Above: Mt Erebus, Antarctica
picture by Sean Brocklesby
A press release today by the University of Washington makes a claim that Antarctica is warming and has been for the last 50 years:
“The study found that warming in West Antarctica exceeded one-tenth of a degree Celsius per decade for the last 50 years and more than offset the cooling in East Antarctica.”
…
“The researchers devised a statistical technique that uses data from satellites and from Antarctic weather stations to make a new estimate of temperature trends.”
…
“People were calculating with their heads instead of actually doing the math,” Steig said. “What we did is interpolate carefully instead of just using the back of an envelope. While other interpolations had been done previously, no one had really taken advantage of the satellite data, which provide crucial information about spatial patterns of temperature change.”
Satellites calculate the surface temperature by measuring the intensity of infrared light radiated by the snowpack, and they have the advantage of covering the entire continent. However, they have only been in operation for 25 years. On the other hand, a number of Antarctic weather stations have been in place since 1957, the International Geophysical Year, but virtually all of them are within a short distance of the coast and so provide no direct information about conditions in the continent’s interior.
The scientists found temperature measurements from weather stations corresponded closely with satellite data for overlapping time periods. That allowed them to use the satellite data as a guide to deduce temperatures in areas of the continent without weather stations.
…
Co-authors of the paper are David Schneider of the National Center for Atmospheric Research in Boulder, Colo., a former student of Steig’s; Scott Rutherford of Roger Williams University in Bristol, R.I.; Michael Mann of Pennsylvania State University; Josefino Comiso of NASA’s Goddard Space Flight Center in Greenbelt, Md.; and Drew Shindell of NASA’s Goddard Institute for Space Studies in New York City. The work was supported by grants from the National Science Foundation.
Anytime Michael Mann gets involved in a paper and something is “deduced” it makes me wary of the veracity of the methodology. Why? Mann can’t even correct simple faults like latitude-longitude errors in data used in previous papers he’s written.
But that’s not the focus of the moment. In that press release they cite NASA satellite imagery. Let’s take a look at how the imagery has changed in 5 years.
NASA’s viewpoint – 2004
Click for larger image
NASA’s Viewpoint 2007 (added 1/22)
NASA’s viewpoint – 2009
Earth’s viewpoint – map of Antarctic volcanoes
From the UW paper again:
“West Antarctica is a very different place than East Antarctica, and there is a physical barrier, the Transantarctic Mountains, that separates the two,” said Steig, lead author of a paper documenting the warming published in the Jan. 22 edition of Nature.
But no, it just couldn’t possibly have anything at all to do with the fact that the entire western side of the Antarctic continent and peninsula is dotted with volcanoes. Recent discovery of new volcanic activity isn’t mentioned in the paper at all.
From January 2008, the first evidence of a volcanic eruption from beneath Antarctica’s ice sheet has been discovered by members of the British Antarctic Survey.
The volcano on the West Antarctic Ice Sheet began erupting some 2,000 years ago and remains active to this day. Using airborne ice-sounding radar, scientists discovered a layer of ash produced by a ’subglacial’ volcano. It extends across an area larger than Wales. The volcano is located beneath the West Antarctic ice sheet in the Hudson Mountains at latitude 74.6°South, longitude 97°West.
UPDATE 1/22
In response to questions and challenges in comments, I’ve added imagery above and have a desire to further explain why this paper is problematic in my view.
The author of the paper himself (Steig) mentions the subglacial heat source in a response from “tallbloke” in comments. My issue is that they don’t even consider or investigate the possibility. Science is about testing and if possible, excluding all potential candidates that challenge your hypothesis, and given the geographic correlation between their output map and the volcanic map, it seems a reasonable theory to investigate. They didn’t.
But let’s put the volcanoes aside for a moment. Let’s look at the data error band. The UAH trend for Antarctica since 1978 is -0.77 degrees/century.
In a 2007 press release on Antarctica, NASA’s describes their measurement error at 2-3 degrees, making Steig’s conclusion of .25 degrees Celsius over 25 years statistically meaningless.
