parmenides3

When TV shows glaciers calving during reports about climate change it is doing so for 'dramatic effect'. Lots of ice melts every year, lots of water freezes every year (in quantities which are hard to comprehend, they are so vast). The important thing to look for is the difference between the average amount which is recorded as coming and going, and the current situation; the anomaly. The anomaly can be positive or negative, meaning more or less ice than average is melting/freezing. A big anomaly (two or more standard deviations from the 'norm') is a cause for concern if it is part of a trend; in reality, the range of variability every year is so vast that one 'extreme' year may or may not carry a larger signal. What is unusual about the Arctic sea ice is that there has been a consistent trend of decline for a long time now, that this trend appears to be accelerating, and that there hasn't been a positive anomaly in ice area or extent since 2003, which is unusual in itself. These are indicators that the pattern of things is changing. The pattern of things changing is, in other words, a 'climate change'. What is worrying to a lot of scientists is that many of the world's natural systems exist in fine balances, which are vulnerable to even small changes. Long term, large scale changes are a source of concern for two main reasons; firstly, they will have a knock-on effect, wherein the disruption to one part of a system will have an impact on another, and secondly, that the process of change may have a 'quantum' element, ie, at certain 'tipping points', a change may become more or less permanent, or a trend of decline or growth becomes 'fixed' and irrecoverable. In such a case, it is clear that there will be substantial consequences, but how long they will take to manifest, and what they will mean for the infrastructure of human societies, is very unclear, and, if you don't like the idea of mass extinctions or population crises, somewhat alarming. Try to ignore the 'scary' stuff the TV/papers show and say; this is not science and it is often barely even based on fact; worry about what the evidence and observations show; this is less spectacular but more important. P Don't confuse the measurement of sea ice area with the rate of melting; they are not the same thing. We use such terms as shorthand, but what the data shows is sea ice area/extent, which can be seen and measured, to a degree. Sea ice depth has been measured occasionally over recent years but this is much harder to do for such a large area, so inferences have to be made from whatever measurements are taken. Again, look at the pattern rather than the detail; it is the trend which matters, which is why the measurers work on the basis of five or seven day averages, or even longer ones; statistically, the accuracy of a longer pattern is more reliable than the accuracy of a subset. P

Hi CJWRC & welcome. No, it's mostly the ice being shifted around. Sometimes, given the weather up there, there might some surface ice formed during the melt season, but generally, once it starts melting, it carries on melting till the end of the season (roughly, September). There are lots of things to know about arctic sea ice, so simple snapshots can be confusing. I'm not sure how it can be propaganda-like to post pictures showing what is; this is simple observation of fact. What the image means, and how it is interpreted, can be subject to bias in the person doing the interpreting, but generally, if there's not much ice there, then it's not there. Is it propaganda-like to show a long-term trend? Surely, propaganda is manipulation of fact ( or disinformation, or straight-out lying) for political purposes. Do you believe that the images shown, or the graphics/facts, are inaccurate? If so, do you have a basis for this belief? P

NADS: apparently, the Fram outflux is more a function of the Dipole Anomaly. This was supposed to produce Northerlies during July but current suggestions are that there more of an Easterly element than expected. The Russian sea ice service has good short-term current and wind flow forecast maps, if you're interested. The perennial problem of the Arctic is its immense natural variability, which makes fools of forecasters. Its generally safer to make use of trends and tendencies over periods than look at synoptics, but the best you can do is gather the evidence on current and recent conditions from every possible source and then make inferences about what they might be indicating. Current indication seem to be that the seasonal sea ice level is about three-four weeks ahead on long term average. Impossible to talk about records, really, but it's a surefire bet that the Summer low point will be very low, and the trend of long-term decline will be fortified, if not slightly worse than anticipated. P Are thos ehtr Rapidfire images, GW ? http://rapidfire.sci.gsfc.nasa.gov/

