Arguments
How does Ljungqvist's reconstruction compare to others?
The skeptic argument...
Ljungqvist broke the hockey stick
What the science says...
Fredrik Ljungqvist created a 2000-year temperature history of the extra-tropical portion of the Northern Hemisphere (30-90°N) based on 30 proxy records. Certain "skeptics" have argued that his reconstruction shows greater natural variability than previous reconstructions, and that it shows the peak of the Medieval Warm Period (MWP) hotter than today's surface air temperatures.
Ljungqvist Compared to other Reconstructions
However, Ljungqvist's reconstruction is not substantially different from the many other millennial northern hemisphere temperature reconstructions, as the author himself states in his paper:
“Our temperature reconstruction agrees well with the reconstructions by Moberg et al. (2005) and Mann et al. (2008) with regard to the amplitude of the variability as well as the timing of warm and cold periods, except for the period c. AD 300–800, despite significant differences in both data coverage and methodology.”
Indeed by plotting Ljungqvist's data along with Moberg et al. (2005), Mann et al. (2008), and the surface temperature record, we can confirm that the three reconstructions are very similar (Figure 1).
Figure 1: Moberg et al. 2005 NH (blue), Mann et al. 2008 EIV NH (red), and Ljungqvist 2010 NH (green). Courtesy of Robert Way and John Cook.
MWP Peak vs. Current Temperature
Contrary to "skeptic" claims that his reconstruction shows the peak of the MWP as hotter than today's temperatures, Ljungqvist says the following when combining his proxy reconstruction with recent instrumental temperature data:
“Since AD 1990, though, average temperatures in the extra-tropical Northern Hemisphere exceed those of any other warm decades the last two millennia, even the peak of the Medieval Warm Period”
Figure 2: Ljungqvist (2010) 30-90°N decadal averages (black) vs. HadCRUT land-ocean 30-90°N decadal averages (red). Courtesy of Robert Way.
What Reconstructions Tell Us
The NIPCC also claims that if the MWP was as hot as today (which it wasn't), that means that current global warming and climate change could be natural. It's true, hypothetically, the current warming could be natural, if there were a natural mechanism causing it. However, there is no such known mechanism. There is a measured energy imbalance caused by the increase in atmospheric greenhouse gases. We know that this energy must cause the planet to warm, and how much it warms depends on the climate sensitivity to the energy imbalance.
In fact, the hotter the MWP, the more sensitive the climate is to these energy imbalances. So arguing for a hot MWP is actually arguing that greenhouse gases must be causing significant global warming - the NIPCC has it exactly backwards.
Summary
Despite the different methodologies and data coverage used in Ljungqvist (2010), his reconstruction is consistent with previous peer-reviewed northern hemisphere temperature reconstructions, and like all previous peer-reviewed reconstructions, concludes that current temperatures are higher than the peak of the MWP. Claiming that the MWP was hotter than today is also counter-productive for "skeptics", because a hotter MWP means climate sensitivity is high.
Last updated on 25 February 2011 by dana1981.
Originally Mann's HS didn't even recognize the MWP and him and others attempted to downplay it in other ways. A truely skeptical science site would hold that up as a discussion point.
If you had you'd likely have seen the part about Ljungqvist conceding that current temperatures being higher than any other point in the last 2000 years.
The reason that Ljungqvist's reconstruction doesn't show the "line flying off into blue sky" late in the 20th century is that... his reconstruction doesn't include the late 20th century. It stops before 1950. Figure 2 above shows the late 20th century warming from the instrumental record added on to the end of Ljungqvist's results in red.
The scientists picked up on the mistakes (the scientists, not McIntyre and McKittrick whose criticisms where mostly either trivial, or wrong), and have produce better recent reconstruction, such as Mann 2008 shown above. Clearly the denier talking point that RyanStarr wants to ressurect doesn't fit well with that graph, so he goes on about it because talking points is all he has.
