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Ned at 05:05 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
No, that's exactly what chris and I are pointing out. A value of +450 GT at the beginning of 2004 just means that there was 450 GT more ice in 2004 than in 2006. In other words, in 2006 Greenland had [X] gigatons of ice. In 2004 it had [X+450], and in 2010 it had [X-800]. We don't actually know exactly what [X] is. Again, the analogy is to temperature anomalies. If a temperature anomaly is calculated with regard to the period of 1971-2000, then temperature anomalies above zero just mean that the temperature is currently higher than it was in 1971-2000, not that it's necessarily rising right now. -
robert way at 04:59 AM on 15 July 2010Part One: How do ice sheets lose ice?
mspelto, I think I have fixed the issue and made my wording more clear. -
actually thoughtful at 04:57 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
So what does figure 2 show? It appears that at the beginning of 2004 the change in Greenland's ice mass was +450 gigatons. At the end of 2004, the change in Greenland's ice mass was +250 gigatons. In 2009 it was -600 and -800, respectively. Shouldn't the anomoly be positive if the ice is growing, and negative if the ice is shrinking?Response: The title for the graph is "Change in Greenland ice mass" but really, what I should've called it was "Greenland ice mass anomaly". I went with the more plain English terminology because anomaly is a technical term. But obviously, there is a reason why scientists use technical terms - they're more precise in meaning and less open to misinterpretation.
Greenland has been losing ice mass every year from 2002 to 2009. So the positive values at the start of the graph don't mean the ice sheet was gaining mass at that point. Those values are just the variation from the average over the whole 2002 to 2009 period. As it's been losing mass over the whole period, that's why the first half of the graph is positive and the second half is negative.
Am strongly considering going back to "Greenland ice mass anomaly". -
JMurphy at 04:44 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
skepticstudent, the argument is not circular at all. Maybe you need to read the whole thing in a more legible form : Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. (MY EMPHASIS) What, exactly, is circular about that ? You may not agree or believe in the scientific conclusion (just as some can't accept evolution) but that doesn't mean the conclusion is wrong or circular in any way. -
tobyjoyce at 04:40 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
@scepticstudent #23. This topic is about appropriate action to mitigate a risk. A doctor may, for example, suggest a different lifestyle to reduce risk of cancer or heart disease, but your example does not make sense. A doctor who is "absolutely sure" is not an appropriate counter-example to scenarios given above. The IPCC wording regarding APW is "very likely". "Relatively sure" is not a commonly used term for risk, and has no meaning in that respect. The rest of your scenario does not make sense. How suggested mitigations like reducing carbon in the atmosphere (of which the earth has sufficient to maintain life) somehow equates with "remov[ing] your reproductive system piece by piece" over 33 years, completely escapes me. If you are somehow suggesting that ideas for mitigating climate change are "a cure worse than the disease", you are a long way from stating your case, let alone proving it. -
Ned at 04:33 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
skepticstudent, if you construct an imaginary scenario that's not a good analogy for climate change, then of course that scenario might be one where it's appropriate to say the costs of action X vastly outweigh the benefits. So? Picture another doctor, one who says that she's found a small but malignant tumor in your body. Operating soon, before it metastasizes, will be relatively easy and will probably save your life. If you wait too long, the operation would become much more difficult and expensive. If you don't get the operation at all, you'll probably die. Slightly different analogy, opposite conclusion. Neither one really helps us decide what to do about climate change. -
robert way at 04:22 AM on 15 July 2010Part One: How do ice sheets lose ice?
mspelto, You have a point. I think I worded that phrase very cumbersomely, i will try to rectify it. -
mspelto at 04:12 AM on 15 July 2010Part One: How do ice sheets lose ice?
