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Comments 64401 to 64450:

  1. NASA Mission Takes Stock of Earth's Melting Land Ice
    Norman - There are two separate conversations going on here, and a certain lack of recognition of that issue. First: Deep aquifers are being depleted at high rates in many ares. This is definitely bad - leading to numerous agricultural issues and relocation costs. Current practices will not be sustainable in many areas. But the best data available indicates that a roughly equivalent amount of water is being sequestered elsewhere, changing the current availability of said water in considerable detail without affecting total runoff. While I don't want to minimize this very important issue, it's not the center of this thread. This thread is on the climate change effects on the cryosphere, on ice melt in areas >100km^2 as measured by GRACE. It is very useful, however, that the GRACE data also supplies some information about aquifer changes. Second: Sea level rise due to anthropogenic is not greatly affected by terrestrial/anthropogenic usage. Milly et al 2010 shows that in considerable detail (with numerous reference of their own). --- So: Aquifer level changes, recharge rates, etc. - all of those are off topic here. Assertions that anthro water usage affect sea level are not supported by the full set of data, your cherry-picking of single numbers from Milly 2010 notwithstanding. Moderators - Perhaps side topics such as aquifer changes need to go elsewhere?
  2. Philippe Chantreau at 14:34 PM on 12 February 2012
    CO2 is plant food? If only it were so simple
    Camburn, "it is established" requires real substantiation, put up the references. This statement leaves a lot to be desired: "By having larger root balls/mass the plant has a larger structure to overcome normal potential weather variations." Provide references to studies showing that it actually does allow them to overcome. Without it, this is nothing but wishful thinking. When they were trying to break the sound barrier, engineers though that a generously reinforced structure would enable a onventional airplane to go there and back safely. It wasn't quite so. If you're so worried about going broke you need to adress the factors that make prices so volatile. They belong with the banks and the speculators trying to profit from commodities markets, good luck going after that. I live in the 40's latitudes too and I was battling mosquitoes on my outing to the falls today with the kids. Never seen them yet in this place at this time of the year. If you are in a place that already was on a Northern margin, then probably you're safe, and warmth in your area is indeed beneficial. I'm sure the ones who live closer to the Southern margin have a different take. Of course, if we stick purely to the capitalistic risk/benefit analysis, in your individual case you're not supposed to personally give a dam* about the problems of farmers who live in other places. In fact, the more they suffer, the better you're likely to make out: production decreased on their part, increased on yours, if the overall production is down, you'll really make a killing without having to do anything special. More power to you I guess.
  3. A prelude to the Arctic melting season
    As presented above: 1. There seems to be a solar influence concerning Arctic Ice flucuations. 2. Black Carbon, an anthorgenoponic emission, is also responsable for the current decline in ice. 3. Increased temperature is also responsable for the decline in Arctic Ice. The loss of Arctic Ice is a multifaceted issue.
  4. NASA Mission Takes Stock of Earth's Melting Land Ice
    KR and Tom Curtis Here is another report which gives even a higher figure for unsustainable water use (being withdrawn at higher rates than replenished meaning it will increase the surface amount by that volume since it is no longer present in the location it had been). Fresh Water Chapter 7. In this book you can scroll down to page 175 and view Table 7.4 In this table they give the World non-sustainable water use. Ranges from 391-830 km^3/year (Note Tom Curtis, even replenishable aquifiers can be pumped at rates exceeding their recharge rates). If you use the highest value for non-sustainable water use it would be a very significant player in SLR. (830/61=13.6)....(13.6 x 0.17 mm SLR for 61 km^3 H2O=2.31 mm). Current SLR rate is 3.4 mm/year so this water use could account for over 50% of the current rate of SLR if the higher figure is used. I am not saying this would be valid. I brought it up to make a point that you should not discount water mining as one possible source of SLR, it may be larger than you currently accept.
  5. A prelude to the Arctic melting season
    Philippe: The observation from the Captains log are not anecdotal. They are reported observations. Observations are 1st hand, anecdotal are 2nd hand. The following paper from DMI is worthy of consideration to explore all avenues that affect Arctic Ice. It has been established that "Black Carbon" may be responsable for 40% of the current temp/melt. Ref link to Schmidt/Shindell posted above. DMI East Greenland Ice
  6. NASA Mission Takes Stock of Earth's Melting Land Ice
    Norman@41: AT the rate of depletion of fixed aquifiers, the problem will come to an end in approx 18 years based on the latest information I read. Not a very comforting thought at all.
