"Smart" and "Stupid" Questions - Feel Free To Ask

[Ned W]

In terms of effects on climate, 1 million is much closer to ice free than to the previous ice/climate regime, so I think it's a good proxy.

Ultimately, any numerical threshold (other than actual zero) is pretty arbitrary.  Whether one says that 0.5 or 1.0 or 1.5 million km2 is "ice-free" doesn't really matter to the physical processes. 

But we want to be able to point to some specific date and say "OK, on this day, the Arctic Ocean was ice free" with perhaps a "(for all practical purposes)" footnote if we're Walt Meier.  It doesn't matter to the climate, but for this kind of "social" purpose everyone seems to have settled on 1.0 million, and I'm OK with that. 

But I think it would produce less cognitive dissonance in the general populace if people had settled on a lower threshold.  That 1 million km patch will look pretty large when people look at it on a map.  We all know people will look at it and say "Hey, that scientist claimed the Arctic Ocean is ice-free but there's a great big patch of ice there!"  I don't mean denialist-types who would complain regardless; I just mean ordinary non-experts who are in good faith but confused.

The 0.5 million patch is still there, but it's smaller and less confusion-inducing.  Just IMHO.

Re-posting the map below, since this has spilled over onto a new page:

[greatdying2]

Volume is reducing at a significantly higher rate than extent. One year extent must collapse. But when !!??**

Yes, they have to reach zero at the same time, but there is more than one way that could happen:

* Extent could speed up to match volume
* Volume could slow down to match extent
* They could meet in the middle

I agree with gerontocrat. Extent loss will eventually speed up to match volume, at the very end dramatically, like a blender full of ice cubes in a warm room.

[greatdying2]

We all know people will look at it and say "Hey, that scientist claimed the Arctic Ocean is ice-free but there's a great big patch of ice there!"  I don't mean denialist-types who would complain regardless; I just mean ordinary non-experts who are in good faith but confused.

They're going to be confused regardless, when the extent "recovers" a few weeks later, once winter sets in (unless we lose the halocline). In my opinion a larger rather than smaller threshold would have been better for public policy, which needs a swift kick in the behind.

[Dharma Rupa]

But we want to be able to point to some specific date and say "OK, on this day, the Arctic Ocean was ice free" with perhaps a "(for all practical purposes)" footnote if we're Walt Meier.  It doesn't matter to the climate, but for this kind of "social" purpose everyone seems to have settled on 1.0 million, and I'm OK with that. 

Ice free (in all its forms) is something we care about and they do not.  When cargo crosses the Arctic and doesn't have to deal with either the NW Passage or the Northern Sea Route then the general public -- and the people with money -- will notice.  (I'd say when they didn't have to deal with national borders, but I think the Bering Strait messes that up.)

BTW -- what was the question?

[numerobis]

On the main thread, Daniel B questions whether the ice trend since 2007 is flat. It's a bit OT for that thread so I'll paste it into here, but overall I'm just citing tamino from October 2015, who says that on some measures it might be (but it might also be shrinking, just at a slower rate than the early 2000s), but on other measures it definitely isn't.

The extent trend is very much down, but if you take a chart of just the last 10 years 2007-2016, and just of the extent minima, you will see a relatively flat chart.

So what? That is just plain cherry-picking. Of course you will get a flat trend, if you start in a year with an exceptional low value and use only a short period of time (so that the overall long-term trend will not beat that short-term variation).This is exactly the same as people bragging about that there was no global warming since 1998 or in the last 10-15 years.
https://skepticalscience.com/graphics.php?g=47

But those trends are not statistically significant, not even close. There is nothing you can get out of such an "analysis". The only thing you see is short-term variation. If you just include 2006 in your time-span, the trend is already strongly downward, so if you have such a dramatic change by just including one more data point, you certainly know, that you have to included to few data points in the first place.

By your method the entire satellite trend is not statistically significant.  That does not mean that it does not exist.  Look at your graph.  This highest data point was 1996, and the lowest was 2012.  Can you confidently say that the entire graph shows a linear decline?  Longer-term data sets show that the extend in 1996 was not too different from that 60 years prior. 

http://neven1.typepad.com/.a/6a0133f03a1e37970b01b7c809c471970b-pi

This is Tamino's post that I was thinking of (among the dozen or two other posts he's done on sea ice):
https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

This is two years old; it'd be interesting to see with 1-2 years of extra data.

