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Hockey stick is broken
Tristan - Do you have a reference to what Joliffe wrote? Decentered means are frequently used in Principle Component Analysis (PCA), and have been for a number of different analysis areas. See a quick look at Google Scholar. The various arguments I have seen about decentering have failed to show that use of decentered means invalidates MBH98, or even significantly changes the results. See Wahl 2007 as linked in the original post. While McIntyre 2004 was able to generate some 'hockey-sticks' from red noise, analysis of the eigenvalues for those shows that McIntyre was looking at noise (low correlation, lots of fairly low value components), while the MBH98 data components have only a couple of very large eigenvalues. That's how you determine whether you are looking at actual correlations (MBH98) or just noise (McIntyre). I will note that MBH98 was a pioneering paper in terms of the reconstructions - much work has followed on in both reconstruction techniques, additional and improved proxies, etc. See Mann 2007 for a partial review. All of the work supports the late 20th century being as warm or warmer than anything in the last 1200 years, and warming faster than anything we have data for. There may well be statistical arguments for/against decentered means in this field, but again - none of them invalidate the multiply confirmed results. --- What's really stunning (IMO) about this entire discussion is the 'skeptic' focus on a paper published over a decade ago, while a dozen later works using several different methods (with what should be refined techniques), are getting the same results. It's the equivalent of someone in an active field of professional research criticizing what somebody did in grade school - even though all work done since then agrees... -
muoncounter at 04:13 AM on 11 February 2012Still Going Down the Up Escalator
"when will we know when we have finally recovered from that LIA...?" Here's a chronology of sorts, putting the end of LIA in the 1850s. That looks similar to the pattern of this graph, which shows flattened temperatures in the mid 19th century:
--source
And then the modern warming began. So LIA over, we're not just 'recovering,' whatever that actually means.
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Tristan at 04:05 AM on 11 February 2012Hockey stick is broken
Ian Joliffe considers MBH98 to contain 'dubious statistics' and says of the use of decentred PCA: It is possible that there are good reasons for decentred PCA to be the technique of choice for some types of analyses and that it has some virtues that I have so far failed to grasp, but I remain sceptical. Is using a decentred PCA the norm in paleo reconstructions or was it just MBH98?Moderator Response: [JH] Please define "PCA". Thank you. [Sph] John, PCA is Principle Components Analysis, a statistical technique whereby components are isolated and prioritized. -
Still Going Down the Up Escalator
Sphaerica - Very interesting references. While the exact causes of the LIA are not entirely fleshed out, it's clear that anthropogenic greenhouse gases are the overwhelming cause of current warming - not natural forcings, which we have a fairly good identification of. If, on the other hand, we have to placate some great Sky God, I definitely want to be on the committee selecting who gets tossed into the volcanoes... -
Bob Lacatena at 03:00 AM on 11 February 2012Still Going Down the Up Escalator
140, KR, A brief digression... another theory for an influence (far from sole cause) on the LIA is the recovery of forest land, which drew down CO2 levels by about 4 ppm, from the combination of population first lost in Europe due to the Black Death and 150 years later in Native American populations due to the introduction of European diseases like smallpox. In effect, we had two major population losses which allowed land that had been cleared to be reclaimed by forests, taking CO2 out of the atmosphere. Forest re-growth on medieval farmland after the Black Death pandemic—Implications for atmospheric CO2 levels (Thomas B. van Hoof et al, 2006) Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest (Nevlea and Bird, 2008) I have no idea how viable the theories are... but it's another example of trying to understand the system and the "natural variations," rather than just saying "Sky God angry... find virgin sacrifice, make Sky God happy... ugh!" -
Yvan Dutil at 02:52 AM on 11 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
From the paper this is aquifer withdrawal. Scary enough for me. -
JMurphy at 02:13 AM on 11 February 2012Still Going Down the Up Escalator
And when will we know when we have finally recovered from that LIA...? -
Still Going Down the Up Escalator