Robert good name change, which makes my comment on annual glacier balance moot. One correction "...an inland shift of the grounding line causes less backpressure through increased calving and basal melting." An inland shift of the grounding line may or may not cause either. If the elevation of the bed is increasing or the glacier fjord is narrowing then this will not occur. It is the thinning and consequent reduction in sidewall and basal friction that drives grounding line retreat, which can make the glacier more susceptible to the same. KR as the glacier goes afloat of course friction is reduced which reduces longitudinal compression and hence tends to increase speed. At the dame time as the glacier goes afloat it loses a principal driving force, gravity, this leads to reduced velocity. And of course it can spread out due to the reduced friction and longitudinal compression. This tends to lead to even more reduction of velocity as thinning and divergence of flow reduce longitudinal extension. -
skepticstudent at 04:04 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
regarded as settled facts. This is the case for the conclusion that the Earth ... is warming and that much of this warming is "very likely due to human activities.” 1. I love the circular logic here, regarded as settled fact, the consensus, the science is settled..... very likely... Picture a Doctor... We are absolutely sure that you have a health issue... We are relatively sure it's your male reproductive system that's causing it so we'll have to remove it. It will take 33 years to remove your reproductive system piece by piece and there's only .06% change in your situation by removing your reproductive organs, but we're very likely sure that is the issue. Who's gonna sign up for that doctor? -
Ned at 03:50 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Er, one could also read chris's comment making the same point as mine, but 93 minutes earlier.... Sorry for the repetitive redundancy. -
Ned at 03:40 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Sense Seeker writes: Second, it [Figure 2] seems to show that up to mid 2006, the ice mass was actually growing. That's a common, and understandable, misconception. The zero line in that figure isn't an equilibrium mass balance. It's an "ice sheet mass anomaly" similar to temperature anomalies that are measured with respect to an arbitrary zero point. In other words, the Y axis is (as stated) gigatons, rather than gigatons per year. Any time the line has a negative slope on that graph, it means Greenland is losing mass, regardless of whether the line is currently above or below 0. -
maintain_integrity at 03:18 AM on 15 July 2010Part One: How do ice sheets lose ice?
It seems as if steve goddard and others at WUWT are having a very hard time explaining why a full one-third, or 20 km of the entire loss of 60 km from the Jakobshavn Glacier in Greenland has disappeared from 2001 to 2006. Seems as if the first third, or 20 km., was lost between 1851 to 1913, or 62 years; the second third or 2o km. was lost between 1913 to 2001, or 88 years; and now the last third of the 60 km. loss, was lost between 2001 and 2006, a mere 5 years! Talk about uproar and disingenuous twisting of the facts to prove global warming doesn't exist or that the Arctic has warmed considerably more than the rest of the globe. -
robert way at 02:57 AM on 15 July 2010Part One: How do ice sheets lose ice?
Dennis, I do have to apologize as there was perhaps too much lingo being used here. One of the main ideas of the post is to create a less technical one over the next few weeks so that there can be a post for the general public and one for those really looking to get in depth. I did try to reduce the jargon however and tried to stay away from getting too complicated in my descriptions. I had a friend proofread who identified many things I had to change in order to make it appeal to more of a viewership. Note I also changed the name to Why do ice sheet lose mass because I feel it is more appropriate. Glacier mass loss would require much more in depth of an analysis for proper understanding. -
robert way at 02:54 AM on 15 July 2010Part One: How do ice sheets lose ice?
Hogarth, I have in fact read up on these papers a little and I find them both very interesting. Particularly Jenkins (2010) as the ridge is something that was previously not understood. I wish there was some paleoclimatic way to be able to ascertain an estimate as to how long the ice remained on the ridge as that would potentially tell us when the last significant retreat was. -
AuntSally at 02:52 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Of course, the other salient point to be made here: Steve Goddard chooses to "publish" his analysis on a blog rather than the the scientific literature. I'd like to challenge him to submit his analysis for legitimate peer review and publication. I'll even help. Journal of Climate, I should think, would be a good place to start ... -
Peter Hogarth at 02:48 AM on 15 July 2010Part One: How do ice sheets lose ice?