“Instead, the team checked the satellite records against ground-based weather station data to inter-calibrate them and make the 26-year satellite record. The scientists estimate the level of uncertainty in the measurements is between 2-3 degrees Celsius.”
That is from this 2007 NASA press release, third paragraph.
http://earthobservatory.nasa.gov/IOTD/view.php?id=8239
Also in that PR, NASA shows yet another satellite derived depiction which differs from the ones above. I’ve added it.
Saying you have a .25 deviation over 25 years (based on one-tenth of a degree Celsius per decade per Steig) with a previously established measurement uncertainty of 2-3 degrees means that the “deduced” value Steig obtained is not greater than the error bands previously cited on 2007, which would render it statistically meaningless.
In an AP story Kenneth Trenberth has the quote of the day:
http://news.yahoo.com/s/ap/20090121/ap_on_sc/sci_antarctica
“This looks like a pretty good analysis, but I have to say I remain somewhat skeptical,” Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research, said in an e-mail. “It is hard to make data where none exist.”
My two cents on the accuracy, precision, and temperature change per year discussion. I have been following the discussion and find points of agreement with both sides here.
It is quite possible, and quite valid, to measure temperatures in whole degrees over a period of years, yet conclude there was a change measured in tenths of a degree per year.
The same principle allows us to state, with a straight face, that a population of people has 2.3 children per woman, on average. I shall explain.
Some women will have zero children, others have 1, 2, 3 or more in their lifetimes. Yet, when adding up all the women (whole numbers) and all the children (whole numbers), then dividing the number of children by the number of women, we obtain some number that is likely not a whole number. Thus, 2.3 children per woman.
Temperature measured over years can have the same result. Example: At time zero, temperature measured in whole degrees is 14 degrees C. At time zero-plus-ten years, temperature is measured at 15 degrees, again in whole degrees. What is the average temperature rise per year? One degree divided by ten years, equals 0.1 degrees/year. No precision errors, no accuracy errors.
Now, there may be calibration errors, but if the measuring device is calibrated equally well at both times of measurement, or even if it reads wrong but by the same amount and in the same direction, the average increase per year is still valid.
We do this all the time in refineries and chemical plants, where erroneous data readings (measurements) are identified via sophisticated data reconciliation algorithms. It may be physically impossible for a temperature reading to be what the instrument displays, so the bias is determined and added to the result. Then the adjusted (reconciled) value is included into whatever computer program is appropriate for the application at hand.
One important commercial application of this is determining the degree of fouling of heat exchangers, by measuring the temperatures of fluids flowing to and from the heat exchanger over a period of time. The optimal schedule to clean the heat exchanger can be determined with this data (and some other data, but no need to go into that here).
I am not sure what went on in Antarctica regarding their temperature measurements, after reading the papers and comments on this thread. But, a tenth degree rise per year can be perfectly valid even when the measuring device gives whole numbers.
Roger E. Sowell
Joel Shore says:
I think this shows astounding ignorance on your part, Joel, or a willful desire to slander McIntyre, because they have submitted them to peer-reviewed literature.
You can see the results in Climate Audit. Steve McIntyre is one very much to be respected person in my view.
Richard Sharpe says:
Well, I would be glad to stand corrected, but if I go to ClimateAudit and look at the “Articles” banner on the lefthand side, I see the last published paper he had was in 2005…and that was on the original Mann work published in 1998/1999. In fact, he has only paper published period in what is considered to be a reputable peer-reviewed journal (GRL; alas, Energy & Environment is not), plus a reply to a comment on that paper.
Perhaps he has been submitting papers to journals regarding the other proxy studies and having them rejected or still being processed? I’d be interested to see any such papers you can point me to.
foinavon (04:00:48) :
There is very little time left for you to make your point.
You are dodging my question and misrepresenting your Christy and Spencer issue. Your approach seems to lack clarity, sincerity and decency.
I have shown you two UAH LT datasets, one published in 2002 and another in 2008.
There is no material difference between them, in spite of all the “errors” you allege were discovered by others.
What is the source reference of your alleged 40% error?
Can you define the “40% of what” that you are referring to?