  7. NASA Mission Takes Stock of Earth's Melting Land Ice
    KR @35 Your link does state that ground water mining will result in a positive increase in SLR of 0.25 mm/year. My problem is with the huge difference in calculating the amount of unsustainable water removal from deep aquifiers. The listed total amount of deep water used in irrigation is 545 km^3 per year. As Tom Curtis pointed out, this amount does not indicate a recharge rate of even the deep water wells. I did find another source that points out that of this amount above, 234 km^3 (in the year 2000) is unsustainable meaning it is not going back into the deep aquafier storage but being removed and added to the total surface water amount. Section 8.4.3 in your linked article are what I question. How are their numbers so much lower than other sited sources? If you use the other value of 234 km^3(which was a 2000 number and may be higher today with expansion of deep water mining) instead of 61 km^3/year that your link uses, the amount of SLR due to deep water mining of fossil aquifiers is closer to 1/5 of the total amount and is a valid player in the SLR equation.
  8. Climate change policy: Oil's tipping point has passed
    Sphaerica: I was talking about large HP needs. When it comes to cars, I am 100% behind you. I have a couple of friends that have a hybrid. Yes, in winter they don't work too well, but for 70% of the year, they work very well. My next car purchase will be a hybrid. I have a hard time understanding why anyone wouldn't buy a hybrid for transportation needs of a few people. And the costs are not high in comparison to many alternatives. The practicality when it comes to large HP needs tho is that many times the large HP needs don't shut off for days and pontentially weeks at a time. There is no time to recharge, and the price of having batteries large enough to supply the power over extended periods of time just does not compute.
  9. Philippe Chantreau at 14:11 PM on 12 February 2012
    A prelude to the Arctic melting season
    Camburn, how am I supposed to be impressed in any way by a record reporting no ice in sight in late August and September? In the anecdotal area, do you remember about the guy who was swimming in open water at the North pole a couple of years ago? Shall we put this up in the anecdote contest? Please... This anectodal record is of very little interest. This winter ice area and extent are low so far. We'll see how it turns out in late September, which is the metric that matters the most. I note that the January extent is so exactly on the linear regression of the overall decline of the month' extent that it's almost as if the ice had been rehearsing. I find the ice area graph at Cryosphere today even more concerning, it's showing the same pattern as last year, but 250k sq. Km lower. In any case, we're nowhere near the 1979-2000 average, in either metric.
  10. CO2 is plant food? If only it were so simple
    Sphaerica@86: 1. It is established that cereal plants respond well to increased CO2. 2. It has also been established by root studies that plants develop larger root mass with the presence of CO2. 3. By having larger root balls/mass the plant has a larger structure to overcome normal potential weather variations. 4. You indicate more volatile precip and temperature patterns. I don't know if you can get much more volatile than the climate I live in. An old saying in the upper plains of the USA is "If you don't like the weather right now, wait 5 mins and it will change." The higher levels of CO2 that increase plant mass that I have read are up to approx 850ppmv. What happens after that, I don't know. The studies done by the Ag community reflect the potential levels that "may" be obtained. The element of risk in production ag is so large, that a small addition of a potential benifit is viewed positively. The upper plains of the USA, and I live very near the 49th parallal. One of the areas that is suppose to be most affected by climate change. At this point and time, there has not been any variation from the long term norms of just right, to too wet, to too dry. From too cold, frost in 2005 in August, to to warm.....that hasn't happened since 1988. I read studies of anything pertaining to production ag with a very critical mind. A small change can be the difference between being profitable, and going broke. And worst of all, not having a crop, as my desire is to feed people. Warmth in my area is benificial to production as most of the time we are on the edge of being too cold. Precip patterns are within the boundaries of a 80 year wet/dry cycle in the Central Corridor of the USA that is part of a longer 400 year cycle: 400 year cycle of precipitation of Great Plains of NA Shorter cycle within the longer cycle:
  11. Global Sea Level Rise: Pothole To Speed Bump?
    Hansen, in a 2005 editorial essay cited Kienast et.al.2003 and said "In melt-water pulse 1A... sea level rose about 20m in approximately 400 years" which "is an average of 1m of sea level rise every 20 years". Which is about 0.14 mm per day. This would be a catastrophic rate for people living near the sea. He noted that the ice sheets disintegrating at the time "were at lower latitudes than the ice that remains today and the period of rapid ice sheet disintegration was undoubtedly preceded by a period in which the ice was preconditioned for collapse". But, he points out climate forcing today far exceeds the forcing that drove melt-water pulse 1A. And, he said, sea level rise doesn't have to add up to 20 m to obligate scientists who expect it to happen to warn that an event anything like it would "wreak havoc" on civilization. Hansen has said in the past that if the planetary energy imbalance is about 1 W/m2 and all that energy was going into melting ice it would raise sea level by about 1 m per decade. Obviously, an armada of icebergs shooting off Antarctica wouldn't have to melt to raise sea level. Pfeffer told a story at the AGU this year about how the sea level rise threat isn't being fully grasped even by those he would have thought must be exposed enough to the data to get it. He said MOMA in NYC exhibited a model showing a New York that by 2100 had protected itself from 2m of sea level rise. He asked the designers, what was the plan for the ongoing steady or possibly accelerating rise after that - how was their design going to cope with another meter and another one after that? Blank stare.
