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Science / Science Events
« on: September 27, 2017, 01:33:18 AM »

In Washington DC Wednesday,   September   27,   2017:

Global   Lessons   from   the   Thawing   Arctic

3:00-3:45   pm:      Panel   Presentation
▪ Introductory   comments   
▪ Opening   of   a   new   ocean:   Rising   stakes   for   security,   economies,   and   conservation   
    Dr.   Henry   Huntington,   Huntington   Consulting      
▪ Threats   to   local   Arctic   communities:   Lessons   for   a   global   audience   
    Dr.   Elizabeth   Marino,   Oregon   State   University      
▪ Global   greenhouse   gas   releases   from   thawing   permafrost      
    Dr.   Christina   Schädel,   Northern   Arizona   University
▪ Sea-level   rise   from   the   melting   Greenland   Ice   Sheet   
    Dr.   Ted   Scambos,   National   Snow   and   Ice   Data   Center
▪ The   Arctic   Meltdown   and   Unruly   Tropical   Storms:   Are   They   Connected?   
    Dr.   Jennifer   Francis,   Rutgers   University      
▪ Imagining   the   Arctic   of   2050   to   inform   actions   today   
    Dr.   Amy   Lauren   Lovecraft,   University   of   Alaska   Fairbanks
3:45-4:30   pm:   Questions   from   journalists   and   audience
4:30-5:00   pm:   Informal   light   reception

Over on Stoat, I wrote and William Connolley replies shown in [ xxx -W] form:

You seemed to believe that tends in area/extent were better than using volume.

[Perhaps that they are more familiar. And certainly they are more strongly observationally based; I know little of PIOMAS or how much I should trust it. Also, its alone: unlike the area / extent, which many centres provide -W]

Is there a test of that with this years low volume at maximum? If it is the volume trend that matters we should expect the 1.8 k km^3 volume below previous lowest to grow over the melt season due to albedo effects. (I.e. thinner ice melts out quicker allowing albedo to fall faster, more heat absorbed by ocean that can melt more ice.) If it is area or extent that shows a more consistent trend as you have seemed to indicate you believe then as we get down to low volumes shouldn’t that volume get harder to melt and so the gap to previous lowest should shrink towards the end of the melt season?

[Yes, that’s kinda what I think. I also think that the volume “matters” less. For the climate, what really matters is the albedo, to first order; which is a function of area, to first order -W]

I am not sure why you believe this and you haven’t seemed able to explain. Perhaps bathymetry effects?

Anyway do you believe the gap to previous lowest volume will shrink towards the end of the melt season. Could there be a bet about this to test the idea?

[Unfortunately I don’t have a strong opinion on that. I think it likely that the gap will shrink, yes. I’d even put money on that, just to formalise things -W]

I suspect I won’t disagree with you enough to bet but maybe others will be interested to see if you propose anything.

This seemed like an important matter to test this season, so hope it is ok to add this poll and we are not having too many.

Feel free to vote and/or add comments. Further reasoning on option 2 particularly welcome eg is it bathymetry effects or ....

Science / Extreme weather event attribution
« on: December 29, 2016, 06:08:32 PM »
A couple of papers arising from / weather@home

Real-time extreme weather event attribution with forecast seasonal SSTs
K Haustein et al 2016

Here we present a new method which can assess the fraction of attributable risk of a severe weather event due to an external driver in real-time. The method builds on a large ensemble of atmosphere-only general circulation model simulations forced by seasonal forecast sea surface temperatures (SSTs). Taking the England 2013/14 winter floods as an example, we demonstrate that the change in risk for heavy rainfall during the England floods due to anthropogenic climate change, is of similar magnitude using either observed or seasonal forecast SSTs. Testing the dynamic response of the model to the anomalous ocean state for January 2014, we find that observed SSTs are required to establish a discernible link between a particular SST pattern and an atmospheric response such as a shift in the jetstream in the model. For extreme events occurring under strongly anomalous SST patterns associated with known low-frequency climate modes, however, forecast SSTs can provide sufficient guidance to determine the dynamic contribution to the event.

