Roughly 145 million people worldwide could be displaced if
water levels from a melting Greenland rise as quickly as they did at the end of
the last ice age, according to a report released this week from a University of
Wisconsin geologist.

UW geology professor Anders Carlson led the team that did
the research and,
published it this week in the journal Nature
Geoscience.

During the last ice age, an ice cap covered much of North
America. In a period of about 2,500 years, it rapidly melted to the north,
raising water levels by seven to 13 millimeters a year.

Serious damage will be done if sea levels rise at those
rates. If, for example, the oceans rise by just one meter, about 2.2 million
square kilometers of land will be overtaken by water, causing over $1 trillion
in damage.

“New Orleans is below sea level, all big cities are by the
coast, New York, Boston, Florida doesn’t look so great, the Netherlands,
Dubai,” Carlson said. “And then there are these various tropical islands that
are basically just little coral reefves
or volcanoes coming out into the sea.”

The possibility of that drastic of a
rise is higher than previously expected by the United Nations’
Intergovernmental Panel on Climate Change.

“They left the question rather open as to how much sea level
rise we could get from the melting of the Greenland ice sheet or the Antarctic
ice sheet,” said Allegra LeGrande of the NASA Goddard Institute of Space
Studies at Columbia University in New York City, who worked with Carlson on the
study.

To determine how fast the old North American ice sheet
melted, Carlson looked at the details on the edge of the current ice sheet and
other climate indicators, including tree rings and some types of fossils.

Temperatures in Greenland will continue to rise due to
greenhouse gases, which will inevitably raise the rate of melting.

By 2100, the average summer temperature in Greenland will be
two to four degrees Celsius higher, nearly identical to summer conditions over
North America 9,000 years ago.

LeGrande said the study does not guarantee anything, just
that it is possible for ice to melt that quickly and with dire consequences.

“I would say that we weren’t really in disagreement with the
IPCC report;, our study
was directed by something that had been an area of relative uncertainty in the
IPCC report,” LeGrande said.

The IPCC will look further into rising sea levels for its
next report. Research simulations for that report will begin in spring 2009,
Legrande said.