  12. CO2 is plant food? If only it were so simple
    muoncounter @77, Fact 1 and 2 are off topic on this thread and moreover not areas where JNG has suggested that SkS has fallen down. Michael sweet @78, I'm not sure what you are getting at. The JNG post was written after considering this very SkS post and finding it wanting. Rob @79, No doubt there are many reasons to reduce CO2, however JNG has suggested that this particular item is a litmus test to determine whether the person you are listening to is honest and knowledgeable. A bold statement and one that I am grateful to see addressed by you and the S(k!)S team. Tom Curtis @80, thanks for the thoughtful and thorough response! Your points are all well taken, although I'm not sure it's a good idea to consider policy turn around time when writing a post. I would like to think of SkS as a place that cuts through all the BS and provides the facts - warts and all.
    Moderator Response: [JH] The auditions for SkS Moderator candidates were held last week.
  13. NASA Mission Takes Stock of Earth's Melting Land Ice
  14. NASA Mission Takes Stock of Earth's Melting Land Ice
    Tom @34 You provide a good challenge "Note that I do not know the recharge rates. Globally they may also be trivial. But you need to either cite them to establish that, or to cite a peer reviewed source to that effect." I did some research into this and found this Nonsustainable grounwater sustaining irrigation: a global assessment. I did sight the 545 km^3 from deep water mining from the other link. I have not found a correct current amount of nonsustainable water mining (fossil aquifiers) so I am not sure what it is in 2012. In 2000 it was found to be 234 km^3 (from the link above). From the abstract: "Results also show that globally, this contribution more than tripled from 75 to 234 km3 yr−1 over the period 1960–2000." Nonsustainable water mining tripled from 1960 to 2000. In 2000 it was estimated to be 234 km^3/year. In 2012 if may be higher than 2000 but probably not as high as the 545 km^3 given in the other article. Nonsustainable means the this water is being removed and not replenished. Here is the general description of aquifier types: "There are two types of aquifers: replenishable and nonreplenishable (or fossil) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge. For fossil aquifers—such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer—depletion brings pumping to an end. Farmers who lose their irrigation water have the option of returning to lower-yield dryland farming if rainfall permits. In more arid regions, however, such as in the southwestern United States or the Middle East, the loss of irrigation water means the end of agriculture." source. Here is another describing fossil water water 75,000 years old in Libyan aquifier.
  15. A prelude to the Arctic melting season
    skywatch#9: Polyak 2010 was discussed here. analysis of several hundred indicators of past Arctic sea ice extent tells us that recent losses appear to have no parallel in records going back many thousands of years (Polyak et al).
  16. Climate change policy: Oil's tipping point has passed
    60, Camburn,
    Note the "at present there are no economic alternatives."
    Bullsh*t. There are no "economic alternatives" because we continue to invest more and more in the existing infrastructure and comparatively ignore other "uneconomical" potentialities. We keep things that way with our behaviors. Hybrid cars have been feasible and economical for a decade. Only the lack of true massive-scale production keeps their costs high. Our dependence on a rickety and failing fossil fuel infrastructure is primarily hampered by our continued investment in that same, dead-end infrastructure. The denial crowd has done a wonderful job of keeping the lack of "economic alternatives" a reality, and on our current course they will continue to do so for several decades until (as you say) the necessary transition comes with a cultural and economic shock. It stuns me that you are unable to see this or, despite your own admission of the problem, to use your foresight to move past it.
  17. CO2 is plant food? If only it were so simple
    85, Camburn,
    The types of plants that feed the world have repeatedly demonstrated increased productivity from higher levels of CO2.
    Do they similarly react well to increased temperatures, increased or decreased moisture, and more volatile precipitation and temperature patterns? Do they demonstrate an unending improvement for higher and higher levels of CO2, without limit or eventual negative result? Are you in a business where you can afford to simplistically look at and focus on a single variable, with complete disregard for other factors?
