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Al Rodger
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Tor Bejnar, You whetted my appetite so I went looking. I soon was finding talk (eg "How the Isthmus of Panama Put Ice in the Arctic" by Haug & Keigwin) that the Panama gap had closed as a significant feature on the climate by 4.2 million years ago but it required something else to kick the Arctic into proper icy conditions a million years later. The orbital obliquity which is one of the theories mentioned as a trigger(or the lack of orbital obliquity stopping the trigger 4.6-3.1My) is plotted in this earlier Haug & Tiedemann & paper.
Toggle Commented Apr 13, 2015 on The Ns are calling the maximum at Arctic Sea Ice
Tor Bejnar, Timing-wise, the appearance of the Panama Isthmus in terms of shutting off ocean currents can be different to the isolation of Pacific from Atlantic eco-systems. In terms of climate, Drakes Passage between Antarctica & S. America wasn't simply open or shut. And it too may have played a part in mid-ploicene climate change. It had been open for some millions of years but was still widening in the mid-pliocene, having suffered a bit of a squeeze in the early Miocene (c25-15my), according to Lagabrielle et al (2009). For ocean currents, it seems size matters.
Toggle Commented Apr 12, 2015 on The Ns are calling the maximum at Arctic Sea Ice
Bill Fothergill, Paul Whitehouse, David Whitehouse? Thank you for correcting my mistake. Names is not my strong point. Chris Reynolds, Regarding wobbles, I think we look in different places. I have been conscious that the annual cycle and trends in that annual cycle can create wobbles with some forms of analysis. So the daily anomaly trace shows wobbles because the summer melt is recently far bigger than the average over the anomaly base period. One approach is to consider different times of the year in isolation, as you have done. Another is to average over a full 12 months, as I have done. One use of rolling 12-month averages was to divide the record into four, carry out a linear regression and subtract the trend (so any change in long-term slope is addresses), then quantify the wobbles by calculating the standard deviation. The results were (from memory, units?) 1.2, 1.5, 0.9, 1.8. Another use of rolling 12-month averages was to calculate the SD for short periods (24-month) as a way of addressing changes in long-term trend. The graphical result is posted here. Again it shows recent times more wobbly but not that greatly so. If you iron out the wobbles to give, say, a set of decadal values (actually 8-year values, ave SD, M sq km) they are 1980-88 0.093, 1989-96 0.119, 1997-2004 0.076, 2005-13 0.140.
Toggle Commented Apr 8, 2015 on PIOMAS April 2015 at Arctic Sea Ice
Chris Reynolds, Yes. You are right to say significant wobbles are present before 2006. Post 2006 they are bigger but a quick comparison of the various parts of the NSIDC SIE data does show the post-2006 wobbles aren't so much bigger. As for the GWPF, you ask whether GWPF are stupid or mendacious. In the past I analysed of some of their work and I can assure you that it is not either/or - they are both (or their denial is so intrenched that they are driven to lying. I think that may be why GWPF stands for Gentlemen Who Prefer Fantasy.) The 'author' of the piece in question here, Paul Whitehouse, is a very low calibre actor in their pantomime although he is one of their alleged 'Academic Advisory Council'. (I say 'alleged' as I doubt they are any of these things.) Whitehouse attempts to brand the decline in Arctic sea ice as not anthropogenic and either not of any consequence or not happening, standard denialist ploys. The decline began "even before human effects were strong" and "decline between 1979 and about the mid-1990s is not that significant" And all this is probably still brought to you courtesy of the UK tax payer who support through tax relief the work of this supposed "educaional charity". (GWPF have retrenched from being entirely a charity but the lying and disinformation is published by a wholly-charity-owned organisation., This still bringing the UK Charities Commission and all other UK charitues into serious disrepute.) Perhaps I should have said somewhere- "Don't get me started"
Toggle Commented Apr 7, 2015 on PIOMAS April 2015 at Arctic Sea Ice
Chris Reynolds, I don't think it is so difficult to argue that the average annual Arctic SIE has not been slipping every downwards since 2006. The annual average (two clicks down here) has actually grown more wobbles in that period as the individual big summer melts appear and disappear from the annual average. Yet, to start using such a measure to argue for a stable Arctic would be a bit of a hostage to fortune. If summers did turn seriously less icy, this may not feed much onto the annual average, and the agent spreading such a message that "All is well with Arctic ice - look at the annual average!" could easily find himself well-&-truly stuck on the I'm-a-total-idiot step.