Cheers J. Hi GW. Check out this forecast: FECN16 CWIS 011800 THIRTY DAY ICE FORECASTS FOR THE EASTERN AND NORTHERN ARCTIC FOR JULY ISSUED BY ENVIRONMENT CANADA ON 01 JULY 2010. THE NEXT 30 DAY FORECAST WILL BE ISSUED ON 15 JULY 2010. Air temperatures in the Eastern and Northern Arctic were above normal during the second half of June, except in Committee Bay where they were below normal. As a result, the retreat and melt of the ice along the eastern margin of the pack ice in Davis Strait and Baffin Bay is proceeding at a faster pace than normal and ice concentrations are currently below normal in this area. The eastern margin of this pack ice lies approximately 150 nautical miles further west than its normal position at the end of June. Ice concentrations over most of Cumberland Sound are also currently below normal. However, as a result of the Arctic sea ice influx through Nares Strait, which did not consolidate this past winter, and due to a recent period of easterly winds over Lancaster Sound, ice concentrations in parts of northwestern Baffin Bay and in Lancaster Sound are currently greater than normal. Old ice concentrations in Nares Strait, Baffin Bay, the mouth of Lancaster Sound and in Davis Strait are also greater than normal. Because of the above, the "open drift or less" and the bergy water routes across northern Baffin Bay, which were forecast to develop in mid-June, have not yet developed. The "open drift or less" and bergy water routes to Thule, however, did develop by the end of June (1 week later than forecast but still approximately 3 weeks ahead of normal). Small openings in the sea ice have developed in Eureka Sound and in Belcher Channel on the southwest side of Norwegian Bay and ice melt in these areas is proceeding normally. Forecast ice conditions for July 1st to July 15th. Air temperatures for the first half of July are forecast to be above normal over the Eastern and Northern Arctic and no significant storms are forecast to affect the region during this period. As a result, ice across the region is expected to continue melting at a greater rate than normal. A brief period of moderate westerly winds associated with a low pressure system crossing northern Ellesmere Island is forecast to affect Jones Sound and Lancaster Sound on the 5th and 6th of July. This event will cause some flushing of areas of fractured fast ice from Jones Sound into northwest Baffin Bay and also cause flushing of the mobile pack ice in Lancaster Sound towards Baffin Bay during this time. As a result of this, as well as due to the continued influx of sea ice from the Arctic Ocean through Nares Strait, ice concentrations in northwest Baffin Bay are expected to remain greater than normal during the first half of July, delaying the development of the bergy water route across northern Baffin Bay by another 1 to 2 weeks. At the same time, these winds will help fracture the fast ice in Jones Sound by mid-July, in keeping with the forecast date for this event. Fracture of the fast ice in Norwegian Bay, Pond Inlet, the northern half of Admiralty Inlet, Wellington Channel and in McDougall Sound is still expected to occur near mid-July, 2 to 3 weeks ahead of normal. In southern regions, ice concentrations along the southern edge of the ice pack in Davis Strait will continue to decrease and the remaining ice in Cumberland Sound will flush out of the region. In Nares Strait, fast ice in adjacent bays and fiords will continue to break off, adding to the old ice floes descending from the Arctic Ocean and to the bergy water in the area. Forecast ice conditions for July 15th to July 31st. While air temperatures over southwestern and western Baffin Island, the Gulf of Boothia and eastern Barrow Strait are forecast to remain above normal during the period, air temperatures over the Northern Arctic, Jones Sound, eastern Lancaster Sound and along eastern Baffin Island are forecast to drop to below normal towards the end of July. This may impact the fast ice fracture in Eureka Sound, the clearing of Pond Inlet and the development of the "open drift or less" route to Cape Dyer, all of which are forecast to occur by the end of the month. However, due to the rapid melt and retreat of the ice that will take place during the first half of July in these areas, fast ice fracturing and clearing in these areas will likely still occur as forecast. The main ice pack in east-central Baffin Bay will continue to shrink and by the end of the period, the ice concentrations in that area will resemble conditions normally seen in the first or second week of August. END GW, if my links aren't working, Google the Canadian Ice Service and navigate through the extensive products. Or try this link: http://www.ec.gc.ca/glaces-ice/default.asp?lang=En&n=D32C361E-1

Useful reference tool: http://www.ec.gc.ca/glaces-ice/default.asp?lang=En&n=4CE72415-1 or: http://www.ec.gc.ca/glaces-ice/4CE72415-E22F-4872-9C3E-8DC170BBFB3D/ar_breakup.gif Context is everything. Check out what is happening at the Fram Strait; if there is a lot of North-South flow there, then older ice can be flushed out of the Arctic and lost, which is bad. P Oh, and this... http://ice-glaces.ec.gc.ca/prods/WIS56DPTCT/20100705180000_WIS56DPTCT_0005069498.gif

Well, it can have existed, perhaps at a relatively stable level, for a long time, but then an increase or decrease over an extended period would have to come in to alter the response of the system to said forcing. Volcanoes are an interesting short-term example; Pinatubo changed several elements of the system, resulting in short term fluctuations which would not have other happened. There is also a degree of hysteresis in the system response, but, once it stopped erupting, the system was eventually allowed to restabilise at close to its previous state. We have to find a mechanism to account for the persistent trend. Actually, we have found a lot of mechanisms, with various degrees of influence; the question still remains which mechanisms matter, and which if any we (humans) can do anything about. Without the change to the system, your solar hysteresis idea would suggest that, over time, the earth would warm indefinitely (I think) P

