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chris at 02:36 AM on 30 April 2010Tracking the energy from global warming
Ken Lambert at 23:04 PM on 29 April, 2010 Ken, your post illustrates pretty much my point about "geting into the "arguing fruitlessly" stage, which is often an indication that the data under discussion is inconclusive". That's exactly the case here. I've taken the raw Jason data from here and done a linear regression from 2002-(nearly) 2010. The slope is 2.3 mm.yr-1. No doubt you'll get a different answer by regressing the data between 2003 and 2010. It would be different again if we did 2004-2010...etc. These are very short time periods. The linear regression is biased "flattish" by the interesting period between 2006-2008 when the slope of sea level rise apparently decreased quite a bit. Short anomalies in very short time series have large effects on the regressed average change. That's why we don't make fundamental interpetations from analysis of very short time series. It's apparent from visual inspection (see sea level time series in my post 76 above) that sea levels have more or less "caught up" with the longer term trend. This is also apparent if one inspects the seasonally-adjusted data on the Univ. of Colorado sea level site. Clearly something interesting may have happened during 2006-2008. The period we're discussing corresponds to the slightly anomalous and extended down-turn in the solar cycle. So we aren't surprised if thermal energy into the ocean (and thus the thermal component of sea level rise) may have been a bit smaller than the long term trend for the last 6-7 years... At some point we need to be clear about what we're arguing over. I'm simply pointing out that the sea level rise over the last several years (e.g. since 2002) is incompatible with Peter's assertion that an energy balance analysis of a few years of data ""bring(s) havoc to standard greenhouse theory". -
Riccardo at 02:02 AM on 30 April 2010Tracking the energy from global warming
Ken Lambert, i looked at the data shown in chris #76 and could not see the jump, a quite huge one following your claim. Could you please clarify how did you detect it? -
gp2 at 01:33 AM on 30 April 2010Common graphical tricks and the Medieval Warm Period
There is an updated version of the Lamb graph that use a 50 years gaussian smooth:
Jones et al. 2009
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dhogaza at 01:25 AM on 30 April 2010Why are there fewer weather stations and what's the effect?
A question that skeptics often ask, and which I can't quite answer, is - why can't a small team be supplied to collect the huge amount of weather data available online. Example is La Paz, which is not included in recent GHCN, but which has an online weather portal with mean/max/min temps, precipitation etc.
Gavin Schmidt has suggested that efforts to do such things would be excellent "citizen science" contributions to climate science efforts. As opposed to, oh, running around photographing weather stations. -
Jesús Rosino at 01:25 AM on 30 April 2010Common graphical tricks and the Medieval Warm Period
"They are showing you that the last decade was warmer than any 50 year period on the graph including the MWP"
Well, but (for the sake of argument, because the graph is probably obsolete) such a comparison might be tricky, might not? Given that this graph doesn't provide us with the decadal averages prior to 1920 and given that the last 50-year average is similar to that in the MWP, it would be conceivable that, similarly, a single decade had reached similar values in the MWP, wouldn't it? (let's say, for example, with temparature rising from 1100 to 1200 similarly to the 20th Century, and falling in a similar way from 1200 to 1300). -
Philippe Chantreau at 01:18 AM on 30 April 2010Why are there fewer weather stations and what's the effect?
