In response to criticisms from Gavin Schmidt, Craig Loehle and J Huston McCulloch have published a correction to Loehle's temperature reconstruction that uses 18 non-tree ring proxies. The pdf of original paper and the correction can be found here.
The corrected Figure 2 can be seen below:
The MWP and LIA remain prominent, in contrast to 'Hockey Stick' style reconstructions. However, in terms of reconstructions involving tree rings, as Steve McIntyre points out, if Yamal instead of Polar Urals update are used, you can get Modern Warm Period higher than MWP and vice versa; similarly with Indigirka versus bristlecones; or depending on Mann PC1 bristlecones versus Ababneh bristlecones.
In short, the jury is still out on whether the MWP had a global influence or if it was warmer than the Modern Warm Period. Nevertheless, the Loehle reconstruction makes a valuable contribution to the debate and should be included in the IPCC spaghetti graph that replaced the Mann et al Hockey Stick in AR4.
To
bring the discussion into the modern era.
Solar magnetic activity peaked in about 1987. There is a statistical analysis from
Usoskin et al of the Max Planck Institute showing that the best correlation of
cosmogenic isotopes and surface temperatures is with a 10 year lag.
The usual story is that trends diverged after the mid
1980's - solar activity declines and temperatures keep rising. If the
solar activity hypothesis is correct, surface temperatures should peak
in about, oh say, 1998. Another way of looking at current influences on global surface
temperatures is with the emergence of a cool La Niña phase of the
Interdecadal Pacific Oscillation (IPO)since 1998. See http://www.bom.gov.au/climate/pi-cpp/FollandSPCZ2002GRL.pdf
for a reasonable introduction to the IPO. La Niña provide a global
surface cooling influence as a result of cool subsurface water
spreading across the central Pacific. Cool La Niña phases of the IPO
bring inceased frequency and intensity of La Niña conditions over 15 to
30 years. It seems possible that the IPO is a dramatic Pacific Ocean
manifestation of global cosmic ray/cloud effects. Regardless, a cool La
Niña phase will moderate global warming over the next couple of decades
and result in higher rainfall over much of Australia. The recent trend
in global surface temperatures is a bit inconvenient for AGW. 10 years
of no global warming? 2007 was the 8th warmest year on the CRU record -
and yes - every year in this century other than 2000 is in the top 10 - although why this is particularly significant escapes me.
Typically, La Niña reduce surface temperatures by
about 0.1 degrees centigrade. The current La Niña could put 2008 out of the top 10.
If the La Niña persists, 2009 could be well down the list. Perhaps somewhere between the top 15 and 20. We live in
interesting times.
I had said at CA: "The absence of a MWP was taken to mean that there were no possible natural factors, therefore recent warming had to be human-caused. The existence of a MWP means that this chain of reasoning is not valid."
Nathan made fun of this and then Gavin defends the making fun as if Gavin and nathan are the same person? The paleo record has been used to test the effect of solar activity. Tested against the hockey stick one concludes that the sun has little effect, but tested against Moberg (which looks a little like mine) the sun has more effect. Further, my quote above refers to the many press releases and interviews with the vocal climate scientists who use the lack of a MWP to call the recent warming unprecedented and to dismiss solar activity as having any chance of causing the recent warming.
I bet cosmic rays still spearhead the MWP hunt though
"There is absolutely no evidence for a connection between cosmic rays and atmospheric warming other than a few correlations. There is also no experimental or observational evidence that cosmic rays form clouds in the Earth's atmosphere."
Bears repeating.
Paul - "The hockey stick affair is, and continues to be a disgrace to the name of objective science, plus the antics of those involved, including data archiving reluctance, beggars belief."
The only disgrace is that fairly obscure study into the paleoclimate could be seized on by vested interests and turned into a wedge issue to prevent action on global warming. There was nothing objective to the attack on MBH99 and the eventual 'criticisms' only affected the outcome by a few percent. Also if MBH99 was such a disgrace as you term it how could it have been confirmed in such a comprehensive manner by subsequent studies?
Data archiving reluctance. What a load of crap. More like professional scientists not wanting to spoon feed an amateur and unprofessional through an analysis that he should have been able to do himself with the normal data that scientists publish. How typical of the bad carpenter that blames his hammer for his poor work.
"Both the CO2 and cosmic ray hypotheses are 'unproven.'"
Sorry the connections between greenhouse gases and atmospheric warming has been demonstrated in and out of the laboratory in many different experiments and the scientific literature is filled with papers on the subject if you would care to read them with the blinkers off.
There is absolutely no evidence for a connection between cosmic rays and atmospheric warming other than a few correlations. There is also no experimental or observational evidence that cosmic rays form clouds in the Earth's atmosphere.
So it seems like the level of contrarian science including about the MWP is that we don't know nuttin' aboout nuttin'.
Wonder why they're so noisy then.
Ender - if you recall - M&M published a critique in GRL. There were also criticisms made by the NAS panel and the Wegman report. All well documented over at climate audit. More recent developments include the PhD thesis by Ababneh, refereed by Malcolm Hughes:
http://www.climateaudit.org/?p=2504
The hockey stick affair is, and continues to be a disgrace to the name of objective science, plus the antics of those involved, including data archiving reluctance, beggars belief.
Both the CO2 and cosmic ray hypotheses are 'unproven.'
Paul - "Ender - I take exception to the hockey stick reconstruction being presented as definitive and flawless - it most definately isn't."
How would you know? No study in science is definitive and flawless. The mindless rantings of a mining engineer do not make MBH98 flawed. Follow up studies that used different techniques and different proxies confirmed and extended MBH99. Of course MBH99 was not completely correct - it was the first go at extracting something out of the different proxies. Later studies using and extending the techniques pioneered by Mann, Bradley and Hughes gave us more accurate studies that essentially confirmed MBH99 and gave us a picture of the past climate.
Anyway you have a real case of MWP and Hockey Stickitis. Is this because this is all you have or is it all you understand? Oh I forgot, you also have some totally unproven cosmic ray theory as well.