Thanks Robert, this is a wonderfully clear and focused article. I've seen first hand some of the charts of high resolution bathymetry from under the Pine Island glacier, which tells a fascinating story. I will ask my colleagues in Norway if any images are available. Very recent publications on this are Jenkins 2010 and Schoof 2010. -
Rob Honeycutt at 02:10 AM on 15 July 2010Part One: How do ice sheets lose ice?
Ned... I suppose Goddard has never seen or heard of a melt water lake. -
KR at 02:09 AM on 15 July 2010Part One: How do ice sheets lose ice?
mspelto - correction taken; I'm still learning some of the basics with regards to glaciers. So a possible reduction of spreading comes from reduced back pressure? That makes sense, but how would it cause reductions in thinning and longitudinal extension? I would think those would increase with lowered friction. -
chris at 02:07 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Sense Seeker at 22:08 PM on 14 July, 2010 "Second, it seems to show that up to mid 2006, the ice mass was actually growing. It cannot have done that forever, and the quadratic fit looks nice by I do not expect that will hold forever, either. As I see it, this picture could just be a small section in a process of random fluctuation. Any thoughts?" The Y axis is an "anomaly" Sense Seeker, and I don't think the "zero" represents a point where Greenland ice mass in balance between mass increase and loss. So the ice sheet wasn't growing up to 2006 as one might infer from the figure. This is apparent if one looks at longer time period analysis of Greenland mass balance. I can't find a linkable version, but a recent paper by Rignot indicates that the Greenland ice sheet grew overall a little between 1957 and 1977, was pretty much in balance between around ~1977 and 1987, started to lose mass slowly between ~1987 and 1997, and that the mass loss has accelerated since then... Rignot, E et al (2008), Mass balance of the Greenland ice sheet from 1958 to 2007 Geophys. Res. Lett., 35, L20502 link to abstract -
HumanityRules at 01:56 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
17.Ned at 00:28 AM on 15 July, 2010 Good point, nicely made. As you say there are consequences to both 'choices'. People need to take ownership of these consequences. -
chris at 01:54 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Ken Lambert at 22:52 PM on 14 July, 2010 Not really Ken. There is certainly evidence for an increase in heat content in the deeper oceans as described at great length previously. There's nothing surprising in that; in a world warming under enhanced radiative imbalance, we expect the oceans to absorb heat and some of this will find its way to depths. Peter has attempted to discount the possibility of reduced thermosteric contribution through deeper ocean heat sequestration by reinventing the laws of physics on thermal expansion of water! It's worth pointing out that he's got that fundamentally wrong. Might Peter's "demolition" of von Schuckmann et al. be of a similar nature? The increased rate of Greenland ice melt apparent in Figure 2 above (say comparing 2002-2004 to 2008-2010) amounts to a few tenths of a millimetre of eustatic sea level rise per year. Since sea level measurements are a little noisy, that may simply not be apparent in the data yet, and of course this small rise (around 10% of the absolute yearly sea level rise) may have been countered by a shortfall elsewhere (e.g. mountain glacier contributions); it's pretty difficult to do this "acounting" on very short time periods. And while you're right that "you can't have more ice melt and more steric rise at the same time for a given SLR" (assuming your measurements are sufficiently precise), you can have a little more ice melt contribution with a similar or even enhanced ocean heat content, if some of the latter has found its way to somewhat deeper parts of the ocean. That might have looked a little unlikely 2-4 years ago when SLR seemed to have slowed down somewhat. However that slow down was likely due to a La Nina period and the SLR is pretty much back on its longish term trend. I guess we'll have a better idea as things develop over the next couple of years.... -
tobyjoyce at 01:54 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
HR @3, The situation comes back to the precautionary principle (or the prudence principle); if the prediction is for a global warming of 4C +/- 5C, should we act on the assumption (or hope) that a -1C cooling is what it going to happen in practice? Besides, the irrevocable events are all on the temperature upside. If actions taken prove to be unwarranted by events, they can be undone. Not many people retrospectively complain about the obvious overkill in nuclear defences, missile arsenals and star wars alternatives in the Cold War, though the trillions spent on them would have had better uses. -
angliss at 01:45 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
I've forgotten most of my Philsophy 101 class from college, but one of the things I do remember is that not choosing is itself a choice. There well be many options to choose from, but refraining from choosing any of the options inherently defaults to one of those options (or to another option that should have been included in the options in the first place). In the case of addressing climate disruption, we have two main choices: we either choose act to address climate disruption or we choose to not address climate disruption. Refusing to choose defaults to choosing NOT to address climate disruption. -
mspelto at 01:42 AM on 15 July 2010Part One: How do ice sheets lose ice?