Toggle Commented Apr 6, 2015 on PIOMAS April 2015 at Arctic Sea Ice
Hey! The PIOMAS traces for 2015, 2014 & 2009 resemble railway tracks with the points being switched in mid-February:-) The 2014-2015 comparison of thicknesses across the Arctic, isn't the important factor that the thin bits will more easily melt out and increase feedbacks? Sticking all your ice in one place may protect the ice, but it will result in a warmer Arctic summer.
Toggle Commented Apr 5, 2015 on PIOMAS April 2015 at Arctic Sea Ice
So why did 2015 have a February icier than March, the first since the 1990s, when the trend has been for the maximum to be later and later? It's more like a big bite was taken out of the maximum (leaving February less bitten than March) rather than the maximum being early per se. Looking at the UH plots on the regional graphs page shows the Pacific gave the low ice levels for the season but the big bite was mainly the Barentz which peaked at the start of Feb before dropping 400k from then to mid-March before regaining half of the drop so as to provide a late March sub-maximum. The Bering had a smaller shorter bite but the big influence was the Barentz. So what was going in in the Barentz? A random wobble? Or something new for the future?
Toggle Commented Mar 30, 2015 on The Ns are calling the maximum at Arctic Sea Ice
WIth the Barentz still showing +30k a day, if that continues with a bit of coincidental stalling/upticking elsewhere, there could yet be a final icy flourish.
Toggle Commented Mar 28, 2015 on The Ns are calling the maximum at Arctic Sea Ice
DavidR. Interestingly, you are right about 2010. Yet when I stuck my ten pen'orth in back on March 15th, the path of the rise to the 2010 maximum from that date was not enough to exceed this year's February maximum in 2015. What has happened is that 2010 dropped between March 15th & 25th increasing the eventual late rise of that year while 2015 has risen between March 15th & 25th, reducing the required rise to top the February maximum. Yet the significance of this year's maximum means nothing of itself. It is as part of a trend that it is significant. And indeed contrarians do love pointing out errors made by those they oppose. What is perhaps exceeding strange is that while such denialist folk do their best to stoke up minor muddles to look like major scientific blunders, they are wholly oblivious to their own record of continual egregious error.
Toggle Commented Mar 26, 2015 on The Ns are calling the maximum at Arctic Sea Ice
Anybody seriously making comment and calling a maximum SIE for the year - I don't think their call really should be accused of being "speculation". Now, I think there is a big difference between somebody like the Ns calling the maximum for the year and somebody like me. When I called it a couple of weeks back I gave my reasoning and for folks like us making such a call, that reasoning will usually have one central dominating reason. How prescient or foolhardy the call can be judged by others, and that holds whatever the outcome. Next year, for instance, my reasoning could be shown to be foolish even though I was right this year. The analysis of the Ns will be a lot more complex, probably having to satisfy a series of seperate analyses before the decision to call is made.
Toggle Commented Mar 26, 2015 on The Ns are calling the maximum at Arctic Sea Ice
g man. (1) DMI use O&SISAF data. (2) O&SISAF do not document on-line why they include lake ice but their code includes it and their graphics of "sea ice" show the Great Lakes and Lagoda with winter ice concentrations. It also shows a far coarser coverage at ocean shorelines. (3) Smaller lakes are not shown to be included, probably because the mapping resolution is too coarse.
Toggle Commented Mar 24, 2015 on Early record, late record at Arctic Sea Ice
Toggle Commented Mar 20, 2015 on Early record, late record at Arctic Sea Ice
g man. A picture tells a thousand words.