Regards, Allan
Richard Sharpe (15:48:37)
Joel Shore (16:45:27)
I’ve had a look in the scientifc data base. As Joel says, Steve McIntyre hasn’t published anything since 2005 (and one of the 2005 “papers” is in the rather unfortunate non-science magazine “Energy and Environment”).
There are some very interesting papers by Wahl and Ammann on this subject quite recently published. These are extraordinarily detailed and assess the original Mann et al reconstructions and the McIntyre/McItrick criticisms. They provide a very nice context for properly assessing these issues, and more importantly, redirecting the focus towards knowledge acquisition and understanding, and away from the long-standing persistent and dreary sniping.
They are:
Eugene R. Wahl and Caspar M. Ammann (2007) Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change 85, 33-69.
Abstract: The Mann et al. ( 1998) Northern Hemisphere annual temperature reconstruction over 1400-1980 is examined in light of recent criticisms concerning the nature and processing of included climate proxy data. A systematic sequence of analyses is presented that examine issues concerning the proxy evidence, utilizing both indirect analyses via exclusion of proxies and processing steps subject to criticism, and direct analyses of principal component ( PC) processing methods in question. Altogether new reconstructions over 1400-1980 are developed in both the indirect and direct analyses, which demonstrate that the Mann et al. reconstruction is robust against the proxy- based criticisms addressed. In particular, reconstructed hemispheric temperatures are demonstrated to be largely unaffected by the use or non-use of PCs to summarize proxy evidence from the data-rich North American region. When proxy PCs are employed, neither the time period used to “center” the data before PC calculation nor the way the PC calculations are performed significantly affects the results, as long as the full extent of the climate information actually in the proxy data is represented by the PC time series. Clear convergence of the resulting climate reconstructions is a strong indicator for achieving this criterion. Also, recent “corrections” to the Mann et al. reconstruction that suggest 15th century temperatures could have been as high as those of the late-20th century are shown to be without statistical and climatological merit. Our examination does suggest that a slight modification to the original Mann et al. reconstruction is justifiable for the first half of the 15th century (similar to+ 0.05-0.10 degrees), which leaves entirely unaltered the primary conclusion of Mann et al. ( as well as many other reconstructions) that both the 20th century upward trend and high late-20th century hemispheric surface temperatures are anomalous over at least the last 600 years. Our results are also used to evaluate the separate criticism of reduced amplitude in the Mann et al. reconstructions over significant portions of 1400-1900, in relation to some other climate reconstructions and model-based examinations. We find that, from the perspective of the proxy data themselves, such losses probably exist, but they may be smaller than those reported in other recent work.
Caspar M. Ammann and Eugene R. Wahl (2007) The importance of the geophysical context in statistical evaluations of climate reconstruction procedures. Climatic Change 85, 71-88.
Abstract: A portion of the debate about climate reconstructions of the past millennium, and in particular about the well-known Mann-Bradley-Hughes (“MBH” 1998, 1999) reconstructions, has become disconnected from the goal of understanding natural climate variability. Here, we reflect on what can be learned from recent scientific exchanges and identify important challenges that remain to be addressed openly and productively by the community. One challenge arises from the real, underlying trend in temperatures during the instrumental period. This trend can affect regression-based reconstruction performance in cases where the calibration period does not appropriately cover the range of conditions encountered during the reconstruction. However, because it is tied to a unique spatial pattern driven by change in radiative balance, the trend cannot simply be removed in the method of climate field reconstruction used by MBH on the statistical argument of preserving degrees of freedom. More appropriately, the influence from the trend can be taken into account in some methods of significance testing. We illustrate these considerations as they apply to the MBH reconstruction and show that it remains robust back to AD 1450, and given other empirical information also back to AD 1000. However, there is now a need to move beyond hemispheric average temperatures and to focus instead on resolving climate variability at the socially more relevant regional scale.
For new visitors to WUWT, the Wegman Report to Congress identifies the corruption of the peer review process within the climate sciences. Professor Wegman is an internationally recognized statistician who chairs the National Academy of Sciences (NAS) Committee on Applied and Theoretical Statistics. [Similar information is available by searching “Wegman, NAS”.]