The grounding line is where the glacier goes afloat and it can be a point of weakness but seldom is it a place where tidal or wave action leads to cracking. Typically the grounding line for most substantial ice shelves (Ross Ice Shelf, Amery Ice Shelf) and floating tongues of outlet glaciers is well inland (Petermann Glacier), is quite insulated from waves and the glacier is both thick and strong here. What the grounding line does represent is a location where longitudinal compression is reduced as friction declines, this would cause acceleration, but longitudinal extension due to downslope flow and gradual ice thinning, and even lateral spreading can also be reduced. -
KR at 01:18 AM on 15 July 2010Part One: How do ice sheets lose ice?
Dennis - excellent questions, it can be hard to follow the terminology. "Buttressing ice shelves" and "Longitudinal compressive force": Ice shelves hanging onto the edge of the glacier and surrounding areas hold back the glaciers ('cause there's an ice shelf in the way!), applying the "longitudinal compression", i.e. pushing back against the glacier. This slows glacial movement. "Glacier's grounding line": Once the glacier gets far enough out into the water to float, wave action helps crack it and calve it, which means that the glacial ablation increases sharply there (fast ice loss). -
John Russell at 00:57 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
Regarding the response to my comment above (#9); it's important to include the link, even if it is behind an annoying paywall. At least it is there, should someone really want to pursue it. If I want to check a quote I usually find that googling the first half dozen words will find the original and perhaps several instances of it being used -- often cited -- which at least helps to establish its credibility. On other occasions, of course, a quote proves to have been taken out of context -- though not in this case! -
mspelto at 00:47 AM on 15 July 2010Part One: How do ice sheets lose ice?
This is well put. It should be noted that surface mass balance such as is reported to the World Glacier Monitoring Service by scientists like myself (I report 12 glaciers annually) is a measurement simply of melt and accumulation. The balance velocity is a key concept that is not analyzed in such observations. The observations for the WGMS are all from smaller alpine glaciers, which typically slow down as they shrink, and have fewer crevasses. The complete opposite often happens on larger calving glaciers with reduced back pressure leading to greater velocity, more calving, more retreat, more thinning, reduced back pressure and so on. The balance velocity is not something that is determined annually. But is something as you correctly note that must be considered along with the basic melt and accumulation at the surface. For the large glaciers we have not had accurate mass balance assessment from the field, only the recent better satellite data has allowed this. So in fact balance velocity was the key in the assessment of a 1990 paper I published from U of Maine work that noted the Jakobshavn Glacier was in equilibrium for the 1950-1985 period. This is obviously not the case their or on Pine Island Glacier or Petermann Glacier. -
Dennis at 00:43 AM on 15 July 2010Part One: How do ice sheets lose ice?
I'm not a scientist, so much of the terminology is lost on me. I'm afraid you lost me at the paragraph that starts "The second mechanism refers to when the forces at the downstream terminus of a glacier or ice stream are disturbed or altered." What does "buttressing ice shelves" mean? And "glacier’s grounding line (point where glacier ice reaches floatation)?" I really like the cross section in figure 2 (pictures are great conveyor of these sorts of things), but those terms aren't in the image. And what is a "longitudinal compressive force?" With your conclusion that this second mechanism is important to Antarctica, these details are key to understanding your post, so if someone can elaborate on this, or point to something that provides more details, it will help. -
RickG at 00:39 AM on 15 July 2010Part One: How do ice sheets lose ice?
