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nukefix

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #400 on: April 14, 2017, 03:06:47 PM »

Eh...hmmm... what "physical" "stuff"?????

There a lot of variables you can use as a proxie for surface melting, ocean melting and so on, means fitting on physical base
I suppose one could run 500 instances of climate models for the next 50 years and use each of those runs to force PIOMAS. But the ocean currents would still be out of whack I guess. This shit is hard.

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #401 on: April 14, 2017, 05:12:42 PM »
unless you ask the right question you will never get the correct answer.

a patent observation, only recently verified by specific models tuned to look at the SO2 emission sea ice impact variation.

Ice free in summer is a colloquial term.  We all know what it means.

100 years is a goddamn joke.
« Last Edit: April 14, 2017, 07:30:58 PM by jai mitchell »
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DrTskoul

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #402 on: April 14, 2017, 05:27:13 PM »
Northern hemisphere temperatures should show the same kink since most SO2 emission in the 70's were in the northern hemisphere mid latitudes ( Europe, Americas )

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #403 on: April 14, 2017, 06:51:42 PM »
Northern Hemisphere LOTI Nasa GISS with Sulfite emissions

GISS data: https://data.giss.nasa.gov/gistemp/tabledata_v3/NH.Ts+dSST.txt

SO2 data:  http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf

Note that Temperature rise began rapidly not when SO2 emissions were reduced globally but rather when the rate of increase of emissions was stopped.  This reveals significant warming potential locked into the system but not allowed by the rate of change of emissions (increase) and then released through slowdowns in emissions.
« Last Edit: April 14, 2017, 08:26:52 PM by jai mitchell »
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oren

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #404 on: April 15, 2017, 12:04:40 AM »
AndrewB, I too am not convinced by the Natural Variation attribution claim for several reasons. However, I think you have taken the criticism way too far, attacking Dr. Ding personally in some of your recent posts. I am sure Dr. ding is an honest researcher with good intentions in mind (even if the paper's method is not to my "liking"), and I am sure he would like to see AGW and CO2 emissions dealt with asap without having to prove himself to you or anyone else. As he is known to be reading this thread and even graciously responding, I am especially ashamed by these attacks and would ask you to avoid such.
In general, I believe your point has been well stated and then overstated, why not give it a rest for a while.

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #405 on: April 15, 2017, 08:33:35 AM »
Oren,
I agree with your entire post, except for your claim that AndrewB was "attacking Dr. Ding personally in some of your recent posts".

I see no evidence of that.

In fact, AndrewB, even though he disagrees with the method used in Ding et al 2017, has been remarkably civil lately. I even see remarks like this from him :

Quote
Last but not least, I would like to thank Dr. Ding, for taking note of the second part of my question no.1 (*) in one of my previous comments, and for continuing to engage in an open and vigorous discussion of his paper here on ASIF.

and

Quote
Dr Ding's most interesting answer is food for thought, and I'll probably spend a few many hours this weekend thinking about it.

This is our planet. This is our time.
Let's not waste either.

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #406 on: April 15, 2017, 09:03:26 AM »
So, if you would want to tease out the contributions of AGW and natural variation to Arctic sea ice loss, what would your "designed research paradigm" be? How would you go about it?
...
However, Ding et al 2017 DOES provide a tool that we can use to 'tease out' particular variables out of a set of correlated variables.
...

After that, we could re-run Exp.6. and see how sea ice is affected (by LOTI).

What we would have done in that case, would be to 'tease out' AGW out of the Arctic variables, and that would be a start (to see what AGW influence is on Arctic sea ice).
...

Hi Rob,
The problem is, you are using the same method as Ding et al 2017, with the same uncertainties associated with the model used (POP2+CICE4) and with similar uncertainties with respect to the data and the basic assumptions.
In the end, you would almost certainly be able to make a similar claim as the one that is found in the Ding et al 2017 paper, which if we really account for the uncertainties in the entire "experiment", would read like:
“Global warming may be responsible (with 95% confidence) for about -40 to +120% of the overall decline in September sea ice since 1979.”

Totally meaningless...

Andrew, you can fight the Ding et al 2017 method of 'teasing out' a variable (Z200GL) from a set of correlated variables, or you can embrace it.
I hit my head hard fighting it, so I now embrace it.
If this method can tease out Z200GL, it can also tease out AGW (using the LOTI data).
Even further, we should be able to 'tease out' the dependency of Arctic sea ice decline from the Pacific ocean temperature. A connection that Ding et al 2017 claims as the cause of the Z200GL trend.
That would be interesting experiments, which would tell us more about how solid the claims made in Ding et al 2017 are.
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Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #407 on: April 15, 2017, 09:09:46 AM »
Winton 2011 writes:
http://journals.ametsoc.org/doi/full/10.1175/2011JCLI4146.1

"Some studies have focused on the dramatic September ice cover decline (Boé et al. 2009a; Wang and Overland 2009; Zhang 2010). Here, annual average sea ice extent is used in preference to September or other monthly values. Observations and models show that Arctic sea ice anomalies typically persist for only a few months (Blanchard-Wrigglesworth et al. 2011). Additionally, September sea ice cover, the focus of many ice sensitivity studies, is particularly variable and its variability is expected to increase with thinning of the ice (Holland et al. 2006; Goosse et al. 2009; Eisenman 2010). Therefore, considerable variation that is not related to long-term trends can be reduced by using annual averages."

His conclusion:
"substantial natural variability is necessary to reconcile even the most sensitive model with observations. The observational constraint will tighten slowly with time but in the interim it is useful to explore the possibility that the models are not sufficiently sensitive. This has been the theme of several analyses of IPCC AR4 models since the Stroeve et al. (2007) study (Bitz et al. 2011; Boé et al. 2009b). The results here support the importance of this work while holding onto the possibility that, at least for some of the models, the model–observations discrepancy may be due solely to natural variability."
« Last Edit: April 15, 2017, 09:23:16 AM by Lennart van der Linde »

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #408 on: April 15, 2017, 09:20:19 AM »
AndrewB, also I think your claim of uncertainty in the models (POP2+CICE4) is unwarranted.
Ding et al 2017 shows quite clearly that POP2+CICE4 models, forced with ERA data, reproduce the observed Arctic sea ice trend quite accurately.
Also, the experiments they run (causation Exp.5/6 and attribution Exp.7/8) are "difference" experiments. Apply a different forcing and see what the effect is.
Thus the choice of model is not THAT important, only the relative effect is.
This is our planet. This is our time.
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AndrewB

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #409 on: April 15, 2017, 09:24:38 AM »
AndrewB, I too am not convinced by the Natural Variation attribution claim for several reasons. However, I think you have taken the criticism way too far, attacking Dr. Ding personally in some of your recent posts. I am sure Dr. ding is an honest researcher with good intentions in mind
...
Oren,
Personally, I admire and respect Dr. Ding, and even more so because he has courageously accepted to spare some of his spare time to contribute to this forum. It is quite obvious that Dr. Ding is a highly intelligent person and an accomplished climate scientist, quite confident in his area of expertise. And his courage to defend his paper publicly tells highly of his character.
I hope he takes my vehement criticism of the Ding et al 2017 paper (assumptions, methodology and conclusion) as a personal compliment, and not as a personal insult.

