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Mike

Yep really good, I recommend this one, very informative. Thanks for that Neven.

Jim_pettit

Very good interview indeed. Of course, the denialist community went ballistic over the NASA report, and--in the finest tradition of cherry-picking--immediately latched onto the sole NASA talking point that they feel provides them solace: that a similar melt appears to have taken place 130 years or so ago. Therefore, you see, the planet isn't warming, and therefore CO2 has no ill effects on the environment, and therefore fossil fuels are healthy. Or something. Anyway, if (when?) a similar or worse melt happens again very soon--which it almost certainly will--I wonder how that crowd will spin it?

Andreas Muenchow

This is a very good interview indeed, because it is nuanced, detailed, and explains the physics and their implications real well without resorting to drama or manipulation-by-omission. Sadly, such tactics are found too often on both sides of the political argument that bends data and analysis to a pre-conceived notion that (a) all change is "unprecedented," (b) global warming is the culprit of all change, or (c) climate change and global warming is a hoax. The ice-ocean-air-land global system is way too complex and nonlinear for any discipline of science to come up with a definite answer. This does NOT invalidated Richard Alley's concise statement that "If the earth warms more, Greenland is going to melt more ..." And yet, I feel, we have to be careful to not over-hype each weather event, even if it is a rare weather event that occurs only every 80-250 years or so. The melt reported by NASA this week was a rare weather event, as Dr. Wagner explains rather well.

Philippe Terrier

"The melt reported by NASA this week was a rare weather event, as Dr. Wagner explains rather well."

We will see tomorrow

Last GFS weather forecast continues to see all Greeland above 0°C:

http://imageshack.us/photo/my-images/19/rtavn3654.png/


IMHO, such global melt event should be analyzed in the context of positive trends in the surface melt. As reported in this study:

http://www.igsoc.org:8080/journal/57/204/j11J003.pdf

The authors observed that "After 1972, the maximum melt extent increased significantly (p < 0.01) by 22% (~3.7x10^5km^2)of the GrIS area". The figure 4 is also very informative.

With a constant increase in melt surface since 1972, the probability of occurence of a global melt event should also increase.

In fact, it was already predicted by J. Box:

"In the 12 years beginning in 2000, the reduced albedo combined with a significant increase in downward solar irradiance yielded an accumulation area net radiation increase from 􀀀0:9 to 􀀀0:2Wm􀀀2. Another similar decade may be sufficient to shift the average summer accumulation area radiation budget from negative to positive, resulting in an abrupt ice sheet melt area increase. The ice sheet mass budget deficit is therefore expected to become more sensitive to increasing temperatures via the ice albedo feedback, especially in negative summer NAO index conditions. Future work should therefore be concerned with understanding potential tipping points in ice sheet melt regime as the average radiation budget shifts from negative (cooling) to positive (heating), as it seems the threshold of this has just been reached. It will take some time, perhaps years for the cold content of the firn to be sufficiently eroded to allow continuous summer melting and an ice sheet surface characterized by 100% melt extent. Further warming would only hasten the amplification of melting that the albedo feedback permits."

http://bprc.osu.edu/~jbox/temp/Box%20et%20al.%202012%20-%20TCD%20-%20resubmitted%20after%20review%20round%202.pdf

Jim_pettit
Andreas Muenchow wrote: Sadly, such tactics are found too often on both sides of the political argument that bends data and analysis to a pre-conceived notion that (a) all change is "unprecedented," (b) global warming is the culprit of all change...

I don't wish to sidetrack Neven's blog with any ideological stuff, but I have to ask: certainly you're not claiming that "both sides" of the climate change argument engage in an equal amount of deception, manipulation, and outright fraud to bolster their POV, are you? I've not seen a single climate scientist argue that the warming planet is the driving force behind all change--but I have seen denialists steadfastly proclaim over and over that GW is the driving force behind none of it. I've not seen any credible scientist claim that all change is unprecedented, but I have heard many denialists just as steadfastly proclaim that none of the observed changes are out of the ordinary.

I absolutely agree that we who support the science have to remain extra-vigilant about not "overhyping" every severe weather event. But I also believe we have to be just as sure to not resort to false equivalency by assuming that both sides are on equal scientific footing. They're not. And pretending that they are--out of a sense of political correctness, or overcaution, or whatever--is plainly foolish at this point.

Andreas Muenchow

It is a very slippery slope to claim that "denialists" are 95% wrong or misleading in their claims while "alarmist" are only 35% wrong or misleading. I do not like labels and refuse to enter this slippery slope making "predictions" that are little more than "educated guesses."

More on topic, please be careful when you argue with the North Atlantic Oscillation Index. It describes variations only, it contains no trends, the average of the NAO is ZERO. So, everytime someone argues with strong NAO+ phases does this, there are NAO- phases which do the opposite. More formally, the NAO is the first and dominant principal component of atmospheric pressure that explains no more than 1/3 of the variance in winter. Variance explained is lower in other seasons.

And finally, also on-topic, a 10-year record is too short to make statements related to warming as this Los Alamos press release https://www.llnl.gov/news/newsreleases/2011/Nov/NR-11-11-03.html and the Santer et al (2011) paper indicates (non-paywalled manuscript is at http://muenchow.cms.udel.edu/classes/MAST811/Santer2011.pdf)

Andreas Muenchow

Sorry for double posting, the Santer et al (2011) non-paywalled version is at

http://muenchow.cms.udel.edu/classes/MAST811/Santer2011.pdf

Jeffrey Davis

from Andreas Muenchow:

"It is a very slippery slope to claim that "denialists" are 95% wrong or misleading in their claims while "alarmist" are only 35% wrong or misleading. I do not like labels and refuse to enter this slippery slope making "predictions" that are little more than "educated guesses."