Do you actually mean "More importantly, removal of the dropped stations does not cause a spurious warming trend."? Yes. That's what is shown by all the data analyses to which the post points. -
Paul D at 01:10 AM on 30 April 2010A visual depiction of how much ice Greenland is losing
Oops sorry, I got the people mixed up in my last comment. Argus wasn't refering to Gallopingcamel, but to Berényi Péter. -
Riccardo at 01:06 AM on 30 April 2010Tracking the energy from global warming
John, I did the math for you to convert 30 Sv in the new unit of measure you like, namely EST (Empire State Building). The EST turns our to be about 10^5 m3, so 30 Sv correspond to 300 ETS per second. Considering that it took 3 years to build one ETS, the new current flowing from Antarctica is almost 10^8 times as powerful as the USA. :)Response: Thanks for converting the water flow to a unit I understand :-) 300 Empire State Buildings per second is pretty impressive! -
Paul D at 01:05 AM on 30 April 2010A visual depiction of how much ice Greenland is losing
Not that any of this is correct anyway, but... Argus, you are misquoting figures, the two commentators (Gallopingcamel and CBDunkerson) have quoted different figures. Gallopingcamel has refered to global sea levels which is linked to global ice melting, the inputs to that include thousands of glaciers, the Greenland ice sheet and Antartica. CBDunkerson has refered to just Greenland ice, which is a fraction of the input to global sea level rises and a fraction of the 3.2mm or so quoted by Gallopingcamel. If you are going to add anything. I suggest you actually pay attention to what your fellow skeptics write! -
MarkR at 00:48 AM on 30 April 2010Common graphical tricks and the Medieval Warm Period
#6 Arjan: I've tried to cover that, the most recent 50 year average is not above the Lamb MWP 50yr average. In order for the 50 year average to _not_ go above Lamb's MWP peak then HadCET will have to cool more quickly over the next 20 years than it has warmed for the past 20. Possible, but seems unlikely unless something special happens (perhaps a collapse in solar activity which may be linked to cool European winters). I thought of including that in the post, but I didn't want to make it any longer! -
nautilus_mr at 00:06 AM on 30 April 2010Common graphical tricks and the Medieval Warm Period
Arkadiusz, I could not read Oppo et al, but am interested that they use coral growth rates as a proxy. I found the Grudd paper very interesting. One cannot draw too long a bow from it, as it's focus is only on the region of Fennoscandia. Grudd's method of combining tree growth ring width and maximum ring density raises interesting questions about the appropriate use of tree ring data as a proxy for temperature. I would be particularly interested to know if Grudd has applied this analysis to the same tree datasets used by Manne et al. I am still getting through von Gunten! I note it is a very recent paper and stands out as one of the uncommon studies set in the southern hemisphere. There are two general points I would make: First, paleoclimate always involves proxies for temperature. Given that there are so many kinds of proxy, be it tree rings, ice cores, sediment analysis or whatever else, a general position can only be formed by synthesising a diverse selection. Therefore no individual study trumps the others. Second, as new studies circulate and new proxy methods are developed, we may well find the majority of studies indicate a medieval warm period comparable to the current period. Personally, I wouldn't be too fussed. I'm not terribly attached to the "hockey stick". It is a supplementary analysis, not a critical one - Alexandre's point. The hockey stick happens to be memorable and therefore was placed in a spotlight during the political vetting of the IPCC report. -
Alexandre at 23:39 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
Oh, and let's not forget the underlying skeptic argument here: "If the MWP was warmer for whatever reason, then the CWP is due to the same reason" That's like arguing "John was responsible for 1957's murders, therefore he killed those people yesterday". There are forcings responsible for the MWP as well as the Little Ice Age. The climate does not change out of sheer bad mood. It would be necessary to show that the forcings active in the MWP are active now as well. Even if Lamb's graph proved to be accurate for global temperatures, and even if temperatures "now" were those indicated by the infamous Global Warming Swindle, CO2 would not stop obstructing longwave radiation because of that. -
chris1204 at 23:35 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
The core issue is the validity of methodologies based on a temperature reconstruction derived from multiple and variously selected proxies statistically homogenised and spliced onto a modern instrumental record. Perhaps you could invite a guest post from Steve McIntyre - that would warm things up :). -
CharlieAus at 23:32 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
I think you should make all the gigaton blocks the same size visually. Your 1 gigaton looks the same size as half the second image. -
Alexandre at 23:30 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