About frequently restating my points: you are absolutely correct. I apologize, and I'll cease posting in this thread unless solicited to do otherwise.

oren

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #410 on: April 15, 2017, 09:39:07 AM »
Well said, AndrewB. I stand corrected.

Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #411 on: April 15, 2017, 10:18:27 AM »
IPCC AR5 WG1 ch12 on Long-term Arctic sea ice decline:
http://www.climatechange2013.org/images/report/WG1AR5_Chapter12_FINAL.pdf

"In the NH, in accordance with CMIP3 results, the absolute rate of decrease of the CMIP5 multi-model mean sea ice areal coverage is greatest in September. The reduction in sea ice extent between the time periods 1986–2005 and 2081–2100 for the CMIP5 multi-model average ranges from 8% for RCP2.6 to 34% for RCP8.5 in February and from 43% for RCP2.6 to 94% for RCP8.5 in September. Medium confidence is attached to these values as projections of sea ice extent decline in the real world due to errors in the simulation of present-day sea ice extent (mean and trends—see Section 9.4.3) and because of the large spread of model responses. About 90% of the available CMIP5 models reach nearly ice-free conditions (sea ice extent less than 1 × 10^6 km2 for at least 5 consecutive years) during September in the Arctic before 2100 under RCP8.5 (about 45% under RCP4.5). By the end of the 21st century, the decrease in multi-model mean sea ice volume ranges from 29% for RCP2.6 to 73% for RCP8.5 in February and from 54% for RCP2.6 to 96% for RCP8.5 in September. Medium confidence is attached to these values as projections of the real world sea ice volume. In February, these percentages are much higher than the corresponding ones for sea ice extent, which is indicative of a substantial sea ice thinning.

A frequent criticism of the CMIP3 models is that, as a group, they strongly underestimate the rapid decline in summer Arctic sea ice extent observed during the past few decades (e.g., Stroeve et al., 2007; Winton, 2011), which suggests that the CMIP3 projections of summer Arctic sea ice areal coverage might be too conservative. As shown in Section 9.4.3 and Figure 12.28b, the magnitude of the CMIP5 multi-model mean trend in September Arctic sea ice extent over the satellite era is more consistent with, but still underestimates, the observed one (see also Massonnet et al., 2012; Stroeve et al., 2012; Wang and Overland, 2012; Overland and Wang, 2013). Owing to the shortness of the observational record, it is difficult to ascertain the relative influence of natural variability on this trend. This hinders the comparison between modelled and observed trends, and hence the estimate of the sensitivity of the September Arctic sea ice extent to global surface temperature change (i.e., the decrease in sea ice extent per degree global warming) (Kay et al., 2011; Winton, 2011; Mahlstein and Knutti, 2012). This sensitivity may be crucial for determining future sea ice losses. Indeed, a clear relationship exists at longer than decadal time scales in climate change simulations between the annual mean or September mean Arctic sea ice extent and the annual mean global surface temperature change for ice extents larger than ~1 × 10^6 km2 (e.g., Ridley et al., 2007; Zhang, 2010b; NRC, 2011; Winton, 2011; Mahlstein and Knutti, 2012). This relationship is illustrated in Figure 12.30 for both CMIP3 and CMIP5 models. From this figure, it can be seen that the sea ice sensitivity varies significantly from model to model and is generally larger and in better agreement among models in CMIP5...

Today, the optimal approach for constraining sea ice projections from climate models is unclear, although one notes that these methods should have a credible underlying physical basis in order to increase confidence in their results (see Section 12.2). In addition, they should account for the potentially large imprint of natural variability on both observations and model simulations when these two sources of information are to be compared (see Section 9.8.3). This latter point is particularly critical if the past sea ice trend or sensitivity is used in performance metrics given the relatively short observational period (Kay et al., 2011; Overland et al., 2011; Mahlstein and Knutti, 2012; Massonnet et al., 2012; Stroeve et al., 2012)....

[V]arious methods all suggest a faster rate of summer Arctic sea ice decline than the multi-model mean. Although they individually provide a reduced range for the year of near disappearance of the September Arctic sea ice compared to the original CMIP3/CMIP5 multi-model ensemble, they lead to different timings (Overland and Wang, 2013). Consequently, the time interval obtained when combining all these studies remains wide: 2020–2100+ (2100+ = not before 2100) for the SRES A1B scenario and RCP4.5 (Stroeve et al., 2007, 2012; Boé et al., 2009b; Wang and Overland, 2009, 2012; Zhang, 2010b; Massonnet et al., 2012) and 2020–2060 for RCP8.5 (Massonnet et al., 2012; Wang and Overland, 2012). The method proposed by Massonnet et al. (2012) is applied here to the full set of models that provided the CMIP5 database with sea ice output. The natural variability of each of the four diagnostics shown in Figure 12.31a–d is first estimated by averaging over all available models with more than one ensemble member the diagnostic standard deviations derived from the model ensemble members. Then, for each model, a ±2 standard deviation interval is constructed around the ensemble mean or single realization of the diagnostic considered. A model is retained if, for each diagnostic, either this interval overlaps a ±20% interval around the observed/reanalysed value of the diagnostic or at least one ensemble member from that model gives a value for the diagnostic that falls within ±20% of the observational/reanalysed data. The outcome is displayed in Figure 12.31e for RCP8.5. Among the five selected models (ACCESS1.0, ACCESS1.3, GFDL-CM3, IPSL-CM5A-MR, MPI-ESM-MR), four project a nearly ice-free Arctic Ocean in September before 2050 (2080) for RCP8.5 (RCP4.5), the earliest and latest years of near disappearance of the sea ice pack being about 2040 and about 2060 (about 2040 and 2100+), respectively. It should be mentioned that Maslowski et al. (2012) projected that it would take only until about 2016 to reach a nearly ice-free Arctic Ocean in summer, based on a linear extrapolation into the future of the recent sea ice volume trend from a hindcast simulation conducted with a regional model of the Arctic sea ice–ocean system. However, such an extrapolation approach is problematic as it ignores the negative feedbacks that can occur when the sea ice cover becomes thin (e.g., Bitz and Roe, 2004; Notz, 2009) and neglects the effect of year-to-year or longer-term variability (Overland and Wang, 2013). Mahlstein and Knutti (2012) encompassed the dependence of sea ice projections on the forcing scenario by determining the annual mean global surface warming threshold for nearly ice-free conditions in September. Their best estimate of ~2°C above the present derived from both CMIP3 models and observations is consistent with the 1.6 to 2.1°C range (mean value: 1.9°C) obtained from the CMIP5 model subset shown in Figure 12.31e (see also Figure 12.30b). The reduction in September Arctic sea ice extent by the end of the 21st century, averaged over this subset of models, ranges from 56% for RCP2.6 to 100% for RCP8.5. In light of all these results, it is very likely that the Arctic sea ice cover will continue to shrink and thin all year round during the 21st century as the annual mean global surface temperature rises. It is also likely that the Arctic Ocean will become nearly ice-free in September before the middle of the century for high GHG emissions such as those corresponding to RCP8.5 (medium confidence)."
« Last Edit: April 15, 2017, 10:44:36 AM by Lennart van der Linde »

Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #412 on: April 15, 2017, 11:05:24 AM »
Thinning causes more thinning, is my interpretation of Bushuk et al 2017, Summer Enhancement of Arctic Sea Ice Volume Anomalies in the September-Ice Zone:
http://cerfacs.fr/wp-content/uploads/2017/03/GlobC-Article-Msadek-Summer-Mars-2017.pdf

"the size of the summer volume anomaly enhancement increases monotonically with the size of the initial volume anomaly, indicating that this phenomenon is always present but most significant in large anomaly years."

Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #413 on: April 15, 2017, 11:59:02 AM »
Livina & Lenton 2013 on potential Arctic sea ice tipping points:
http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf

"there has been an abrupt and persistent jump in the amplitude of the seasonal cycle of Arctic sea-ice cover in 2007 (Ditlevsen, 2012), but the underlying causal mechanism remains uncertain. We describe this as a (non-bifurcation) “tipping point”, because it involved an abrupt, qualitative change in the sea-ice dynamics, without any evidence for a large forcing perturbation; i.e. the abruptness resides in the internal dynamics of the Arctic climate system."

And Serreze 2011:
http://www.nature.com.sci-hub.cc/nature/journal/v471/n7336/full/471047a.html

"with ice-free summers, the ocean picks up a great deal of extra heat, delaying autumn ice growth. If there was a tipping point, this summer heat gain would lead to ice cover the following spring being thin enough to completely melt out over the following summer. Instead, so much ocean heat is lost during the darkness of the polar winter that enough ice grows to survive the next summer’s melt."

Will it? Or will Arctic amplication feedbacks cause much of this extra heat uptake to stay in the Arctic? How large will this amplification be?
« Last Edit: April 17, 2017, 12:53:38 PM by Lennart van der Linde »

Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #414 on: April 15, 2017, 12:46:26 PM »
Pithan & Mauritsen 2014 on Arctic amplification:
http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html

"Besides quantifying the different contributions to Arctic amplification in the ensemble mean, it is valuable to understand why models differ in their degree of Arctic amplification. Our analysis shows that intermodel spread in Arctic warming is dominated by the spread in local feedback mechanisms, not meridional transport changes (Fig. 3). Changes in atmospheric heat transport dampen intermodel spread because they are more positive in models with little Arctic warming. This is consistent with results from an energy balance model used to reconstruct warming and transport changes in the Coupled Model Intercomparison Project Phase 3 (CMIP3; ref. 28). In the ensemble mean, atmospheric heat transport does contribute to Arctic amplification by enhancing Arctic and reducing tropical warming (Fig. 2a). Contrary to physical intuition, poleward atmospheric energy transport does not scale with themeridional temperature gradient within individual models, but increases in most models despite a reduction in the Equator-to-pole temperature gradient. Increasing latent energy transports overcompensating the decrease of dry static energy transport have been shown to cause such behaviour of climate models. Changes in ocean transport and ocean heat uptake are not correlated with total Arctic warming across different models.
To develop confidence in model projections of future Arctic warming, it is necessary to quantitatively understand the role of different physical mechanisms for Arctic amplification. Contrary to a widespread assumption, temperature feedbacks are the most important contributors to Arctic amplification in contemporary climate models. The surface albedo feedback is the second main contributor, whereas other suggested drivers of Arctic amplification either play minor roles or even oppose Arctic amplification in the ensemble mean."

An older synthesis on Arctic amplification by Serreze & Barry 2011:
http://www.sciencedirect.com.sci-hub.cc/science/article/pii/S0921818111000397

"The degree of Arctic amplification, assessed as the ratio in the annual mean trend for the region 70–90°N to the trend for the globe as a whole, was 2.9 for the 1970–2008 period, compared with 6.9 for 1910–1940. For winter the ratios for the two periods, respectively, were 2.9 and 12.5, compared to 3.6 and 5.7, respectively, for summer. Corresponding ratios during the cooling period from 1940 to 1970 reached 16.7 for autumn and 16.0 for spring (stronger cooling in the Arctic), with an annual value of 12.5. More recently, Bekryaev et al. (2010) document a northern high-latitude (for land stations north of 59°N) warming rate of 1.36 °C per century for the period 1875–2008, almost twice as strong as the Northern Hemisphere trend (0.79 °C per century),with an even stronger warming rate for the last decade (1.35 °C/decade). Their study included many sites along the Arctic Ocean coast. Fig. 3 shows the annual and seasonal temperature time series from that study.
Surprisingly, apart from the effort by Johannessen et al. (2004), none of the studies discussed above specifically examined the Arctic Ocean, where the strongest Arctic amplification is projected to occur. While coastal sites certainly provide some information as to conditions over the ocean (the Arctic Ocean warming seen in Fig. 2 is strongly influenced by interpolation from coastal stations), a fuller picture requires the use of gridded fields from satellite retrievals or atmospheric reanalyses.
Atmospheric reanalyses provide long time series of atmospheric and surface conditions through data assimilation techniques that blend observations with short-term forecasts from a numerical weather prediction model. Time series from atmospheric reanalyses are standard climate research tools.
Serreze et al. (2009) examined the evolution of temperatures over the Arctic Ocean from 1979 to 2007 using data from two different atmospheric reanalyses. Anomalies were computed with respect to the period 1979–2007. Starting in the late 1990s, surface air temperature anomalies over the Arctic Ocean were seen to turn positive in autumn, growing in subsequent years, and building into winter. Development of the autumn warming pattern was found to align with the observed reduction in September sea ice extent, with the temperature anomalies strengthening from the lower troposphere to the surface. The recent autumn warming was found to be stronger over the Arctic Ocean than over Arctic land areas and lower latitudes. No enhanced surface warming signal was found in summer.
Screen and Simmonds (2010a) examined temperature trends from 1989 to 2008 using output from ERA-Interim, the newest reanalysis from the European Centre for Medium Range Weather Forecasts. They confirmed that the strongest recent warming lies over the Arctic Ocean, most pronounced in autumn and winter, and strongly allied with the observed downward trend in September sea ice extent."