Toggle Commented Mar 20, 2015 on Early record, late record at Arctic Sea Ice
My brave call on Sunday of the maximum SIE being behind us - it is looking pretty solid today, just four days later. The reason for this early timing of the SIE maximum (JAXA & NSIDC both) is perhaps worth discussion (although likely has no answer, this being the Arctic). This will be the first time since the 1990s that February average SIE exceeded March average SIE, punctuating a strong trend in the opposite direction, abet a trend with a lot of noise on it. So is this year's timing the result of a super icy February, a seriously melty March, or is it a combination of the two?
Toggle Commented Mar 19, 2015 on Early record, late record at Arctic Sea Ice
Using the NSIDC data, the timing of the annual maximum in Arctic SIE, as discussed at the end of the Mad Max thread, can be shown to have a statistically significant trend by using 29-day rolling averages. Since the late 1980s the 29-day maximum has been getting later at a rate of 6 days/decade (+/-4 days to 2sd). But the early 1980s, when the NSIDC data is every other day not daily, perhaps shows an opposite trend. The early 1980s timing of the maximum 28-day period averaged at 8th March. The late 1980s 29-day period averaged 3rd March while the central trend up to 2014 was at 17th March.
Toggle Commented Mar 18, 2015 on Early record, late record at Arctic Sea Ice
So having heard me call the minimum as that back in February, the Jaxa SIE stops its faffing about and puts on 69k over two days. Still 186k to go before my bravery turns into foolhardiness. I might have been less brave given a bit of anslysis I was prompted to do by an enquiry elsewhere. The later timing of the SIE maximum can be made to look a bit illusory, lots of noise on an underlying trend that can appear very small. For instance, the NSIDC climatology maximum for 1981-2010 gives a timing very close to the average JAXA timing for 2003-2014. But it occurred to me that the NSIDC monthly data allows a comparison of the average ice in February and the average ice in March all the way back to 1979. And that shows quite a strong trend, but only since the mid 1990s = 24k/yr +/-10k (2sd). When I have a few moments, I double-check that result and try to convert it into a shift of timing in the maximum. What does stand out is that average Feb SIE had not exceeded average March SIE since the mid 1990s. But that looks mighty likely this year.
Toggle Commented Mar 17, 2015 on Mad max? at Arctic Sea Ice
Well, I threatened to do it so I shall. The comment that there is less ice so more open sea in line of fire (or frost) is greater which could allow a bigger rise - that is true. But it hasn't been evident within the JAXA numbers. 2003 is the biggest post-13th March rise in JAXA but there was over a million sq km more ice back then. I did a quick check at the NSIDC ch Arctic page and, guess what, over the same period the biggest post-13th March increase there was actually just last year, 2014, when 225,000 sq km was added. But to top the NSIDC February figure, 2015 would need 230,000 sq km. So, bravely, I say we have seen the maximum Arctic daily SIE for 2015 back in February. It is a safer bet to say that 2015 will see a record daily low. JAXA is presently 440,000 sq km below that daily record and NSIDC 380,000. All that said, the headline figure is always the highest monthly NSIDC average and it looks pertty certain that will be the February figure of 14.41M sq km, the previous record being 14.43M sq km in March 2006. For March 2015 to exceed the Feb 2015 average, the average for the rest of March would have to be 14.50M sq km to the end of the month, that is 200,000 sq km above the latest figure, from tomorrow and right to March 31st. I don't see that happening.
Toggle Commented Mar 15, 2015 on Mad max? at Arctic Sea Ice
I reckon that unless there is some big big reason to think otherwise, two more days of SIE faffing about with no sign of a rise and I would call 15th Feb as the maximum. JAXA gives the latest SIE (13th March) as more than 250,000 sq km below 15th Feb and there are no years on the JAXA record that have gained/regained that amount of SIE from this date on. All bar 2003 managed less than 150,000 and by 15th March 2003, the gain/regain was below 200,000 and dropping by the day. In fact, I would give it just one day and call it tomorrow. (Of course the last time I made a sea ice announcement, the big trend stalled the very next day.)
