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In Which Decade will the Arctic Sea Ice Extent experience its LAST September with a minimum ABOVE 1X10^6 km^2?

2020-2030
67 (48.9%)
2030-2040
36 (26.3%)
2040-2050
13 (9.5%)
2050-2060
6 (4.4%)
2060-2070
6 (4.4%)
2070-2080
0 (0%)
2080-2090
0 (0%)
> 2090
9 (6.6%)

Total Members Voted: 129

Voting closed: May 29, 2017, 07:46:52 PM

Author Topic: Poll: When Will the Arctic Experience THE LAST Year With Sept. Sea Ice Extent  (Read 34071 times)

jai mitchell

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In the absence of geoengineering activities, when do you think the Arctic will experience its LAST year with a Sept minimum sea ice extent ABOVE 1 million square km? 

This is looking at human lifetime scales, not century or epoch scales so no, it won't be the absolute last unless the sun explodes.  Just global warming impacts, not nuclear winter etc.
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AndrewB

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What geoengineering activities?  ???

Just kidding...

Anyways, just voted 2020-2030, and just noticed I was the first and only to have done so, so far.  :P

Edit: Hmmm, the 2020-2030 category has suddenly become the "popular" answer. Can we have a 2010-2020 category? Can I change my vote?  ;D
« Last Edit: April 14, 2017, 08:56:21 PM by AndrewB »

seaicesailor

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This one calls for very wild speculation.
Since ASI (Artificial Super Intelligence) is predicted to emerge around 2050-2060, and I optimistically believe that there will be some ocassional summers with enough ASI (Arctic sea ice) left until then, my guess is this entity will fix the AGW problem in a couple of years while deciding what to do with us terrified humans, whether remove us from existence or preserve us with some genetic modding so as to not destroy own own planet while the entity self replicates and populates the galaxy after discovering interstellar travel in a picosecond of relax.
https://medium.com/ai-revolution/when-will-the-first-machine-become-superintelligent-ae5a6f128503
http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html

So I go with >2090

Jim Williams

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This year....

I don't really know when it will happen, but I am convinced that when the flip happens it will be sudden and complete.  Depending upon what time of year essentially ice free happens it will be the same year as ice free all year.

I define essentially ice free as the DMI 80N jumping a few degrees above 0C for several days running.

Cid_Yama

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You need a before 2020 choice.  That's what I vote.
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gerontocrat

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I vote 2030-2040 (even though that means my chances of being alive to collect the prize are not so good, having not yet found the elixir of life).
"Para a Causa do Povo a Luta Continua!"
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AndrewB

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I vote 2030-2040 (even though that means my chances of being alive to collect the prize are not so good, having not yet found the elixir of life).
The prize is 1km3 of Arctic sea ice, for your refreshment pleasure in a very warm world. Delivery not guaranteed in September, though.  ;)

jai mitchell

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my pick was 2043
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AndrewB

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my pick was 2043

Well, the correct answer is of course, that the Arctic will experience ITS LAST year with September sea ice minimum extent ABOVE 1 million km2 the year BEFORE it experiences ITS FIRST year with September sea ice minimum extent BELOW 1 million km2, or do you expect September sea ice extent to keep BOUNCING BELOW AND ABOVE 1 million km2 for a few years?
'Cos I don't.  :)

Oh, and I was just thinking: once the shit hits the fan Arctic sea ice is gone for good (presumably, that will be in 2044?), the ASIF will have to change its name and URL, but it can still be called ASIF for ANTARCTIC Sea Ice Forum, so people can continue debating about the weather and other related issues, and the old timers from 2017 can reminisce about "the good old cooler times" ...
« Last Edit: April 14, 2017, 10:20:39 PM by AndrewB »

jai mitchell

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I was being very conservative  8)
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AndrewB

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I was being very conservative  8)
For one second I thought you were a "lukewarmist", and I was ready to pull the trigger and torch you!  :P

oren

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my pick was 2043
Well, the correct answer is of course, that the Arctic will experience ITS LAST year with September sea ice minimum extent ABOVE 1 million km2 the year BEFORE it experiences ITS FIRST year with September sea ice minimum extent BELOW 1 million km2, or do you expect September sea ice extent to keep BOUNCING BELOW AND ABOVE 1 million km2 for a few years?
'Cos I don't.  :)
This "bouncing" as you put it is quite probable.