Hind et al 2016:
https://www.nature.com/articles/srep30469

"Uncertainty in the estimated range of the Arctic amplification factor using the latest global climate models and climate forcing scenarios is expanded upon and shown to be greater than previously demonstrated for future climate projections, particularly using forcing scenarios with lower concentrations of greenhouse gases...

Figure 2 shows the multi-model mean Arctic (orange/yellow) and global (red) temperature changes projected for the period 2081–2100 in contrast with those simulated for 1986–2005 using the four RCP scenarios. The 90% confidence intervals for the spread of Arctic and global temperatures are presented here as provided in Table 12.2 of IPCC AR5 and are essentially very similar for all RCP forcing scenarios. Here, we apply the Fieller method in an attempt to give representative confidence intervals at a 90% significance level for projected Arctic amplification using the Ratio of Means approach, based on the model spread for each RCP forcing scenario (black in Fig. 2). The RCP4.5 and RCP6 simulated future scenarios show a similar uncertainty in the Arctic amplification factor, with potential values ranging from approximately 1.2–3.8 at a 90% significance level (second and third columns in Fig. 2), whereas the RCP8.5 scenario has a somewhat smaller uncertainty, ranging from 1.5–3 (fourth column in Fig. 2). On the other hand, for the RCP2.6 simulated future scenarios an Arctic amplification factor of less than 1 or even negative values are quite possible. In other words, the Arctic region may be able to undergo temperature changes in opposition to the direction of any global changes if the global radiative forcing follows the RCP2.6 pathway. It generally seems as though the uncertainty bounds calculated for future projected Arctic amplification factors indicate that higher numbered RCP forcing experiments (analogous to higher greenhouse gas concentrations) show less uncertainty than the lower RCP experiments. This is perhaps not an unexpected result given that higher greenhouse gas forcings would be expected to increasingly overcome differences in the physical models and internal climate variability."
« Last Edit: April 15, 2017, 01:00:21 PM by Lennart van der Linde »

gerontocrat

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #415 on: April 15, 2017, 01:01:25 PM »
Is the phrase "natural variation" itself a cop-out for a blog such as ASIF ? As an over-curious kid I am sure I asked my parents "Why are summers warm and winters cold ?", and did not accept the answer - "Natural variation, my dear". To learn for the first time about the tilt in the axis of the earth, and from that so much else,  was amazing.

So the question I never asked this thread but hoped for the answer is "What is this natural variation of which Dr Ding speaks?". Or should I be posting this in Stupid Questions ?

Simple, natural variation is the internal variability of the Earth system ( mostly atmospheric and ocean dynamics ) absent anthropogenic and feedback greenhouse gas emissions....

It includes the Sun, the moon, volcanoes, orbital parameters, etc. which result into patterns and cycles and variability of the trajectory of the atmospheric, ocean and biosphere dynamics, and albedo.

Hullo Doc,

Thanks for the list. BUT (there is always a but)
that is like a climate sceptic/denier asking me "What causes AGW ?", and me answering "CO2". CO2 is what, but what is missing is - what changed - ,   and  - how  did that change the temperature of the biosphere -. I am a non-scientist but I do  basically get the story.

So I ask again, "What changed and how did it cause the Natural Variation of which Dr Ding speaks?"

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Andreas T

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #416 on: April 15, 2017, 01:49:07 PM »
Without claiming that this is the definition of "natural variations" used by Dr Ding, I think that natural influences which are outside the average conditions on planet earth don't count as variations but as drivers. So changes in output from the sun, earth orbit and axis orientation, or volcanoes count as drivers, inputs into the climate system. Internal variations are changes which occur if all external inputs remain the same. Because there are so many feedbacks in the system fluctuations in, say sea surface temperature distribution and cloud distribution can reinforce each other (el nino is a prime example) in a way which doesn't average out by making one part of the globe warmer while another colder. El nino of course does of course move energy from a reservoir (sea water) into the atmosphere so has a time span and frequency which is limited by how quickly this reservoir is replenished. I believe such variations can also change the amount of energy which is taken up from the sun but again there are limitations on how much and for how long. Such variations do occur in climate models  as part of the interdependent processes which they describe mathematically.

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #417 on: April 15, 2017, 03:33:56 PM »
Pithan & Mauritsen 2014 on Arctic amplification:
http://www.nature.com.sci-hub.cc/ngeo/journal/v7/n3/full/ngeo2071.html

(1) Changes in atmospheric heat transport dampen intermodel spread because they are more positive in models with little Arctic warming. This is consistent with results from an energy balance model used to reconstruct warming and transport changes in the Coupled Model Intercomparison Project Phase 3

(2) In the ensemble mean, atmospheric heat transport does contribute to Arctic amplification by enhancing Arctic and reducing tropical warming (Fig. 2a). Contrary to physical intuition, poleward atmospheric energy transport does not scale with the meridional temperature gradient within individual models, but increases in most models despite a reduction in the Equator-to-pole temperature gradient.

Hind et al 2016:
https://www.nature.com/articles/srep30469

(3) "Uncertainty in the estimated range of the Arctic amplification factor using the latest global climate models and climate forcing scenarios is expanded upon and shown to be greater than previously demonstrated for future climate projections, particularly using forcing scenarios with lower concentrations of greenhouse gases...

On the other hand, for the RCP2.6 simulated future scenarios an Arctic amplification factor of less than 1 or even negative values are quite possible. In other words, the Arctic region may be able to undergo temperature changes in opposition to the direction of any global changes if the global radiative forcing follows the RCP2.6 pathway. It generally seems as though the uncertainty bounds calculated for future projected Arctic amplification factors indicate that higher numbered RCP forcing experiments (analogous to higher greenhouse gas concentrations) show less uncertainty than the lower RCP experiments. This is perhaps not an unexpected result given that higher greenhouse gas forcings would be expected to increasingly overcome differences in the physical models and internal climate variability."

(1) models with greater arctic amplification result in lower amounts of mid-latitude latent heat intrusion, models with lower arctic amplification result in higher amounts.  this is because the models expect (are designed to show) atmospheric circulation changes as a result of the  temperature gradient changes produced by a globally averaged forcing and regional (but slow) feedbacks.

(2) In the model mean, the primary force for meridional transport is the temperature gradient, however other circulation changes (feedbacks) bias the mean somewhat so that the amount is slightly greater than the rate of change of the meridional temperature gradient (not scaled).

