a level that
would prevent dangerous anthropo-
genic interference with the climate
system" under Article Two of the
U.N. Framework Convention on Cli-
mate Change. Exactly what consti-
tutes "dangerous interference" can
be debated, but substantial ice-sheet
shrinkage causing meters of sea-level
rise is a strong candidate.
In 2001, the U.N.
on Climate Change
(IPCC) described the
great di culties in pre-
dicting ice-sheet changes
but projected slight net
growth over the next cen-
tury. By 2007, ice- ow
instabilities had occurred in Green-
land and Antarctica, apparently from
war ming, and the ice sheets were
contributing slightly to sea-level rise.
The IPCC noted that whole-ice-sheet
models had not anticipated and could
not reproduce the changes, and so
could not adequately project future
changes. Although our understand-
ing of most factors a ecting sea-level
rise had improved, 2007 projec-
tions by the IPCC excluded "future
rapid dynamical changes in ice ow"
because "understanding ... is too lim-
ited to provide a best estimate or an
upper bound for sea level rise."
Work is under way to improve and
test the existing ice-sheet models. I
know of no plausible scenarios under
which an ice sheet would be lost over
the next few decades, but the ongo-
ing work does suggest that in the
next decades, warming may initiate
substantial change, perhaps crossing
a threshold leading to much greater
shrinkage or loss over centuries.
Ice sheets spread like pancake
batter, on a greased griddle in some
places but on a bumpy wa e iron in
others, with islands blocking oat-
ing ice shelves that restrain the ice
behind them. Warming s most imme-
diate impact may be to cause melting
beneath those ice shelves, but in some
places we don t know the water depth
well enough to build models. Despite
heroic e orts, the wa e-iron and
greased-griddle characteristics of the
substrate are only partially mapped.
The ability of surface meltwater to
penetrate the ice and enhance lubri-
cation is poorly understood. Recent
changes were obser ved by satellites
and other platforms, some of which
may be lost to inadequate funding.
And in global-climate models, the
ice sheets remain inert white lumps,
uncoupled from their surroundings.
Small, mostly academic groups are
working on ice- ow models, but the
big, primarily government-r un cen-
ters that guide policy makers do not
have the funding
for ice-sheet mod-
eling that they do
ocean, and land-
ing. Having played
a small role in
the 2007 IPCC, I
believe that the
assessment of the ice sheets was done
well and that lack of a "best estimate
or upper bound for sea level rise"
re ects the science. But policy makers
seeking economically and ecologically
wise ways to avoid dangerous anthro-
pogenic climate interference surely
deserve additional guidance. That
will not come soon without addi-
tional focus on the ice sheets.
Richard Alley, a professor of geosciences at
Pennsylvania State University, was lead au-
thor of the chapter on Earth s cryosphere in
the most recent IPCC report.
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