Assessing mid‑latitude dynamics in extreme event attribution systems
Daniel Mitchell et al 2016
Atmospheric modes of variability relevant for
extreme temperature and precipitation events are evaluated
in models currently being used for extreme event attribution.
A 100 member initial condition ensemble of the global circulation
model HadAM3P is compared with both the multimodel
ensemble from the Coupled Model Inter-comparison
Project, Phase 5 (CMIP5) and the CMIP5 atmosphere-only
counterparts (AMIP5). The use of HadAM3P allows for huge
ensembles to be computed relatively fast, thereby providing
unique insights into the dynamics of extremes. The analysis
focuses on mid Northern Latitudes (primarily Europe) during
winter, and is compared with ERA-Interim reanalysis.
The tri-modal Atlantic eddy-driven jet distribution is remarkably
well captured in HadAM3P, but not so in the CMIP5 or
AMIP5 multi-model mean, although individual models fare
better. The well known underestimation of blocking in the
Atlantic region is apparent in CMIP5 and AMIP5, and also,
to a lesser extent, in HadAM3P. Pacific blocking features
are well produced in all modeling initiatives. Blocking duration
is biased towards models reproducing too many shortlived
events in all three modelling systems. Associated storm
tracks are too zonal over the Atlantic in the CMIP5 and
AMIP5 ensembles, but better simulated in HadAM3P with
the exception of being too weak over Western Europe. In all
cases, the CMIP5 and AMIP5 performances were almost
identical, suggesting that the biases in atmospheric modes
considered here are not strongly coupled to SSTs, and perhaps
other model characteristics such as resolution are more
important. For event attribution studies, it is recommended
that rather than taking statistics over the entire CMIP5 or
AMIP5 available models, only models capable of producing
the relevant dynamical phenomena be employed.

Arctic sea ice / Ice free predictions and their uncertainty
« on: August 28, 2016, 12:47:24 AM »
How predictable is the first ice-free Arctic summer?

In conclusion, our findings suggest that we cannot predict the timing of an ice-free Arctic summer with an uncertainty of less than about 25 years.

Hmm, possibly I suppose, but: If the central estimate is 10 years or less away then I wouldn't think that 25 years uncertainty would be needed. If the central estimate is over 50 years away then an uncertainty of more than 25 years might be needed?

Science / Mauna Loa CO2 2016 Thread
« on: May 16, 2016, 09:29:13 PM »

Arctic sea ice / What's new in models?
« on: September 11, 2015, 12:26:50 PM »
The sea ice orchestra

Since 2012, several new parameterisation schemes have been incorporated into sea ice models, including:

Melt ponds (accumulation of melt water on the ice surface).
Brine drainage through sea ice.
Atmospheric/oceanic form drag (obstructions to air/water flow caused by the variable ice morphology).
Anisotropic rheology (ice stresses in specific directions determined by ice floe shape).
Lateral melt which accounts for variable sea ice floes.

Huge advances have been made in recent years, but there is still some way to go before we can reliable simulate and predict the fate of the Arctic sea ice cover.

Science / Satellite Temperature Record
« on: April 10, 2015, 11:01:40 AM »
A quote:

All of this will soon be moot, anyway. Since last year we have been working on v6.0 of the UAH datasets which should be ready with the tropospheric temperature datasets before summer is out.

Not hard to guess this is from Roy Spencer. But when is the interesting part. It was 9 May 2012!, and guess what? v6.0 still isn't out.

Obviously it is proving difficult. Question is, how long should it be before he gives up and makes V6 the Po-Chedley Thorsen Fu version?

(Yes I know that is horribly snarky, but he does seem to be steadfastly ignoring Po-Chedley Thorsen Fu and preferring to whine about being attacked by Guardian by at least partly ignoring the problem they are attacking and focusing on something else. See Stoat comments for more
WC thought my quote was good enough to make a post out of it so I hope people don't mind if I share it here.)

Edit: Authors correction

Consequences / What is your reaction to this Newsroom climate change video?
« on: December 23, 2014, 04:29:02 PM »
Newsroom Climate change

has previously been posted. However there just seemed just such a huge range of possible reactions to it, it seemed hard to know what others thought.