(3) These results show that the model mean is dominated by GCMs that do not allow for tropical anthropogenic aerosol emission reductions to significantly increase regional Tropopause heights, with increased regional water vapor and lapse rate feedbacks.  The resulting changes in the Tropic geopotential height gradient will produce rapid expansions of the ITCZ, a significant expansion of the Hadley Cell, the greatly increased export of mid-altitude water vapor pulses in the form of atmospheric rivers, the strengthening of (slowing/standing - even short reversal!) Rossby wave activity (due to extreme upper latitude blocking events) that will eventually result in tropical wave/pulse formations that are unprecedented in scope and scale since the early Pliocene.

---  This makes me think that it is time to do a more rigorous  means testing of the climate models as qualification for inclusion in the CMIP6 and drop about 1/2 of them from the ensemble --- as harsh as this would be to the people who have worked incredibly hard on them, we simply cannot let these poor performers continue to bias the ensemble results anymore.
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Archimid

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #418 on: April 15, 2017, 05:02:07 PM »
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

I am an energy reservoir seemingly intent on lowering entropy for self preservation.

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #419 on: April 15, 2017, 10:58:34 PM »
Hi everyone,

I have no time to read all these threads posted in the past week. So I just started with some points I really want to make first.
 
I think the main reason that someone here don't believe that there is a natural factor to drive the sea ice change is that sea ice only showed a decline trend recently over the past 1000 years ( I remember AndrewB showed some September sea ice curves from some datasets ).

But based on what I learned from these data and literatures, I don't think this is 100% correct. I think it is very likely that there was a very low frequency internal mode ( or a random thing)  that had caused another early warming in the Arctic around 1930s-1940s.

You can find a lot of evidence to support the existence of this early warming event in and around the Arctic, especially over Greenland. ( that is why we used Z200 over there as the index in Ding et al 2017. I will say more about this for Rob) 

 http://onlinelibrary.wiley.com/doi/10.1029/2006GL026510/abstract

please go to this website and check all available surface temperature in the past 100 years over some stations in the high latitudes

https://data.giss.nasa.gov/gistemp/station_data/

I also checked all these old sea ice reconstruction data from month to month before 1950s. I think they used a climatology of September from some periods later for all September sea ice before 1950s or 60s. As I know, old sea ice data/charts only recorded sea ice information from April to Aug.  I can plot some old ice data later. you will see what I mean here.

In my view, our understanding of September sea ice variability before 1950s or 60s is very limited because of this data limitation.

if you check old sea ice chart ( I add it as an attachment, I am not sure whether you can see it at the bottom of my post)  in 1938/Aug, you can see a pretty bad sea ice melting in that year. So we should expect a worse melting in 1938/Sep but all sea ice reconstructions in September don't show this because data uses a climatology in September.

 In 1940s and 1950s, due to WW2 and the Cold war, there were no reliable sea ice information so we don't know the real situation of sea ice in that time period. But based on the land surface temperature over Greenland and some high-latitude regions in Russia and Canada we still can figure out that there was a very signifcant warming event before 1950s .

I will add more later today.
« Last Edit: April 15, 2017, 11:05:07 PM by Qinghua ding »

Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #420 on: April 15, 2017, 11:03:25 PM »
I have no idea why I cannot post a figure here. I need help!

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #421 on: April 15, 2017, 11:11:11 PM »
one paper on the circulation change in the Arctic

"Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

A. Belleflamme, X. Fettweis, and M. Erpicum
Laboratory of Climatology, Department of Geography, University of Liège, Allée du 6 Août, 2, 4000 Liège, Belgium
Correspondence to: A. Belleflamme (a.belleflamme@ulg.ac.be)
Received: 18 July 2014 – Published in The Cryosphere Discuss.: 10 September 2014 Revised: 4 December 2014 – Accepted: 7 December 2014 – Published: 7 January 2015


Abstract

 A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500hPa geopotential height data from five reanalysis data sets (ERAInterim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.



jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #422 on: April 15, 2017, 11:14:08 PM »
Quote
#421 on: Today at 11:11:11 PM »

thought this timestamp was pretty cool.

there are two ways to post an image here: 

1.  click the + attachments and other options button below the data entry screen and upload as an attachment (note large files will not be auto sized so >450px will be larger than the viewing window or

2.  click the 'image link' button (second from the left) above the data entry window and add the image url as a link to show in your post.
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Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #423 on: April 15, 2017, 11:25:31 PM »
Dr. Ding, if you're reading this, have a look at my question to you in reply 388 above:
http://forum.arctic-sea-ice.net/index.php/topic,1920.msg109633.html#msg109633

There I wrote:

I was just reading this:
https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science

Quote
Ding said his findings in no way minimize the role of anthropogenic warming in melting sea ice. "I don't want people to take the wrong message in our study, that we're not to blame for Arctic warming," said Ding. "The message is that it's more complex than we expected. In the long term, maybe 100 years from now, the Arctic will become ice free in summer because eventually this internal variability will be overwhelmed by anthropogenic forcing."

Dr. Ding, if you're reading this: were you quoted correctly, and if so, what is your assertion based on, or how should it be interpreted?

As far as I know the Arctic could become ice free at the end of summer much earlier than 100 years from now, and ice free during summer probably (or maybe) also quite a bit earlier than 100 years from now.

So what do you mean by "ice free in summer"? Three months of ice free Arctic from June 21st - Sept 21st? Or is one day without ice in those months also ice free in summer?

And what do you mean by "maybe": would that be your best estimate (so should we read "probably"? Or do you mean " maybe as early as 100 years from now"? And does that imply say a 33% chance, or 25%, or 17% or 10%, or even 5%?

In short, what message exactly do you want to give us, the public?

jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #424 on: April 15, 2017, 11:27:31 PM »
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

thanks Arch. 

you know the real issue here is that a significant (possibly VERY significant) portion of the cooling impact of upper troposphere SO2 is simply not addressed in the climate models since the physical interactions are not well known. 

With only a modest addition of these impacts and with the recently documented impacts to PDO, AMO and related atmospheric circulation patterns (based on regional emissions/reduction trends in the modern record) much of the supposed variability is washed out INCLUDING the early warming phase in the 1930s that is currently NOT being 100% assigned to anthropogenic activity (just like the intensity of PDO/AMO was also missing significant anthropogenic components).

However some interesting things happen when you work from this assumption that SO2 impacts are severely understated.

1.  The Ruddiman early agriculture hypothesis is proven correct
2.  Arctic sea ice is going to disappear in the next few years (summer minimum)
3.  ECS is closer to 5.5K/2X CO2
4.  we have locked in +3.5C at current atmospheric abundances
5.  We have to start right away with a WWII scale mobilization effort to radically eliminate all fossil fuel consumption in the next 10 years AND begin large scale BEECS/Biochar/Regenerative Agriculture to offset carbon cycle emissions to prevent going over +4C and possibly losing global modernity.
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bbr2314

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #425 on: April 15, 2017, 11:32:48 PM »
jai mitchell  +1

I've been meaning to say this for a while, and this is offtopic, but your coal/aerosols/sst argument is a courageous one. You are saying that shutting down Coal plants causes short term global warming.  I bet you get a lot of flak for that.