Steven Goddard has never heard of "sublimation"? Oh my. -
mspelto at 00:34 AM on 15 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
I published a paper back in 1990 called the Equilibrium balance of the Jakobshavn Glacier. This paper looked at the consistent velocity data from 1950-1986, the consistent terminus position and field measurements of snow depth and snow melt, all lines of data suggested a near equilibrium balance for this system, which now is anything but. That is the long range evidence we actually have. That study was undertaken by the U of Maine partly because we saw the Jakobshavn as an analog for other glaciers particularly Pine Island which might accelerate in a similar fashion. -
chris1204 at 00:32 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
HR @ 16 I almost mentioned the Nazis but thought it would be too off topic :-). The Nazis were the first government to run a serious anti-smoking public health campaign highlighting its links to all the nasty diseases we recognise today. It helped that Adolf was a fanatic anti-smoker (by the standards of his time) and a vegetarian to boot. Pity the rest of their ideology had some shortfalls! -
Ned at 00:28 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
HR writes: The problem I see here is that you assume all the partial knowledge suggests we should act. This is one of my pet peeves, although it's hard to use the word "peeve" for something that is potentially of vast importance to future generations. The situation is not one where we're deciding whether to act or not. We are going to act, one way or another. We either take one action (cutting back emissions to avoid doubling the CO2 concentration in the atmosphere) or we take a different action (burning lots of fossil fuels and doubling the CO2 concentration in the atmosphere). There is no way to "not act" here. We have to choose among possible actions A, B, C, etc. each of which involves some expected changes to our technological infrastructure and/or the climate. The right way to make this choice isn't to pretend that action A (doubling the CO2 concentration of the atmosphere) is some kind of non-action "default" choice that we can safely take for granted right up until the point where the need for "action" becomes obvious to everyone. The right way is to weigh the expected costs and benefits of each potential action, including the uncertainties associated with each. Unfortunately, there's no straightforward universally accepted way to do this -- it's going to be messy, and the uncertainties create lots of opportunity for disagreement. But it's better than just fatalistically pretending that the choice we're making (burn lots of carbon and ignore the climate) is not itself a deliberate choice! -
HumanityRules at 00:23 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
6.Chemware at 16:33 PM on 14 July, 2010 Chemware gets the prize for first to mention the Nazi's. Congratulations! -
HumanityRules at 00:21 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
4.caerbannog at 15:16 PM on 14 July, 2010 You should tell GRL and the like because they are the journals publishing the C- papers. Your comment suggest you do wish to simply ignore anything that questions AGW. -
robert way at 00:18 AM on 15 July 2010Part One: How do ice sheets lose ice?
enSKog, I actually have not looked into that question but I could make an assumption that where sea ice forms primarily from salty ice and then becomes desalinized over time, it is maybe more difficult for it to form in high calving regions because the water is usually quite "freshened" with the inflow of land ice. -
Ned at 00:10 AM on 15 July 2010Part One: How do ice sheets lose ice?
enSKog, the short answer is "no". People make that suggestion a lot, but calved ice from land ice sheets doesn't make any significant contribution to sea ice area or extent. -
Ned at 00:09 AM on 15 July 2010Part One: How do ice sheets lose ice?
Goddard has been using the same argument with Greenland (implying that it can't be losing mass because air temperatures over much of the interior are below freezing). He doesn't seem to understand how glaciers (or ice sheets) work. -
SNRatio at 00:07 AM on 15 July 2010Does partial scientific knowledge mean we shouldn't act?