  18. CO2 is plant food? If only it were so simple
    Tom@83: I am in production agriculture Tom. The "quarter" I am most interested in is feeding people. As most of the worlds food stocks are annual in nature and derived from grasses, the area of research most intersting is the responses to co2, etc. The types of plants that feed the world have repeatedly demonstrated increased productivity from higher levels of CO2. Rob@84: I will have to re-read Lobell (2011). There were problems with that study that a farm paper talked about. When I have time to read it and reference it, I will comment on said link. Thank you for the Link.
  19. The Year After McLean - A Review of 2011 Global Temperatures
    Doug H - You might then be interested in the Separating signal and noise in climate warming thread. The answer appears to be a minimum of 17 years for any trend to be statistically identified in the presence of observed climate noise. Others (ahem) might want to read that as well. Decadal trends are just not enough to identify any trend, whether it's plus, minus, or flat.
  20. Climate change policy: Oil's tipping point has passed
    The first major impact of a significant increase in oil price is probably famine in Africa. I'd suggest that it is non-trivial for Africa to switch from oil-dependent farming.
  21. Northwest passage has been navigated in the past
    JMurphy: The Voyage of 1944 was not quite as difficult as you maintain. Capt Larsen was a skilled Captain. At times there was heavy ice, at times there was no ice to be seen. To have accomplished this without the benifit of satillite images is really a feat in and off itself.
  22. CO2 is plant food? If only it were so simple
    Camburn - you are misinterpreting what I wrote. Young forests, which are not nutrient-limited in some other way, can indeed benefit enormously from more CO2. The FACE trials indicate that mature forests don't - there's only so big trees can grow and therefore a limited capacity to soak up CO2. Young forests on the other hand have a large capacity for growth and drawdown of CO2. It makes perfect sense. In the real world, however, many areas are nutrient-limited - phosphorus, nitrogen and especially water. That's perhaps why the CO2 fertilization effect (a global increase in plant biomass due to more CO2) has not been found. All the extra CO2 seems to be going into forest re-growth. This tallies with global estimates of growth in pastural coverage- they have plateaued in recent decades. As far as corn is concerned, that too is under threat see SkS post: Maize harvest to shrink under Global Warming - based on Lobell (2011)
  23. CO2 is plant food? If only it were so simple
    Camburn @82, I know you enjoy looking at a very carefully selected quarter of the picture. Just don't expect us to be mislead by your propensity. In other words, read the main post. If you can't rebut the points it raises, you have nothing worth saying.
  24. A prelude to the Arctic melting season
    JMurphy: I did not suggest that the voyage was benign. I am showing what was in the log. They also encountered a lot of ice in places. The point I was trying to establish is: resolution. I will read your link forthwith. Thank you.
  25. CO2 is plant food? If only it were so simple
    Tom@80: Elevated CO2 benifits C3 and C4 structured plants. All cereal grains are grasses, so this study has a very strong relation to wheat/corn/ etc. NASA study on C3 and C4 grasses with elevated levels of CO2 It is also well known that enhanced CO2 promotes larger "root balls". Because of this, the plant is more efficient at using the available nutrients/water in the soil. With enhanced levels of CO2 there are indications that farmers will be able to reduce the N input and achieve the same yield. This would allow 3rd world countries to increase the mass of their food production. From a plant perspective, higher CO2 is good. Most plants evolved when CO2 was higher on earth and have not seemed to have lost that desire. But, even with enhanced bio-mass, the lowered PH of the oceans is a mighty concern that MUST be taken into account in the balance.
  26. A prelude to the Arctic melting season
    Camburn, you will find further details about the St. Roch's Northwest Passage voyages, written by myself, on Skeptical Science here. Things were not as benign as you seem to be suggesting.
  27. Zero Carbon Australia: We can do it
    Sapient. I wouldn't consider Cinas population small. China implemented a one child policy in the cites not rural areas. China recognized their population was going to exceed the resources of their land and did something quite controversial about it. A two child policy from the outset might have been more palatable. Quite the contrary, if china didn't have the one child policy, today under the per capita basis they would be entitled to more of the CO2 budget, they would have been rewarded for their population growth. Shouldn't all countries manage their population level to the food and water and other resources their land can provide? By the same thinking the amount of land would factor into the CO2 budget. Not merely the population number.