Arkadiusz #7 What happens when you put all those in a statistical, comprehensive reconstruction (global or at least hemispheric)? To cite local reconstructions is like cherry picking 100 Chinese companies that are having bad results to "prove" that Chinese economy is not growing. -
silence at 23:16 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
I assume "They are showing you that the last decade was warmer than any 50 year period on the graph including the MWP." is meant to read: "They are not showing you that the last decade was warmer than any 50 year period on the graph including the MWP. -
Ken Lambert at 23:06 PM on 29 April 2010Tracking the energy from global warming
Typo in #88 "If you average *Jason* you get a linear fit from +14mm to +26mm in the period 2003-2010 say 7 years. This is 1.7mm/year not 3.2mm/year." -
Ken Lambert at 23:04 PM on 29 April 2010Tracking the energy from global warming
Chris #86 We indeed have different eyesight. Your graph in #76 has two distinct sections - Topex to 2002 and Jason 2002-2010. If you average Topex you get a linear fit from +14mm to +26mm in the period 2003-2010 say 7 years. This is 1.7mm/year not 3.2mm/year. There is a jump from +6mm to +12mm at the transition between Topex and Jason, likely indicating a calibration error. 1.7mm/year is consistent with the number mentioned in Dr Trenberth's Aug09 paper. Interestingly the CSIRO paper cited in Dr Trenberth's discussion finds a much better fit of sea levels with a model including volcanic forcings than not; which indicates that these might be more significant than the transient effects hitherto assumed. -
CharlieAus at 23:01 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Could we get some more info on you talking at UQ? Do you need to be a student to attend?Response: Just got the final details myself - will add a post later today giving details. You don't need to be a student to attend. -
nautilus_mr at 22:45 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
Nicely done Brendon. This thread goes straight into my "saved" list. A quick comment on the Sicre-2008 link: I'm not sure I agree with you that the Labeling of MWP on the chart is misleading. CO2 Science do use the actual SST chart, including labels, from Sicre et al. They have altered it though, by adding their own green "modern temperature line". They put the line at 9°C -a modern day "average' of their own selection to be sure. I couldn't find a modern day SST average for the seas around Iceland, but This paper by Jiang et al demonstrates on page 2 that the peak warmth of the medieval period was a good 2-3°C lower than recent peaks. I am not in a position to calculate averages from this data, but I would suggest CO2 Science's 'thin green line' deserves some skepticism. -
Arkadiusz Semczyszak at 22:33 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
Oh well. 1950 y - proxies finished? Let me quote (one of the most recent - 2009.) 2 publications that I was able to quickly find: 1. von Gunten, L. et al. 2009. A quantitative high-resolution summer temperature reconstruction based on sedimentary pigments from Laguna Aculeo, central Chile, back to AD 850. The Holocene 19 : 873-881. „Von Gunten et al. developed a continuous high-resolution (1-3 years sampling interval, 5-year filtered reconstruction) austral summer (December to February) temperature reconstruction based on chloropigments derived from algae and phototrophic bacteria found in sediment cores retrieved from Central Chile's Laguna Aculeo (33°50'S, 70°54'W) in 2005 that extended back in time to AD 850.” "... quantitative evidence for the presence of a Medieval Climate Anomaly (in this case, warm summers between AD 1150 and 1350; ΔT = +0.27 to +0.37°C with respect to (wrt) twentieth century) and a very cool period synchronous to the 'Little Ice Age' starting with a sharp drop between AD 1350 and AD 1400 (-0.3°C/10 years, decadal trend) followed by constantly cool (ΔT = -0.70 to -0.90°C wrt twentieth century) summers until AD 1750." It is obvious here, that max. warmth of the MWP is about 0.5°C higher than that recorded for the past two decades (!!!) of the 20th century ... 2. Oppo, DW, Rosenthal, Y. and Linsley, BK 2009. 2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool. Nature 460 : 1113-1116. Here MWP was about 0.4°C warmer than the Current Warm Period. Well, it is worth mentioning: Grudd H, (2008): Torneträsk tree-ring width and density AD 500 – 2004 [!!!]: A test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers. Climate Dynamics, 31: 843-857. “The new data show generally higher temperature estimates than previous reconstructions based on Tornetra¨sk tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around AD 750, 1000, 1400, and 1750 were EQUALLY WARM, OR WARMER.” These are just some "cherry picking" from my references. Which is interesting: the recent - later works - the MWP warmer ... -
aj1983 at 22:23 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
What they will usually propose as a counter argument is that 1) the proxy dating can be off somewhat, 2) the proxy data is a >50 year average, so you have to compare it with the >50 year average now, which is (not yet?) the highest. If the temperature keeps on rising it will be a waiting game until the latest 50 year average will be above those of the previous 1000 years. They should include the resolution of the proxy data in the graph so that you can find out if the "peaks" are for example 5 year, or 50 year "averages". -