DrTskoul

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my pick was 2043
Well, the correct answer is of course, that the Arctic will experience ITS LAST year with September sea ice minimum extent ABOVE 1 million km2 the year BEFORE it experiences ITS FIRST year with September sea ice minimum extent BELOW 1 million km2, or do you expect September sea ice extent to keep BOUNCING BELOW AND ABOVE 1 million km2 for a few years?
'Cos I don't.  :)
This "bouncing" as you put it is quite probable.

It is not going to "zero" and then poof no more internal variability.

Pi26

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Before 2019. And were the previous generations of most of our geoengineers (and someone hundret other different "actors" in "our" "modern" world) farmer kids less than two centuries before?



« Last Edit: April 15, 2017, 01:12:47 AM by Pi26 »

epiphyte

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Eventually, the sun will dwindle to a cinder. Of course, Earth will have been inside the photosphere of a red giant for a billion years or so by then, so the ice may be 1mm thick on top of bare rock.

Whatever, My guess is ~ 3,500,000,000 AD

...and no-one will be around to prove me wrong :)

Edit - just noticed the human timescale qualification on the question. Dick Cheney will probably be the last one to go; I sometimes wonder if he might possibly be the pre-incarnation of Beelzebub in the next iteration of the universe. So my answer still stands :)
« Last Edit: April 15, 2017, 07:13:49 AM by epiphyte »

Darvince

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If you're talking about that far into the future, then you're talking about compounds of silicon as "sea ice" on a lava world (but with no atmosphere to enable global warming).

Anyway, I voted 2030-2040, but that does not mean I think that's when the *first* essentially ice-free Arctic will occur. And I also disagree with a few posters here that there is absolutely no way ice will regrow across the Arctic during the following fall and winter of the first essentially ice-free Arctic. Ice does spontaneously generate away from existing pack ice sometimes, and much more often in rivers and lakes.

AndrewB

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my pick was 2043
Well, the correct answer is of course, that the Arctic will experience ITS LAST year with September sea ice minimum extent ABOVE 1 million km2 the year BEFORE it experiences ITS FIRST year with September sea ice minimum extent BELOW 1 million km2, or do you expect September sea ice extent to keep BOUNCING BELOW AND ABOVE 1 million km2 for a few years?
'Cos I don't.  :)
This "bouncing" as you put it is quite probable.
Hi oren,
Seriously, no, I don't think so. There will be probably some "noise" just above the zero ice volume limit, but no "bouncing below and above 1 million km2 for a few years". That is not very probable.
Why do I say that? Because the Arctic climate system will have flipped into a new state, with positive feedbacks (albedo, water vapor, warm moist air from lower latitudes, waves, etc) accelerating the demise of sea ice not just in September but in all the other months.
In any case, not many years to go until I am proved right or wrong.

AndrewB

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my pick was 2043
Well, the correct answer is of course, that the Arctic will experience ITS LAST year with September sea ice minimum extent ABOVE 1 million km2 the year BEFORE it experiences ITS FIRST year with September sea ice minimum extent BELOW 1 million km2, or do you expect September sea ice extent to keep BOUNCING BELOW AND ABOVE 1 million km2 for a few years?
'Cos I don't.  :)
This "bouncing" as you put it is quite probable.

It is not going to "zero" and then poof no more internal variability.

That is correct. But neither is the energy imbalance forcing (AGW) going to disappear, actually we all know it is going to continue to increase, over the coming decades.

You can choose to believe that natural variability has accounted for 30~50% of the observed Arctic sea ice melt since 1979, and that it will suddenly flip in the reverse direction and help Arctic sea ice bounce back - or you can choose to accept simple extrapolation from existing data.

I have already posted all the charts anybody could care for, but just to mention them again: global average temperature datasets, Keeling Curve, and PIOMAS. None of them indicate the possibility of "natural variability" suddenly reversing and making AGW and all its effects simply "go away". On the contrary. They all indicate positive feedback mechanisms are accelerating global warming and worsening its effects.

Somebody in another thread was blaming me for using an exponential function in the trendline fitting PIOMAS. This is so absurd, it reminds me of Galileo being accused of heresy, forced to recant and spending years in house arrest, for claiming that it was the Earth that orbited around the Sun, and not the other way around. Perhaps we should forbid all climate scientists from using the exponential function from now on, and ban the mathematical function because it tells of the impending catastrophe that nobody wants to recognize is our own doing?


