Tim Helweg-Larsen & Richard Hawkins

The Arctic

1989

2007

1989 2007

Arctic Sea Ice ExtentArea of ocean with at least 15% sea ice

1989

2007

1989 / 2007

+ 5 years − 5 years Ocean

Age of Arctic Sea Ice

IPCC, WG I (2007)

… late summer sea-ice is projected to

disappear almost completely towards the end of the 21st century

“The Arctic Ocean could be nearly ice-free at the end of summer by 2012”

Dr Jay Zwally, NASA

“Our projection of 2013 is alreadytoo conservative.”

Dr Wieslaw Maslowski, US Navy

“Worst-case scenarios about sea-ice loss are coming true: the Arctic Ocean could be ice-

free in summertime as soon as 2010”

Louis Fortier, Université Laval

Mark Serreze, NSIDC

No matter where we stand at the end of the

melt season, it’s just reinforcing this notion that the Arctic ice is in

its death spiral.

So what?

Over and above existing model projections

1989 2012?

Albedo%

of

rad

iati

on

refl

ecte

d

Hugo Ahlenius,UNEP/GRID-Arendal

≈

0.3°C

Permafrost extent in the Northern Hemisphere, http://maps.grida.no/go/graphic/permafrost-extent-in-the-northern-hemisphere

1672billion

tonnes

0.1% melt = 1600mtc

80% global cut

=1600mtc

Existing coupled climate models lack a

robust treatment of soil carbon dynamics.

The [IPCC] range does not include

… contributions from rapid dynamic processes in the

Greenland and West Antarctic ice sheets which… could

eventually raise sea level by many meters. Lacking such

processes… projections based on such models may seriously

understate potential future increases.

Oppenheimer et al.

IPCC, Synthesis (2007)

“Because understanding of some important effects driving

sea-level rise is too limited, this report does not assess the

likelihood, nor provide a best estimate or an upper bound for

sea-level rise… therefore the upper values of the ranges are

not to be considered upper bounds for sea-level rise.”

Over and above existing model projections

Additional

endthe

Tim Helweg-Larsen & Richard Hawkins