Brendon at 21:38 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
mautilus_mr, here's the main part. Note this is part of an argument about MWP. -------------------------------------------- CO2Science is pretending to be thorough and systematic by listing a lot of research and categorising them by wether they are warmer than today or not. And thus they prove MWP was warmer ... but do they really? Well it's not hard to debunk them. It's taking me far longer to write this up than it did to see their errors. And I'll also point out how some of the graphs are trying to Not only that, there's some examples of misleading graphs that are obscuring the fact that the data for their MWP is not warmer than today. Temperature reconstructions are done using a lot of studies from around the world. Each one contributes a small picture of what it was like in that part of the world, depending on the geography this can be a very localised effect, or it can be representative of a much larger area. What CO2Science are doing is looking for any warm part in each of localised data, then labelling that as the MWP, regardless of the dates involved. Firstly take notice of what is commonly regarded as the MWP period, a time from AD 950–1250, that's 300 years centered around AD 1100. Now lets examine a few of the examples from CO2Science that I listed earlier. Sicre-2008 notice that their label for the MWP sits over the AD 1000-1300 and avoids the lower temps in the 950-1000 period. Take that into account and the average temps are below CWP. Look at the smoothed red line (running average) and it sits below modern day temps for almost the entire MWP. Paulsen-2003 – they have the MWP centered around AD1300. For the actual MWP, 950-1250 the average is well below todays temp (shown on the left). Althoug even if you did take their proposed relocation of the MWP, it still would be cooler than today. Kitagawa-1995 – (note graph is inverted here – warming is downwards). On initial viewing this show mostly good warming but some radical cooling amongst it too. So what's up with that? Well firstly have a look at the number of samples used to construct this graph. It contains very few samples and hence you can't get good confidence from it. The graph only goes to 1950 so it doesn't include more recent decades of warming. It also has a baseline (horizontal line) that is well below (temp-wise) the CWP, but this baseline is not the CWP. The average person might be fooled ito thinking the basline was "normal" temps, but if you look closely you'll see todays temps are higher than the average for the MWP. Zhang-2003 – the label for MWP is again off by a couple of hundred years in order to make the reader think it includes the higher parts of the graph rather than one high and one low. Abcde would also probably point out that this is tree-ring data, hence the large variation would also attract large error bars. Loso 2008 sadly for you this one completely fails to provide evidence that the MWP was warmer than today. Even though they did their best to move the MWP away from AD950, the warming it shows doesn't compete against the decade upon decade of recent warming. -
nautilus_mr at 21:28 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
Brendon, your link denied me access! 'tis a shame, I'd very much like to check that stuff out. Perhaps a different pathway into the thread? CO2 Science is a slippery example, isn't it? Not as blatant as the example in Mark's article - it looks like a duck, walks like a duck, only when you listen closely it's saying "woof". -
nautilus_mr at 21:25 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
A very clear and useful article, Mark. I think that Durkin, Plimer, Monckton et al are extended an undeserved courtesy by being called 'skeptics', however. These people are not within a bull's roar of real skepticism. It is appropriate to call them deniers. Yikes, it seems the trouble with 'skeptics' these days, is they'll believe anything! -
Brendon at 21:23 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
CO2science do a similar dodgy job with their analysis of the various studies into temperature reconstruction of the MWP. They classify each localised study by whether it (MWP) was warmer than the current period (CWP) or not. But for each study they vary the time period they call the MWP. They pick out the highest part of the data near the MWP and then label that as the MWP even if it's a few hundred years away from other studies. Sometimes they label the MWP as being centered around 1300AD, sometimes at 800AD. Good description with examples in Whirlpool thread -
MarkR at 21:14 PM on 29 April 2010Common graphical tricks and the Medieval Warm Period
If anyone can pick holes in my approach, please let me know. I added the lines to the graph using pixel counting and may have made a mistake there so I'll double check later but if you notice a mistake, do shout out! -
