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I'd been thinking that Greenland melt looked like stalling again this year. Maybe not though, based on this forecast.
We had a sudden, sharp decline in Arctic ice in 2012. I didn't see many apathetic people wake up then.
@Bill, The discussion was a long and messy one in the comments on a blog article... somewhere. I remember they based their argument on this graph (or at least the most recent part of it) though:
I won't be hoping for unambiguous proof myself, jdallen. Particularly given how many people report their beliefs actually being strengthened by contradictory evidence. Also, ice area and extent have so much noise and so many disparate measures as indicators that people can easily interpret it selectively and seize on apparently contradictory "evidence"; the latest one that sceptics have been wheeling out in debate is that global sea ice area has been equal to the 1979-2008 average for the past two years ( Never mind that they liked to completely ignore it for the previous two years, when it was well below said average, or that if you drew a regression line through the whole history, it would go down :S
Let's have an alternative, shorter term betting game: is this downwards pre-melt season trend in declining sea ice cover going to carry on, flatten out, or bounce back a little? Please make your predictions between now and the 15th of March as to the sea ice extent (NSIDC) on 01.04.2015. Whoever guesses closest to the actual amount wins the prize of one virtual cookie. I'm going to start the guessing game at a nice, round, 14.00 million square km. (A bit of a drop further from where it is now, but not much).
Toggle Commented Mar 11, 2015 on Mad max? at Arctic Sea Ice
Going to try not to get too exciting about this myself, as we're still in the lower-insolation half of the year. (But I know I'll be checking back come the equinox in 11 days time to see if we're still at record-breakingly low levels :) )
Toggle Commented Mar 9, 2015 on Mad max? at Arctic Sea Ice
@NJSnowFan, We looked into the potential impact of increased ship traffic, including but not limited to ice breakers, over on the sea ice forums, and based on some basic number-crunching it really didn't look like they could account for very much of the melt. @Hans Verbeek "Anyway, it costs a lot of diesel fuel to break up Arctic seaice. Peakoil will also mean peak-icebreaker. ;-)" Not necessarily; the biggest ones are nuclear-powered.
@Pete, 5.632 million square km as of August 27th (you can see the most recently reported extent by scrolling over this graph: I now reckon we were way out, and the September average will be about 5 to 5.3 million square km.
@John, I completely agree. I wouldn't expect to see zero ice in winter at any point in the next hundred years - months of sunless winter are sure to freeze at least a thin layer of the ocean surface, even if the amount formed continues to slowly fall, and melts away earlier each year. Even if arctic temperatures went up 10 degrees celsius, they'd still be regularly going below -30 degrees. So why would the ice stop forming?
Does anyone know what impact the increased shipping, drilling, harbour investment, fishing and other activity as the ice melts is expected to have on the rate at which what ice is left declines? Because such activity should probably start rising to a peak now... and I have to wonder if this particular positive feedback mechanism may not have been one of the reasons last year's melt went on as long as it did.
4.2m again. PIOMAS volume seems to be lagging a long way behind the last couple of years, meaning a big catch-up would be needed to get close to last year. But with all that first year ice, there should still be a big melt to come... so I'm still betting it'll reach 2nd place, if only barely. (BTW, I really don't know all that much about what I'm talking about).
Also, my congratulations on some excellent work :)
Toggle Commented Jul 2, 2013 on Problematic predictions 2 at Arctic Sea Ice
Do any intrepid mathematicians want to see if including a variable for ice thickness improves the model further? (Thinner ice should melt faster, after all).
Toggle Commented Jul 2, 2013 on Problematic predictions 2 at Arctic Sea Ice
@Mdoliner, Even though it's been rare in the past, I wouldn't count out a possible volume increase this year, since when last reported, the PIOMAS ice volume was tracking "425 and 901 km3 above those of 2011 and 2012 respectively":
I feel we could do with a little more discussion of the extent of our individual uncertainties. Personally, I'd be very surprised if the extent this year was either less than 2.6 million sq km (a drop of more than 1 million sq km from 2012's record, and a very steep drop from where we stand today), or more than 5.1 million sq km (ie, more than any year since 2007, and a rise of more than 1.5 million sq km from 2012). But anything in between seems possible, especially with the great uncertainty and disagreement about what the implications of the cyclone's behaviour might actually be.
