Has the Arctic melt passed the point of no return?

I think this is a pretty disturbing finding.  It's never good when global warming effects occur faster than climate scientists expect, and there are several examples of this happening.

I believe it was gcnp who mentioned that we don't really know if this means the Arctic had passed a tipping point because we don't understand the Arctic well enough, or something along those lines.  Maybe he'll elaborate on that for us.

But I thought the ice-albedo feedback has been occuring for years; isn't this the main reason the arctic has been warming so much faster than the rest of the world?

Hi folks. 

The situation, as I understand it anyway, is that the positive warming from CO2 and other long-lived radiative trace gases (e.g., methane) cannot account for the observed warming in the arctic.  In other words, the polar amplification seen is much larger than current models can account for using only CO2.  The explanation for this follows a couple of different tracks, depending on whether you are a climate skeptic or not.  There is some overlap between these since the atmosphere-ocean dynamics of the arctic are poorly understood, especially in the case of coupling between the arctic and known decadal processes like the North Atlantic Oscillation and the Pacific Decadal Oscillation.

Track 1:  It's all natural variability.  Skeptics will argue that a shift in the NAO or PDO from one phase to the other shifts circulation in the arctic and that has caused the sea ice to melt.  There are NASA websites around with articles by Jamie Morison detailing how this might work.  There are however, arctic scientists who do agree with the conclusions of the IPCC that also believe dynamics might be at least partly responsible for the warming (and loss of sea ice) in the arctic (Cecelia Bitz is, I think, an example of this and her article on RealClimate.org is excellent and highly recommended, at least by me). 

Track 2:  There is some other feedback going on that is warming the arctic that isn't accounted for by greenhouse forcing from CO2.  If you search the website from Atmos. Chem. and Physics for "P. K. Quinn" you can find a paper detailing what this entails.  In a nutshell, current climate models don't account for warming from black carbon (i.e., soot) or from short-lived greenhouse gases like ozone.  Atmos. chemists like Quinn et al. know that Europe, Russia, and N. America to a lesser extent, deliver these to the arctic.  The warming from these might be enough to provide the missing forcing since black carbon has a huge effect on albedo. 

Anyway, the thing that is interesting from my perspective is this is a huge hole in climate models.  The one thing that all models predict and that has been observed is a polar amplification, especially in the arctic.  Yet the models crater severely reproducing the extent of the observed warming.  This is a very active area of research, and going here:

http://www.agu.org/meetings/fm08/waisfm08.html

and searching for "arctic warming" returns 40 sessions (not papers, but sessions containing anywhere from 10 to 35 individual papers) discussing arctic warming.  Skeptics haven't picked up on this model failure and beat the everloving snot out of it simply because the professional skeptics don't want to do point it out because they would have to admit the arctic is warming and the ditto-heads on the internet who parrot what the Balls and Lindzens say don't understand the problem. 

My personal opinion is that Quinn et al. (and I might be a little biased here) are on the right track and that dynamics has less to do with this than radiative forcing.  If it were all circulation, the interior of Greenland wouldn't be melting like it is.  But I can't back that with data. 

-Bill

gcnp = Got Creek, No Paddle

References:

Bitz:  http://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/

Morrison news release:  http://www.engr.utexas.edu/news/articles/200711131355/index.cfm  (not sure if Morison put this in print yet)

Quinn et al.  http://www.atmos-chem-phys.net/8/1723/2008/acp-8-1723-2008.pdf

Oh wow, I didn't realize Arctic warming was such an uncertainty in the models.  That's really funny that the 'skeptics' never talk about it because essentially it's counter-productive for them.

With the extensive use of diesel in Europe (and associated particulate emissions), offhand the Quinn explanation seems plausible.  Some skeptic or other was talking about how there was extensive Arctic ice melt around the time of the MWP too, so perhaps that supports the natural variabillity explanation if true.

Interesting stuff.  Thanks for the explanation gcnp/Bill.  I'll have to read up on those links when I've got some free time.

Honestly, this science is a little bit over my head.  I'm going to pull a Michael in the Office.  Why don't you explain this to me like I'm an 8 year old?  :-)  Thanks, guys!

Woot for The Office!  You mean this subject in particular?

Basically the Arctic ice is melting much faster than climate models have predicted.  So the 2 possible explanations for this as described by gcnp are:

1) It's due to a natural climate variation that we don't fully understand.