I think the issue of foundation of political action is more of a decision problem than a purely scientific issue. It can be extremely dangerous, at the very least counterproductive to accept the ordinary rules underlying scientific consensus as the basic rules in cases like AGW. There is an asymmetry built into science, in that we are much more afraid of accepting wrong hypotheses than rejecting correct ones. For building a corpus of secured knowledge, this is nesessary, but for the managment of a global civilization, it can be dangerous. Because the "alternative" hypotheses will always get the benefit of doubt, and that doubt may, in effect, paralyze us. The basic phenomenon, is that when we start large-scale irreversible experiments (they constitute a big part of our civilzation enterprise), we will, very often, not have enough knowledge and data for precise assessment of the consequences before it is too late to avoid them. This applies to a large number of environmental issues, AGW is a prominent one. We may, for example, be well past the point of no return for the melting of Greenland's ice cap, for considerable ocean acidification etc. And still, it is only during the recent years we have accumulated knowledge about these processes to such a degree that we should have a broad scientific consensus on them. And still, we don't have really narrow estimates for climate sensitivity, maybe the most important environmental parameter of all. This has little to do with lack of basic understanding, it is mostly mere real-world complexity. In such situations, the basic issue is not one of precise estimation and scientific penetration, but of risk assessment and management. Expected benefit/loss is the main parameter in the first place. It is a decision problem, and rather than producing precise predictions, workable prabability estimations are needed for handling them. For example, because the cost to society of a Greenland meltdown will be huge, it is enough to have a rather small probability for that in order to warrant drastic measures. Og course, some denialists will say that the probability is about nil, and here is where the game gets interesting. They must provide reasons for that, which not only implies that they must argue their case, but that they must argue against other explanations. And this agrumentation must be held within the observable and predictable. Now, we have a case where we handle everything symmetrically, in probability assessments nothing, in principle, gets the benefit of doubt. And wrong predictions and assessments invariably leads to the probability estimates based thereupon get weighted down. In adequate risk management, lack of precise knowledge directly results in larger safety limits, while in the AGW political debate, it results in NO safety limits. Think about it: There may still be quite a few unknowns, after more invstigation, the Greenland ice loss may seem to be partly periodic, with a larger time frame for complete meltdown, the climate sensitivity may turn out to be closer to 1 than expected etc. Which means that we may have some more time to fix things, but they still have to be fixed. But presenting this as solely a scientific problem, less drastic estimates are almost bount to result in less efficient measures - the result being that we lose life-saving time. -
enSKog at 23:59 PM on 14 July 2010Part One: How do ice sheets lose ice?
When faced with the 'Antarctic sea ice is increasing' argument I have been tempted to respond with 'That will be all the ice sliding off the land into the sea!'. Does increased glacial calving actually make any significant difference to sea ice extent/area? -
Tom_the_Bomb at 23:26 PM on 14 July 2010Part One: How do ice sheets lose ice?
This isn't to do with the post, sorry. Can I suggest that John moves the article "Peer reviewed impacts of global warming" into a more visible place? I think it is one of the most useful articles on this site, comparing peer-reviewed impacts of warming both good and bad, and it deserves more attention. Personally I think it should be up there with the two blue boxes on the home page, but that's just my opinion. Also, the version of this article on the iPod app, called "Global warming is good", doesn't show up on the unless you search for it. Again, I think it's one of the most important pages and should be as visible as possible. Can something be done about that? Thanks! -