On annual average extent, he finds that it collapsed 2003-2007, then went back to a rate that's simultaneously indistinguishable from zero AND indistinguishable from the statistically significant rate in the earlier part of the record. So Tamino does see statistical support for a change in trend occurring in 2007.

On annual minimum, he finds a change point in the mid-90s, but not recently. He notes this data is noisier and a smooth does suggest that maybe there's a change point more recently, but you'd need more years before you could be sure (I'm not sure if one more year is enough).

On annual maximum, he finds no support for any change in trend.

In all cases, the trend is down.

I note that Neven frequently posts his volume graph, which looks pretty much like a straight line down. It's not mathematically possible for all of area, volume, and thickness to all be linear trends down, except that every curve looks linear if you focus in close enough.

[deconstruct]

On annual average extent, he finds that it collapsed 2003-2007, then went back to a rate that's simultaneously indistinguishable from zero AND indistinguishable from the statistically significant rate in the earlier part of the record. So Tamino does see statistical support for a change in trend occurring in 2007.

That doesn't make any sense (and IMO Tamino does not claim that). When the trend after 2007 is indistinguishable from the former trend, than there is no statistical support that the former trend has changed in the first place. For that to claim, the later trend rate would need to have an uncertainty range, so that the former trend rate would be outside of that range.

As Tamino wrote in his conclusion:
"All we can say for sure is that it was trending downward, and all the evidence points to the fact that it still is."

But it would be interesting, if that would change when one includes the two additional years since then, however I doubt that i would.

[greatdying2]

That doesn't make any sense (and IMO Tamino does not claim that).

See box pot here: https://tamino.files.wordpress.com/2015/09/fig03.jpeg

What Tamino is saying is that although the average rate of decline 2006-2015 is slower than the average rate of decline 1979-2002 (big dots on the plot), the error bars from 2006-2015 overlap both zero and the 1979 error bars (indeed, they overlap the error even in the opposite direction). So yes, by that analysis, 2006-2015 is not statistically different from zero nor the 1979-2002 trend.

It does make sense because the 2006-2015 error bars are large compared to those of 1979-2002 due to having far fewer data points in the analysis. I.e., Even disregarding the cherry-picking (a major no-no), you can't draw very strong conclusions from so few data points with highly variable data. This is the main point.

[numerobis]

If someone came to you and claimed the trend was the same from 2007-2015 as it was from 1980-2003, you'd say "sure, that seems reasonable" because the error bars include that value. But if someone else claimed the trend from 2007-2015 was nil, you'd be forced to admit "seems unlikely, but it might be" because again the error bars include that value (according to tamino).

Given that 2016 and 2017 had record-low extent for a good part of each year (just not at the minimum in 2016), I'd guess that if tamino threw the new data in, he'd find increased support for the proposition that trend is negative, and reduced support for the proposition that the new trend is zero.

This is all just stats, there's no physics. Physics obviously suggests the ice is going to melt; the debate is merely about how fast.

[deconstruct]

It does make sense because the 2006-2015 error bars are large compared to those of 1979-2002 due to having far fewer data points in the analysis. I.e., Even disregarding the cherry-picking (a major no-no), you can't draw very strong conclusions from so few data points with highly variable data. This is the main point.

That is what i said. And therefore it is IMO just wrong to say (and to that i was refering):
"So Tamino does see statistical support for a change in trend occurring in 2007."
No, he does not.

[deconstruct]

I'd guess that if tamino threw the new data in, he'd find increased support for the proposition that trend is negative, and reduced support for the proposition that the new trend is zero.

That is what I showed in my graphic. If you include 2016, the trend over 2007-2016 is even upward.
But that won't change the fact, that the error bars will still overlap. Just including one more year (2006) makes the trend-rate clearly downward (shown also in my graphic, and that is indicative of how uncertain the trend-rate over such a short period of time is).

And what the effect of including 2017 is, that is still unknown. It could very well be, that including 2017 would make the trend-rate (2006-2017) go downward.

This is all just stats, there's no physics. Physics obviously suggests the ice is going to melt; the debate is merely about how fast.