When you first started to state that point, I was suspicious of you because it sounded like a very convenient argument for a climate change denier to take advantage of. But then as you refined the argument and presented more and more evidence I realized that my suspicions of your argument  were nothing but my own personal bias. You are probably right and your argument is very important if coal is going to be phased out.

For example phasing out coal plants during warm cycles of the planet will compound the problems of the warming. Closing them during cool earth cycles will reduce the impact of the short term warming at the cost of maintaining the Earth at a higher temperatures for longer.

This might be an important consideration that is impossible to talk about because of the nature of the debate.

thanks Arch. 

you know the real issue here is that a significant (possibly VERY significant) portion of the cooling impact of upper troposphere SO2 is simply not addressed in the climate models since the physical interactions are not well known. 

With only a modest addition of these impacts and with the recently documented impacts to PDO, AMO and related atmospheric circulation patterns (based on regional emissions/reduction trends in the modern record) much of the supposed variability is washed out INCLUDING the early warming phase in the 1930s that is currently NOT being 100% assigned to anthropogenic activity (just like the intensity of PDO/AMO was also missing significant anthropogenic components).

However some interesting things happen when you work from this assumption that SO2 impacts are severely understated.

1.  The Ruddiman early agriculture hypothesis is proven correct
2.  Arctic sea ice is going to disappear in the next few years (summer minimum)
3.  ECS is closer to 5.5K/2X CO2
4.  we have locked in +3.5C at current atmospheric abundances
5.  We have to start right away with a WWII scale mobilization effort to radically eliminate all fossil fuel consumption in the next 10 years AND begin large scale BEECS/Biochar/Regenerative Agriculture to offset carbon cycle emissions to prevent going over +4C and possibly losing global modernity.
I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants, the "shroud" produced by industry during the roaring 20s would've rapidly been reduced as GDP sputtered by double digits on an annual basis. Of course, wartime efforts beginning in the late 30s revved economies back up in many regions, but I wonder if the 7-8 year period of stagnation and decline could've been a contributing factor to the loss in sea ice, adding a few tenths of a degree to global temps overall before the economy came roaring back to life (along with dirtier industry emitting SO2).

Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #426 on: April 15, 2017, 11:59:41 PM »
If you could understand my thoughts behind our 2017 study, I think it is not hard to understand why I said we probably will see an ice free Arctic summer in 100 years. Actually, I remember that I said "50 to 100 years" to some of the media. Anyway, my point in these interviews is that I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics. So when the next one comes after some decades, stronger CO2 forcing and this additional one will cause a much stronger sea ice melting. I only honestly say what I learned from my research. If you don't agree with me, I have no any problem with that.     

Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #427 on: April 16, 2017, 12:05:07 AM »
Please read this one.
http://neven1.typepad.com/blog/2012/08/similar-melts-from-1938-43.html

I cannot post a picture  from my Pc using that attachment function.




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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #428 on: April 16, 2017, 12:51:45 AM »

I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants.



it should be noted that coal was a common heating fuel during this time and that the reduction of coal use during this time was predominantly in higher temperature processes (rail transport and steel production).  These higher temperature emissions appear to have a much greater impact than lower-temperature combustion products that stay much lower in the atmosphere (and rain out much sooner).
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #429 on: April 16, 2017, 01:18:26 AM »

I wonder if the global recession beginning in 1929 could be to blame for the spike in Arctic temperatures? Similar to what we are seeing as China winds down its dirtiest pollutants.



it should be noted that coal was a common heating fuel during this time and that the reduction of coal use during this time was predominantly in higher temperature processes (rail transport and steel production).  These higher temperature emissions appear to have a much greater impact than lower-temperature combustion products that stay much lower in the atmosphere (and rain out much sooner).

What are high temperature emissions vs lower temperature combustion prosucts??

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #430 on: April 16, 2017, 02:45:56 AM »
in industrial applications coal typically burn at 1350C and some more efficient high-temp pulverized coal power plants operate at 1500-1700C.

open burning of coal in a home fire box typically burns at 600C (at most).

In addition, larger volumes of smokestack emissions allows for greater plume resistance to dispersal and higher altitude atmospheric loading. 

note that the coal smokestacks that we see with white steam coming out are cooled during the scrubbing process to remove (most of) the sulfite.  Non-scrubbed smokestack emissions are clear and very very fast.
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #431 on: April 16, 2017, 03:35:53 AM »
Wrong thread to discuss, but composition wise they are for all practical purposes similar. Lower temperature combustion emits more CO and hydrocarbons, but other than that it is similar. And since all emissions are in the lower well mixed atmosphere, it does not matter much. CO2 is CO2 no matter the source....

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #432 on: April 16, 2017, 05:20:13 AM »
Dr T.

The discussion is about SO2 emissions and their impacts on what we have previously called 'natural variability'.
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Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #433 on: April 16, 2017, 08:22:09 AM »
Qinghua Ding,
Thank you for sharing more of your thoughts about natural variability in the Arctic with us.

Regarding your statement
Quote
I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics

I don't think there is much evidence in support of this "70 year cycle" hypothesis.

For starters, your reference (from 2006) mentions "Greenland warming of 1920–1930 and 1995–2005", but the end of that last period is now 12 years ago, and the really low sea ice extents happened after that.

More applicable to your paper, if this cycle affects summertime Z200GL then we should see that cycle show up in the summertime NAO index :



However, there does not seem to be any specific 70 year cycle there, and there certainly does not seem to be any similarity between the 1930's-40 and the recent decades. If anything the summertime NAO moved positive in the 1930's and moved negative in the last decade.

Regarding Arctic sea ice records dating back to 1850, there is the Walsh reconstruction.

Not much of a 70 year (or any) cycle there either.

Regarding the Walsh reconstruction, you may be interested in the work done by Diablo and me in the comment section of this thread :
http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html
Specifically, we determined that the Walsh reconstruction contained a few flaws (misplaced Kelly fields and a bias in one of the sources). We then re-computed the Walsh reconstruction with these flaws removed and arrived at a slightly different result, specifically for August :

Still no evidence of any multi-decadal cycle.
Read backward from this post if you are interested in the details :
http://neven1.typepad.com/blog/2016/01/september-arctic-sea-ice-extent-1935-2014.html?cid=6a0133f03a1e37970b01b8d22fd62a970c#comment-6a0133f03a1e37970b01b8d22fd62a970c

And for the long term sea ice reconstructions, here is Kinnard et al 2011 :



One could argue that there is a small decadal (20-40 year) cycle in there, but the amplitude is miniscule compared to the recent decline in sea ice extent. And that plot ends in 2000, with the big drops happening AFTER that.