F. Murdoch at 23:14 PM on 14 July 2010Part One: How do ice sheets lose ice?
Excellent, very informative, and clearly written piece. Well done. -
Riccardo at 23:06 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
John Russell, the full report is not free but the Report in brief is. It starts with: "A strong, credible body of scientifc evidence shows that climate change is occurring, is caused largely by human activities, and poses signifcant risks for a broad range of human and natural systems." You could have found it yourself before saying that "hese guest posts are little better than the sceptic's blogs that we rail about." -
John Brookes at 22:58 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
Tony Noerpel @8, relativity is not so esoteric. The GPS satellites actually do have to correct for the time effects of special and general relativity. Without this correction, positions measured by GPS would drift by about 12km per day. The clocks are synchronised regularly as well. -
Ken Lambert at 22:52 PM on 14 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Chris#33, BP#36 "In other words, some of the apparent shortfall in the thermosteric (ocean heat absorption) contribution to sea level rise during the period ~ 2003/4-2007/8 may be due to a larger than "average" transfer of heat to the somewhat deeper layers of the ocean" "May be due" is sheer speculation. At the time the paper was written (Aug-09), Dr Trenberth was not aware of the Von Schukmann paper which claimed to find a large chunk of the 'missing' heat down to 2000m. In fact I drew the Von Schukmann paper to Dr Trenberth's attention in February this year, and he has since used it in a banter with Dr Pielke in April - calling it a 'nice analysis'. Well, BP produced a pretty convincing demolition of the Von Schukmann paper and its 'bumpy' OHC chart elsewhere in this blog. Willis subsequently came up with a 'small' number for deep OHC of about 0.1 W/sq.m which is only about 16E20 Joules/year. The 1.22E22 Joules in the Trenberth paper is a typo - not a serious one - but I read this some time ago and could not make out the following 1.35E20 as a 12.5% increase on the former number. Who said this stuff was 'peer reviewed? Anyway, the essential point is that the SLR budget and the energy budget do not come close to consistency, and more ice melt component for a given SLR worsens the shortfall in the energy budget. In reality you can't have more ice melt and more steric rise at the same time for a given SLR. -
JMurphy at 22:43 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
John Russell, the nearest I could find to what you are looking for, is this - Open letter: Climate change and the integrity of science, in THE GUARDIAN. Supposedly the original is behind a paywall in SCIENCE. Doesn't seem to be exactly related, though. -
Sense Seeker at 22:08 PM on 14 July 2010Watts Up With That concludes Greenland is not melting without looking at any actual ice mass data
Can anyone explain Figure 2 to me? First, it shows a very short timeframe - the sort of thing I would expect from denialists, not here. Second, it seems to show that up to mid 2006, the ice mass was actually growing. It cannot have done that forever, and the quadratic fit looks nice by I do not expect that will hold forever, either. As I see it, this picture could just be a small section in a process of random fluctuation. Any thoughts?Response: Figure 2 is a short time frame because that's as long as the GRACE satellites have been measuring the gravity around the Greenland ice sheet. Would be lovely to have more data but that's the hand we've been dealt. In fact, we're lucky that the latest data through to early 2010 fell into our hands in May, giving us an even longer data series than was publicly available until then.
That's why Figure 1 is so important - it shows other estimates of Greenland mass balance back to 1960. The fact that the other estimates are consistent with the gravity data gives us confidence in the estimated rate of ice loss.
I don't expect the quadratic fit to hold forever either. The ice melt has continued to accelerate because the ice loss has spread to the northwest but I expect the rate of ice loss will eventually reach a peak. So how do we know the current ice loss isn't just a random fluctuation and things will bounce back to mass balance?
We get a good sense of Greenland's trajectory by considering all the evidence. We see accelerating ice loss from both Greenland and Antarctica - similar patterns from opposite sides of the globe. We look at past sea level and see it closely copuled to changes in temperature. Looking at the Earth's past, we see that the last time temperatures were 1 to 2 degrees warmer than now, sea levels were at least 6 metres higher than present levels. This tells us that the Greenland and Antarctic ice sheets are highly sensitive to sustained warmer temperatures.