But we won't find that out by looking on time-periods so short, that the trend-rate is so uncertain, that it could be anything, from growing to melting like hell.

And that is even more true, when other parameters, like ice volume, were still decreasing strongly in that period of time and that makes it even more probable, that the slower ice/area decrease in that 10-year-period is just a random fluctuation (i.e. that is was just weather that led to those years having more ice at the minimum, and not a climatic change). And weather and climate are still two different things.

[Steven]

https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

This is two years old; it'd be interesting to see with 1-2 years of extra data.

Here is an update of that graph for annual average extent, with data up to July 2017:




I used annual averages from August to July.  So the last data point is Aug 2016 to July 2017.

Note that Tamino used annual averages from October to September, so the values in his graph are somewhat different from mine.  Moreover he used data from Oct 1978 onward whereas I started with Aug 1979.

I used this tool to calculate the piecewise linear fit.  The algorithm finds two change-points (where the slope changes): one near 2002 and another one near 2006.

Alternatively, the calculation could be done with only a single change-point.  In that case the change-point is near 1998 and the graph would look like this: http://i.imgur.com/SgtlXrE.png.

[magnamentis]

the terms:

1) TREND

2) SHORTTERM

contradict each other, even though all kind of thinking is welcome and allowed it would not even spend a second to read anything from short periods in a graph. value is close to zero on the positive side while all the discussions it often is causing makes it inefficient at best IMO.

nobody is meant, this is meant to be a general statement to consider for those who do like to use their resources in time and energy efficiently

[Shared Humanity]

https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

This is two years old; it'd be interesting to see with 1-2 years of extra data.

Here is an update of that graph for annual average extent, with data up to July 2017:




I used annual averages from August to July.  So the last data point is Aug 2016 to July 2017.

Note that Tamino used annual averages from October to September, so the values in his graph are somewhat different from mine.  Moreover he used data from Oct 1978 onward whereas I started with Aug 1979.

I used this tool to calculate the piecewise linear fit.  The algorithm finds two change-points (where the slope changes): one near 2002 and another one near 2006.

Alternatively, the calculation could be done with only a single change-point.  In that case the change-point is near 1998 and the graph would look like this: http://i.imgur.com/SgtlXrE.png.

Nice chart. Another interesting way to capture trends.

[Pavel]

What is the Laptev bite? Is it the same as "Великая Сибирская полынья" ("The Great Siberian polynya") or what?

[Jim Hunt]

What is the Laptev bite?

The term was coined a few years ago now. It refers to open water in the CAB north of the Laptev Sea:

http://neven1.typepad.com/blog/2011/09/some-more-flash-melting.html

[Pavel]

Thanks Jim Hunt. So the Laptev bite is even more Great than "The great Siberian polynya" - the polynya that usually opens near New Siberian islands

[gerontocrat]

Stupid questions that have nothing to do with Arctic Sea Ice.

I am currently an ASIF citizen. I like being a citizen.
But if I keep on posting I will become "middle class".

Will that make me a Trump supporter ?
If I delete a load of my old posts will that keep me as a citizen? (some of those early posts are embarassingly full of ignorance).

[Neven]

As long as it doesn't say 'Goldman Sachs employee', you should be fine. 

[numerobis]

I'd guess that if tamino threw the new data in, he'd find increased support for the proposition that trend is negative, and reduced support for the proposition that the new trend is zero.

That is what I showed in my graphic.

the terms:

1) TREND

2) SHORTTERM

contradict each other,...

You both are arguing that throwing away most of the data and doing very short-term trends is silly, which of course is true. This is indeed not what tamino argues.

Tamino's analysis uses all the data, and finds support for the claim that on some metrics, the rate of decline in Arctic ice is not linear. You do see it speed up significantly for a few years last decade, then slow down (but still, as Steven shows, down). You see that either with a smooth or with a piecewise linear fit.

The critical assumption that tamino makes is that his non-linear fit should be continuous. Implicitly, if you're computing short-term trends by throwing data away, you allow the trend you're calculating to be discontinuous. That assumption of continuity is the key difference between his analysis and the bad analysis that deconstruct and magnamentis are arguing against.

On the flip side, if you insist that there must be one single linear trend line through the data, you implicitly insist that there's no possibility for the rate of change to either accelerate or decelerate. I'm sure you both disagree with that assumption in the long term (because ice hasn't been melting continuously forever, and because ice can't melt once there's no ice left). Tamino shows you have good reason to disagree with it even from data just in the satellite era.