  28. CO2 is plant food? If only it were so simple
    Rob: There is no question that CO2 enhances plant growth. This is documented in this Wisonsin Study. Tree growth with elevated CO2 As far as temperature, the temperature, at least in the main corn growing areas of the USA would have to elevate by over 4.0C to be a growth hinderance. This would have to occur at precise times as well, as corn is sensative to higher temperatures for approx 2 weeks time in the growing season. Outside of the pollination and early fill window, higher temperatures help with the conversion to starch in the ear and can allow greater kernal depth. This is benificial. However, the lowering of PH of the oceans as a result of higher levels of CO2 is a huge concern. The lower PH benfits some crustaceans, but in my humble opinion, the overall benifits do not outweigh the potential negatives. Woods Hole Study of PH
  29. CO2 is plant food? If only it were so simple
    Layzej @76, among the interesting things John N-G writes is:
    "As long as the climate effects are small, they don’t matter much, but to the extent that climate changes faster than plants can move around to keep up with it, climate change will be bad for native plants. Worse, in the tropics, the climate may change into something with no existing analogue on Earth and thus no pre-adapted species ready to move in. Computer models with an interactive biosphere generally agree that incremental increases of CO2 help plants overall, and most say that the global ecosystem will continue to gain biomass through 2100. In other words, the better growing conditions due to more CO2 outweigh adverse conditions due to the changing climate for the foreseeable future. The crossover point, where net global growth is actually inhibited by the combination of CO2 fertilization and resulting climate change, is poretty much the most poorly known number relevant to climate policy. Certainly as the climate changes there are concerns about the extinction of species and the loss of the ability to grow adequate crops in some areas. But in the meantime, as long as one is not concerned about the fate of individual vulnerable species, CO2-induced climate change is a net positive for plant growth. This is true based on the most basic numbers of the man-altered carbon budget."
    By my reading, that is in complete agreement with the more detailed discussion above. His objection to this post seem to come down completely to the absence of a sentence saying that despite these grave concerns, for the future, there will be a short term (20) year benefit for plants in general, although not necessarily for crops. Given the turn around time of climate change policy, and the even longer turn around time for any action to start reducing growth in global temperatures, I do not think pointing out a possible short term benefit is either necessary or helpful. Still less so as it is not certain that that short term benefit exists. As noted by Steve Bloom in comments at John N-G's blog, his method of estimating the benefit to plants is indirect, and necessarily includes aquatic as well as land plants. More generally it potentially shows in increase in plant life, not in human agricultural productivity. It is of scant benefit to us if over the coming decades Net Primary Productivity (ie, the total global growth of plant life) increases if that increase is in the form of algal blooms and weeds. Further, I say talk of a potential increase, as even John N-G mentions a possible mechanism whereby the observations of increased carbon take up are compatible with decrease plant growth, ie, a larger decrease in plant decomposition. Although he dismisses that possibility, a recent study (whose title and authors I can't remember unfortunately) showed that production of oil and coal generating strata peak in periods of high CO2 content. Production of fossil fuels requires the burial of organic carbon without decomposition, so that study suggests that high CO2 content may indeed lead to reduced rates of decomposition, primarily by promoting anoxic conditions in warm waters. It seems to me that John N-G would have done well to read the title above. "If only it were that simple". Because of that complexity, Dawei's conclusion was, "The global increase of CO2 is thus a grand biological experiment, with countless complications that make the net effect of this increase very difficult to predict with any appreciable level of detail." That is, he has neither endorsed claims of benefit or of harm to plants from CO2, but merely drawn attention to some of the many complicating factors. In the end, difference between his and SkS's discussion of the topic is that we did not rush to a simplistic conclusion.
  30. A prelude to the Arctic melting season
    The paper presented is worth getting a copy from the local library: Bowhead Whale Historical Range in the Canadian Archipelago What this provides is evidence of Hisotrical Arctic Ice extent. One can then look at historical climatic patterns during the times of limited ice extent to understand what may lie ahead for our planet.
  31. A prelude to the Arctic melting season
    Tom@8: Ice loss is a regional item in the Arctic. On the whole, there has been ice loss on an annual basis. I am not confident that there are aduequate records of ice extent prior to satillites with enough resolution to provide the degree of certainty that is currently exibited. I have to logs of the St. Roch voyage in 1944. There were times when no ice was evident as far as the eye could see. This log is not in the public domain so I can't post a link to it. I can however post this: Page 92: Aug 22, noon. Barrow St. No Ice in sight. Page 93: Sep 3rd 6:pm Princess Royal Is. No ice in sight. RCMP 1945 Reports and Other Papers Realating to the Two Voyages of the R.C.M. Police Schooner "ST. Roch" This is first hand observations by the ships Master. Also, after reading the logs it is very apparant that the currents in the Arctic Sea play a huge role in ice transport etc. There is no doubt that the ice since Satillite measurements has been in decline. The reasons for said decline can be partially attributed to Global Warming, but a very significant part are the result of black carbon. Nasa Aerosols May Drive Arctic The long term picture is a complicated one that deserves much more research.