Also, this critique by the grandfather of climatologists, Prof. Richard Lindzen, the Alfred P. Sloan Professor of Meteorology, in the Department of Earth, Atmospheric and Planetary Sciences department at M.I.T., is must reading in order to understand the shenanigans involved in climate science peer review and the government grant process: click
The links above show that the peer review process in the climate sciences has been thoroughly corrupted. It is unfortunate, but true, as Professors Wegman and Lindzen make crystal clear.
Roger Sowell:
That reminds me of a factoid I once read: on average, a person has fewer than two feet.
This genuflection at the altar of publication reminds me of an experience early in my career as an industrial scientist. A paper appeared in a “prestigious internationally well-regarded journal” claiming the discovery of a great new catalytic process. The lead author was someone whom I had heard was fond of keeping a numbered list of his many publications on his office door.
The work attracted the attention of many companies that expended considerable resources trying to reproduce the work, all without success. I heard of at least five through the grapevine, including one that had hired some poor guy for the express purpose of commercially developing this process.
As it turns out, the process was not reproducible even in the original lab.
Fortunately or unfortunately, unlike climate science, commercially significant research has a very clear measure of success. Coulda’, shoulda’, woulda’s don’t count for much, nor do chest thumping arguments based on whose CV is longest.
Allan M R MacRae (17:11:49)
I’ve cited this paper twice already in response to your request!
Here it is again:
Carl A. Mears and Frank J. Wentz (2005) The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature Science 309 ,1548 – 1551
In which the authors demonstrate that Spencer and Christy made an incorrect “correction” of the diurnal effect on satellite MSU tropospheric temperature data by introducing the wrong sign, which made the tropospheric temperature trend appear rather cooler (or less warm) than reality. A very weird error for Spencer and Christy to have made.
Spencer and Christy acknowledged their error here:
J.R. Christy and R.W. Spencer (2005) Correcting Temperature Data Sets Science 310, 972 – 973 in a rather embarrasing bit of correspondence in which their dodgy analysis was rather openly highlighted.
They described that as a result of this latest error that they were making yet another correction to the UAH analysis and that in version 5.2 the tropospheric temperature trend (Dec 1978-July 2005) was being raised by 40% from 0.088 oC per decade to 0.123 oC per decade.
That’s the 40% correection you’ve asked about.
If you go back and look at the references I’ve given you already, you can identify the other papers in which spurious cooling trends were introduced into their analysis by Spencer and Christy. In their early work they asserted that the trend was actually a bit negative, and as you’ve already shown with the web page you linked to earlier, even up to 2002 (12 years after their first report of their “methods”) they were still asserting that there was no warming trend.
“” foinavon (03:50:22) :
George E. Smith (17:37:42) :
Stangely to a man, all the AGW fans declined the invitation; which would also have been an opportunity for “Debate” to take place.