More recently he's been doing the same analysis with sea level rise, showing that it's also not been a straight line -- but over a longer term. And before his 2015 post about sea ice he was doing the same analysis on temperatures, notably using it to argue that actually there was no pause at all.

[greatdying2]

Question #1: Is there a way to block comments from specific users, and if so how?

Question #2: What thread do stupid questions like #1 belong in?

Thanks.

[oren]

Question #2: What thread do stupid questions like #1 belong in?

I'd say in "The forum" section. Find an existing thread or start a new one.
https://forum.arctic-sea-ice.net/index.php/board,22.0.html

[greatdying2]

Already looked there. Can't find a thread with a posting this year that seems appropriate. And I don't like starting threads just to ask a question.

[Neven]

Yeah, the topic where this is discussed, is buried on page 2 of the Forum board. But here's the solution:

If you view your Profile, there's an option for "Buddies/Ignore List" under Modify Profile. Not the most obvious place, true.

[greatdying2]

Thanks Oren and Neven.

[Pavel]

What is the Garlic Press somewhere in CAA? I still don't get it and couldn't find the answer myself

[ghoti]

What is the Garlic Press somewhere in CAA? I still don't get it and couldn't find the answer myself

The straits between the northern islands where the old ice gets squeezed through once the more southern ice melts out each melt season. Animated gifs of the ice movement are reminiscent of garlic being squeezed through a press.

[Pavel]

Thanks ghoti

[Gray-Wolf]

I'm struggling to find a NSIDC EMail response to a query on the 15% cut off for extent/Area? I think it was raised at the back end of last year by one of our better known posters but my 'searches' are not pulling up the exchange?

I seem to recall NSIDC accepting that the measure was good when it was only dealing with peripheral ice but now, with such a dispensed pack, the measure leads to a positive skew on the numbers?

Helllppp! I'm being trolled and I know a copy of the exchange will end the debate but also secure the reputation of this forum as a 'credible' place for knowledge , learning and growth.
Ta in advance!
Ian.

[crandles]

Not sure if it might have been

Sea Ice Index V1 applied this 15% ice concentration threshold twice when computing the monthly average gridded fields. The threshold was applied first to the daily gridded concentration; any grid cell with a concentration less than 15% was set to zero. After the monthly average of those daily grids was determined, the 15% threshold was applied again to define the outer limit of that month's ice. Area and extent data values were calculated from this monthly field. Applying the threshold twice made these values smaller than they would have been with the threshold only applied once. This was updated in V2 so that the threshold is only applied to the monthly data after the gridded average has been computed from the daily data.

from
http://nsidc.org/data/docs/noaa/g02135_seaice_index/#jul-2016

Found above when looking for something different:

The monthly data was using 15% for the whole month so that with more mobile ice there was more cases of some ice being in one location for several days then another location for several days such that both locations passed the 15% threshold.
I thought this was mentioned in an sea ice news and analysis, with suggestion they were considering making a change but I can't find that now.

[Wipneus]

I'm struggling to find a NSIDC EMail response to a query on the 15% cut off for extent/Area? I think it was raised at the back end of last year by one of our better known posters but my 'searches' are not pulling up the exchange?

I seem to recall NSIDC accepting that the measure was good when it was only dealing with peripheral ice but now, with such a dispensed pack, the measure leads to a positive skew on the numbers?

I am not sure, are you talking about this?
http://forum.arctic-sea-ice.net/index.php/topic,1837.msg109059.html#msg109059

[Gray-Wolf]

Thanks for the effort chaps but I do not think this is what I'm after?

I recall it being an actual e Mail response to a question as to whether the current 15% cut off was fit for purpose after we saw the kind of dispersion across the central pack last Min ( 2016)?

I seem to recall the chappie saying they were aware that this measure was not performing well with inner pack ice levels as the measure was devised to deal with the ice edge ( before the notion of swathes of open water between floes in the middle of the pack was a thing?).

I shall continue as I know it was a question that was asked of them in the midst of a debate about just how low last years extent had got when we compared just how 'open' the pack was compared to the other years it was lined up against?