Eric (skeptic) - "...since then there is a mixture of AGW and recovery from the LIA." (emphasis added) This is a meme I've been seeing more often recently. I will simply note that this is discussed in some detail on the We're coming out of an ice age threads. The LIA was (as far as can be determined at the moment) a combination of solar minimum and possibly (recent evidence) a triggering tipping event of high volcanic activity. While the climate warmed from that low point, that does not explain recent warming. Only AGW can account for the magnitude of climate change over the last 50 years or so. -
Jim Eager at 01:39 AM on 11 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
What's with the large area of mass loss south of the Himalaya? Soil moisture loss? Top soil loss? -
muoncounter at 01:09 AM on 11 February 2012Still Going Down the Up Escalator
Eric#137: "The single number for the trend is inadequate and oversimplified." All curves (including sine curves) can be linearly approximated on a local basis; that's one of the things that makes calculus work. Fitting a linear trend is an essential first step because it forces you to justify the cause of the linear trend and it alerts you to look for departures from linearity. If those are merely residuals, you look for sources of 'noise,' as in FR2011. If those are changes in slope, you suspect acceleration (+ or -) and again go looking for causes. You seem to be suggesting a variant of the 'we don't know nuthin' myth' because we can see a linear trend and use it as a descriptor. Rather than address what is underlying the trend, imposing these arbitrary jumps doesn't seem like a valuable exercise to me. -
Bob Lacatena at 01:01 AM on 11 February 2012Still Going Down the Up Escalator
137, Eric, I'm not exactly certain what you're saying... are you saying that there is no trend that is reliable? But you are right in that simply looking at the numbers and trying to tease things out without an underlying understanding isclimatologyclimastrology [oops -- Sph]. The solution is to study and tease out the mechanics of the system, like the physics (e.g. radiative emission and absorption) and the component systems (e.g. ENSO and aerosol sources) and then to put it all together, rather than looking at any one piece of information in isolation. The wrong thing to do is to attribute great power to unknown acronyms, like a savage giving homage to the Sun God and the Wind Spirit, and then to just throw up your hands and say that no one could possibly know anything, and anyone who says they do is a nutter. -
Eric (skeptic) at 00:36 AM on 11 February 2012Still Going Down the Up Escalator
As a purely hypothetical example, if we had a time series with some underlying physical properties that suggested a sinusoid, it would be possible to do a linear regression on a small portion of the sinusoid (e.g. from below the origin to above). But the slope from that section would only "make sense" in the context of the sinusoid and the underlying physical causes. In the same sense a linear trend of some portion of the global average temperature should be considered as part of a bigger picture. A shorter interval (e.g. the 80's and 90's or the 2000's) would involve some natural GW and GC, AGW and possibly some counteracting aerosols. The single number for the trend is inadequate and oversimplified. Looking at longer intervals is even more problematic since then there is a mixture of AGW and recovery from the LIA. This does not seem like a valuable exercise in analysis to me. -
Composer99 at 00:22 AM on 11 February 2012Check With Climate Scientists for Views on Climate
Carbon500: I fail to see how your comment on Gore & mosquitoes affects my point at all. Where anyone speaking on climate science comports to the evidence, they have a certain degree of authority. Where they don't, they don't. One correct statement does not an infallible authority make, nor does one error completely discredit them.Moderator Response: [muoncounter] Let's all avoid being dragged into a discussion that revolves around 'things Al Gore said.' This post's topic is 'what climate scientists say.' -
michael sweet at 00:08 AM on 11 February 2012Check With Climate Scientists for Views on Climate
Carbon500, A google of "global warming Kenya mosquitoes" yields thousands of hits. This peer reviewed paper, among many others documents the spread of mosquito born disease. Perhaps Gore thought there were so many references that he did not need to supply one. -
JMurphy at 23:59 PM on 10 February 2012Check With Climate Scientists for Views on Climate
Carbon500, I notice from your link that Reiter states : "It will be interesting to see how the health chapter of the fourth report is written." In that fourth report, for which he is a Reviewer, he is referred to 3 times and has 4 references. Any idea whether he was happy with that, or if he is going to contribute to the next report ? I ask because I assume you are interested in him and his work and wouldn't just rely on 7-year old information ? -