What’s a “AGW fan”? The science is debated in research labs, at scientific meetings, in the scientific literature and other scientific arenas. We can do without these contrived set piece “debates” that shed very little light, and are very often a means for a paricular position to play to an audience. “”
>>Sorry for using non specific colloquialisms; perhaps I should have said ‘promoters of the man made globals warming thesis’ And as I said, all of the more publicly prominent ones in that group were invited to present papers at the conference, and declined a perfect opportunity to “instruct” all those poor souls who are lost among the ‘deniers’ <<>You seem very swift to simply dismiss that whole group as inconsequential; what are your credentials that qualify you to do that; they put their trousers on one leg ata time same as you do; if their scientific arguments are unsound, that is a perfect opportunity for you to show them why<>>That’s a rather hollow charge. if Dr Roy Spencer is unable to get a paper accepted in the peer reviewed journals; because a single reviewer perceives his paper not in line with the approved position; is that the scientific process we want?<<<
Of course I’m sure everyone will have fun at the Heartland meeting, and will come away feeling empowered and ready to take up the cudgels and so on…
In our normal predictions from our understanding of atmospheric physics, we are used to the idea of having the cause happen before the effect, rather than the other way round. this quirk of human nature would lead us to conclude that it is rising and falling global mean surface temperatures (however caused) that give rise subsequently to rising and falling atmospheric CO2 concentrations.>>Well it is in no way a contradiction; even in al Gore’s book, the 650,000 years or so of ice core temperature and CO2 data, show incontroveribly that the CO2 changes always follow the temperature changes, and by delays of the order of 800 years. And although Gore pulled a cheap trick that even an 8th grade science student would avoid; namely separating the temperature and CO2 graphs vertically to hide the relative timing; it is still irrefutable that the temperature changes happen first, and the CO2 changes follow. Whats’s more, the very same original data that Gore used somewhat poorly in his book, and the raw data itself still shows the same time relationship. And what do you know; in the half dozen or so peer reviewed journal papers in which I have seen this same data presented; evn those authors did not overlap the two graphs so that the reader could immediately grasp the only significant data that is in those graphs; and that is that the temperature changes either up or down ALWAYS happen first, and the CO2 changes, either up or down ALWAYS happen later. Moreover the falling edges of the CO2 curves are ALWAYS slower than the rising edges, and ALWAYS slower than the temperature falling edges. Physicaql processes have a general tendency to slow down from cause to effect; we typically don’t see acceleration in propagation delays. You simply cannot make a case that those Temperature changes were CAUSED by those CO2 changes.
And guess what happend 800 years ago before today’s rising CO2 edge? Well lookey here; I do believe that was smack in the middle of the mediaeval Warming period. Well we can forget that; Michael Mann says there was no such thing; well he also said his hockey stick was just a local phenomenon, and not a global effect. Well to be pedantic; since you like that, his hockey stick graph was labelled “NORTHERN HEMISPHERE”. Well I’ll let you look that up for yourself in the original IPCC report where he announced it. <<>>Well I’ll just leave that to you to explain to Al Gore; he’s the one who pointed out to the world at large in his science fiction movie, that the temperatures, and the CO2 are correlated; he just never got it straight in what order they occur<<<
And I wish you would stop spreading this CO2 feedback nonsense. Water vapor is a much more powerful greenhouse warming gas that CO2 ever was even at is’s maximum concentrations that we know about ever occurring; so water vapor by itself is perfectly capable ofgeberating all the positive feedback warming you want to have, and it does; so it needs and gets no help from CO2 or any other GHG since Water can absorb the very same iR wavelengths that they can; and then some.
Unfortunately, CO2 and methane don’t form clouds of liquid or solid compositions like water does, and water clouds produce an overwhelming negative feedback cooling that can more than swamp any puny effect that CO2 causes. Which is why,w e see CO2 continuing to rise precipitously,and meanwhile the temperature has decided to not co-operate with the AGW theory, and is clearly going the other way.<<>> if CO2 produced any significant amount of positive feedback; with all the propagation delays built into the system; we would have a thermal oscillator; but for some reason; the climate modellers don’t seem to worry about the feedback stability of their feedback models or the transient time response of them.
When somebody shows me the frequency response and the transient response to say an impulse function of one of these CO2 feedback amplifiers; I might start paying attention.
Well even publishing some some temperature rise data with proof of the mechanism by which some CO2 rise data caused it, I would note that too.
The Arrhenius model of CO2 warming is the flimsiest piece of non-science I have ever seen; and the total failure of any of the predictions of the IPCCs predictions/projections/suppositions to actually come about is proof enough. <<
George
Allan M R MacRae says:
What does “no material difference between them” mean? Have you fit linear trend lines through both data sets? The fact that they look sorta the same doesn’t cut it…The problems with these data sets are not the shorttime up and downs but subtle and not so subtle issues that affect the long term trends.
Furthermore, your comparison doesn’t show the full extent of the corrections over the years. I think by 2002 a lot of the corrections of errors (such as the correction for orbital decay of the satellites) had already been made.
What is the source reference of your alleged 40% error?
Can you define the “40% of what” that you are referring to?