Thanks again, I knew the crew wouldn't leave me hanging!!!

EDIT: Have fired a note off to NSIDC myself regarding the continued use of the measure over the coming , lower ice , years. I'll re-post once I have their answers!

[crandles]

Wip's answer leads to this (presumably an email) on the blog

Al Rodger wrote

And with all that, NSIDC inform me:-
“We have received similar questions in the recent past about our December numbers, and the science leads have decided to switch the way in which the averaging is completed. The current method is really just a legacy way of doing things as the dataset's original intended purpose was to simply produce coarse resolution figures (c.a. 2007) on a monthly interval for our site. The dataset is now clearly the most popular product we have due to our blog-style publication and thus changes will be made after considering any impact to the community.“

[Anne]

Does anyone have a good elevator pitch for sceptics (assuming anything would sway them anyway)?
Scientists outside the sphere are the stubbornest, IME. 

[CalamityCountdown]

Is the smoke from wildfires having a meaningful and/or measurable impact on the 2017 arctic sea ice melt season?

In a Robert Scribbler 2015 post, he discussed both the positive and negative feedback that can come from wildfires due to "Lofting large amounts of brown carbon into the Jet Stream level of the atmosphere is an amplifying feedback to human-caused warming. One occurring in addition to the added rate of carbon release generated by these wildfires as well as to a transient negative feedback coming from generating thick, low level clouds, that block out sunlight."

I would not be surprised to learn that the impact of a season with extensive wildfires is a negative short term impact on sea ice extent due to blocked sunlight, but conversely, with a multi year impact of a positive feedback due to: 1) dark snow and 2) carbon released into the upper atmosphere
https://robertscribbler.com/2015/07/13/wildfire-smoke-over-north-pole-web-cam-shows-melt-ponds-beneath-dark-haze/
https://www.nasa.gov/feature/langley/smoke-from-wildfires-can-have-lasting-climate-impact

[solartim27]

Does anyone have a good elevator pitch for sceptics

Check these out:
https://skepticalscience.com
https://climatecrocks.com
https://climatecrocks.com/2015/02/02/new-series-climate-change-the-elevator-pitch/

[CalamityCountdown]

Does anyone have a good elevator pitch for sceptics

I took a shot at that question in this blog post:
Probability Only 0.7 Percent of Record Global Temperatures In 3 Consecutive Years
http://calamitycountdown.blogspot.com/2017/08/probability-only-07-percent-of-record.html

[mdoliner]

Heat goes from hot to cold. In the arctic this happens through currents, winds, and insolation. What  change does the Greenhouse effect have on each. Are the changes in each, in terms of heat transported, comparable? Or is one an order of magnitude more important than another?

Second question: If the weather we have seen in the arctic the last two years becomes the climate, insolation will decline, but so will radiation from the arctic back out into space. What would be the net effect?

[Anne]

Thanks, solartim27 and CalamityCountdown. I sometimes need to give an instant response to fuckwittery and it can be hard to know where to start.
One of my lines is "It's global climate change, not <insert villlage name> climate change."

[Anne]

Erm, it occurs to me that my stupid question isn't specifically Arctic and maybe someone should start a Stupid Questions thread on The Rest forum. 

[Dharma Rupa]

I hear about vertical wind shear with respect to hurricanes, and it seems to me that the vertical motion of air is rather important to our understanding of what is going on in the Arctic.  I was wondering if there was anything similar to what nullschool does with displaying wind, but up and down rather than east and west.  This is generally the Hadley Cell and friends, but I'm interested in near real-time, not theory.

[gerontocrat]

Hullo Dharma Rupa - wind shear. Verical wind shear is not actual movement of air vertically but the difference in wind speed and or direction at different heights in the atmosphere. Suggest you go to Wikipedia for explanations well above my pay grade.

[Dharma Rupa]

Hullo Dharma Rupa - wind shear. Verical wind shear is not actual movement of air vertically but the difference in wind speed and or direction at different heights in the atmosphere. Suggest you go to Wikipedia for explanations well above my pay grade.

OK, but it is still vertical movement of the air over large regions with which I am interested,  Is there anything that displays that fairly well?  I know that lows tend to fill in and highs tend to empty, but with all the things going on at different levels in the atmosphere looking at cyclones and anti-cyclones doesn't really tell me where the air is coming from and going to.  That only tells me where the air is spinning at.