Peter Ellis

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Somebody in another thread was blaming me for using an exponential function in the trendline fitting PIOMAS. This is so absurd, it reminds me of Galileo being accused of heresy, forced to recant and spending years in house arrest, for claiming that it was the Earth that orbited around the Sun, and not the other way around. Perhaps we should forbid all climate scientists from using the exponential function from now on, and ban the mathematical function because it tells of the impending catastrophe that nobody wants to recognize is our own doing?

This is one of the least mathematically literate and most histrionic paragraphs I've ever seen, on this forum or WUWT.  Please stop, you're embarassing yourself and all of us. 

Several people in this thread seem to be drawing a distinction between "modellers" and other types of scientific analysis.  That's a false distinction. Your own exponential extrapolation IS a model. It's a naive and unsophisticated model that's not based in any empirical understanding of the underlying processes, sure, but it's a model nevertheless.  EVERY mathematical description of the system is a model.  That's what models are.

AndrewB

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This is one of the least mathematically literate and most histrionic paragraphs...
...
EVERY mathematical description of the system is a model.  That's what models are.

No. Here is a partial cure for your ignorance:
https://en.wikipedia.org/wiki/Climate_model

Climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate.

All climate models take account of incoming energy from the sun as short wave electromagnetic radiation, chiefly visible and short-wave (near) infrared, as well as outgoing long wave (far) infrared electromagnetic. Any imbalance results in a change in temperature.

Models vary in complexity:

    A simple radiant heat transfer model treats the earth as a single point and averages outgoing energy
    This can be expanded vertically (radiative-convective models) and/or horizontally
    Finally, (coupled) atmosphere–ocean–sea ice global climate models solve the full equations for mass and energy transfer and radiant exchange.
    Box models can treat flows across and within ocean basins.
    Other types of modelling can be interlinked, such as land use, allowing researchers to predict the interaction between climate and ecosystems.



DrTskoul

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Somebody in another thread was blaming me for using an exponential function in the trendline fitting PIOMAS. This is so absurd, it reminds me of Galileo being accused of heresy, forced to recant and spending years in house arrest, for claiming that it was the Earth that orbited around the Sun, and not the other way around. Perhaps we should forbid all climate scientists from using the exponential function from now on, and ban the mathematical function because it tells of the impending catastrophe that nobody wants to recognize is our own doing?

This is one of the least mathematically literate and most histrionic paragraphs I've ever seen, on this forum or WUWT.  Please stop, you're embarassing yourself and all of us. 

Several people in this thread seem to be drawing a distinction between "modellers" and other types of scientific analysis.  That's a false distinction. Your own exponential extrapolation IS a model. It's a naive and unsophisticated model that's not based in any empirical understanding of the underlying processes, sure, but it's a model nevertheless.  EVERY mathematical description of the system is a model.  That's what models are.
+1

crandles

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Somebody in another thread was blaming me for using an exponential function in the trendline fitting PIOMAS. This is so absurd, it reminds me of Galileo ......

Not sure if this is referring to my post:

and confirms the exponential trend.

How many fails are needed before you decide gompertz is better trend than exponential?

I think 2017 will be exceptionally low but is this an outlier due to FDD outlier or has FDD stepped down or new trend or ... ?

Anyway, one potentially outlier year shouldn't be seen as confirming a trend that has been doing badly over the last several years.

If it is then
I think there is a difference between 'blaming you for using exponential' which would be harsh (I think you can use it as a model if you wish but don't consider it to have been confirmed) and taking you to task for seeing one year as **confirming** the trend is exponential.

If your answer to the question 'how many fails does it take?', is answered by whining about persecution of Galileo, then I might wonder if this means it doesn't matter how many fails there are you will still believe in an exponential trend. If this is the case, it would seem deeply embedded in belief and well past the point of not taking account of scientific evidence.

jai mitchell

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When the data is highly variable, assigning future projections to either exponential or gompertz trends is simply a matter of confirmation bias.

It is much more likely that the 2013/2014 anomalous years were black swan events that will not be duplicated.  The Ridiculously Resilient Ridge and the massive and persistent Negative PNA index values for that period stand distinctly apart from the historic trend.
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AndrewB

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Somebody in another thread was blaming me for using an exponential function in the trendline fitting PIOMAS. This is so absurd, it reminds me of Galileo ......

