Arctic Sea Ice 2016

The sentence is a hyperlink to the article referencing several peer reviewed studies.The graph is the past 3500 years where sea ice was much less than today while CO2 was much lower than present.

 

So you cherry pick a graph of sea ice which occurred during the coldest period of the past 15,000 years!!!!!!!!!
Thats some desperate cherry picking you have going on there.

 

Those interested will read about proxies used by Zhang and Polyak and form their own conclusions.

Others, just interested in reading our banter, will wonder if mojo just said now is the coldest period in 15,000 years??? The same mojo has told us Earth before has been warming* consistently over that period.

*Because CO2 needs to be refuted (somehow)

 

Not about polar ice, but those interested in Medieval Warm Period (also known as Medieval Climate Anomaly), and Little Ice Age will see evidence of them in Polyak's reconstruction. Not in Zhang's though. This is another thing to do when comparing proxies - do they reveal other things, beyond the matter at hand?

 

I found it useful to read Zhang (2015), and hope my comments below do not dissuade anyone else from doing so. There may be something ‘teachable’ here about examining different proxy studies, so I’ll give it a shot.

Proxies used by Zhang (2015) are all recognized aspects of ocean-circulation dynamics. Extension beyond their (most recent) 30-year calibration period depends on such dynamics influencing sea-ice extent. I would not dispute that at all. Second that such ocean dynamics, as they occurred in the past 3500 years, would have similar effects on sea ice. Also sounds reasonable, although not amenable to any direct test. Third, perhaps most important is whether the climate model (GFDL CM2.1) accurately reveals those patterns of ocean dynamics over 3500 yr. This seems much less certain, but is amenable to other testing (such as my observations above about MWP/MCA and LIA). Essentially, are proxies, even if perfect for a given time period, appropriate for a much longer time period? Here, ~110 times longer. Maybe so, but it stands as an unanswered research question.

Proxies used by Polyak et al. (2010) are identified and justified by them (so, read it). Those justifications are for others to agree or disagree with. But the key difference is that those proxies are known for the entire time period examined (~800 years in the figure presented above). Polyak et al. (2010) also consider longer time periods, where some proxies ‘drop out’, but that would be a separate discussion.

Comparison here is between the latter ‘full-extent’ proxy study; and the former where proxies were found indirectly with a coupled-climate model. I think that recognizing this can enrich our reading of proxy-based studies in general.

It would be interesting to know Zhang’s thoughts about Polyat’s proxies and analysis, and vice versa. Mojo, you email Z, I’ll email P, and we’ll reconvene over their responses. Deal?

 

As above, this is a great day. Not made less so by seeing the most recent 800 years called cherry picking. It includes MWP, LIA, and the entire ‘Industrial CO2’ era. Some cherry, eh?

 

You showed a period ,"The Little Ice Age" which was one of the coldest periods in the past 15,000 years .Obviously that period would have a greater amount of sea ice.
Then you misdirect your lie, by making up a ridiculous diversion accusation that I claimed that today is the coldest in 15,000 years.Today, in the present the Earth has recovered from the little ice age and ,as you well know, is not the coldest period I referred to.
To clarify,your graph cherry picked a period called"The Little Ice Age "which was the coldest in the past 15,000 years and would obviously have a great amount of sea ice.Today, the present, is not part of the Little Ice Age as you well know.
You are only trying to confuse my accusation of your cherry picking.


Then you claimed that I stated that the present is part of thath the little ice age ,

 

Some actual links:
Mechanisms for low-frequency variability of summer Arctic sea ice extent
http://research.bpcrc.osu.edu/geo/publications/polyak_etal_seaice_QSR_10.pdf

I'd like to point out that Zhang did not put an average line into the graph posted here.

The paper he sourced that graph from goes back much, much farther than that.

"Arctic paleoclimate proxies in lake and marine sediments, tree rings, and ice cores indicate that from the mid-19th century the Arctic not only warmed by more than 1C average in comparison with the ‘‘Little Ice Age’’ (Overpeck et al.,1997), but also reached the highest temperatures in at least the last two thousand years (Kaufman et al., 2009). This warming sharply reversed the long-term cooling trend that had likely been caused by the orbitally-driven decreasing summer insolation with the positive feedbacks from ice and snow albedo (e.g.,Otto-Bliesner et al., 2006b). Subglacial material exposed by retreating glaciers in the Canadian Arctic corroborates that modern temperatures are higher than any time in at least the past 1600 years (Anderson et al., 2008). An even longer perspective for the outstanding magnitude of the modern warming and related ice loss is provided by the history of ice shelves at the northern coast of Ellsemere Island, which are made of super-thickened landfast ice supported by pack ice in the adjacent Arctic Ocean. These ice shelves have been stable for most of the last 5.5 kyr based on driftwood ages(England et al.,2008), but declined by more than 90% during the 20th century and continue to break at a notable rate (Mueller et al., 2008)"

Unfortunately, I can't cut and paste the graphs out of the PDF I linked too, but the authors went back farther to check that their proxies for ice extent coincide with what is known for past, pre-industrial age climate.

The Zhang graph you posted isn't based upon any physical proxies, but is a computer model.

 

Trollbait, when (as Polyak) pdf figures cannot be directly highlighted, you can screen capture the active window (Alt PrtSc) and paste it into a bitmap editor. Recipe is slightly different for MacOS but not more difficult. This is my usual procedure for pasting Figures from journals here - dancing on the edge of copyright infringement.

I did have concern that a close look at Zhang (2015) would show some, um, weaknesses. However, there are points well worth considering. About three times (s)he* says that future changes in ocean circulations could delay further opening of Arctic shipping. It's clear (to me at least) someone writing this expects further opening of Arctic.

*Rong is gender-ambiguous given name. No basis to guess.

We should see if anything new and comprehensive has come out since Polyak et al 2010.

+++
Aw mojo lower the bellyaching. You did a fine thing by bringing up Zhang. Stimulating interest in use and limitations of proxies. On redaction you made it clear that you consider the coolest period within 800 years to be the coolest period within 800 years. Your opinions and personal characterizations are welcome here, but they are really not your best work.

 

I lifted an old Arctic sea-ice thread instead of starting anew. There is news:

https://www.nature.com/articles/s41467-023-38511-8

Kim et al. suggest that Arctic sea ice will be gone in few decades under all CO2 increase scenarios. Timings vary among those. This cannot quite be called a 'tipping point' as it will (or might) come slowly. It is tippy, if Arctic sea ice cannot come back for centuries of future climates now not foreseeable. A less scary description is needed, maybe slipping point.

Polar bears might need to revise their procedures. Other predators up there might be very happy. I mean, if they read what you might.

 

Greenland is organizing a constitution. Soon enough to be an independent country with land for sale. Antarctica is a different kettle of fish.

The subglacial melting has the potential for substantial sea level changes, ~10 m, over relatively short periods of time, decades. Uninhabited now except for national 'laboratories', it would be easier to colonize than Mars or a couple of larger moons.

Bob Wilson

 

they must be expecting a trump election:

watch