Toggle Commented Mar 14, 2015 on Mad max? at Arctic Sea Ice
The UAH Lower Troposhphere Temperatures for the Arctic Ocean continue to drop from the record levels of Jan & Feb and are now (ie for April) down to more 'normal' levels (as graphed here). The Surface Sea Temperatures from NOAA's nomad3 shows the Arctic Ocean as a whole & the high Arctic continuing at record temperatures for the time of year (as graphed none-too-clearly here).
Toggle Commented May 11, 2014 on PIOMAS May 2014 at Arctic Sea Ice
Hi Kevin, Yes. He has put his latest Global figure up here. But the page you link to with all the sea/land figures for different latitudes (ie the Arctic) is still only showing to February. It usually is updated quite promptly. Nomad3 is updated for March with SST showing record warmth above 65deg & 80 deg. But it seems to me that ice is more affected by TLT figures.
Toggle Commented Apr 9, 2014 on PIOMAS April 2014 at Arctic Sea Ice
The link that hopefully now works.
Toggle Commented Apr 8, 2014 on PIOMAS April 2014 at Arctic Sea Ice
The data from Rutgers Uni shows NH snow cover now tracking 2012, the record year for early snow melt. It's early days mind. (The graph here (usually 2 clicks to "download your attachment) shows the 2014 anomaly against previous decadal & the 2010-3 averages). UAH should update for March soon so we'll know whether the Arctic's Lower Troposphere record temperatures remain or have dropped down a little.
Toggle Commented Apr 8, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Chris Reynolds, I think the discrepancy between our two figures is you have managed to use 1 hour days. 67 ZJ x 24 = 1608 ZJ ≈ 1,600 ZJ (Note a comma is used not a decimal point. Sorry for the confusion caused.) Perhaps to add reason for why I see a 3m 2100 SLR is "exceedingly pessimistic", it is worth pointing to Vallis & Farneti (2009) who show a figure for the meridional heat transfer into the two polar regions of 2 x 1.5 PW or ~100 ZJ pa. This represents about 3% of the planet's 3,850 ZJ solar heating being sucked towards the poles because they are comparatively so cold. My exceedingly pessimistic" SLR would require 20% of the additional warming to be sucked towards the far smaller Greenland & Antarctic ice sheets due to a far smaller temperature differential.
Toggle Commented Mar 22, 2014 on PIOMAS March 2014 at Arctic Sea Ice
I think a few numbers may benefit the discussion. To give 1m SLR from melting ice, you will require 125 ZJ for the melt plus probably 10% coz the ice is actually well below freezing = 140 ZJ. Solar insolation is mainly used to keep the planet at 288ºK. Start pinching it to melt ice & the global temperature plummets. What is relevant is the TOA energy imbalance. If this is 1 Wm^-2, the extra energy sloshing round the climate after a century will be 1,600 ZJ. But if the ice remains awaiting melting at the poles, most of that 1,600 ZJ will end up heating the tropics, and then keeping it warm. And if the poles also heat up, there will be more energy needed to maintain that polar temperature increase. So let's say a very very generous 20% is the maximum that will be available to melt ice. Using 20% of the 1Wm^-2 imbalance for melting, that gives 2.3 m SLR in a century/Wm^-2 imbalance. Say the imbalance is a third the forcing & forcing rises from 2Wm^-2 today to 6Wm^-2 in 2100. The average over the century would thus be 4Wm^-2 forcing = 1.3Wm^-2 imbalance = 3m SLR. And that's from both poles. These numbers are in my view exceedingly pessimistic. But that is what is required to get multi-metre SLR by 2100 without the ice leaving the poles in search of the heat.
Toggle Commented Mar 21, 2014 on PIOMAS March 2014 at Arctic Sea Ice
folke_kelm, The famous paper on the internal temperatures of the Greenland ice sheet is Dahl-Jensen et al (1998), memorable because it presents a temperature record preserved within the temperature gradients.
Toggle Commented Mar 20, 2014 on PIOMAS March 2014 at Arctic Sea Ice