So I don't see any evidence for any significant "70 year" cycle in either Z200GL, Arctic temperature, nor Arctic sea ice extent.

P.S. To insert an image, you can put the URL in between [img] and [/img ] tags (or use the image icon).
I know there is a way to upload a picture too, but I don't know how to do that.
« Last Edit: April 16, 2017, 09:17:25 AM by Rob Dekker »
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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #434 on: April 16, 2017, 09:15:44 AM »
Hi Rob,

Thanks. As I said, sea ice reconstruction data you shown uses a climatology of September sea ice ( for some regions ) for September in 1930s -1940s.
You should be very careful to use that data to understand the long term sea ice change.

the NAO refers to  a dipole mode with a high latitude one and a midlatitude cell. But for sea ice, the most important one is the circulation change over Greenland ( I only used it as the index to do regression , right?). I didn't find a good correlation between sea ice and the other cell over the midlatitudes or the difference between two cells in our 2017 paper. So I didn't use the NAO index to explain sea ice. You misunderstood my idea again. 

 Please read"  Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

A. Belleflamme, X. Fettweis, and M. Erpicum
Laboratory of Climatology, Department of Geography, University of Liège, Allée du 6 Août, 2, 4000 Liège, Belgium
Correspondence to: A. Belleflamme (a.belleflamme@ulg.ac.be)
Received: 18 July 2014 – Published in The Cryosphere Discuss.: 10 September 2014 Revised: 4 December 2014 – Accepted: 7 December 2014 – Published: 7 January 2015


Abstract

 A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500hPa geopotential height data from five reanalysis data sets (ERAInterim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #435 on: April 16, 2017, 09:19:20 AM »
Hi Rob,
for your interests, please read this further. A good review of that earlier event.
http://www.sciencedirect.com/science/article/pii/S1873965211000053

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #436 on: April 16, 2017, 09:40:41 AM »
Hi Rob,
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug. 

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #437 on: April 16, 2017, 09:41:36 AM »
Qinghua,

Hi Rob,

Thanks. As I said, sea ice reconstruction data you shown uses a climatology of September sea ice ( for some regions ) for September in 1930s -1940s.
You should be very careful to use that data to understand the long term sea ice change.

What exactly do you mean when you state that the "sea ice reconstruction data you shown uses a climatology of September sea ice" ?

Are you suggesting that the Walsh reconstruction is flawed ? And if so, in which way ?
Also note that Diablo used a 'climatology' to fill in spatial and temporal gaps, but my method does not. Yet we arrived at very similar results.
And still no notion of a multi-decadal cycle.

Quote
the NAO refers to  a dipole mode with a high latitude one and a midlatitude cell. But for sea ice, the most important one is the circulation change over Greenland ( I only used it as the index to do regression , right?). I didn't find a good correlation between sea ice and the other cell over the midlatitudes or the difference between two cells in our 2017 paper. So I didn't use the NAO index to explain sea ice. You misunderstood my idea again. 

 Please read"  Recent summer Arctic atmospheric circulation anomalies in a historical perspective"

I understand that you did not use NAO index for your paper, but for Z200GL is still a major, direct contributor to NAO. If the 'other' (mid-latitude) cell in NAO does not correlate well with sea ice extent, but the cell over Greenland does, then could it be that the cell over Greenland was affected more by sea ice extent than the mid-latitude cell ?

So a major 'cause' of Z200GL increase (and temperature increase) may be global warming or sea ice extent reduction.

In that line of reasoning, Liu et al 2016 makes sense :
Quote
In recent decades, the Greenland ice sheet has experienced increased surface melt. However, the underlying cause of this increased surface melting and how it relates to cryospheric changes across the Arctic remain unclear. Here it is shown that an important contributing factor is the decreasing Arctic sea ice. Reduced summer sea ice favors stronger and more frequent occurrences of blocking-high pressure events over Greenland. Blocking highs enhance the transport of warm, moist air over Greenland, which increases downwelling infrared radiation, contributes to increased extreme heat events, and accounts for the majority of the observed warming trends. These findings are supported by analyses of observations and reanalysis data, as well as by independent atmospheric model simulations using a state-of-the-art atmospheric model that is forced by varying only the sea ice conditions. Reduced sea ice conditions in the model favor more extensive Greenland surface melting. The authors find a positive feedback between the variability in the extent of summer Arctic sea ice and melt area of the summer Greenland ice sheet, which affects the Greenland ice sheet mass balance. This linkage may improve the projections of changes in the global sea level and thermohaline circulation.
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0391.1
« Last Edit: April 16, 2017, 10:02:46 AM by Rob Dekker »
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Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #438 on: April 16, 2017, 09:45:44 AM »
we cited Liu 2016 in our 2017 paper. So we also tested his idea in exp4. We didn't see this response. I can give you some other papers that show that it is hard to get this Z200 pattern if a model is forced by observed sea ice melting in JJA.

Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #439 on: April 16, 2017, 09:47:47 AM »
btw, Liu 2016 only showed the Z500 response not Z200, if I remember it correctly. 

Rob Dekker

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #440 on: April 16, 2017, 09:58:30 AM »
Thank you Qinghua.
I understand that you dispute Liu et al, and honestly, I have not formed an opinion about that.
But I don't understand why you dispute the Walsh reconstruction.
Quote
Please see this plot. The sea ice extent in 1938/sep is even larger than that in 1938/aug.
Please let me understand this : You claim that in the Walsh reconstruction, September 1938 extent is larger than August 1938 extent. I need to check the numbers on that, but if true, is this a reason for you to claim that there is a 70 year cycle in the record ?
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Neven

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #441 on: April 16, 2017, 10:22:21 AM »
If you could understand my thoughts behind our 2017 study, I think it is not hard to understand why I said we probably will see an ice free Arctic summer in 100 years. Actually, I remember that I said "50 to 100 years" to some of the media. Anyway, my point in these interviews is that I believe there is a low frequency mode ( occurs about every 70 years) to partially warm the Arctic in the recent decades and also around 1930-40s and these two warming events may share a similar feature in their dynamics. So when the next one comes after some decades, stronger CO2 forcing and this additional one will cause a much stronger sea ice melting. I only honestly say what I learned from my research. If you don't agree with me, I have no any problem with that.

Qinghua, this suggests that you expect the influence of the 'additional one' to fade soon, warming will lessen, as will the current rate of Arctic sea ice loss. But when I asked whether "we have any way of knowing when this natural variability might switch again and thus slow down the current rapid rate of Arctic sea ice loss", you answered "To be honest, I don't know the answer."