Riccardo at 21:13 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Argus, explicit or not, there are always assumptions when talking about the future. Here comes the physics of climate, which we cannot ignore so easily. -
JulianRGP at 21:12 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
Hi, can you clarify for me the statement near the end of the article, which says "More importantly, the dropped stations do not cause a spurious warming trend." At first, it seems like it's saying "The dropped stations when considered by themselves do not cause a spurious warming trend." In the context of this article, I think you don't mean that. Do you actually mean "More importantly, removal of the dropped stations does not cause a spurious warming trend."? Apologies for being picky, but it puzzled me when I looked at it at first. Thanks for fixing the glitch that prevented comments being added (after #10).Response: Good point, your wording is an improvement and I've updated the text in the final paragraph. Thanks for the feedback. -
Argus at 20:59 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
#15 Berényi Péter I would very much like to know the background for the 'LOL' in the editorial response to his graph: ''Response: LOL, can I ask what value you used for the total ice mass of the Greenland ice sheet and your source?'' As far as I can see his figures are correct (also noted by #22 CBDunkerson), and it would take 10000 years for the ice to completely melt at the present rate. Of course if we assume various kinds of increased ice loss rate, it will take less, but such assumptions are nothing more than assumptions based on a very small number of years. Why worry when we can do nothing about it anyway?Response: The LOL wasn't meant to cast doubt on BP's graph - I just thought it was cool that he went to the trouble to track down the Greenland ice sheet total mass and draw a graph about it. -
kdkd at 19:52 PM on 29 April 2010Has Arctic sea ice returned to normal?
Just to follow up from Riccardo #62, the polar amplification has been a prediction of warming caused by greenhouse gas pollution for a very long time. Run the models with e.g. a solar cause of warming, and the polar amplification doesn't happen, but with increased greenhouse gasses, and TADA there it is. I'm afraid I can't provide a reference without going and digging on my bookshelf, but I can assure you that it's a clearly stated prediction in at least one of the ~ 20 year old environmental science textbooks in my possession. And being in a textbook, that makes it a mainstream prediction. -
Riccardo at 19:17 PM on 29 April 2010Has Arctic sea ice returned to normal?
Not exactly in topic but related. A new paper in Nature used the latest ERA reanalysis product (called ERA-interim) to study the possible causes of the well known polar amplification. They found that the impact of sea ice reduction is the largest contribution to the effect, more than atmospheric transport which is commonly believed to be dominant. They also considered humidity and cloud cover as possible causes. One of the improvements of ERA-interim reanalysis is a more realistic troposheric temperature derived from satellite based irradiance measurements, which overcomes the lack of land based temperature measurements. -
Paul D at 19:03 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Gallopcamel said: "Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it." The Ville: 1. I don't see why anyone is obliged to persuade you. 2. No one has suggested that they want to control sea levels directly, which is what you are implying. 3. The issue is the control of human influences on the environment that they inhabit. That we do have a responsibility for. -
Paul D at 19:00 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
GallopingCamel said: "TOPEX is providing really accurate measurements. Currently the rate of sea level rise is averaging ~3.2 +/- 0.4 mm/year." The Ville: And those rates are changing and have been changing. Also the proportion attributed to thermal expansion and melting ice has changed over a relatively short period. -
Paul D at 18:52 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
@52 and GallopingCamel: "At the present rate it will take 1,000 years for the seas to rise 3 meters. If that rise happens, our distant ancestors will have plenty of time to move to higher ground." As pointed out, current rates will not be maintained. So the scenario is unlikely. But to clarify your point. Time is what most skeptics and deniers ignore. You yourself are proposing to ignore the problem because you believe it to be a distant problem. The result of such a stupid philosophy is that the infrastructures that are permanent will be expanded and in 1000 years from now, under your scenario they will have even bigger problems then if the same occurs in only 200 years. The longer you leave it, the bigger the problem gets. Your attitude is the problem, not the time scales or the science. -
barry1487 at 18:03 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