mspelto at 23:25 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
GRACE has demonstrated itself to be quite sensitive to glacier and ice sheet mass change and has been validated in several regions. The recent paper is an ambitious step assessing all of the worlds ice covered areas. GRACE has problems with small glaciers and has not been validated in such areas. The results from the Himalaya do not appear robust, when compared to the very extensive inventories that have documented the changes in extent of thousands of glaciers in the region and have found significant changes in areal extent across all ranges except the Karakoram. The glacier by glacier mapping completed by GLIMS or ICIMOD for example tell a different and better verified story, from Kyrgyzstan to Bhutan and Afghanistan -
Carbon500 at 22:19 PM on 10 February 2012Check With Climate Scientists for Views on Climate
Composer99: Re your comment'With regards to non-scientists such as Gore or Flannery, such authority as they possess in communicating climate science comes from the degree to which their claims are based upon the available evidence' I wouldn't take anything Gore writes or claims at face value. For example, have a look at his book 'An Inconvenient Truth' on page 173 he states 'mosquitoes are profoundly affected by global warming.' No references, of course. Now have a look at this. www.publications.parliament.uk/pa/ld200506/ldselect/ldeconaf/12/12we21.htm -
Dikran Marsupial at 22:02 PM on 10 February 2012Newcomers, Start Here
@debunked, just to add another example to CBDunkerson's excellent answer, the theory of plate tectonics was only suggested about a hundred years ago. We have accurate measurements of the movement of plates for much less time than that. However the plates have been in constant movement for billions of years. Is the theory of plate tectonics inherently flawed? Does this mean we can't predict the future movement of the plates? No, of course not. -
CBDunkerson at 21:45 PM on 10 February 2012Newcomers, Start Here
debunked, the argument you present disproves itself. How do we know that "the Earth's been here for many millions of years" if we "only have data running back to a 100 years"? If these 'skeptics' accept the proxy analyses which allow us to determine that the Earth is over 4.5 billion years old then they can't claim (without hypocrisy) that we only have the 131 year (since 1880) detailed surface thermometer record on which to base global warming. There are, of course, proxy records (e.g. ice and sediment cores) which allow us to gather data on temperatures, GHG levels, and other factors stretching back "many millions of years". Of course, in addition to being self-defeating, the argument is also a clear logical fallacy. You might as well say, 'Given that the universe has been here for nearly 14 billion years, Newtonian physics can't possibly be accurate because we only have data on it going back a few hundred years.' There is no inherent connection between the age of something and the amount of time it takes to understand it. Joseph Fourier first identified the Greenhouse Effect in 1826... if that isn't sufficient time to understand something then clearly we are not communicating through these computers which cannot possibly exist yet. -
Dikran Marsupial at 21:14 PM on 10 February 2012Still Going Down the Up Escalator
RobertS wrote: "The data we are attempting to model isn't a simple straight line, else we wouldn't attempt to model it with one." That seems rather a non-sequitur. It is the underlying data generating process that we are interested in, rather than the data themselves. We do not expect this to be a linear function, we are merely trying to approximate the local gradient of the function by fitting a straight line. "We could just look at it and calculate the slope and intercept. But we do plot some straight line onto this data, and attempt to estimate the parameters of that model based on the data." There is no difference whatsoever between these two activities, the parameters of the model are the slope and intercept (other than fitting by eye is subjective and likely to be biased and hight variable). Both inferential and descriptive statistics assume that something, somewhere in the sample we are hoping to analyze is measured without error" This is simply incorrect. There are methods for inferential and descriptive statistics that assume measurement without error and there are other methods that don't make that assumption. Just because you are unaware of them, doesn't mean they don't exist (many are based on the EM approaches). Because he is not interested in the credible interval of the linear regression. He's not interested in the linear regression at all. This is Dr Briggs main failing, he