Not sure if this is referring to my post:

...

No. I am referring to this post:
Quote from: seaicesailor
Funny that use a model that suits your preconceived conclusion (zero volume), given one of the arguments you use to discredit that paper over the other thread (to use a model that suits a preconceived conclusion).

And here is my reply to seaicesailor:
Quote
Three things, seaicesailor:
1. You are confusing a climate model with a simple trendline fit. That they are completely different mathematical tools is an obvious fact that seems to have escaped you.
2. I am not the author of the charts with the trendlines above. Wipneus is. That the trendline crosses the X axis at some point in the near future is not a "preconceived conclusion", it's a mathematical evidence, as in 2+2=4.
3. You are distorting what I wrote "over the other thread". Again, a scientist should use whatever instrument/tool allows her/him to gather the best possible data. And models are an essential tool for scientists, not only in climate science, but in many other areas. I already countered this distortion of what I wrote "over the other thread", so please refer to my comments there for the details, as I can't be bothered with repeating myself here (yet again).

Obviously I have to repeat myself here and remind some people of the difference between a chart that includes an exponential trendline, and a climate model.

It appears that merely by pointing out that the exponential trendline in the chart (by Wipneus) crosses the X axis at some point in the near future (meaning the trendline indicates we'll reach zero Arctic sea ice volume around 2022, +/- 2 years), I have committed heresy.

And here is the chart in question, which some people appear to think is extremely controversial, but is relevant to the present thread/poll.

(I should add: the chart and trendline is by Wipneus and I took the liberty of adding the blue pixels to highlight the expected September 2017 minimum PIOMAS; the PIOMAS data we have up to April this year more or less confirms the exponential trendline and the expected 2017 PIOMAS range, confirmation of this in 6 months time)

One last note: Wipneus has more fabulous data visualizations on his website here https://sites.google.com/site/arctischepinguin/home
« Last Edit: April 15, 2017, 05:05:47 PM by AndrewB »

gerontocrat

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If one changes the y-axis from km3 to stored cold, then one can extrapolate below zero. Below zero being acquired energy and increasing in the future. From that then in 3d one can add the entire year to model how additional energy acquired in summer affects winter freezing.

Then Gompertz can go take a hike.
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AndrewB

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If one changes the y-axis from km3 to stored cold, then one can extrapolate below zero. Below zero being acquired energy and increasing in the future. From that then in 3d one can add the entire year to model how additional energy acquired in summer affects winter freezing.

Then Gompertz can go take a hike.

The choice of a Gompertz, linear, exponential or other function fit is really a technical choice. Each function has a specific significance but the real thing is the data that is plotted. This is why Wipneus actually has a chart of PIOMAS with the various trendlines plotted simultaneously. One can easily see that apart from the linear fit, all the other trendlines are a close fit to the data until more or less 2017, and Gompertz starts to slow down only next year or so, with all the other trendlines accelerating to zero.



gerontocrat

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I was :-
- attempting to reduce the heat generated in this thread,
- flying a kite about impact of reducing km3 in summer on autumn / winter refreezing.

You say exponential , I say Gompertz, they say linear ,
Let's call the whole thing off.
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RoxTheGeologist

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Several people in this thread seem to be drawing a distinction between "modellers" and other types of scientific analysis.  That's a false distinction. Your own exponential extrapolation IS a model. It's a naive and unsophisticated model that's not based in any empirical understanding of the underlying processes, sure, but it's a model nevertheless.  EVERY mathematical description of the system is a model.  That's what models are.


This is entirely accurate: There are more or less complicated ways to fit data. An exponential function is a model. In this case it is a exponential relationship between year and SIE. Of course this has little meaning. If you go far enough back, or far enough forward the model breaks down. It's good for illustrating to the scientifically naive how bad the situation is in the Arctic.

The next step in building a model is look at what we know about each year and take parameters that we think might affect SIE, and build something a little more sophisticated; try to move the model from a simple correlative data fit over a narrow range of years towards a historically accurate predictive model that would allow us to make real world decisions regarding emissions and where and where not to buy real estate.

A think a more analogous historical description is fitting a curve is like finding canals on Mars. One is looking though a rather poorly focused lens. Its worth reading Popper if one is struggling to understand scientific method.