For example, there appeared to be some stunned shock, but was this from climate message being given or that the expert would say such things?

First statement by 'expert' that had shock effect was

A person has already been born who will die due to catastrophic failure of the planet.

Feel free to elaborate more than the choices I have suggested in the poll which are probably poor and are unlikely to give a full enough range of reactions. Distinguish between your reaction to video and your own beliefs if you wish.

Consequences / six degrees
« on: December 16, 2014, 02:57:32 PM »
Title of a book by Mark Lynas, often recommended as reading for some courses.

Here is a six minute video:

Arctic sea ice / First Ice free day poll
« on: December 10, 2014, 04:01:24 PM »
Since 2013 and 2014 minimums were so high, I thought it might be an idea to have another poll to see how much later if at all people think ice free conditions will occur.

Other long term outlooks are welcome. Feel free to describe what you think will happen. If you wish that can include downloading the attachment and drawing what you think is more plausible.

To explain the attached graph:

Blue data is April Average PIOMAS volume
Yellow data is September average PIOMAS volume

Red and green are 4 parameter gompertz fits.

The straight blue line is intended to show acceleration as MYI over 2m thick collapsed due to less area, less age and thinner MYI mainly as the MYI stopped making it around the Beaufort Gyre. Once there was little MYI over 2m thick this accelerated phase dies out so that the thinning was only at a rate consistent with just FYI thinning.

The purple line descends more quickly than the blue line again aiming to be consistent with past. If there is less ice at the start of the season then albedo will be lower allowing more open water to form and more energy to be absorbed so that more ice melts. I have the difference between the two straight lines increasing from 17.8 K Km^3 in 2014 to 18.8 K Km^3 when we reach ice free.

This purple line first goes below 1000 km^3 in 2028.

Also note that the difference between 2012 and 2014 minimum volumes is nearly 3200 Km^3. Therefore while the purple line only gets down to 1000 Km^3 by 2028, it could occur any time after the purple line gets below 2600 km^3 which could be as early as 2022. I am therefore going to average 2022 and 2028 to arrive at 2025.

Science / LGM Review
« on: November 15, 2014, 03:08:51 PM »

A perspective on model-data surface temperature comparison at the Last Glacial Maximum (LGM)
Annan and Hargreaves 2015?

3.3. Climate sensitivity
One major reason for the interest in the climate of the LGM — though certainly not the only one — is the hope that it might also provide insight into the response of the climate to external forcing in the future. This is commonly summarised by the concept of (equilibrium) climate sensitivity, expressed as the long-term change in temperature in response to a doubling of the atmospheric CO2concentration (roughly 3.7 Wm−2). While it is doubtful that the full earth system is ever truly in equilibrium, the atmosphere-ocean system can be considered to be close to this condition over the millennial time scale associated with the LGM state (since a sustained and significant radiative imbalance over this long a time interval would result in major changes in temperature and/or ice volume). The stability of the climate system at that time, together with the reasonably well-known temperature anomaly and radiative forcing, suggests that the LGM may be a particularly useful interval to constrain the possibility of a very high equilibrium climate sensitivity (Annan and Hargreaves, 2006).