I believe he is referring to the last major correction of the UAH dataset in ~2005 that raised the trend from 0.088 to 0.123 C/decade, an increase of 40%. And, the source for it is this README file at Spencer and Christy’s UAH website documenting the corrections:
And, while they note that this error was still within the margin of error of +/- 0.05 C/decade that they claimed in their 2003 paper, it still constitutes a significant systematic error…and, as I noted, there were other major ones corrected before 2003. You can read a bit more about them in that README file although there is not generally systematic documentation of how the trend has changed with the correction of each one. From that file, here is what I can piece together about how the trend has changed with time (although some of this might be due to the changing length of the data series, I think that has generally been a smallcontribution at least after the first 15 years or so of data):
Pre-1999: (not sure of the number but it was negative)
Jan 2001: +0.044 C /decade
Before Aug 2005 correction: +0.088 C / decade
After Aug 2005 correction: +0.123 C / decade
Hope that helps to clear up your confusion on this issue.
AARGH! To say MBH-98 is “robust” since 1450 is a little like saying that by 1960 Hitler’s defeat was assured.
And to say it is robust back to 1000 is to ignore completely the historical and archaeological record (and contemporary literature).
If proxies say there was no MWP, that doesn’t refute the existence of the MWP, it just refutes the alleged accuracy of said proxies.
Sorry, I meant to include a link to their README file: http://vortex.nsstc.uah.edu/data/msu/t2lt/readme.03Jan2008
John M (18:00:11)
That’s a very nice reminiscence, but it’s not obvious what it’s relevance is to our understanding of paleoproxy analysis of past temperatures!
evan jones says:
What record are you talking about? The point of Mann et al. is not that a MWP did not exist in some regions of the northern hemisphere (particularly the North Atlantic) but rather that it was not a global phenomenon…Or, more precisely, to the extent that there were warm periods in records from various places if you take a broad enough definition of the Medieval Period, these warm periods tended to be asynchronous from one place to another so that when you average over the whole hemisphere all you get is a modest broad bump over the Medieval Period rather than the more dramatic peak you would get if the warm periods happened at the same time.
Hmmm…Well that sounds a lot like denying the evidence that goes against your pre-conceptions. I admit that more work needs to be done, and is being done, to understand and improve the proxy data…but to simply dismiss it out-of-hand is kind of ridiculous.
Here’s a quote from a 1998 paper by Spencer and Christy ( http://ams.allenpress.com/archive/1520-0442/11/8/pdf/i1520-0442-11-8-2016.pdf ) that gives us another couple of data points for my chart of how their trend has changed with time:
So, in other words, before this 1998 paper their trend was -0.076 C / decade and after it, it was -0.046 C / decade.
And, note that their Aug. 2005 estimate of +0.123 C / decade lies well outside the +/- 0.05 C / decade error bars on that -0.046 C number (which, as per this paper has already been corrected at least once). [And, while some of this change could be due to the longer data series, from what I recall by some investigation of looking at the trends in their current data set out to various end-dates, I don’t think that much of it is. It would be easy enough to check this by computing the trend on their current data series restricted to that Jan 1979 – April 1997 time frame.]
Foinavon, no reference to Amman and Wahl would be in context without this:
http://bishophill.squarespace.com/blog/2008/8/11/caspar-and-the-jesus-paper.html
foinavon (18:19:43) :
Then one has to wonder why you bothered to pen this masterpiece.
Should I add an exclamation point to the end of my statement too?
Joel Shore, the work summarised here, some very recent, makes it clear your statements on the MWP are questionable:
http://www.co2science.org/data/mwp/mwpp.php
One interesting aspect of the Nature article is the NASA graphic, the third map on this page, which has been specifically designed for maximum media impact. It is the graphic that is used on the cover of Nature and by news organisations around the world. The colours used are ‘hot’ colours. The Antarctic peninsula is portrayed as bright red. So in the eyes of the general public it must be hot. Apart from the fact that it represents a very minor warming trend as generated by the computer models in the study and not absolute temperatures. Graphics can be very powerful in the manipulation of public opinion.
