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"It means that the decrease could be regressing to the linear trend, instead of deviating from it and becoming more of an exponential downward trend."

It'd be nice if this were the case, but honestly I doubt it. Given the feedbacks inherent in the system, nonlinearity of some sort (negative or positive; it could follow a Gompertz-esque curve, after all, as the models would have it) seems likely. I can't see much physical justification for an assumption of linearity.

...But then, I've been wrong before. I thought 2013 was going to be a year of dramatic melt, for example...


I agree it could be a temporary regression to the mean. It has been in the past.


when would the linear trend line hit zero?


Wanderer, here's Wipneus' PIOMAS graph depicting the linear trend.

Shared Humanity

And doesn't this linear trend graph by Wipneus, showing an ice free Arctic in 2031 and, more generally, between 2025 and 2040 agree with an emerging consensus from a large number of climate modelers?

David Appell

The Arctic SIE mean of CMIP5 models is about 2 Mkm2 for the year 2100.

The -1 sigma line hits zero about 2060. (Current Arctic SIE is more in line with the -1 sigma value than the mean.)

A couple of models show SIE=0 as early as 2025.

Julienne Stroeve et al reviewed Arctic SIE trends and CMIP5 & CMIP3 models last year in:

"Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations," Julienne C. Stroeve1 et al, Geophysical Research Letters
Volume 39, Issue 16, 28 August 2012

From the paper:

"Several CMIP5 models (CanESM2, GISS E2-R,
show essentially ice-free conditions by 2050, with the CanESM2 model having an ensemble member reaching nearly ice-free conditions as early as 2016 (0.54 x 10^6 km2). By contrast, despite the more aggressive emission scenario
(SRESA1B) driving the CMIP3 models, an overall more extensive sea ice cover is retained, with the minus 1 standard deviation reaching nearly ice-free conditions in 2075."

They define "ice-free" as less than 1 Mkm2, and use the RCP4.5 scenario.


I blogged about that paper back in September 2012: Models are improving, but can they catch up?

Tor Bejnar

I've been reading only Neven's posts for months (rarely any comments, and haven't visited the Forum since about the ASIE minimum), and thought to drop in to say hello.

Two images stand out to my mind. 1) The Central Arctic Basin (CAB) sea ice may respond more slowly to global warming than do the surrounding basins. (Chris and others write on this.) and 2) I expect the next El Nino year (or the northern summer following) will torch a lot of Arctic ice! (I came to understand sometime last year that as the Earth surface warms, the threshold for an El Nino goes up, and wonder if it will get harder for an El Nino to form. But I know I don't know what I'm talking about.)

I too was surprised by the slowed down melt, but given that it happened, I'm not too surprised by the fairly robust freezing.


I don't know whether this has been linked here, but it strikes me as a good (if grim) overview of our current predicament, from the good folks at ClimateCodeRed:


The second (brief) chapter focuses on the Arctic.

Hans Verbeek

Pretty amazing: average thickness gained 15 cm compared to last year. If another 15 cm is added this year arctic seaice wil be back to 2005-thickness.


Questions: There have been a number of posts about all the extra snow in the Arctic this year...so is the extra snow counted as extra ice thickness or is the snow not counted as extra ice thickness? Or, is there a way the snow is factored in based on % water content?

Chris Reynolds


The snow is not counted as ice in a deliberate way. For CryoSat 2 thickness estimates areas of first year ice use the W99 profile divided by 2, for multi year ice the profile of W99 is used. The W99 profile is a climatological average thickness of ice from a 1999 study by Warren et al.

In PIOMAS reanalysis precipitation is used to calculate snow depth.


Hey, ASI blog just got a shout out of sorts from Skeptical Science for displaying the Hiroshima Bombs of GW Heat widget.


The second image is of the top of this very thread with the widget next to it!

Thanks again, neven, for including this striking presentation of this vital information at the top of your blog. Keep at it!

Hans Gunnstaddar


'U.N. Report: World Must Cut Carbon Emissions By 2030'

"The Verge says time is running out for the world to address the situation: "The panel's findings have become increasingly dire, and it's clear that governments will have to act soon if they want to prevent its next report from having an even bleaker outlook.

But even trying to hit the U.N.'s current goal will be a pricey task. Businessweek notes the U.N. report also estimates containing climate change could cost up to 4 percent of the world's total GDP by 2030.
And the issue hasn't gotten much public or political attention in recent years. According to a recent Media Matters study, major broadcast networks devoted less than two hours of their combined nightly news coverage in 2013 to climate change."

We can't give up 4% of GDP to save the climate from spiraling out of control or spend more than 2 hours a year on network news on the topic. Sorry we have other priorities, like Sochi Olympics! /sarc


Waiting for the februari PIOMAS update.

It is clear, see Wipneus’ work on the Forum, that the Schweiger-Zhang team is very busy. Since the remarkable 2013 Arctic summer there’s a lot of speculation on the near future of the climatologic trend in the Arctic. That goes for the more detailed aspect of Arctic sea ice, too.

Meanwhile, new work by Cowtan and Way on the global temperature trend makes clear that there’s nothing uncanny in the direction of the basic trend. Thanks to Tamino, here’s a graph with the lastest December 2013 values included:

 photo CowtanandWayDec2013inGTempgraphsmall_zps40abbc54.jpg

Based on this work, it seems all doubts and diversions can be dismissed. The climate models are generally quite accurate. The actual measured data are in line. The climate sensitivity for forcing is probably close to the worst/highest scenario in the IPCC projections.

The role of clouds might remain elusive. There may be issues like the effects of aerosols and recent ‘sulphur’-emissions from intensive coal-burning in China and India.
There’s also a scientific side to understand what ‘kriging’ is all about. Because it is the method used by Cowtan and Way to get to their results. No doubt that the fake-sceptics will eventually crusade that.

But essentially, there’s not much suggesting a temporary weather-induced extent, area or volume growth might be relevant for the global trajectory of the anthropogenic forcing.

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