Simple calculations in which the global temperature anomaly at the LGM is divided by the total estimated forcing relative to the pre-industrial state have long been used to generate estimates of the equilibrium climate sensitivity. These estimates have remained close to 3 °C throughout changes in estimates of both components (Hansen and Lacis, 1990, Hoffert and Covey, 1992, Annan and Hargreaves, 2006 and Rohling et al., 2012). The most modern estimates for the (negative) forcing of 8 W m−2 (Annan and Hargreaves, 2006 and Jansen et al., 2007) and temperature anomaly of 4 °C (Annan and Hargreaves, 2013) would suggest a figure of just under 2 °C, which is at the lower end of the previous range of values. However, there are substantial uncertainties and perhaps biases associated with this approach. It is not expected that the response of the climate system to large negative and positive forcings will be perfectly linear, even at the global scale. In fact, model simulations show significant (and model-dependent) nonlinearity (Hargreaves et al., 2007). Moreover, the response to different forcings is not linearly additive. Thus, the climatic effect of large ice sheets, when combined with a reduction in greenhouse gas concentrations, is not equal to that of the same forcing when produced by changes in GHGs alone (Yoshimori et al., 2011). Various researchers have attempted to account for these factors by using climate models to simulate the past and future climates (Hansen et al., 1984 and Manabe and Broccoli, 1985). Annan et al., 2005, Schneider von Deimling et al., 2006b and Holden et al., 2009 and Schmittner et al. (2011) all used ensembles of models with a range of parameter values. In all cases, a strong response between the LGM cooling and 2 × CO2 warming was found across the ensemble, but the relationship itself was considerably model-dependent. When a range of GCMs was examined, the relationship between past and future was much weaker. Crucifix (2006) found no significant relationship at all across a small ensemble of PMIP2 models, but, in a larger ensemble, Hargreaves et al. (2012) did find a significant relationship between tropical SST at the LGM, and climate sensitivity. When constrained with the proxy-based observation of LGM cooling, this implies an equilibrium sensitivity of around 2.5 °C with a 90% confidence interval of about 0.5–4 °C. However, this result must be considered somewhat provisional, due to the small ensemble size and the previously mentioned uncertainties in forcings and proxy data.

0.5C to 4C sensitivity but this is only from LGM. Other sensitivity work makes 0.5C to 1.5C sensitivity unlikely leaving a range of 1.5C to 4C ... hmmm sounds familiar.

Science / Global warming slowdown 'could last another decade'
« on: August 22, 2014, 01:21:30 AM »

Paper is
Varying planetary heat sink led to global-warming slowdown and acceleration

A vacillating global heat sink at intermediate ocean depths is associated with different climate regimes of surface warming under anthropogenic forcing: The latter part of the 20th century saw rapid global warming as more heat stayed near the surface. In the 21st century, surface warming slowed as more heat moved into deeper oceans. In situ and reanalyzed data are used to trace the pathways of ocean heat uptake. In addition to the shallow La Niña–like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.

Full text pay-walled.

It is in science, so reliable?

More of an ocean cycle and presumably less sensitivity to CO2?

The rest / Could geoengineering be started and hidden while illegal?
« on: August 12, 2014, 12:59:13 PM »
I think it is crazy to think any has started. However just out of interest I wonder how hidden could it be?

Obviously depends on the type of geoengineering. I am thinking about using temperature differences in winter between air temp and water 50-75m down to power a motor that pumps water to above the ice where it can lose heat to space and thicken the ice. You would need quite a lot of these to make any impact and deploying and servicing such equipment might involve too much in the way of trips to be disguised as deploying and servicing scientific buoys.

Is this at all feasible? Are there other types of geoengineering that could be hidden?

Antarctica / Sea Ice peak at or just before Y/E?
« on: January 09, 2014, 03:51:53 PM »

It may be a bit of self fulfilling prophesy to suggest that if there is a peak at or just before the year end than there is a change in direction of the short term trend.

However it does seem to happen quite a bit in above graph or am I deluding myself?

Antarctica / Records and oddities
« on: December 22, 2013, 12:43:14 AM »
CT area has reached 5th highest daily area anomaly, the 4 higher days are consecutive days in 2007:

2007.9672   1.8403077
2007.9644   1.7662096
2007.9698   1.7593303
2007.9727   1.7178568
2013.9644   1.6992683

It was exactly the same time of year. That may not be a co-incident but there are other times of year when there are high anomalies: near .3 .5 and .6 of a year seem to feature quite frequently among high anomalies as well as near the end of the year. Didn't find any rounding to 0.1 of a year until 427th highest anomaly. I guess it isn't too surprising for there to be a change in the seasonal pattern over a long period of time.

Arctic sea ice / Predicting PIOMAS [s]Max[/s] now on to minimum volume 2014
« on: December 19, 2013, 07:05:59 PM »
The data seems to be indicating that relationships are changing over time.

Chris Reynolds suggested using gains early in the freeze season as a guide to gains at the end of the season.

looking at gains from 30 Nov to max compared to gain up to 30 Nov I found a correlation co-efficient for 1979 to 2005 of -0.19 but for 2006 to 2012 of +0.47. I probably need to de-trend the numbers.