So, pretty much like any warming we might have seen this century, not global by any means.
The believers in AGW are attempting to prop up Michael Mann’s ruined reputation, but the facts of his scientific misconduct cannot be expunged from the record:
In other words, Michael Mann deliberately misrepresented the facts. And he knew it at the time. And to this day he stonewalls anyone who asks about his flawed data and methodology. Who in their right mind would trust or believe someone like that?
Mann [who is paid out of the public purse] then hid his data and methodology, claiming that it is his ‘personal intellectual property.’ When confronted with the fact that he used provably incorrect data, he still has refused to delete it — for the past two years.
When Mann finally, grudgingly disclosed some of his methodology [after being caught red-handed hiding data behind the “CENSORED” directory by statistician Steve McIntyre, which discredited Mann’s paper], Prof. Wegman proved that any random red noise that was fed through Mann’s algorithm would produce the same hockey stick pattern. Noise! Since Mann knew this, he acted fraudulently when he provided the IPCC with his hockey stick results — which the IPCC has used extensively to extort money from U.S. taxpayers.
The Wegman Report to Congress showed conclusively that McIntyre was right and Mann was wrong regarding the discredited hockey stick. Yet to this day Mann continues churning out bogus hockey stick patterns, indicating a high degree of official corruption within the climate sciences. They are a small, closed clique that never allows conflicting views or answers uncomfortable questions. And our tax dollars are paying for this ongoing fraud.
The AGW political contingent can go on blithely claiming that there is no MWP, but that new hypothesis is destined for failure. The MWP has been repeatedly demonstrated over decades, and is accepted by the mainstream climate scientists and geologists. The current futile attempt to pretend it didn’t happen reeks of desperation.
It comes down to this: who are you going to believe, a discredited inventor of bogus data, or the mainstream scientists who overwhelmingly accept the fact of the Medieval Warming Period?
I said:
Well, I’m back after fighting with Excel for a while: I did the trend computation and it turns out that the endpoint makes more difference than I expected. Nonetheless, my basic point still holds…Here is a list of the trends under various versions of their algorithm but now all for the period from Jan 1979 thru Apr 1997:
Pre-1998 correction: -0.076 C / decade (from their paper linked to above)
Post-1998 correction: -0.046 C / decade (from their paper linked to above)
Current version: +0.029 C / decade (from my Excel calc using their online dataset)
So, to summarize here:
(1) From their pre-1998 version to their current version, the trend changes by +0.105 C / decade using the same data. [I don’t know if there had been any prior corrections to their analysis between when they first published in the early 1990s and their analysis just prior to their 1998 corrections.]
(2) Even from their post-1998 version to their current version, the trend changes by +0.075, which is outside of the +/- 0.05 C errorbar they gave in that 1998 paper. [And, this change is just due to the systematic corrections. I presume that their errorbar was also meant to include statistical error in the trendline.]
(3) As it turns out, just because of the longer data set, the trend has also increased significantly…which, of course, is not due to the errors that they made. I.e., while their current version of the analysis gives a trend of only +0.029 C / decade over that Jan 1979 – Apr 1997 period, the trend for the period running up through Dec 2008 is +0.127 C / decade. Much of this rise in trend occurred during the 1998 El Nino … since the trend ending in Oct 1998, just 18 months additional data from what was in their paper, was already +0.109 C / decade.
(4) Their trend still remains a bit lower than that found by the RSS analysis and other analyses (I believe there are analyses from a group at UMd and U Wash.).
Alan Wilkinson says:
As you probably know, that link is to a summary by an advocacy group, not a group with any scientific standing. So, their summary is selective both in the papers they choose to include and what they choose to say about them.
Mind you, I’m not saying that the evidence on the MWP is completely settled…But the real summaries of the scientific literature (e.g., by the IPCC or the NAS) have concluded that the evidence favors an MWP that was never as warm as the late 20th century. The way the 2006 NAS report ( http://books.nap.edu/openbook.php?record_id=11676&page=4 ) states it is:
An interesting demonstration that when people think their work is “socially” relevant, there seems to be incentive to fake the data.