You're correct in identifying the dangers of looking at narrow pieces of data. You need to take in the full body of evidence to get an accurate picture. All this evidence taken together indicates Greenland will contribute sea level rise in the order of metres over the next few centuries. -
chris1204 at 22:04 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
The cancer example is very pertinent. We have excellent remission rates for some cancers and very poor remission rates for most. Much depends on early detection - however, once a cancer has metastasised, remission rates (measured as five year survival rates) are poor save for some of the leukaemias and lymphomas. Cancer chemotherapy/radiotherapy once a cancer has metastasised essentially buys time and relieves discomfort. However, most cancer therapies act by killing fast growing cells (malignant tumour cells are the fastest growing) whilst trying to avoid damaging other fast growing cells (which include out immune system which is part of our defence against infection and cancer cells). Chemotherapy/radiotherapy can thus cause major discomfort or even kill for example through infection following immune suppression. So really, much chemotherapy and radiotherapy may prolong life a bit and palliate some of the discomfort at the end often at a heavy price. Your best bet as an individual lies in avoiding cancer (lifestyle choices - eg quit smoking) and early detection. However, governments face questions as to resource allocation. Paradoxically, far more is spent on chemotherapy/radiotherapy than prevention and early detection (the former two are very expensive. However, if you're unfortunate enbough to develop a nasty cancer, you're likely to curse a government that won't fund cutting edge therapies for you. At the same time, much early detection involves difficult decisions around determining the true significance of screening measures at both population and individual levels. An equivocal biopsy result represent hard choices in the face of, say, surgical risks, for the individual, and for governments looking at resource allocation (surgery is expensive and for those without health insurance subject to waiting lists). So, coming back on topic, our current state of knowledge about climate may equate to early detection of malignancy calling for imnmediate action, a grey area in which the costs of intervention may or may not exceed benefits, or metastatic cancer in which we face likely catastrophic outcomes at best partially responsive to costly and burdensome mitigation strategies. The choices aren't straightforward. All I know as an outsider to climate science is that seemingly intelligent, honest, and articulate people espouse variants of all three positions. -
John Russell at 21:58 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
It's clear from the ellipsis that The US National Academy of Sciences' statement has been heavily edited. Is it possible for us to have a link to the original? Otherwise these guest posts are little better than the sceptic's blogs that we rail about.Response: Here's the full quote:Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.
The National Academy report comes from America's Climate Choices which is behind a pay wall.
I know, it annoys me too. -
Tony Noerpel at 21:53 PM on 14 July 2010Does partial scientific knowledge mean we shouldn't act?
I'm not sure this is a good analogy. Newtonian mechanics (plus Maxwell's EMT) is exact and rigorous when dealing with virtually everything we have to deal with in our lives here on Earth (excluding all of our fancy electronic devices). We only need quantum mechanics when dealing with small particals and Einstein's general theory of relativity only comes into play if one is interested in a very precise description of the orbit of Mercury. But Newtonian mechanics is sufficiently accurate to getting a man on the moon. The force of gravity is 40 orders of magnitude smaller than the electromagnetic force so gravitrons will likely elude discovery for another few years. I think this is Kip Thorne's view. We need to build a sufficiently sensitive device and be able to cancel out lots of noise. The uncertainty associated with climate physics is of a somewhat different nature. I think suitable analogies might be what caused dinosaurs to go extinct, did snowball Earth events happen? plate tectonics? ice ages? evolution? I suggest you might say that we are as certain about anthropogenic global warming as we are about plate tectonics and evolution. Which is to say there isn't really much room for uncertainty. :+) We can freely discuss and embrace plate tectonics, today, because it doesn't threaten anything (though it did threaten cherished scientific opinion back in the 20's and up until the 60's). Many folks find evolution to be very threatening to their entire belief system. And this is true of climate change as well. Tony -
Berényi Péter at 21:10 PM on 14 July 2010Hotties vs Frosties?
#174 KR at 09:59 AM on 14 July, 2010 That's really rough with radon - it's estimated at 330 mCi/GW, and you really can't filter it. I don't see why. The radon isotope with the longest halflife is 222Rn (3.82 days). It's just emissions have to be delayed a bit (a month or so) to decrease radiation levels by three orders of magnitude. It is much easier than permanent sequestration.
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