Arctic Sea Ice

Irreversible loss of world's ice

We need only look to the world's ice cover to see the urgency with which emissions need to come down, scientists told delegates at this week's climate talks in Bonn, Germany.

At a press conference today, US and German scientists updated negotiators and journalists with the latest science on the state of Arctic sea ice, the Antarctic continent and thawing permafrost.

New observations gathered since the Intergovernmental Panel on Climate Change (IPCC) report show the cryosphere in serious and irreversible decline, they warned.

That's the first few paragraphs of an article on The Carbon Brief blog.
I'm highlighting the parts concerning the Arctic below:

Irreversible loss of world's ice cover should spur leaders into action, say scientists

(...)

Pam Pearson, director of the International Cryosphere Climate Initiative, the network of policy experts and researchers holding the event, told the audience:

"This is not like air pollution or water pollution, where if you clean it up it will go back to the way it was before."

Sea ice in decline

Arctic sea ice has been retreating rapidly in recent years as a result of greenhouse gases building up in the atmosphere, explained Dr Dirk Notz, sea ice expert at the Max Planck Institute in Germany. The biggest losses are happening in summer, he said:

"Over the past 10 years or so, we've roughly seen a 50% loss of Arctic sea ice area. So, the ice in the Arctic is currently retreating very, very rapidly."

In March, Arctic sea ice reached its lowest maximum extent in the satellite record. Last week, the US National Snow and Ice Data Centre confirmed Arctic sea ice extent for May was the third lowest on record.Arctic sea ice extent for 2015 compared to the 1981-2010 long term average. Source: NSIDC

Antarctic sea ice has been at record high levels in 2015 but this should be viewed in perspective with what's happening at the other end of the planet, Notz said:

"There is a slight increase, but it's nothing compared to the very, very rapid loss that we've seen in the Arctic."

Scientists' current understanding is that temperature changes as a result of greenhouse gases are causing winds to blow stronger offshore in the Southern Ocean that surrounds Antarctica, driving the sea ice outwards. Notz said:

"Both in the Arctic and the Antarctic, the changes we are seeing in the sea ice are very clearly driven predominantly by human activities."

Are scientists conservative about sea ice?

An interesting entry on the NSIDC Icelights blog (hat-top to GreenOctopus) that I also indirectly discussed a couple of months ago:

Are scientists conservative about sea ice?

Guest post by Walt Meier, NSIDC Scientist

Arctic sea ice set a record minimum extent in September 2012, far below the previous record low in 2007. Summer extents have been far lower than average for the last decade, with several record or near-record years. Looking at the numbers, one is tempted to think that the Arctic Ocean may reach nearly sea ice-free conditions within just a few years. But most expert analyses indicate that we’re likely at least a couple decades away from seeing a blue Arctic Ocean during the summer.

So what is going on here? Readers have asked if scientists are being too conservative in their assessment of the recent ice loss. We asked Walt Meier, NSIDC scientist, to address this question. Following is his response.