Some more climate change stuff; old records broken in some cases...

reply to post by talklikeapirat

The only reason you've posted the Svalbard study plus the quote from the press release twice in this thread alone is because you thought it would support your pseudo-scientific argument that there has been no other time in recent history when the climate has changed in ways like we have seen in the last couple decades.

No. I posted the Svalbard study to show that the MWP was not necessarily a global effect.

And there is no consistency in your argument itself, you constantly switch positions in your attempt to make the facts fit your beliefs.

I have not switched my position. I do however, read and consider evidence when it is offered.

The single study you've posted in support for your claim that any past Global Warm Periods didn't really happen at all doesn't even deserve to be called scientific research.

Straw man. I have never said that global warm periods never have happened. I brought up a very recent study which shows that the the MWP may not have been a global phenomenon.

If you're trying to argue that the number of proxies and the spatial distribution has any relevancy for the accuracy of the reconstruction, contemplate in a quiet moment why you've posted a study where only three proxies were used from a single site.

The accuracy (of the temperatures) is questioned by many of the researchers themselves. I was pointing out that 16 proxies do not demonstrate that the MWP was a global phenomenon. A single location with summer temperatures which are significantly higher now than during the MWP would tend to indicate that it was not a global phenomenon.

In addition, every other single or multi-proxy reconstruction from the same area completely refutes the overconfident claims made by authors of the study, unsurprisingly.

Are you sure? Did you read the study? For what season were those reconstructions done? D'Andrea addresses prior ice core studies from the region, including Devine,2011.

There is weak correlation (r2 = 0.15) between ice core δ18O and Svalbard mean annual air temperature during the instrumental period (Isaksson et al., 2005), and it has been proposed that Svalbard ice core δ18O is a better proxy for winter temperature (Divine et al., 2011); however, the complications outlined above remain and additional paleotemperature records are needed to evaluate temperature changes outside of the winter season.

www.geo.umass.edu...
Devine uses "indirect indicators" for summer warmth during the MWP. D'Andrea uses direct proxies for summer temperatures. Do you think that a winter reconstruction which shows "that the Medieval period was at least as warm as the end of the 1990s in Svalbard" carries more weight that a summer reconstruction which show a much lower level of warming?

You have no problem accepting data from other locations which use the same technique (you quoted at least one) but you want to reject D'Andrea because it doesn't support your position? Are you sure you want to be accusing me of confirmation bias? Which of the studies you have posted have I rejected?

We both know you don't make these claims after a careful examination of all availble evidence.

On the contrary. Much of the evidence you yourself provided makes this very point. That ocean currents had much, to do with the warming during the MWP. In any of the studies which you posted, can you provide one which says that ocean and atmospheric conditions were similar during the MWP to modern conditions?

What makes you believe we could have a reasonable discussion that wouldn't end up with me having to respond to your circular logic?

At least I could be more confident that you had actually read the material. Because so far it doesn't seem like you have. It seems more that you have selected portions which support your position.

reply to post by Phage

No. I posted the Svalbard study to show that the MWP was not necessarily a global effect.

Who are you trying to fool. You've posted a specific quote from the press release along with the study exactly because you thought it would confirm your presumption modern global warming is unprecedented in recent history. How many times have you repeated that claim now? There was no relativization in the way you've presented the study.

Again, if the Svalbard reconstruction would show what you believe it does it would be at best be an example for a regional exception. Ironically, Svalbard is exactly that, today and in the past. The authors indicate as much in the study itself but have tried hard to conceal this fact and do not mention it in the press release at all.

Generally, you're dealing with science long enough to understand how this is suppose to work. You examine all available evidence before you make a claim with any kind of certainty.

As of now, your entire line of reasoning is a classic example of circular logic while you're conflating a number of separate issues.

If you're trying to argue that past nonuniform climate changes would prove something different is going on today, your argument falls apart here. The planet has not warmed uniformly in the last couple decades, the only period where it could be assumed that a temperature rise might be attributable to increasing Co2 levels.

Straw man. I have never said that global warm periods never have happened. I brought up a very recent study which shows that the the MWP may not have been a global phenomenon.

Yes, your straw man. Your argument was not, evidence for a global MWP would need reexamination in light of the study you've posted. No 'may' included. Svalbard does not show the MWP hasn't been a global phenomenon, the authors only claimed it wasn't - hence, the reason you've inserted the quote from the press release with no mention of the inconsistencies (you're apparently not aware of, because you've never bothered to check) in the study itself. Straw man.

The accuracy (of the temperatures) is questioned by many of the researchers themselves. I was pointing out that 16 proxies do not demonstrate that the MWP was a global phenomenon. A single location with summer temperatures which are significantly higher now than during the MWP would tend to indicate that it was not a global phenomenon.

Uncertainties are pointed out. Exactly the way how scientific research should be adequately presented. In this particular case the proxy selection has nothing to do with the absence of a low-frequency signal that could be correlated to regional temperature variability. Contrary to the Svalbard reconstruction you've posted, Ljungquvist et al take a lot of care to explain precisely how and why a proxy ensemble is selected. The follow-up reconstruction i've posted were an extended proxy network is used should have made that undoubtedly clear.