A question that skeptics often ask, and which I can't quite answer, is - why can't a small team be supplied to collect the huge amount of weather data available online. Example is La Paz, which is not included in recent GHCN, but which has an online weather portal with mean/max/min temps, precipitation etc. My initial response is that it takes time to sort the online data into GHCN format - there's no one chip catches all computer program that can be utilised to translate data from a variety of websites with a variety of formats. GHCN rely on participating Met stations who provide the monthly data in the format required. But I'm not dead sure that this description is precisely accurate, just what I've gleaned from reading blogs. It would be nice to get a straightforward but detailed description of the challenges the data collectors face, especially so skeptics can understand why, in the age of light speed information and broad access, it is not a simple matter to retrieve the abundant, daily updated online data for many stations/met services not covered by GHCN. -
gallopingcamel at 17:02 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
scaddenp (#59), You will find that my numbers in (#57) are consistent with those in the link that you sent me. Look closely at "Figure 3" and you will see 1,900 mm of sea level rise by 2010. If the rate of sea level rise is going to increase by a factor of more than six during the 21st century, something dramatic needs to happen very soon. I don't disagree with your qualitative arguments; the problems appear when one tries to quantify them. Likewise, Phila (#60). Let us suppose that you could reduce the amount of CO2 in the atmosphere by a factor of 2 (to 194 ppm). This would be close to the concentration that will cause most plants to die but what would be the effect on sea levels? -
nautilus_mr at 16:56 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
re # 18, sorry, but I don't see how the D'Aleo article you link to shows at all that "if you look at only the U.S. temperature sensors that remain in a 'rural' environment, you will not see the 'hockey stick' increase." The claim is false in any case, but your source doesn't even support you. In fact, the D'Aleo article is confused about many of the same matters already discussed in this thread. I strongly recommend any readers of this site check out the US EPA's response to these questions. The EPA, following its recent "Endangerment and Cause or Contribute" findings, was obliged to respond exhaustively to over 300,000 emails -many objecting to the findings. For the UHI, start from page 16 of the PDF: EPA RTC Volume 2 ) It is a thorough and methodical treatment. A resource to keep. (EPA report previously reported here, by the way: EPA Report -
Phila at 16:18 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
#52 gallopingcamel "Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it." Echoing scaddenp (#51), if temperature can influence sea level, and GHGs can influence temperature, and human beings can influence GHG emissions, then it seems logical to say that human beings can influence sea level. For which of these propositions do you feel there is "no credible scientific evidence"? -
JRuss at 14:48 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
If you look at only the U.S. temperature sensors that remain in a 'rural' environment, you will not see the 'hockey stick' increase in global temperature. Most of the 'hockey stick' increase is due to sensor contamination of human heat sources. sensor contamination You also might find the following interesting: Space & Science Research Center -
scaddenp at 14:47 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
gallopingcamel - your questions about future sea level rise predictions are better placed in sea level rise predictions -
scaddenp at 14:39 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Nor does modelling expect there to be. What is expected is acceleration as ice melt gains pace, albedo reduces and sea temperature rise bring rain onto icecaps. Try looking at sealevel rise rates over last millennium, compared to this century, compared to last 50 years. More in is sealevel rise exaggerated? Are you prepared to admit by the way that a greenland ice melt that contributes to a 1m rise by end of century might actually be a problem? -
gallopingcamel at 14:12 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
scaddemp (#56), TOPEX is providing really accurate measurements. Currently the rate of sea level rise is averaging ~3.2 +/- 0.4 mm/year. The rate of rise is not showing any kind of "Hockey Stick" tendency that should be evident if sea levels are to rise by 1,900 mm (AR4 worst case) in the next 90 years (21 mm/year). -
scaddenp at 14:11 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Climate is not single-variable. Try the extremely strong correlation between temperature and all forcings. eg Benestad & Schmidt for an example of a statistical approach but the models are even better. The science has worked hard to estimate the size of all feedbacks and so far any globe-saving negative forcing has been extremely illusive. John Cook's summary on why GHG is the dominant forcing acting now is mighty good summary. If you have data to dispute this, then please post and continue the argument in the relevant place. So far this is a long way from your opening gambit that greenland's melting ice is a good thing. -
johnd at 13:49 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