is not interested in the climatology and is ignoring the purpose of the analysis (to estimate the local gradient of the data generating process). Which is why the points he is making would be valid if his assumptions about the purpose of the analysis were correct, but unfortunately they are not. "He has calculated the predictive interval of the "observables" and found a much larger uncertainty in estimates of global temperatures than stated by BEST" This is becuase he is using a definition of "warming" that is highly sensitive to the noise (i.e. unforced variability), which a proper analysis should aim to ignore. This is the reason that climatologists don't use his definition of warming, it is not a reliable indicator of underlying climate trends. "And no, not all of statistics is "predictive," but "prediction" is often implicitly assumed in some way in an analysis or interpretation" No, that is not correct, descriptive and inferential statistics do not implicityly aim to predict, they are about explanation and description. In this case, the aim is to estimate the local gradient of the (unobserved) data generating process from the data. This does not involve any attempt at prediction as we are using only a local approximation to the function of interest, so it would be unwise to use it for prediction outside the data we already have. -
Paul D at 21:07 PM on 10 February 2012Book review of Michael Mann's The Hockey Stick and the Climate Wars
owl905 I made the mistake of reading Von Daniken when I was a teenager and the Daily Mail which is very similar. I won't make that mistake again with Chrichton. -
michael sweet at 20:55 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Camburn, Your article cites 30 cm sea level rise due to melting of Greenland and Antarctic by 2050, 38 years from today. You say "no one on the continent is in peril because of this." How many million farmers in Bangladesh will be displaced in only 37 years from this sea level rise? Miami will lose close to 20% of their storm water drainage, are they "in peril" due to greater flooding? In addition, your article says that the sea level rise from the ice sheets is greater than expected from the models. Perhaps it will rise more than 30 cm as now expected. If you ignore the data it is easy to say "no one on the continent is in peril because of this." Think of the people who live near the sea. -
Ernst at 20:52 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
@8,The study does not deal with ice areas of less than 100km2. -
Sascha Tavere at 20:06 PM on 10 February 2012Global Sea Level Rise: Pothole To Speed Bump?
In a laboratory setting (constant temperature, no wind) how does ice melt? Any acceleration? (Please tell me to go away if I'm too ignorant. I'll still read your comments trying to understand.) -
pikaia at 19:33 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
What a horrible graphic! I don't understand what the maps mean, and I don't like the way they change before you can look at them properly. Why can't we have four separate maps with their own descriptions? -
debunked at 18:43 PM on 10 February 2012Newcomers, Start Here
I was going through the Most Used Climate Myths post.. I went through it in as much detail as possible.. My belief in human-induced climate change is based on some scientific facts as well as personal observation.. 'Course I'm no scientist..not even close..So when I come across people who say science on global warming can't possibly be accurate because we only have data running back to a 100 years.. And that the Earth's been here for many millions of years so any scientific analysis is inherently flawed.. I have to say, I am unable to come up with a compelling argument.. Now I don't know if this particular sceptical argument was addressed and I overlooked it.. So I'd like to know what the answer to this is.. -
Rob Painting at 16:26 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
The Guardian has a table from the study here. Skip the silly intro by Leo Hickman, and just check out the table: Land-based ice has been lost at the rate of 536 (+/-93) billion tons per year over the period 2003-2010, and added 1.48 (+/-0.26) mm per year to sea level rise. -
DSL at 16:16 PM on 10 February 2012Book review of Michael Mann's The Hockey Stick and the Climate Wars
For more on Crichton, see the Aliens Cause Global Warming thread and the salute here, and a scientific review of State of Fear here. -
owl905 at 15:55 PM on 10 February 2012Book review of Michael Mann's The Hockey Stick and the Climate Wars