AndrewB

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I was :-
- attempting to reduce the heat generated in this thread,
- flying a kite about impact of reducing km3 in summer on autumn / winter refreezing.

You say exponential , I say Gompertz, they say linear ,
Let's call the whole thing off.

Ah, OK, it was a geoengineering initiative.  ;)

AndrewB

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This is entirely accurate: There are more or less complicated ways to fit data. An exponential function is a model. In this case it is a exponential relationship between year and SIE.

Not SIE, the chart plots PIOMAS (volume).

Quote from: RoxTheGeologist
Of course this has little meaning. If you go far enough back, or far enough forward the model breaks down. It's good for illustrating to the scientifically naive how bad the situation is in the Arctic.

Why just to the "scientifically naive"? It's a mathematical tool, just like a pen is a tool for writing. You can use a pen to write children stories or to write a philosophy book.

Quote from: RoxTheGeologist
The next step in building a model is ...

I think there is a thread about climate models somewhere here in this forum where you could propose your idea that an exponential function is actually a very simple climate model, and you could probably get some traction out of your argument.

But let's keep things in perspective, shall we? A PIOMAS chart with an exponential trendline fit is to a climate model like a sparkplug is to a Mercedes S600.

Peter Ellis

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But let's keep things in perspective, shall we? A PIOMAS chart with an exponential trendline fit is to a climate model like a sparkplug is to a Mercedes S600.

Quite so.  An exponential trend is a simplistic, naive mathematical model with no direct connection to the many many years of accumulated scientific knowledge of Earth's climate system.  Which is why I'm so baffled that you prefer it.

AndrewB

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...
Quite so.  An exponential trend is a simplistic, naive mathematical model with no direct connection to the many many years of accumulated scientific knowledge of Earth's climate system.  Which is why I'm so baffled that you prefer it.

Again distorting what I wrote...

1) Trendline fitting is a mathematical/statistical tool. As the name implies, it extracts a trend from noisy data. There is nothing "naive" or "simplistic" about it. And no, it's not a climate model, and the exponential function is not a climate model either.

2) A climate model: see the Wikipedia definition which, while not perfect, is good enough. Let's stick to it and not try to redefine the meaning of the term.

3) "Which is why I'm so baffled that you prefer it." I have no idea whatsoever what you could mean by that. But if you want to further explain your point of view, may I suggest you start a new thread?
« Last Edit: April 17, 2017, 11:25:34 AM by AndrewB »

AbruptSLR

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I voted in the 2040 to 2050 range because we are talking about the year with the LAST Sept. Arctic Sea Ice Extent above 1 million sq km.  My logic for selecting this range is as follows:

- I believe that as soon as Hansen's ice-climate positive feedback mechanism kicks in for real (i.e. when the Byrd Subglacial Basin, in West Antarctica collapses), the associated multi-decadal surge in planetary energy imbalance will push the Arctic Sea Ice over a tipping point.

- DeConto & Polland 2016 have indicated that the WAIS will begin to rapidly collapse before GMSTA reaches 2.7C (due to hydrofracturing & cliff failures of the marine glaciers), and the first image shows the timeframe assuming ECS = 3C.

- However, I believe that ECS = 4.5C which corresponds to the upper curve in the second attached image showing final GMSTA vs the equivalent atmospheric CO2 concentrations & by the end of 2017 I expect us to reach a CO2 eq. level of about 500 ppm which corresponds to a final (circa 2100) GMSTA of about 4C.

- However, as ECS responds logarithmically about two thirds of the final GMSTA will occur within 10-years.  This indicates that GMSTA may likely reach 2.7C by about 2028 (if ECS =4.5), and assuming that it takes about 15 years for Hansen's ice-climate mechanism to kick in give an approximate date of 2043 for the Last September above 1 million sq km of Arctic Sea Ice extent.
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jai mitchell

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just for the record:



ASLR:  very astute but you are neglecting aerosol forcing,  If we completely halt aerosol emissions in 2027 then I am likely to agree that 2028 will reach +2.7C but under current conditions, with moderate reductions in aerosol emissions, continued significant anthropogenic carbon emissions and rapid sea ice-albedo feedback, I still expect (conservatively) to move above +2C by 2036.
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icefisher

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I chose 2030-2040 because extent will become thin enough to be blown about by every passing storm.  Reliability?  Expect volume to displace extent as the best indicator of ice health between 2025-2030.  When ships start plowing through 10 cm. of ice cube arctic water without ice breaker assistance the end is near.   