Phila at 12:05 PM, if anyone does follow up with a post perhaps they could illustrate it by using the Global Land Index, figure 2 above, with the base period set as 1880-1890. I don't know what period is used at present, I'm guessing 1960-70 as that was used for figure 3. A graphic illustration should be easier to demonstrate what difference, if any, different base periods make. -
gallopingcamel at 13:45 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
scaddenp (#54), The world is in an "Ice Age" as we still have polar ice caps. Currently we are fortunate to be experiencing an "Interglacial" period characterised by relatively high temperatures. Over millennia, sustained high temperatures cause ice to melt and oceans to rise. Hopefully we are in agreement up to this point. When you say that we are causing temperatures to rise by generating GHGs I still agree with you. When it comes to quantifying humanity's contribution to the undeniable "Global Warming" that has occurred since 1850 we may diverge. While basic physics can show that a doubling of CO2 concentration should increase global temperatures by ~1.2 degrees Celsius, there is the question of feedback. Do other natural processes increase or diminish the effect of radiative forcing? Given the poor correlation of global temperature with CO2 concentration I consider it likely that natural effects are overwhelming the "Anthropogenic" influence. -
scaddenp at 13:11 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
"Mother nature" is a very confusing term. Global sealevel responds to changes in temperature. I dont think you can postulate any other causes on time scale of million years or so. Do you seriously contest that temperature is NOT the cause of global sealevel temperatures? Since we are causing temperatures to rise thanks mainly to our GHG emissions, then of course we are influencing sea level. -
gallopingcamel at 13:03 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
Phila (#45), I can't prove that it is "impossible" to influence the rate of rise of sea levels. To the contrary, Mother Nature does it all the time, proving that it is possible. Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it. -
gallopingcamel at 12:54 PM on 29 April 2010A visual depiction of how much ice Greenland is losing
The Ville, (#40), As you say, the consequences of rising sea levels will be "huge". I got a feel for this issue while living in Rotterdam on a street 7 meters below mean sea level. Today I live in Florida, less than 5 meters above mean sea level. At the present rate it will take 1,000 years for the seas to rise 3 meters. If that rise happens, our distant ancestors will have plenty of time to move to higher ground.Response: The key point is that sea level will not remain at the current rate - ice sheet melt is accelerating and past history tells us the ice sheets are very sensitive to sustained warmer temperatures. The latest peer-review analyses of future sea level rise, using various independent methods, predict sea level rise of 1 to 2 metres by 2100 (and don't forget that sea level rise will continue after 2100). -
nautilus_mr at 12:36 PM on 29 April 2010Why are there fewer weather stations and what's the effect?
Further to that topic, when I first got into the climate change issue, one of the things I initially found confusing was the term "temperature anomaly". Anthony Watts' site was one of the first that I read, which undoubtedly added to my confusion. For about the first 6 months, I was deeply skeptical about the temperature record. My background is in biology and philosophy of science, but I had to work very hard to grasp statistical principles. Once I got my head around the issues, I realised the whole approach of Watts et al is confused. The issue isn't whether a given weather station is close to buildings, while another one is in a forest. Obviously the first will be affected by urban heat production. What matters is whether the temperature trends differ widely, or indeed whether there is no trend at all. When the trend is similiar across a wide variety of stations, then there is clearly a general influence that is greater than the local, variable influences. You must explain the data, and the urban heat island effect just doesn't do it. That realisation was one of the first major steps for me in satisfying my skepticism. Watts' famous photos of weather stations are total red herrings. And let's think about this - if the actual trends in weather station data were chaotic, the skeptics would have been all over it like a rash. He really is dumbing down the debate. I suspect the use of temperature anomalies is actually inherently conservative, because it compares the current year's temperature to the average of the last century. As real temperatures increase, the average must increase slightly, thereby modestly reducing the difference between the two. I remember reading a study showing that, if we separate out the rural and urban weather stations, the rate of temperature change is almost identical. I don't have the article saved -perhaps somebody can help with a link..?Response: How urban heat island has little effect on temperature trends is examined in Does Urban Heat Island effect add to the global warming trend?
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