Paul D wrote:- "I did start reading it (like I started reading Hansens book) but got bored." Try a flea market; copies of Michael Chrichton's book "State of Fear" should be around for a five-and-dime price. It's the amazing story of an exile from the Caliphate of Baghdad discovering that the Vikings built a huge imitation volcano that destroyed the vineyards of Greenland and caused a 400-year cold hangover. They encoded their deception into the Sagas, where it was discovered by IPCC Scientists who were on the verge of starvation due to an impending Ice Age. Seriously, Crichton revealed it to Congress ... you can't make that stuff up. -
Camburn at 15:06 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
muoncounter@10: This doesn't give the percentages, but it does talk about the melting acceleration. Accelerating Greenland Mass Loss 2011 If I run accross the paper that gave values to ice and meltwater, I will post it. -
Camburn at 14:55 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
muoncounter@10: The water comes from melted snow/ice on Greenland. When the ice/snow turns to water and runs off, it is gone. I will try and find the paper that I read concerning this. Whether it is glacial calfing or running water isn't important to the mass. Once gone, it is gone. No, I am not questioning that Greenland is loosing mass. I am not even questioning that it is loosing mass at a greater rate per year for the past 20 years. IF you were talking about pure ice calfing, that changes the dynamics of the discussion. Note in my comment that I indicated "mass is lost". -
muoncounter at 14:45 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Ian F: "If ice is melting but is being damned up in glacial lakes could this be another interpretation of the GRACE data." Why would ponding glacial meltwater produce such a large mass difference? From your link: Mountain regions from the Andes to the Himalayas are warming faster than the global average under climate change. Ice turns to water; glaciers are slowly reduced to lakes. Camburn#9: "more mass is lost per year by fresh water leaving than is by ice calfing." Do you have a source for this? Where is the fresh water coming from, if not melting ice? Are you seriously questioning the observations that Greenland ice is melting? It is not just GRACE data that support this. -
Camburn at 14:22 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Ian@8: A similiar mention should be made about Greenland as more mass is lost per year by fresh water leaving than is by ice calfing. In Greenland's case, no one on the continent is in peril because of this. -
Bob Loblaw at 14:06 PM on 10 February 2012Still Going Down the Up Escalator
I'm with Eli: this whole thing reminds me of the McKitrick "there is no such thing as a Global Temperature" claim. Deltoid has done at least one discussion of this McKitrick nonsense. I also remember Bob Grumbine doing a takedown on how McKitrick's argument against the concept of a mean temperature, pointing out that McKitrick's version basically becomes a useless definition with no practical application. It was buried on Usenet, so finding stuff is a bit hard, but I did come up with this somewhat-related discussion: Google search of newsgroups Look for Grumbine's comments about half way down (although the link as presented puts you near the bottom of the thread). This Briggs stuff seems to be a new variant on the "if you don't know everything, you don't know anything" meme. -
Ian Forrester at 13:55 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Here is a cross post on some ideas on this that I posted on Deltoid. I think that there may be a problem with the Nature paper. Anyone who researches what is going on in that area will have found that the most immediate problem there is the quickly growing glacial lakes which threaten to flood villages down the valley if they burst. Some of these lakes are huge. The Nature paper is based on GRACE data which measures gravity difference over time. If ice is melting but is being damned up in glacial lakes could this be another interpretation of the GRACE data. i.e. the glaciers are melting but the water is not moving to any significant extent but is staying close to where it melted thus making it seem as if the glaciers had not in fact melted. Here is a link to an article about these growing glacial lakes. I'm no expert in this area but it does seem another explanation for the GRACE data. Any one care to comment? -
bill at 13:53 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Re Camburn: While I was referring to another article, it is notable that The Guardian is reporting for 'the last 10 years' even though they refer to 8 years of results in the body of the text! And now there's even a Live Q&A What does the Himalaya glacier study mean for climate change?Asia's highest peaks have not lost ice over the past decade, according to new research. Glaciologist Prof Jonathan Bamber answers your questions.
Well, here's question one:Professor Bamber - as a result of these findings is the scientific community concerned that people might start to believe some of the other things that Jeremy Clarkson says?
