And since I am pontificating on statistics, here are some take away messages from the recent graphical posts by Oren, binntho, Archimid and El Cid (and thanks to all).
RE binntho's Extent and Area straight line trend
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227604.html#msg227604 While it certainly looks like a significant downward trend, you can't say the slope is different from zero without doing the stats. It probably is, but your use of the visual assessment method is no more valid than it is for the folks arguing that the process has stalled because it looks that way in the last 10-13 years (again I am shameless, the same applies to me too, my sinful nature was noted in previous post. We are all fallen creatures.)
RE Oren's CAB volume trend and thickness graph
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227570.html#msg227570 That's almost the chart I was hoping for, but it would be even better with a straight line regression trendline, tested for difference from zero, and then extended out 20 years to 2040. FWIW, if you squint and draw a straight line through the CAB volume trend for Day 243, aka end of melt season, the slope of that line will indicate about 4 million km3 decline from 2000 to 2019, i.e. 19 years. If that trend continues, then take another 4M km3 over next 19 years and it reaches zero in ca. 2038. That's only a few years later than the Wipneus straight line projection of sea ice volume trend for the entire Arctic.
The key characteristic about Oren's chart is that it is limited to ice volume in the CAB. Thus, it presumably removes possible inflation of losses by peripheral seas that are melting out sooner than the CAB. What started this phase of the discussion was the notion that future loss rate would decline because the CAB would be more resistant to melting. I think the Oren chart refutes that.
I was surprised how strongly negative the CAB end-of-melt-season (i.e. annual minimum, day 243 data) volume is. The CAB may look like it's been hanging on, but apparently that is the deceptive Extent curve at work. The CAB has been rotting out from the inside. As for the future, the presence of ice in the peripheral seas late into the summer might have reduced past losses in CAB. Their presence has kept Arctic Ocean albedo high and almost certainly reduced pack rotation and transport out through the Farm Strait (and thanks to Tor for insight on importance of export losses). With less protection from ice in those peripheral seas as they melt out earlier in the year, the rate of CAB losses could markedly increase in the future.
Archimd's graph shows that CAB volume losses appear to already be increasing
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227455.html#msg227455.
In addition, the wider amplitude of the fluctuations in El Cid's graph
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227470.html#msg227470 gives me a bit of the willies because one of the predictors for a nonlinear chaotic system reaching a tipping point is higher variability. I may be misapplying that concept because max to min amplitude is not the same as variability between years, but I allow myself my own superstitions.
But 2038 as the projected zero year for CAB sea ice volume is over a century earlier than binntho's trend extension showing Extent not reaching zero until 2187. How can that be? Extent is not declining as fast as volume because the remaining volume is being contained in thinner and thinner ice, and thus the Extent does not decline as much as it would if thickness remained constant. But as the thinnest ice contributing to Extent reaches zero thickness, it stops contributing to the Extent number. In the end, the Extent curve and the Volume curves have to meet because zero volume provides zero ice for Extent.
Which brings me back to Oren's thickness graph. Total conjecture, but my guess is that once average thickness gets below 1 meter we will start to see the end-of-melt-season Extent curve start catching up with its parent Volume curve. Ice melting comments elsewhere on ASIF point to the much lower melt resistance of thin vs thick ice. Regardless of my conjecture, the Extent curve HAS to catch up to the Volume curve eventually.
Stay tuned. I think there are wild times ahead for ASI in the very near future because it is on the edge of the precipice. It will be entertaining for those of us who like to watch numerical systems evolve. Too bad it isn't just a horse race or some other innocuous event, but is instead the loss of a crucial component for meteorological and climatic stability on the only planet in the universe known to host self-aware, so-called "intelligent" life (actually any life, but I think we will soon see that microbes are just about as common as water). As my brother, a conservative who bought into the climate hoax BS for a while, but who is too smart to stay ignorant, said when he came to see the big picture: "This story does not end well".