  32. CO2 is plant food? If only it were so simple
    Layzej - John NG needs to bone up on the latest research. No one is suggesting that increased levels of CO2 won't benefit plant growth - all things being equal. But that's just it, they are not equal, and recent studies find little evidence for it on a global scale. We (SkS) know that the carbon cycle models used in the last IPCC (2007) report expect a CO2 fertilization effect, a huuuuge CO2 fertilization effect. But isn't it interesting that previous work on historic forest growth in North America over the last few centuries found no evidence for it? The latest global forest inventories show that the uptake of CO2 by land plants is occurring because of forest re-growth, (forests chopped down and allowed to grow back) not because plants are lapping up the extra CO2. The prime areas of reforestation are in the former Soviet Union, China and in the tropics. On a global level there seems to be little evidence of the CO2 fertilization effect. This makes perfect sense, re-growth areas can chew through a fair amount of CO2 as they grow into mature forests and incorporate the extra CO2 into plant mass, but mature forests have a limited capacity for further growth. " I had looked at the site...unfortunately they can't bring themselves to admit that the evidence, while complex, does point to a net overall benefit to plant growth for the next few decades." Or perhaps the correct answer is that John Nielsen-Gammon is conflating forest re-growth (areas where forest has been allowed to re-establish) with the CO2 fertilization effect. I get the impression he can't be bothered accurately researching this topic. Maybe he needs to consult Stephen Pacala? As far as the consequences for human agriculture - which is the subject of Dawei's post, that doesn't look too flash either. Many human crop foods will be negatively impacted by rising temperatures and drought over the next few decades, including main staples such as corn and rice. And what about ocean acidification? Global warming's evil twin? Dude, there are many reasons to limit CO2 emissions, focusing on one tiny detail blinds one to the 'big picture.'
  33. A prelude to the Arctic melting season
    #4, and yet when the full context of the whole Arctic ocean is considered with a broad range of historical and proxy evidence (and not just the seas marginal to Russia), in this thorough review by Polyak et al 2010, they find:
    The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.
  34. The Year After McLean - A Review of 2011 Global Temperatures
    Bernard J @ 12 I am frustrated by my lack of the maths knowledge to answer your questions, but they seem to me to be interesting.
    can you tell us what period of time is required to discern from the short-term noise in the global surface temperature record, a warming signal of, say, 1.0 C/century? What period of time would be required to discern a signal of 0.75 C/century, and what period of time would be required to discern a signal of, say, 1.25 C/century? Conversly, and importantly in the context of your fixation with periods of approximately a decade, what rate of temperature change would be required to discern a signal from noise over a period of ten years? What rate of temperature change would be required to discern a signal from noise over a period of five years, and what rate of temperature change would be required to discern a signal from noise over a period of fifteen years?
    I imagine the answers would involve quantifying the average magnitude of the observed noise over the periods in question and then establishing the magnitude of signal required to skew the slope of the total data (noise + signal) by a statistically significant amount. It is so frustrating to be able to frame such problems, but not have the education to address them. If only I could go back to about year 10 at school and have teachers who could inspire me with the enthusiasm for math and physics that I have now, in later life. As it is, I have to rely on other minds to spoon feed me. So much to learn, so little time. To put me out of my misery, are those questions valid and are there answers to them? (And where can I go on the web to study high-school math and physics at my own pace ... I wish.)
  35. A prelude to the Arctic melting season
    Camburn @4, the abstract of your cited paper reads:
    "Examination of records of fast ice thickness (1936–2000) and ice extent (1900–2000) in the Kara, Laptev, East Siberian, and Chukchi Seas provide evidence that long-term ice thickness and extent trends are small and generally not statistically significant, while trends for shorter records are not indicative of the long-term tendencies due to large-amplitude low-frequency variability. The ice variability in these seas is dominated by a multidecadal, low-frequency oscillation (LFO) and (to a lesser degree) by higher-frequency decadal fluctuations. The LFO signal decays eastward from the Kara Sea where it is strongest. In the Chukchi Sea ice variability is dominated by decadal fluctuations, and there is no evidence of the LFO. This spatial pattern is consistent with the air temperature–North Atlantic Oscillation (NAO) index correlation pattern, with maximum correlation in the nearAtlantic region, which decays toward the North Pacific. Sensitivity analysis shows that dynamical forcing (wind or surface currents) dominates ice-extent variations in the Laptev, East Siberian, and Chukchi Seas. Variability of Kara Sea ice extent is governed primarily by thermodynamic factors."