Then there are questions about whether the rest of the cryosphere is actually melting after all, even though the report clearly states that it is, which is why the result in the Himalayas was an anomaly! It's like a text book study on how not to report something! [sigh] -
bill at 13:39 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
I was a little surprised not to see the name 'Fred Pearce' in there, frankly! ;-) What annoys me is that while, yes, this is all you could expect from the Daily Mail or WSJ, now The Guardian - and it really does know better - has done its bit to ensure the public will now remember the result as 'but they said the glaciers weren't melting after all'! -
Camburn at 13:26 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
bill@2: How would they get 10 years from this article? It appears to be either 6 years or 8 years. Unless Britian has developed a different parameter concerning time, a year is still a year.Moderator Response: [DB] Bill refers to a separate news article. -
Rob Painting at 13:22 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Bill - ".......and The Guardian's own reporting of it! It's clearly incongruous, at least if it's simplistically reported as 'the Himalayas have lost no ice in the last 10 years" Yes, strange how when it involves global warming the all-important context is missing. Imagine what would have happened if, when that asteroid last year was hurtling toward Earth, the media conveniently neglected to mention that it was going narrowly avoid a collision with Earth. They remembered the context then, why not now? -
Rob Painting at 13:15 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Bill, one of the SkS authors is putting together a post on this too. Needless to say, the accumulation of snow in the high Asian mountains is likely under conditions, such as the recent La Nina-dominant period, where a much warmer western tropical Pacific intensifies the Asian Monsoon, and dumps more snow on the high plateau. None of which changes the rapid loss of ice at lower elevations, being much warmer, or the rapid global loss of ice already underway. -
bill at 12:58 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Sadly, and predictably, this was cherrypicked and turned into a bunfight about the Himalayas. Even The Guardian is guilty of this. This doesn't seem to fit well with experience on the ground and The Guardian's own reporting of it! It's clearly incongruous, at least if it's simplistically reported as 'the Himalayas have lost no ice in the last 10 years'; it will be interesting to see how the discussion pans out -
Camburn at 12:39 PM on 10 February 2012NASA Mission Takes Stock of Earth's Melting Land Ice
Is the time period between 2003-2010 6 years? Under the image, it indicates during 2003-2010 which would indicate 8 years. Which set of years is correct? -
RobertS at 12:19 PM on 10 February 2012Still Going Down the Up Escalator
After this, I'll let you guys have the last word - I've spent far too much of my precious little free time here as it is. Tom Curtis @131 "Going back to your example, the formula for the linear regression of a time series does not have a slope of 0.175 C/decade (+/- 0.012°C/decade). Neither does the computer, or the pages of paper on which the calculation was performed. That slope is the property of the NCDC temperature data. In other words, it is simply incoherent to say the linear regression is a property of the mathematical manipulation rather than the data." This is a backwards interpretation of what I've attempted to argue, but perhaps I could have been clearer. The data we are attempting to model isn't a simple straight line, else we wouldn't attempt to model it with one. We could just look at it and calculate the slope and intercept. But we do plot some straight line onto this data, and attempt to estimate the parameters of that model based on the data. In a linear model y=a+bx+e, only the x and y are variables which we "observe" (even if we "observe" them with error which must be treated probabilistically; i.e. a model). The parameters a, b, and e must be "estimated", with their value and uncertainty dependent on your chosen method of estimation (OLS, MLE, LAD, etc.), and how you treat the underlying process. Simply, it's the linear model of temperatures which have a slope of 0.175 C/decade, not the temperature record itself (as you allege in the above quote). Not NCDC, or GISS, or HadCRU, or BEST. The temperature record helped to determine the slope of the linear model, but the temperature record and the model are not the same thing. As far as the "pragmatic distinction" goes, Tom seems to be hung up on the words "temperature" and "observation" - he's using a highly specific physical definition, rather than as a useful statistical designation (as I attempted to explain above @128). Both inferential and descriptive statistics assume that something, somewhere in the sample we are hoping to analyze is measured without error, and hope that this oversight doesn't greatly affect our conclusions. If we can, however, minimize or quantify and include as many sources of uncertainty as possible, that would be a good thing. Dikran @133 "You might want to ask yourself why Briggs hasn't already performed this analysis before making a fuss about it on his blog." Because he is not interested in the credible interval of the linear regression. He's not interested in the linear regression at all. He has calculated the predictive interval of the "observables" and found a much larger uncertainty in estimates of global temperatures than stated by BEST, with increasing uncertainty the further back we go. A linear regression is not the only (or necessarily ideal way) to answer a question about a change in some dataset. And no, not all of statistics is "predictive," but "prediction" is often implicitly assumed in some way in an analysis or interpretation, so perhaps it should be. In practice I too use descriptive parametric statistics, because that it the way the world works, but it's fun to opine on the way we should view things from an epistemological standpoint. -
skywatcher at 11:40 AM on 10 February 2012Global Sea Level Rise: Pothole To Speed Bump?