Is it possible that the 'additional one' doesn't flip in the next 10-15 years, and that the Arctic goes ice-free in September (below 1 million km2 area/extent)? Because if it is, I don't understand how you can say you expect the Arctic to go ice-free 50 to 100 years from now.
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Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #442 on: April 16, 2017, 10:23:48 AM »
Dr. Ding, thank you for your reply.

Yamanouchi 2011, to which you refer, says:
"It is likely that the early 20th century warming in the Arctic was due to a combination of intrinsic internal natural climate variability and positive feedbacks that amplified radiative and atmospheric forcing (Kaufman et al., 2009). Most of the internal climate variability explained by models was of decadal or shorter time scale. However, observed early 20th century warming was inter- or multi-decadal. So, additional factor needs to work, and that should be external forcing and positive feedbacks exist in the Arctic climate system. It is not possible for a single factor to explain the entire warming event. The relative importance and contribution of each warming agent has not yet been resolved. A quantitative estimate of the role of each factor is still to be made not only for the early 20th century warming but also for the recent warming."

Supposing there's a 70-yr natural cycle warming and cooling the Arctic, how would it interact with an AGW-trend? Or put differently: how much sea ice loss would we have seen naturally since 1979 without AGW? And how much could a potential natural cooling trend in de coming decades slow down AGW-driven sea ice loss? Could there be a tipping point, as suggested by some, which makes it hard for the sea ice to recover once a critical part has been lost?

TerryM

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #443 on: April 16, 2017, 10:39:55 AM »

Dr. Qinghua

Would the beginnings of the breakup of Ellesmere's ice shelves over 100 yrs ago, after thousands of years of growth, have any effect on what you consider, "natural variation", and what I might consider to be, "early evidence of AGW"?


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oren

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #444 on: April 16, 2017, 12:00:05 PM »
Dr. Qinghua, seeing as you expect the arctic to go ice-free in 50-100 years based on your research and other knowledge. Should the arctic somehow go ice-free in 5-10 years, will that cause you to revise your estimates of the large role of natural variability?

ktonine

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #445 on: April 16, 2017, 05:09:13 PM »
Obviously they've gone over the models dozens of times trying to figure out why they don't match observations.  At some point (Ding et al) someone was bound to come up with the rational idea that maybe it's not being entirely forced, but simply natural variation.

We always hesitate to put anything down to cycles because they're generally the first refuge of deniers like the denizens at WUWT.  But occasionally there *are* cycles that need to be taken into account.  If I recall iceberg records in the north Atlantic do tend to  show a 60 year cycle and this could be part of that natural variation.

As Dr Ding points out, there are numerous lines of evidence that point to a low extent in the 1930s.  This is one of the papers I was thinking of when I wrote the above.

Trends and Variability in Sea Ice and Icebergs off the Canadian East Coast, Peterson, Pettipas, & A. Rosing Asvid, 2015

Qinghua ding

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #446 on: April 16, 2017, 09:22:53 PM »
Thanks for all your follow-up questions to my yesterday's threads . I will try to answer some of them. 

To Rob,

I didn't make it very clear last night since when I wrote those posts I was responding to some other personal messages/questions from this forum.

As we know, sea ice experiences the minimum state in September. So we should expect to see less sea ice in Sep than that in Aug in all sea ice data. But some old sea ice reconstruction data sets show the opposite way around 1930s because there was no reliable information for Sep sea ice in that time so it has to use a Sep climatology from the later period or the entire period to fill September in that period (1930s-1940s). So we see a bad melting in 1938/aug ( this is from the observations to some extents) but more sea ice in 1938/Sep ( in this month, we actually see a climatology, rather than the reality).

Another thing I am very cautious about when I use these data is that there was no sea ice observation over the Canadian side of the basin in 1930s. So when we compare sea ice in August in that period with Aug sea ice in the present day, I think it is better to only focus on sea ice over the Russian side.

I think Walsh reconstruction is a great resource because it is the almost best data we can use but we still should be cautious about its limitation.

To Oren,

If we would see an ice fee summer in Arctic in 5-10 years. I will say my prediction of 50 to 100 years is wrong.


To TerryM,

Sorry. I am not familiar with that place. I will take a close look at that specific location.

  to Lennart van der Linde

As I said yesterday, I think an internal factor could partially cause the 1930-1940event.
The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

The timing of black-carbon forcing seems to be a little bit earlier.

Co2 could be one factor to cause the fast warming rate of the 1930s event but it should be weaker than its effect in 1990s to 2000s.

What is the key factor?   
 

To Neven,

You asked a very tough but great question. If you agree with my thoughts, I think it is very natural to develop an outlook of the Arctic that we should see a slow down of current melting or a little bit recovery in the near future if the tropical Pacific SST pattern would reverse to a pattern with a warming in the east and a cooling in the west. Actually, this is a pattern we observed from 1960s to 1980s.
 
In our 2014 paper, we argued that the Z200 change over Greenland is due to something originated form the tropics. If we really want to understand and predict the evolution of the very low frequency mode in the tropics, we need good and reliable observations to cover the tropical ocean from the surface to the deep ocean. But we only have good deep ocean observations  ( not only SST) since 2003.

My main message is that we still have some time to save our arctic since some melting was not due to Co2 in the past 20 years. But we should work fast because when the next internal warming period comes, we will see very bad melting. if you ask me how fast, my prediction is 50 to 100 years.


 
 

 



jai mitchell

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #447 on: April 16, 2017, 09:38:37 PM »
The most intriguing part of that event is that warming exhibited a pretty large scale feature in the Arctic and the area was warmed by something very fast from 1920s to 1930s.  So causes  of this fast warming rate has puzzled me for a long time.

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Lennart van der Linde

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #448 on: April 16, 2017, 10:02:19 PM »
Qinghua,

Thanks again for your reply. Let me specify my question:

How much sea ice loss would we have seen naturally since 1979 without AGW? Average Sept extent was about 7.35 million km2 from 1979-1988 and about 4.73 million km2 from 2007-2016, according to NSIDC (see fig below).

That's a loss of about 2.62 million km2. If natural variability caused about 40% of this loss, that would be about 1.05 million km2, So about 1.57 million km2 would be due to AGW. Is that a correct interpretation of the conclusion of your recent paper?

And my other question: could there be a tipping point, as suggested by some, which makes it hard for the sea ice to recover once a critical part has been lost? What's your opinion on this?
« Last Edit: April 16, 2017, 10:08:39 PM by Lennart van der Linde »

Darvince

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Re: Arctic sea ice changes: Natural variation vs human influence
« Reply #449 on: April 17, 2017, 03:32:40 AM »
Thanks for all your follow-up questions to my yesterday's threads . I will try to answer some of them. 

Since the IPO and PDO, which are the main tropical variability you discuss, were mainly positive in the early period of 1979-2014, and negative in the later period, and are now once again positive, do you expect the trend in Arctic sea ice minima to be essentially zero over the coming years?