Yes. Here we need to find something which is/has changed which has led to an observed trend; a long-term positive forcing which did not previously exist. P

Neatly explained, Songster. http://polar.ncep.noaa.gov/seaice/Analyses.html contains some good explanations (scroll down the page. Bob Grumbine is also a good egg and has recently started blogging, to cover some of the enquiries he gets about science and GW: http://moregrumbinescience.blogspot.com/ if you have technical questions about the Arctic, he may well address them for you... P

'As I have said before (though you may have missed it since you've been away, P3) the temperature increase over the last 100 years or so would require the Earth to retain no more than an extra 1/1000th of a degree Celsius every month, which is not a great deal.' If the System retains 'extra' heat, this suggests that something has changed, either to the system, or the external forces working on it. But consider a tropical desert at night, or a temperate location through the seasons; to what extent do these places exhibit hysteresis? If I recall rightly, for example, temperatures in the UK respond to our relationship to the Sun with an approximate six-week lag (variable), so that we get our warmest months after the period of greatest insolation, and vice versa. Where the global surface temperature may well exhibit hysteresis is in the case of our old friend the Arctic, sea ice and sea surface temperature. This has to do with the way in which the measurements works today compared to 30 years ago. The reason why the lower Arctic waters show such a high anomaly is at least partly because, 30 years ago, areas which were perennially ice-covered are no longer; therefore there is a large anomaly recorded. It is also important to understand how much of the long-term global trend is affected by these anomalies (though also important to recognise that models account for the phenomenon to some degree). So, is the sea ice reducing at 8% per decade because of warming oceans, or are the oceans showing warming because the sea ice is reduced? The two are obviously demonstrating the same overall pattern - one of warming - but establishing cause and effect is less obvious. So, a suggestion here might be that the leaky integrator model could work quite effectively in relation to the Arctic Ice; think of single-year and multi-year ice as the 'new' and 'carried over' elements of the system. For a year like 2007 to happen, there has to be a loss of multi-year ice as well as the expected seasonal variation in the single year ice. This is, in part, what happened on 07; because of the currents, the winds and the Summer synoptics, multi year ice was pushed out of the 'bowl' of the Arctic Ocean, via the Fram Strait, out into the warmer Greenland Sea, whence it melted. If the system is 'in balance', then, over time and allowing for variability, the proportion of multi-year and single year ice remains broadly similar. This is because the steady build-up of the hysteretic element is countered by the occasional 'burst' of the system, leaking what has been gained out into the oceans surrounding. Is this suggesting anything?...

Blast, why would NOAA scientists conspire to falsify data? :)P

Question: have we accumulated enough information to confidently state that a trend does or does not exist? next: if a person is not satisfied with the information that is currently available or used, given its incredible quantity and variety, then said person is not going be satisifed with the addition of further data. It's not the input, it's the result which some people find unpalatable, so, in order to avoid the result, the easiest thing to do is deny the validity of the evidence. we have several hundred years worth of measurements, and several hundred thousand years worth of proxy-based estimates. But it would make no difference if we had sizteen zillion signed affidavits by Saint Joan; if you want to deny scientific results, you will. This is not the same as refuting scientific hypotheses, or demonstrating errors in research work; these are rational and methodological practices. If you feel uncertain about GW, it should ideally be because you have a reason to doubt the science, not a need to run away from it. P

I'd have to spend some time hounding out the latest papers to give a proper answer to what's been happening since the AR4, it's really more my sense of 'what's been discussed' rather than hard theory. In 2007, thought was as you suggest; I think it may have modified a bit since then. P

Ah, but how much of a 'blip' was it, and did it have an impact which makes long-term reversal more difficult in future? I don't know, but my suspicion is that 2008 and 2009 might have been less extreme, given the conditions, if 2007 hadn't happened. Finally, is it likely that we'll get another 2007 soon, and what would the impact of that be? P

Hi J. Does this mean you've forgiven me? P

Hi Shandiman; there is still uncertainty about whether changes in oceanic currents will result in considerable cooling in N Europe in the decades to come. Recently. the feeling seemed to be that the odds of a consistent slowdown in the THC, effecting our local climate, were about 1/4 for this century, and perhaps 50/50 for the next. But the uncertainties are very large, and various measurements and research seem increasingly to suggest that the THC is a lot more variable than we used to think, and that it is already exhibiting possible signs of long-term changes. I don't think anybody, even the top scientists, are really comfortable that we have got to grips with this yet. Small side point; best guess is that, even if there is a general THC slowdown and a localised cooling, GW will still continue globally, and temps. in 2080 in the UK are still more likely to be higher on average than they are now. P weathereater; ta mate.