2) The original MBH 98 graph did not even cover the medieval warm period. Their follow on MBH 99 did, and shows medieval temperatures approximately equal to those shown by Lungqvist. It then followed a more or less straight line, with decadal but not multidecadal variation to approximately the temperaure shown by Lungqvist in 1850. Consequently it was not the MWP that was supressed by the limitations in MBH's first time efforts, it was the Little Ice Age. That, of course does not fit the denier narrative, so RyanStarr ignores it and goes on about the MWP.
3) As noted above, and by Lungqvist in his paper, Mann et al 2008 shows a very similar curve to Lungqvist. Indeed, Mann 2008 shows a slightly warmer MWP (0.32 vs 0.29 11th century mean) and a very slightly colder LIA (-0.18 vs -0.17 in the 17th century), thus showing greater variability than Lungqvist, and two years before him. Therefore if Lungqvist "slaughters" MBH 99 (the hockeystick), he arrives late on the scene and only manages to slay a corpse. The real action came two years before, when Mann "slaughtered" MBH 99. Again, that doesn't fit the denier narrative, so only Lungqvist gets credit in the denier rant.
This of course beautifully illustrates my first point. Scientists, because they pursue truth, move on. Deniers because they are only using talking points to sow confusion, cling to those talking points regardless, leaving them not only wrong, but ten years out of date to boot.
Cue more empty denier talking points from RyannStarr ...
The Hadcrut overlay is... not right. The abstract of the paper itself only suggests the late 20th century is likely the warmist. How does the author here then manage to show recent years as being > 0.5 C above the highest Ljungqvist peak. I've googled and found other overlays too, they don't even come close to this result.
Decadal mean temperatures seem to have reached or exceeded the 1961-1990 mean temperature level during substantial parts of the Roman Warm Period and the Medieval Warm Period. The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia, although this is only seen in the instrumental temperature data and not in the multi-proxy reconstruction itself.
[dana1981] The figure in the post is correct. Ljungqvist terminates the data in his paper at 2000, so that's probably where the overlays you found on Google terminate as well. However, NH land temps did not stop warming in 2000. Our figure is up-to-date and uses the correct data, as other commenters have noted.
Well, without you citing these other overlays we can't really determine what they did differently.
One possible explanation might be that they could have used global temperature anomalies rather than just the 30 to 90 degree range of the Northern hemisphere like Ljungqvist and the HadCrut data in figure 2.
Or they could have stopped the data in the 1980s. Or mixed up the baseline values the anomalies were computed from. Et cetera.
None of which changes the fact that even Ljungqvist concedes current temperatures are higher than the MWP. Further, his results are largely within the error bounds of the original 'hockey stick' and thus confirm rather than 'slaughter' it's findings.
Something has to be in error here. OK Ljungqvist is a reconstruction so we expect the accuracy of that to fall well below an instrument record, are we saying Ljungqvist's late 20th century result is in error by up to 0.7 C?
[dana1981] The error is that your "10 years" is more like 30 years. Each yellow dot represents a new decadal average. Some of the red data is included in Ljungqvist's study, but he omitted the final data point.
Evidence of proxies failing now in the face of warming?
There was also a 0.2C jump from 1990-2000 (the last year of shared record) to 2000-2010 in HadCrut NH. The fact that the extratropical data will have larger anamolies than the NH data contributes even more to the discrepancy.
In any case, the current measured decadal NH anomalies (>0.5C) are clearly well above any reconstructed values. And the extratropical values will differ even more. I don't see what RyanStarr is complaining about.
The error in Lungvist's reconstruction in the final decade, as is easily determined from the NOAA data, is only 0.332 degrees. It should be noted that the upper limit of the 90% confidence interval peaks at 0.377 in the middle ages (950-959). That is 0.011 degrees less than the instrumental record for the 1990s, and over 0.4 degrees less than the instrumental record for the 2000s. Even allowing an allowing an error in the 950s as large as that in the 1990s, the temperature anomaly (reconstructed plus 1990s error) is still only 0.528 degrees, still around 0.3 degrees below the level of the 2000s. The probability that any decade in the last 2010 years has been hotter than the 2000s is very remote.