Using minimum volume as a guide to the gain from min to max I get correlation coefficients (again I haven't detrended) from 1979 to 2005 of -0.38 and for 2006 to 2012 of -.70

High rates of change in correlation coefficients probably don't make for reliable estimates. In addition the gain to 30 Nov 2013 is high suggesting further rapid increase, but the minimum is high suggesting a low total gain.

I am not really sure if it is possible to make sense of all this. Nevertheless I shall give it a go and probably make a fool of myself:

Many people have suggest the situation has changed at some point between about 1998 and 2007. The changing correlation coefficients might be an indicator of this.

As the area of thick multiyear ice has declined there are increased areas of no and thin ice which can rapidly gain volume early in the freeze season. Later in the freeze season, this slows down as these areas approach their equilibrium thickness. So later in the freeze season, perhaps the volume of ice plays a more important role.

The gain in ice from minimum to 30 Nov increases from 4.7 K Km^3 in 1979 to 6.7 K Km^3 in 2011.

The gain from 30 Nov to max is less clear possibly declining a little from 1979 to 1994 before increasing.

The biggest two gains are after the minimums of 2007 and 2012 which were particularly low minimum volumes so after a high minimum volume I am expecting a fairly low volume gain.

I am therefore not giving too much attention to the high volume gain so far as I expect the volume effect to occur later in the freeze season.

I could be completely wrong, the variations in volume at max may be due to weather rather than any trends or volume gains early in the freeze season may be a better guide, or lots of other things not considered here.

It will be interesting to see what happens.

Other thoughts welcome.

Arctic sea ice / Arctic report card 2013
« on: December 14, 2013, 12:14:09 AM »
Arctic report card 2013 is out:

The press conference is also available as a video in AGU fall virtual options which requires registration - free providing you use promotional code clearly visible.

Questions on sea ice link to weather at more southerly locations were answered with

There is a growing body of evidence for these links. It is an area for research. There is vigorous debate about it but there seemed suggestion that it was largely accepted that the links existed but the precise causation were subject to debate.

Arctic sea ice / Feedbacks
« on: November 28, 2013, 04:08:25 PM »
Started this thread for any comments on what might or might not be an arctic sea ice feedback and how well established or otherwise they might be.

A couple discussed recently:

methane cycle: more release of methane when windier and less ice cover causing methane GHG effect which in turn causes less cover and stormier weather. Positive feedback.

Ice cracking in February 2013 from thinner more mobile ice allows more ice to form in February and March. Negative feedback -  though cracking later that approx mid April is likely to be positive feedback though albedo effect. Probably only speculation not established.

Arctic sea ice / Land snow cover effect on sea ice
« on: May 09, 2013, 06:21:15 PM »
April Rutgers graph:

Is it a co-incidence that lowest of last few years are 2007, 2010 and 2012 are the same years as have seen large melt outs?

Is the high value for 2013 therefore good news?

Arctic sea ice / PIOMAS Maximum
« on: April 07, 2013, 01:26:47 PM »

Larger version:

Trend has moved day of maximum from 113 to 105. So early/mid May would seem rather late. About day 100 (10 April) would seem an appropriate day if you expect it to be earlier than the trend. This would probably mean little increase from 21.612 on day 90.

Gain day 60 to 70 = 0.761
Gain day 70 to 80 = 0.451
Gain day 80 to 90 = 0.455

2012 (late max) had 0.858 0.497 0.498
2011 (early max) had 0.602 0.554 0.431

Probably not sensible to read too much into this but 0.455 of last 10 days is nearer the 0.431 of 2011 which had an early max.

Please feel free to add your guesses of day and amount.
I am going for: day 103 21.78

Arctic sea ice / Records and oddities
« on: February 22, 2013, 12:50:53 AM »
Looks to me like we have just had coldest day north on 80N per DMI since 2004.

Walking the walk / Is this for predictions?
« on: February 04, 2013, 03:08:02 PM »
Predictions and how well they fare?

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