...Except that Church and White (2011) themselves estimate an accelerating sea level rise:The linear trend from 1900 to 2009 is 1.7 ± 0.2 mm year-1 and from 1961 to 2009 is 1.9 ± 0.4 mm year-1. However, there are significant departures from a linear trend. We estimate an acceleration in GMSL by fitting a quadratic to the time series, taking account of the time variable uncertainty estimates. From 1880 to 2009, the acceleration (twice the quadratic coefficient) is 0.009 ± 0.003 mm year-2 (one standard deviation). This estimate is slightly less than but not significantly different from the (one standard deviation) estimate of Church and White (2006) of 0.013 ± 0.003 mm year-2, but still significantly different from zero at the 95% level.
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Global Sea Level Rise: Pothole To Speed Bump?
Steve Case - The Church and White 2006 paper, if that is what you are referring to, does show a jump in acceleration around ~1930. "The slopes are 0.71 ± 0.40 and 1.84 ± 0.19 mm yr^-1 respectively, respectively, implying an acceleration of 0.017 ± 0.007 mm yr^-2 (95%)" They relate this to the more rapid rise in temperatures (with a 20 year lag) beginning in the early 1900's. From their conclusions: "From 1993, the rates of rise estimated from tide gauge and altimeter data (after correction for GIA effects) are about 3 mm yr^-1, faster than the quadratic (about 2.3 mm yr^-1) at this time." (the quadratic for the entire 20th century). There are ~10 year +/- variations in the rate of sea level rise, but it's definitely accelerating if you look at all of the data, rising faster than quadratic in rate. -
Trent1492 at 11:29 AM on 10 February 2012Book review of Michael Mann's The Hockey Stick and the Climate Wars
I have a Nook and Barnes and Noble is only selling the hard copy, so far. -
Trent1492 at 11:10 AM on 10 February 2012Book review of Michael Mann's The Hockey Stick and the Climate Wars
I was just at the Amazon site for the book and I see that one R. Hooper has uploaded a inappropriate image of the product. I do not see any where to complain about this behavior for a customer image. -
Rob Honeycutt at 10:50 AM on 10 February 2012The real doping scandal: Weather on steroids
I think videos like these are an extremely worthwhile effort. They're simple, short, easy to understand. More climate scientists should endeavor to do these. -
Steve Case at 10:41 AM on 10 February 2012Global Sea Level Rise: Pothole To Speed Bump?
#66 Skywatcher @ 8:59 According to the Church and White paper I've seen, the big jump in acceleration occurred in about 1925 for what reason I don't know. -
bill at 09:52 AM on 10 February 2012The real doping scandal: Weather on steroids
Good point, Paul D, and we'd also have to pause frequently to observe the behaviour of passing seagulls. Cracking vid! Nice animations, nice level of humour, nice length. (Jerry Meehl's voice reminds me of Noam Chomsky!)
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