@ Fufufunknknk, About 10 years and a 1.
4.2 million square kilometres. This is an adjustment upwards of 0.5 million square kilometres from my prior prediction of 3.7 million square kilometres, based on the slow start to the melt season. However, it would still be the second lowest on record...
3.7 million square km. (+/- 1 million square km). I'm guesstimating that it'll be about the same as last year based on current PIOMAS volume, NSIDC extent and Cryosphere area being about the same this year as last year, and based on general drivers not changing that much year-to-year. Put me down as an optimist, I suppose.
@Bosbas, Crandles, Thank you for your responses. If the lower average monthly ice extent for past years is indeed because ice has been more mobile in 2012, and thus seemed more extensive over the course of a month, then it would indeed seem to explain it. And if that is the explanation, then personally, I think it makes sense to place more emphasis on the daily figures, representing the extent of sea covered by ice at any one time, rather than on the monthly figures which would instead seem to represent the extent of where the ice has been. But that may just be my bias talking...
@P-maker, I am indeed pretty dubious of the metric in question - it seems to have been seized upon by some sceptics simply because it is a "last hold-out", as it were. But if it looks like it'll fall soon enough, it's one more bit of debating ground they'll have to abandon. @crandles, One thing I don't get from the nsidc data in the latest bit of Arctic Sea Ice News. Based on Figure 2, November ice extent seems to track lowest in 2012 for most of the month, and 2012 seems to clearly be the lowest in average overall, but in Figure 3 it's only the third lowest November on average. Do you know if there's some difference in how the extent figures are calculated across the two different graphs? (I noticed something similar in the previous installment, but it wasn't quite so stark a contrast as in this month's).
Further record speculation (probably not this year): how long before we see a new record low 365-day Arctic average? That's about the only unbroken Arctic ice record which I've seen sceptics still holding onto; the 2007 record remains the lowest yet, due to the fairly high peak 2012 extent and low peak 2007 extent. But with the average for the last six months of 2012 having been considerably less than the 2007 average for that period, I'd expect this record too might well be broken some time in the next six months. (Although it's far too early yet to speculate on where peak 2013 extent might fall). See this graph for a rough illustration of this metric:
On the record high shipping: I'd very much expect a new record next year, even without a new low in sea ice area or extent (not that those are unlikely either). There's an increased interest in building ships designed for the arctic, now that the business model's been established and the advantages have been made clear.
@Chris, I hadn't yet leapt so far as to suggest more dams as a deliberate measure to hold back warming, more wondering what the effect of the current trend towards more dams (for other reasons) might be. TBH, I'd be a little surprised if we're creating enough new water cover to seriously alter the climate very much, but I was really wondering if anyone here had some idea of the numbers. To answer your question as best I can, though: I believe that most such projects use freshwater, due to the dual utility value for irrigation and for hydroelectricity (you don't get a lot of salt water flowing downhill to harness for hydroelectric power). But some applications, particularly the creation of a power reservoir from an irregular power supply (e.g. wind) by pumping water uphill, could conceivably use seawater.
I'm interested by this talk of the benefit of making new reservoirs through dam-building in ameliorating sea level rise. Does anyone know the effect on warming and cooling (thinking particularly of albedo, convection-driven cooling, and possibly cloud formation) of trading land for water?
"As for the tail of the Gompertz projection: Gompertz is a logistic function that has a sigmoid form. So a tail is to be expected. Exponential crashes to zero. Projections using either function tell us nothing about the real physical processes." This. Also, the ice following such a projection at one stage in its decline does not mean it will continue such a projection in future stages in its decline when conditions are altered by the absence of ice.