    (My emphasis) How small are the long term trends, to 2000, can be seen by noting the ice extent trends across all all four Russian Arctic seas of -0.5 thousand km^2 per decade. That means, averaged across all four seas Arctic sea ice extent fell by about 5 thousand km^2 over the twentieth century. In stark contrast, August Arctic sea ice extent has fallen by approximately 2.3 million km^2 over the last three decades: That is not an apples and oranges comparison in that it compares the entire Arctic to just the four Russian Arctic seas. Comparing summer Arctic extents over the 20th centuries show those seas to have been unusual in their limited reduction in August sea ice. That calls into question your extrapolation from a regional study to the full Arctic. Never-the-less the full comparison still shows Arctic summer sea Ice Extent to have fallen almost as much in the 21st century as it did throughout the twentieth. It is interesting to note that all of the fall in the twentieth century is post 1950. In other words, the clear pattern is that while NAO may influence Arctic sea ice extent, that influence is now imposed on an unprecedented (in modern times) long term decline in sea ice extent which is a consequence of global warming. Put differently, the difference between the 2011 and 2012 sea ice extent near Novaya Zemlya may be due to the NAO, but the difference between 2012 and the 1976-2006 mean is due to global warming:
  36. CO2 is plant food? If only it were so simple
    Layzej: You have come to the right place for answers. All you need to do is read the opening post for the thread you have posted on and you will find Skeptical Sciences response to your question. If you have any more questions after you have read the opening post feel free to post them.
  37. CO2 is plant food? If only it were so simple
    lazej#76: Curious that you omit Fact #1: A small concentration of CO2 is a big deal. and Fact #2: The fraction of CO2 molecules in the atmosphere that were produced by man is different from the fraction of CO2 molecules in the atmosphere that are there because of man. He goes on to say that man-made CO2 is indeed causing warming. Both of these are part of the same litmus test. If you hear or read somewhere that the amount of carbon dioxide in the atmosphere is so small that it must be unimportant, your source is either too naive to know better or trying to deceive you. ... If you hear or read somewhere that the amount of man-produced CO2 in the atmosphere is only a small fraction of the total CO2 in the atmosphere and that therefore man is having a small effect, your source is either too naive to know better or trying to deceive you. Further comments on JNG's post take issue with his dismissal of SkS' argument.
  38. A prelude to the Arctic melting season
    I'm curious to know what the pro ice-watchers think of this: NASA Finds Russian Runoff Freshening Canadian Arctic Increasing freshwater on the U.S. and Canadian side of the Arctic from 2005 to 2008 is balanced by decreasing freshwater on the Russian side, so that on average the Arctic did not have more freshwater. Here blue represents maximum freshwater increases and the yellows and oranges represent maximum freshwater decreases.
  39. The Year After McLean - A Review of 2011 Global Temperatures
    "Well of course it should be. When you are on a plateau, the height sort of 'plateaus'." There is, of course, another way of looking at this, in a situation with a trend and variation, the most likely place to have a new high, is following a new high. Random means up and up is as likely as up and down.
  40. A prelude to the Arctic melting season
    Philippe, I was thinking in terms of total global sea ice area. But you are of course correct, even with low ice in the Kara and Barents, there isn't much in the way of solar insolation hitting those areas right now. That open water is probably losing more heat than gaining I would guess (neglecting inflows of warm water through currents). Still, if the Kara and Barents remain ice-free until the traditional melt season really kicks in, it could portend 2012's summer sea ice minimum really smashing 2007's mark.
  41. CO2 is plant food? If only it were so simple
    John Nielsen-Gammon has thrown down the gauntlet! (http://blog.chron.com/climateabyss/2012/02/three-simple-facts-about-carbon-dioxide/) He says that "Some things about carbon dioxide in the climate system are so firmly established and fundamentally important, you can use them as litmus tests to determine whether the person you are listening to is honest and knowledgeable." Fact #3 in his list is "Carbon dioxide is good for plants, in the sense that it makes them grow more rapidly. If you hear or read somewhere that man’s addition of CO2 to the atmosphere has been generally harmful to plant productivity, your source is either too naive to know better or trying to deceive you. He says of this site: "Unfortunately they can't bring themselves to admit that the evidence, while complex, does point to a net overall benefit to plant growth for the next few decades" Is Skeptical Science ignorant, [-snip-] or has JNG overstated his case? I very much respect both the Skeptical Science team and JNG. I look forward to seeing this apparent disagreement reconciled. P.S. possibility #4 is that it is me who is overstating his case, however he says that he "had looked at the (skeptical science) site" - presumably before writing the piece. So while the statements aren't targeting SS directly, SS had at least been considered. P.P.S. Interestingly JNG is typically very conservative with statements regarding what the science can tell us. Skeptical Science on the other hand is often addressing the "We don't know everything therefor we know nothing" crowd. In this case the roles appear reversed.
