Tim Helweg-Larsen & Richard Hawkins

The Arctic

1989

2007

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

1989

2007

1989 / 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 already too 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?

energy

So what?

Over and above existing model projections

?

Albedo % of radiation reflected Hugo Ahlenius, UNEP/GRID-Arendal ≈ 0.3°C

Permafrost extent in the Northern Hemisphere,

1672 billion tonnes

0.1% melt = 1600 mtc 80% global cut =1600 mtc

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

What does this mean?

2°

next ? What

end the

Tim Helweg-Larsen & Richard Hawkins