****

Who said any of that? Where did those numbers come from?

Espen Olsen

I am happy to be just an amateur in this field, so I am not in any way depending on funds, but I am aware of so called scientists who are not telling the world what I and many others could tell. Science is too commercialized today, I do not trust them either, sorry! But I am happy to be a "non expert", and for some time I can say what I think, but for how long, time will tell?

R. Gates

This was a very well done interview. Excellent and well-measured response. True, this wide-spread melting on Greenland is not "unprecedented" but it certainly is rare, and get's back to the entire issue raised by Hansen, Trenberth, et. al. It is not the fact these things are occurring, for certainly pretty much everything weatherwise has happened sometime in Earth's past, but it is the frequency and severity of the occurrances that is the telling sign of something changing. Formerly "once in a century" events happening every few years is sure sign that a system has crossed a threshold or tipping point. In terms of the Arctic, we've seen many of these, with the widespread melting of Greenland just the latest. Will it occur every year? Perhaps not. Would AGW tip the balance to favor that it begins to happen more frequently than every 150 years or so. Absolutely. What will the deniers say if we see more of this kind of widespread melting? Who can say? Irrational thought is never predictable.

idunno

Irrational thought is never predictable.

But at least some people try to study it.

http://www.guardian.co.uk/environment/blog/2012/jul/27/climate-sceptics-conspiracy-theorists?intcmp=122

Finally all of the deniers have provoked some serious discussion among scientists of their numerous theories. The million-dollar question being "Are these people batshit mental?"

AmbiValent

No, they have merely wet feet and can see the pyramids...

As for batshit mental: 1979 Warsaw pact put new nukes into East Europe, pointed at West Europe. NATO threatened to put in new nukes on their own in place if the Warsaw Pact didn't remove their new nukes. The Warsaw Pact didn't do so. 1983 NATO replaced their old Pershing I in Germany with the more modern Pershing II.

The kicker: Both before and after 1983 missiles on both sides were deadly enough to turn all of Europe into a radioactive wasteland. Both before and after 1983 the attacked side would have time enough to react and destroy the other side, too. The difference was after 1983 Pershing II missiles could reach the Soviet Union in mere minutes (Pershing I couldn't). Meaning, if the Soviet Union got a false alert... they didn't have time to find out whether it was correct.

Compared to the politicians in charge back then, WUWT and all the others are harmless little old ladies.

Glacierchange.wordpress.com

I was disappointed in the lack of glaciologic awareness in the video. This one event is certainly primarily related to the weather event. However, the fingerprints of climate change have been all over the melt record in recent years, which was ignored, as if the 2012 event was singular. As noted in the Arctic Report Card, " An average of 31% of the ice sheet area was melting during June through August 2011, compared to 33% in 2007 and 32% in 2010. No other year since 1979 had an average greater than 30%; the 1981-2010 average was 24.1%." The albedo reported by Box earlier this month is also exceptional. The Petermann Glacier was the glacier with the longest floating tongue in Greenland not just any glacier. The acceleration and retreat of so many glaciers as summarized by many researchers. The latest melt finding was the tip of the iceberg, not the only thing in the recent record

Steve Bloom

Thanks, Mauri. That was my view as well, although I lack the professional chops to back it up.

To restate the general point, an extreme event taken in isolation can't be evidence for AGW, rather that can only be the case when it is considered as one of multiple lines of evidence.

Kevin McKinney

Yes, I've read my share of "oh, they say this happens every 150 years, so there must be nothing to worry about" comments.

Unfortunately.

D

Review of the ice core record shows that there is no 150 year cycle as "skeptics" have concluded based on the NASA press release and this video. The 1889 event was the only Greenland-wide melt in the last 700 years. When the northern hemisphere solstice aligned with perihelion about 8000 to 5000 years ago melt events were much more frequent.

http://www.igsoc.org/annals.old/21/igs_annals_vol21_year1995_pg64-70.pdf

A small cluster of melt events is seen in the medieval warming period. Before the medieval warming period melt events are much less frequent than 150 years on average until 4000 years before present.

The paper says:
The frequency of melting at the GISP2 site in central Greenland has decreased significantly from a maximum about 7000-7500 BP. This could have been caused by a change in summer temperature variability Over time, but probably represents a cooling of summer temperatures.

Calibration of this signal suggests that the cooling has been within a few tenths of a degree of 1.3° C.

And a paper just published showed, in agreement with these data, that the earth was cooling for the past 2000 years until recent massive GHG emissions rapidly reversed the trend.

NASA's failure to cite Jason Box's data showing Greenland darkening over the past decade helped make this sound like a one-time weather event which it was not. It was part of a multi-year trend of warming, darkening and increasing melting.

-FishOutofWater, aka George

Steve Bloom

Is this the FOoW of DK fame? If so, hiya, and thanks again for the good work there.

Jason's paper was in-press, so I suppose there's some possibility that the NASA folks didn't know about it. OTOH I think there are lots of scientists who are just plain scared of being associated with predictions of abrupt change, especially as the GCMs don't really do abrupt change and so such predictions must to a great degree depend on physical intuition, even if it's something as simple as just saying that a clear trend will actually end up where the observations are pointing it.

D

Yes, I post at DK as FishOutofWater. Thanks. I'm a regular reader of Neven's blog. This blog has one of the best discussions on the internet, hands down.

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