DrTskoul

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...
Quite so.  An exponential trend is a simplistic, naive mathematical model with no direct connection to the many many years of accumulated scientific knowledge of Earth's climate system.  Which is why I'm so baffled that you prefer it.

Again distorting what I wrote...

1) Trendline fitting is a mathematical/statistical tool. As the name implies, it extracts a trend from noisy data. No, it's not a climate model, and the exponential function is not a climate model either.

2) A climate model: see the Wikipedia definition which, while not perfect, is good enough. Let's stick to it and not try to redefine the meaning of the term.

3) "Which is why I'm so baffled that you prefer it." I have no idea whatsoever what you could mean by that. But if you want to further explain your point of view, may I suggest you start a new thread?

An exponential assumes an ever increasing melt rate whule Gompetz assumes that after a spike the melt rate will reduce and approach a small number as we get to zero.  What do you think is more probable. All the easy to melt areas will melt first and the difficult to melt areas at the coldest spots if the Arctic will take longer.  Therefore an exponential is not possible. 

AbruptSLR

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ASLR:  very astute but you are neglecting aerosol forcing,  If we completely halt aerosol emissions in 2027 then I am likely to agree that 2028 will reach +2.7C but under current conditions, with moderate reductions in aerosol emissions, continued significant anthropogenic carbon emissions and rapid sea ice-albedo feedback, I still expect (conservatively) to move above +2C by 2036.

jai,

You may well be correct; however, the linked reference indicates that the remaining carbon budget from 2015 may be as low as 590 GtCO2; and as CO₂-e emissions are around 50GtCO2 (which exceeds RCP 8.5 50%CL), it is easy to see that assuming ECS is 3C we could readily exceed the 2C limit by around 2030, or if ECS is 4C then we could exceed 2.7C by around 2032 to 2035, if we continue on our current BAU pathway for another 16 to 19 years. 
 
Joeri Rogelj, Michiel Schaeffer, Pierre Friedlingstein, Nathan P. Gillett, Detlef P. van Vuuren, Keywan Riahi, Myles Allen & Reto Knutti (2016) "Differences between carbon budget estimates unravelled", Nature Climate Change, Volume: 6, Pages: 245–252, doi:10.1038/nclimate2868

http://www.nature.com/nclimate/journal/v6/n3/full/nclimate2868.html

However, I note that the estimate of exceeding 2.7C by 2032 to 2035, does consider lag-time after the carbon budget has been exceeded, but does not consider the risk of accelerating Arctic Amplification due the potential early seasonal loss of Arctic Sea Ice Extent, nor the fact that the GWP of methane is higher than the authors of the reference assume; so even considering aerosol impacts, it may be possible that GMSTA could reach 2.7C around 2028.

Best,
ASLR

Edit: According to NOAA the CO₂ -equiv at the end of 2015 was 485 ppm; however, if one assumes that the GWP100 for methane is 35 instead of 25 (as assumed by NOAA), then NOAA's calculated value for the CO2-eq for 2015 would be 518ppm.
« Last Edit: April 16, 2017, 01:55:44 AM by AbruptSLR »
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Pmt111500

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 ::) :o ??? :-\ Given the old ice is gone soonish, the equations of melt and freeze simplify and the correct answer to this maybe read in a letter I'm enclosing now to an envelope to be opened by the future generations... oops... correct that one... and which, if inaccurate will show the openers of the time-capsule what a fool I was... Oops... That might need a correction too.
« Last Edit: April 16, 2017, 11:02:26 AM by Pmt111500 »

AbruptSLR

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Seeing as I raised the topic of the influence of methane, the linked reference (with an open access pdf) presents a 2015 observation-based model findings of permafrost carbon fluxes when accounting for deep carbon deposits and thermokarst activity.  What I find to be particularly disturbing is the pulse of CH4 emissions circa 2050 from thermokarst lakes (TKLs) under RCP8.5, as indicated in the attached image.  I find this thermokarst lake CH4 emissions disturbing because the researchers' 2015 RCP 8.5 run did not consider the increase in Arctic rainfall that will occur as the sea ice extent retreats; thus the 2050 date likely errs (considerably) on the side of least drama:

Schneider von Deimling, T., Grosse, G., Strauss, J., Schirrmeister, L., Morgenstern, A., Schaphoff, S., Meinshausen, M., and Boike, J.: Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity, Biogeosciences, 12, 3469-3488, doi:10.5194/bg-12-3469-2015, 2015.

http://www.biogeosciences.net/12/3469/2015/bg-12-3469-2015.html
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Dr. Ding has just posted a reference to a paper (Armour et al 2011) that posits - based on model simulations - the total reversibility of the observed loss of Arctic sea ice*, if we just remove CO2 from the atmosphere as fast as we have added it (by what means is not specified, but refer to the "geoengineering activities" jai mitchell mentions above).