    Moderator Response: [JH] The correct acronym for Skeptical Science is "SkS".
  42. A prelude to the Arctic melting season
    At this point there is probably no chance to build up anything but ephemeral ice thickness.
  43. Zero Carbon Australia: We can do it
    JMykos that's an interesting point you make. My understanding is that while China implemented an official one child policy, western cultures such as Australia haven't ever attempted an official birth control policy of any kind. Are you suggesting that China should be rewarded with more of the carbon pie than Australia, as a reward for their population control policy?
  44. NASA Mission Takes Stock of Earth's Melting Land Ice
    Hansen's Figure 14 "Current Contributions to Sea Level Change" in Earth's Energy Imbalance and Implcations shows his latest assessment of the literature which is just prior to the publication of the Jacob, Wahr, Pfeffer and Swenson Nature paper under discussion. If you add the Hansen Greenland and Antarctica middle of the error bar values (0.85 mm/yr) and compare to Jacob et.al. data (1.06 mm/yr) for those areas you see that one thing Jacob et.al. discovered is that more ice may be melting in the places where most of the ice on land on the planet is than a type like Hansen thought. Hansen commented on the error bars in his Figure 14 by referring to sea level data, i.e. his Figure 12 saying "the recent measured sea level rise favors the lower estimates of ice sheet melt". So if you add up his "lower estimates" for Greenland and Antarctica from Figure 14 you get an even lower total, 0.44 mm/yr in comparison to Jacob et.al.'s 1.06 mm/yr. A wild headline could have read "Ice sheet disintegration doubles at poles - scientists stunned!" which might have as much basis in reality as some of the headlines on articles about the Jacob et.al. paper. All of Hansen's low estimates add up to a low estimate for total global ice on land melt contribution to sea level which equals 1.27 mm/yr. The Jacob et.al paper finds the total to be 1.48 mm/yr. Pfeffer, in his Nye Lecture presentation to this years AGU commented that observation of glaciers has tended to be in areas that are easy to get to, as opposed to a representative or comprehensive set of glaciers someone knowledgeable might choose for a dataset.
  45. 2010 - 2011: Earth's most extreme weather since 1816?
    Camburn - Truly a fascinating link there. I particularly appreciate the authors statements that the ice ages are caused by nearby supernova, rather than the Milankovitch cycle of insolation changes. Perhaps next time you could try actual science, rather than, well, tin-hattery?
  46. A prelude to the Arctic melting season
    It has been documented for quite some time that the NAO and the AO play a role in the level of ice in the Arctic Sea. Long Term Arctic
  47. Zero Carbon Australia: We can do it
    I understand the requirement of reducing CO2 emissions globally. But why is the CO2 quota budget "per capita"? Why should a country be rewarded with a higher CO2 budget because they allowed and continue to allow their population to grow uncontrollably?
  48. The Year After McLean - A Review of 2011 Global Temperatures
    Further to Robert Murphy's response at #16 (and on topic this time) the ENSO acts to relocate heat around the planet; it does not generate net heat. As Robert notes, removing the confounding influence of this oscillating phenomenon does not affect detection ofunderlying warming trends.
  49. Philippe Chantreau at 09:30 AM on 12 February 2012
    Climate change policy: Oil's tipping point has passed
    Do your own homework
  50. Monckton Myth #17: Debate vs. Denniss, Part 1
    Monckton spend the first part of the speech (which is all I saw) speaking as if virtually every single accepted theory is to be doubted. This is a reasonable approach to take initially as an honest skeptic or if you are in a debate and really are skeptical about every such point, but then he treated as a matter of fact virtually every point he put forward. This is an approach taken in debates not in science. If he treats the majority of research as doubtful, it does not follow an honest skeptic would then treat as a matter of fact a bunch of side research, for, if the research paper itself is good enough to allow one to take it on faith as he did, then he should have accepted everything. To me this looks like dishonest scientific skepticism. It looks like professional debate.. like what you might see in US trial courts by opposing trial lawyers (whose goal isn't usually to get to the truth but to convince a jury to side with their client).

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