I do not know where to find the Hadcrut 90 to 30 degree index, but out of curiosity I compared the 1990-1999 average with the 2000-2009 average. The difference is 0.243 degrees. As that includes the tropics, which are noted for much lower increase in temperature, the 0.35 degree increase for the extratropics is very plausible. If you doubt it, the onus is on you to look up the extratropical data and make a comparison.
Of course we expect some disagreement here, proxy vs instrument, but lets put this difference into some perspective.
In the space of 2000 years the Ljungqvist reconstruction hits a low of -0.7 and a high of 0.2, suggesting a range of 0.9 for that period. That is to say, taking this as an arbitrary (though recent) climate window suggests min/max extents 0.9 degrees apart.
Allow via subtraction 0.2 degrees for the 10 years and the difference is still 58 % of the 2000 year min-max range.
HadCrut plots
http://www.skepticalscience.com/news.php?p=4&t=168&&n=394
a) The range of temperatures between the highest reconstructed temperature (0.196 for 950-959) and the lowest reconstructed temperature (-0.692 for 1690-1699) is 0.888 degrees C;
b) The difference between the instrumental value for the decade 1990-1999 (0.388 degrees C) and the reconstructed temperature for the same decade (0.056) is 0.332 degrees C; and
c) The increase in the instrumental temperature record over the last three decades has been very large compared to the range of temperatures shown in the reconstruction, with a total increase over the three decades of 0.883 degrees over the three decades, or 99.4% of the reconstructed range of temperatures over the preceding two thousand years, and an increase of 0.4 degrees C in the last decade, or 45% of the range of temperatures over the last two thousand years.
The first thing I thought of when you started comparing the appropriate figures above is that it highlights how extraordinary has been the increase in temperatures over the last three decades. What is more, this increase comes from a high base with final reconstructed decade only exceeded by eight other reconstructed temperatures out of 200, or just 4%. This absolutely underlines how implausible are claims that recent temperature increases are due primarily to natural variability, both because of the extreme temperature rise in so short a time, and because the temperature has risen in just three decades to exceed the previous highest value by approximately two thirds of the range of variability over the last two thousand years, with no indication that the temperatures will not continue rising.
Now, knowing you, I'm sure that is not your point. It escapes me how you can avoid noticing the implications of those facts, however. Thank you for bringing it to my notice.
Knowing you, I believe that you are attempting to cast doubt on either the reconstructed temperatures or the instrumental temperatures (or both) based on the discrepancy. I do not know which, so you will have to elucidate. However, in doing so, please confine yourself to the relevant facts. Specifically, it is irrelevant how high the instrumental value for 2000-2009 is above the reconstructed value for 1990-1999. There can be no discrepancy between the two because they do not cover the same period.
The discrepancy between the 1990-1999 reconstructed and instrumental values, on the other hand, is relevant. It amounts (as noted) to a difference 0.332 degrees, or 37.4% of the total range of the reconstructed value.
( -Accusations of deception, fraud, dishonesty or corruption snipped- ).
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Given that, unless you have substantial reasons to think Dana has misrepresented the instrumental data (and the way you have futilely flayed around seeking anything to latch a criticism on strongly suggest you do not), then your suggestions of dishonest manipulation ("a manual adjustment") are out of order. Rather than playing true to the denier stereotype, how about allowing the data to actually influence your opinion for a change?
Indeed he does say that when you combine the instrument readings with his proxy reconstruction then the temperatures are higher than in the Medieval warming period. Since there were no instrument readings in the MWP this is comparing apples to oranges n'est pas.
Looking at his graph I notice there is a hockey stick around 1700.