2) It's due to black soot.  Because black soot is..well...black, it's good at absorbing light.  So the more black soot - particularly in the Artcic where the snow and ice is very effective at reflecting solar radiation - the more radiation absorption you get, causing the planet to warm.

A nice explanation here.

Some main sources of black soot are from burning diesel, coal, and biomass.  I was reading an article the other day talking about how although diesels emit less CO2 per mile than gasoline, they contribute at least as much if not more to global warming because of their black soot effects.

Also, black soot appears to be the second largest contributor to the current global warming behind CO2.

As for the Arctic ice, it's a big potential global warming feedback.  As previously noted, Arctic ice reflects a lot of sunlight.  As it melts, it exposes more dark oceans which absorb more sunlight, causing the planet to warm further.  Which in turn causes more Arctic ice to melt, decreasing the planets' reflectivity (a.k.a. albedo) further, etc. etc. in a sort of feedback loop.  Hence the fact that this ice is melting faster than models expect is rather alarming.

Very glad this forum started up - already some great information, and also some breakdown so that us dunces can get on board :)

The black soot phenomenon is definitely a bit scary because it seems like it has the potential to "snowball" more than CO2 emissions, no? The more black soot, the more solar reflection, the more ice melts, the more black soot...and on...

Ah but CO2 also has a number of potential feedbacks.  For example, CO2 is less soluble in warmer water.  So as the oceans warm, the absorb less CO2.  This causes more CO2 to remain in the atmosphere, the planet warms, the oceans absorb less CO2, etc.

Then there's a feedback relating both of them in melting permafrost.  There's carbon trapped underneath permafrost.  As the permafrost melts due to a combination of increasing CO2 and black soot, this releases the trapped carbon (often in the form of methane, which is a greenhouse gas 20 times more potent than CO2), which leads to another feedback loop.

Don't forget about how a warmer atmosphere leads to more H2O in the air, a very strong greenhouse gas.

David Archer, a realclimate contributor, believes if it were not for this effect there would be no reason to worry about the greenhouse effect at all.

Ah yes, good point, water vapor may be the most important feedback of all.  There's a lot of confusion about water vapor, which is why I devoted Myth #9 to it.

Water vapor accounts for the largest percentage of the greenhouse effect - much more than CO2.  Some people thus conclude that water vapor is much more important than CO2 in regards to global warming.  But the thing is, the amount of water vapor in the atmosphere depend s on the atmospheric temperature.  We can increase the concentration of CO2, but we can't directly increase the concentration of water vapor.

However, if the planet and its atmosphere warm for another reason (i.e. increasing greenhouse effect from increasing atmospheric CO2), then it can hold more water vapor, which as a greenhouse gas in turn causes more warming - a (positive) feedback.

But water vapor also forms clouds, which reflect sunlight - a (negative) feedback.

There's a lot of uncertainty as to how big each of these feedback effects will be, and what the net effect will be.  Some skeptics think the negative feedback will be bigger and this will save us from the worst effects of global warming.  They basically think the Earth will balance its own temperature.  However, most climate scientists think the positive feedback will be bigger, and the net water vapor effect will be to increase the warming.

This is one of the biggest uncertainties with climate models.

Well said dana. And I assume by "skeptics" you just mean "Spencer", unless there are some other scientists out there who share his beliefs. But the complexity of clouds makes me think it is impossible to be sure about whether their effects will be positive or negative.

I mean:

Smaller drops of water in the clouds make scattering more efficient which contributes to cooling, whereas larger drops contribute to warming.

Ice crystals vs water comes into play, as ice crystals are better at reflecting light upwards compared to liquid drops.

The altitude of the clouds plays a huge role, as the higher ones (cirrus) contribute to warming whereas the tropospheric clouds contribute to cooling (even the question of whether or not cirrus clouds are positive or negative is not well established)

We can only hope the negative feedback of clouds will indeed be significant, but as of now (and as was reflected in the IPCC reports) scientific certainty of cloud formation and how they affect climate (other than the fact that scientists all agree they have a huge effect) is very low.

Actually I was thinking of Richard Lindzen when I said that.  You're right, I think I recall Roy Spencer saying the same.

Water vapor's effects are definitely very complex.  I'm sure we'll have a good understanding of them all someday, but it will take a while.