* >80% loss of September Arctic sea ice volume in < 40 years, according to Axel Schweiger, one of Dr. Ding's co-authors in the latest Ding et al paper on natural variability attribution.

Personally, I think anyone that voted anything other than 2020-2030 in the poll above is a denialist, consciously or not.

jai mitchell, you posted a link to a YouTube video of a Kevin Anderson interview during COP21. At 9 minutes there is his opinion on negative emissions (removal of CO2 from the atmosphere). Needless to say, I agree with Kevin Anderson on all the points he makes during that interview. Basically, relying on future negative emissions (for which the technology does NOT exist), or on a carbon budget (which we have exhausted a long time ago), or on "natural variability" that is supposed to bring a comeback of Arctic sea ice, are all distractions and wishful thinking.



This is the reality of CO2 atmospheric concentration, and there is no denying it:

« Last Edit: April 17, 2017, 12:24:05 PM by AndrewB »

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Personally, I think anyone that voted anything other than 2020-2030 in the poll above is a denialist, consciously or not.

There wasn't a 2017-2020 slot, so I didn't vote.

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2030 to 2040.

LAST year with that means a freak cold year/several that allow some ice to survive as a black swan event.

FIRST year could be this decade.

MORE YEARS THAN NOT might be the better metric.

jai mitchell

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Dr. Ding has just posted a reference to a paper (Armour et al 2011) that posits - based on model simulations - the total reversibility of the observed loss of Arctic sea ice*, if we just remove CO2 from the atmosphere as fast as we have added it (by what means is not specified, but refer to the "geoengineering activities" jai mitchell mentions above).

* >80% loss of September Arctic sea ice volume in < 40 years, according to Axel Schweiger, one of Dr. Ding's co-authors in the latest Ding et al paper on natural variability attribution.

Personally, I think anyone that voted anything other than 2020-2030 in the poll above is a denialist, consciously or not.

jai mitchell, you posted a link to a YouTube video of a Kevin Anderson interview during COP21. At 9 minutes there is his opinion on negative emissions (removal of CO2 from the atmosphere). Needless to say, I agree with Kevin Anderson on all the points he makes during that interview. Basically, relying on future negative emissions (for which the technology does NOT exist), or on a carbon budget (which we have exhausted a long time ago), or on "natural variability" that is supposed to bring a comeback of Arctic sea ice, are all distractions and wishful thinking.



This is the reality of CO2 atmospheric concentration, and there is no denying it:

Andrew

Negative emission technology does indeed exist, however I was referring to global atmospheric dimming as a geoengineering stopgap to 4C above.

The methods are: 1. reforestation, 2. agricultural practice shifts and 3. industrial processes that remove CO2 from the atmosphere.

reforestation and agricultural practices do not have the capability to remove CO2 fast enough so industrial activities must be engaged.  However there are chemical and technical processes for removing CO2 they do not exist are not currently in operation because we do not have a reimbursement mechanism to make them worthwhile.  I believe it would take a cost of carbon over $1,000 per metric tonne. 

It will take over 80 years to remove the CO2 needed to restore a stable climate regime.  and yes, the Sea ice will come back if we do. 

there is roughly a 20% chance per year, cumulative year-on-year over the next 5 years that we will have our first effective ice free September.
« Last Edit: April 17, 2017, 04:55:17 PM by jai mitchell »
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Quote
I was referring to global atmospheric dimming as a geoengineering stopgap to 4C above.

Global dimming.... nothing can go wrong with that

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http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50868/abstract

Quote
Global precipitation is reduced by around 4.5%, and significant reductions occur over monsoonal land regions: East Asia (6%), South Africa (5%), North America (7%), and South America (6%).
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Andrew

Negative emission technology does indeed exist, however I was referring to global atmospheric dimming as a geoengineering stopgap to 4C above.