Read both studies again and try to find out why you've misinterpreted the part you've quoted.

Devine uses "indirect indicators" for summer warmth during the MWP. D'Andrea uses direct proxies for summer temperatures. Do you think that a winter reconstruction which shows "that the Medieval period was at least as warm as the end of the 1990s in Svalbard" carries more weight that a summer reconstruction which show a much lower level of warming?

Completely irrelevant in context of the question. The reason why Svalbard ice core reconstructions 'carry more weight' is because of the strong agreement with every other recent high resolution reconstruction for the same area and period. Summer, winter or annual. So far i've posted four. D'Andrea et al make a number of claims that are inconsistent with the findings of these recontructions, they've put a lot of effort into their attempts to explain the discrepancy, probably in anticipation that the inconsistencies will be pointed out.

One of the 'key findings' is summarized in the press release.

In looking at how summers on Svalbard varied, researchers also discovered that the region was not particularly cold during another recent anomalous period--the “Little Ice Age” of the 18th and 19th centuries, when glaciers on Svalbard surged to their greatest extent in the last 10,000 years and glaciers in many parts of Western Europe also grew.They suggest that more snow, rather than colder temperatures, may have fed the growth of Svalbard glaciers.

Part of the corresponding paragraph in the study.

Tree ring studies from Scandinavia and northern Europe do not reveal cold summer temperatures during 18th century glaciations (Nesje et al., 2008), while proxy-based NAO studies suggest positive NAO mode dominance during the 19th and early 20th centuries (Glueck and Stockton, 2001; Luterbacher et al., 2004; Trouet et al., 2009), supporting our interpretation that winter precipitation exerted primary control on LIA glaciations on Svalbard.

Significantly colder summers during 18th and 19th century is exactly what tree ring studies from Scandinavia, Northern Europe and the Arctic-Atlantic reveal and all high resolution recontructions also show significantly warmer average temperatures during the MWP, unmatched until the early 20th century warming, except for your D'Andrea paper.

Single site, three proxies, inconsistent with all other reconstructions and a region that is strongly influenced by local expressions of the NAO and the AMO. I don't need to look for any other reason why that study is not representative for Northern Europe, let alone for the Globe.

On the contrary. Much of the evidence you yourself provided makes this very point. That ocean currents had much, to do with the warming during the MWP. In any of the studies which you posted, can you provide one which says that ocean and atmospheric conditions were similar during the MWP to modern conditions?

None of the studies i've posted is able to provide conclusive evidence with regards to past conditions of ocean/atmosphere coupled processes. They propose theories, that's it. Even for a 'smart guy' like you it would require months to gain enough knowledge about that aspect of the climate system to make statements with any kind of authority. I don't know how i can make myself any clearer. You, personally, have absolutely no clue what the causes were for changing climate conditions over the past two thousand years or the last century. All you know is the climate has changed, the rest is conjecture.

It seems more that you have selected portions which support your position.

I refer you to that quiet moment again.

www.thegwpf.org...
A new paper published in Geophysical Research Letters finds the natural North Atlantic Oscillation [NAO] controls temperatures of the Northern Hemisphere 15 to 20 years in advance, a lagged effect due to the large thermal inertia of the oceans. The authors find the NAO index can be used to predict Northern Hemisphere mean temperature multidecadal variability and the natural oceanic Atlantic Multidecadal Oscillation (AMO) 15–20 years in advance. A simple linear model based upon this theory predicted the ‘pause’ of global warming since about 2000 that IPCC models failed to predict, and projects Northern Hemisphere temperatures will “fall slightly” over the 15 years from 2012-2027.
The NAO, in turn, has been linked to solar activity.

NAO winter index:

NAO implicated as a predictor of Northern Hemisphere mean temperature multidecadal variability: Jianping Li 1,*, Cheng Sun 1, Fei-Fei Jin 2
DOI: 10.1002/2013GL057877
The twentieth century Northern Hemisphere mean surface temperature (NHT) is characterized by a multidecadal warming–cooling–warming pattern followed by a flat trend since about 2000 (recent warming hiatus). Here we demonstrate that the North Atlantic Oscillation (NAO) is implicated as a useful predictor of NHT [Northern Hemisphere Temperature] multidecadal variability. Observational analysis shows that the NAO leads both the detrended NHT [Northern Hemisphere Temperature] and oceanic Atlantic Multidecadal Oscillation (AMO) by 15–20 years. Theoretical analysis illuminates that the NAO precedes NHT multidecadal variability through its delayed effect on the AMO due to the large thermal inertia associated with slow oceanic processes. A NAO-based linear model is therefore established to predict the NHT, which gives an excellent hindcast for NHT in 1971–2011 with the recent flat trend well predicted. [Northern Hemisphere Temperature] NHT in 2012–2027 is predicted to fall slightly over the next decades, due to the recent NAO weakening that temporarily offsets the anthropogenically induced warming.

I always try to keep up with the latest findings as I come across them; and let the cards fall where they may.