[jai mitchell]

great noaa article on vertical wind shear and its impacts on hurricanes.  The projected increase in this negative force that suppresses hurricane formation within a warming world is one of the reasons many models predict fewer total hurricanes but stronger ones when they do form.

http://www.aoml.noaa.gov/keynotes/keynotes_0715_windshear.html

[Adam Ash]

Given hurricane's intense circular motion, do they contribute much to equator-pole energy transfer? 

From Hansen's Storms of our Children papers, obviously there is the anticipation of some storms which will produce the very long fetches required to get sea states that will lift rocks weighing many tonnes to hundreds of metres inland.   I doubt that hurricanes would be persistent enough to achieve that.  So are we looking at some form of massive persistent atmospheric cell formation which touches down at sea level to create the requisite storminess?

[Forest Dweller]

What i noticed with Maria was some high speed winds crossing the equator south int he jet stream.

[Dharma Rupa]

The clouds in the winter block heat from radiating into space.

That brings up some interesting questions about the relative importance of the different greenhouse effects of H2O, re-radiation, and enthalpy; which I think I shall bring up in the Stupid Questions thread.

OK....What is the major current effective contribution of H2O to Arctic warming during Polar Night?

Is it the cloudy effect reducing total longwave radiation?  Or is it the water vapor restraining cooling because there is a lot of open water?

Actually.....Is it more cloudy in Winter than it used to be?   I know it is more humid.

[Adam Ash]

Re increased cloudiness, this from the now redundant 2017 melting season thread...

The chart also shows a distinct cooling of summer months (May thru August), beginning in 2013.

Yes, this is due to the global rise of water vapor (and other greenhouse gases). Seasonal changes are going to diminish within the blanket of GHGs. At some point, and we don't know when, it even reaches a level of equalization because of the shielding effects. Less heat is getting in, but the heat energy that does get in, stays there and spreads out evenly globally, regardless of lower layer content. This is best seen with this correlation: https://www.facebook.com/photo.php?fbid=10155019017687201&l=59fe6bcf60

To which I asked... 
That sounds ominous!  So are you saying, Liefde, that - with smaller seasonal variation under a thicker GHG blanket - in the summer at each pole it will be cooler but (probably) above freezing point while in winter each pole will be warmer.  So slightly slower summer melt (tho it is melting anyway already) but potentially fewer freezing-degree-days.  All of this adding to the general warming trend experienced already. 
Right?

[Daniel B.]

Re increased cloudiness, this from the now redundant 2017 melting season thread...

The chart also shows a distinct cooling of summer months (May thru August), beginning in 2013.

Yes, this is due to the global rise of water vapor (and other greenhouse gases). Seasonal changes are going to diminish within the blanket of GHGs. At some point, and we don't know when, it even reaches a level of equalization because of the shielding effects. Less heat is getting in, but the heat energy that does get in, stays there and spreads out evenly globally, regardless of lower layer content. This is best seen with this correlation: https://www.facebook.com/photo.php?fbid=10155019017687201&l=59fe6bcf60

To which I asked... 
That sounds ominous!  So are you saying, Liefde, that - with smaller seasonal variation under a thicker GHG blanket - in the summer at each pole it will be cooler but (probably) above freezing point while in winter each pole will be warmer.  So slightly slower summer melt (tho it is melting anyway already) but potentially fewer freezing-degree-days.  All of this adding to the general warming trend experienced already. 
Right?

Sounds similar to what is happening in the mid-latitudes.

[sidd]

I think winter cloudiness at the poles, especially north pole, is very important. If I had the time, that's something i would watch closely, since winter cloud is a huge brake on winter cooldown.

sidd

[Daniel B.]

I think winter cloudiness at the poles, especially north pole, is very important. If I had the time, that's something i would watch closely, since winter cloud is a huge brake on winter cooldown.

sidd

Sidd,
I think the cloud cover has a greater effect on the sea ice in the summer, during the 24-hour days.  There is no incoming solar radiation to block during the winter at the north pole.  Just looking over the past decade, the maximum sea ice extend this year was 4% lower than the average, while the minimum was 3% higher.  This does support the cloud theory.  However, we need significantly more data, before we can come to any real conclusion.