The methods are: 1. reforestation, 2. agricultural practice shifts and 3. industrial processes that remove CO2 from the atmosphere.
...

Hi Jai,
According to Kevin Anderson, the reliance on negative emissions is a risk we are assuming in the name of future generations (and, if I may add, a cost we are leaving behind for future generations to pay for, just like the management of radioactive waste and the decommissioning of nuclear reactors).
Here is his relevant paper (free download PDF): http://smartstones.nl/wp-content/uploads/2016/12/Kevin-Anderson-2016.10.13-the-Trouble-with-Negative-Emissions-Science-2016.pdf
And a response and his response to the response: http://www.geoengineeringmonitor.org/2016/11/responses-to-the-trouble-with-negative-emissions/

"If we rely on these and they are not  deployed  or  are  unsuccessful  at  removing  CO2 from  the  atmosphere  at  the  levels  assumed,  society  will  be  locked  into  a  high-temperature pathway."

And in the response to the response:
"... we stand by our conclusion that given the breadth and depth of fundamental uncertainties associated with negative-emissions technologies, a program of timely and deep mitigation in line with 2°C budgets should assume that they will not be deployed at a large scale."

I guess the same objections or even more severe ones would apply to unproven geoengineering or global atmospheric dimming technologies.

I am surprised to see that I am even more pessimistic than you in relation to Arctic sea ice. I don't believe it is possible to avoid its demise, or bring it back on a human time scale, or that it will magically make a comeback because of some "natural variability".

I think we are already committed to the irreversible disappearance of Arctic sea ice and to CO2 atmospheric concentration levels above 450ppm, for the next couple of millennia at the very least, with all the changes to a new and unknown global climate state that these imply.

jai mitchell

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Andrew,

you are probably right.

the discussion about the pure-time discount rate for multi-generational accounting of the social cost of carbon assumes that future generations will have more technical and societal capability to alleviate these massive impacts.  In the event that the opposite is true, that the fight against societal collapse, adaptation AND the need to implement technical solutions to combat global carbon cycle feedbacks and reduce atmospheric CO2 to 350 ppmv will take more resource than is available would demand a NEGATIVE discount rate. 

but there is hope that a global climate 'pearl harbor' event will shift the global focus to address this global threat to humanity in the next 10 years, with a rational response. 

I understand your pessimism.
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I'm convinced the first year with Sept SIE less than 1m will also be the last. However, when will that be is much harder to answer. Before I emit my vote I want some time to see how this thin first year ice reacts to the melting season. It could very well be that the first and last <1m SIE happen this year.

However if it doesn't happen this year, maybe the Pacific and the Atlantic end their warm cycle, lowering atmospheric temperature and humidity. Maybe then that Arctic makes a recovery. If so, then the Arctic might be safe for maybe a decade or two.


I'll vote after I see more. So far it is not looking good.
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wili

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Andrew wrote: "...irreversible disappearance of Arctic sea ice..."

Well, in theory anyway, perhaps not completely irreversible:

https://scripps.ucsd.edu/news/research-highlight-arctic-sea-ice-loss-likely-be-reversible

Arctic Sea Ice Loss Likely To Be Reversible

I sure hope these guys are right. But personally, I too rather doubt that, once it's gone, we will ever see a recovery.
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I'm convinced the first year with Sept SIE less than 1m will also be the last. However, when will that be is much harder to answer. Before I emit my vote I want some time to see how this thin first year ice reacts to the melting season. It could very well be that the first and last <1m SIE happen this year.

However if it doesn't happen this year, maybe the Pacific and the Atlantic end their warm cycle, lowering atmospheric temperature and humidity. Maybe then that Arctic makes a recovery. If so, then the Arctic might be safe for maybe a decade or two.


I'll vote after I see more. So far it is not looking good.

I'll agree with this analysis.  Depending upon the time of year of melt-out the first year which has a point in time with no significant ice will also be the last year with significant ice for a very long time.  I'm inclined to include Winter as well as Summer in that, though with a bit less conviction.

I don't know when it will happen, but when it does happen it isn't going to care whether it is Summer or Winter and it isn't going to care about the following Winter a whole lot.

The permafrost will slow down the continents a bit, but it will not be all that long before they too will not have significant Winters.