Documenting the Global Medieval Warm Period[W:196]

Jack Hays · Jan 3, 2017

The Medieval Warm Period (MWP) is a touchstone for the climate debate. Indeed, the deceit of Michael Mann and some others in trying to make the MWP disappear is the genesis of much skepticism about climate science. Here is a project to document the global MWP.

Documenting the Global Extent of the Medieval Warm Period

Guest essay by Angus McFarlane Introduction In this article I pose the following questions: Was the Medieval Warm Period (MWP) a global event? Where the MWP temperatures higher than recent times? The reasons for asking these questions are that climate establishment have tried to sideline the MWP as a purely local North Atlantic event. They also…

Conclusions
A review of the global extent of the MWP is presented and the following conclusions are offered:

The MWP was a global event and a large number of studies show that warming events overwhelming outnumber cold events.
However, the not insignificant number of dry or wet events recorded in the MWP Mapping Project would suggest that perhaps the Medieval Climate Anomaly would be a better description than the MWP.
NH temperatures during the MWP were at least as warm those in 1980-1989 instrumental record.
Recent instrumental temperatures show higher temperatures when compared with the MWP proxies. However, instrumental temperatures should not be compared directly with proxy temperatures because this is not an “apples for apples” comparison. Proxy temperatures are dampened (flattened) out on decadal or greater scales.
Recent proxy records diverge from instrumental temperatures – instruments show higher readings when compared with proxies.
The divergence problem in item (e) above is probably due to a linear proxy-temperature response being assumed in current temperature reconstructions. A nonlinear proxy-temperature response would achieve more accurate results for historical high and low temperatures and achieve a better correlation with recent instrumental data.

Until there is a good correlation between instrumental temperatures and proxies, no reputable scientist can definitely state that current temperatures are the highest ever.

Threegoofs · Jan 3, 2017

Jack Hays said:
The Medieval Warm Period (MWP) is a touchstone for the climate debate. Indeed, the deceit of Michael Mann and some others in trying to make the MWP disappear is the genesis of much skepticism about climate science. Here is a project to document the global MWP.

..deleted blargh..

Until there is a good correlation between instrumental temperatures and proxies, no reputable scientist can definitely state that current temperatures are the highest ever.[/FONT][/COLOR]

Oh, look.

Deniers clinging to their idea that the world was warmer once, so it cant be warmer now. Thus their obsession with making the MWP a real thing - regardless of the data.

They are so invested in this, they are starting a BLOG PROJECT! :allhail

Of course, in the scientific literature, it looks like the fabled MWP was neither global nor particularly warm.

Heres the last thing I saw on it. Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement | Science Advances

Abstract

The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP—a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region.

I think the general scientific consensus is last stated in the last IPCC report, which states:

For average annual NH temperatures, the period 1983–2012
was very likely the warmest 30-year period of the last 800 years
(high confidence) and likely the warmest 30-year period of the
last 1400 years (medium confidence).

Continental-scale surface temperature reconstructions show,
with high confidence, multi-decadal periods during the Medieval
Climate Anomaly (950 to 1250) that were in some regions as
warm as in the mid-20th century and in others as warm as in the
late 20th century. With high confidence, these regional warm periods
were not as synchronous across regions as the warming since the
mid-20th century. Based on the comparison between reconstructions
and simulations, there is high confidence that not only external orbital,
solar and volcanic forcing, but also internal variability, contributed
substantially to the spatial pattern and timing of surface temperature
changes between the Medieval Climate Anomaly and the Little Ice Age
(1450 to 1850). {5.3.5.3, 5.5.1}

Of course, the 2012-2016 data has only moved the average of the last 30 years higher, which would probably give more confidence that the NH is warmer now than in the past.

Jack Hays · Jan 3, 2017

Threegoofs said:
Oh, look.

Deniers clinging to their idea that the world was warmer once, so it cant be warmer now. Thus their obsession with making the MWP a real thing - regardless of the data.

They are so invested in this, they are starting a BLOG PROJECT! :allhail

Of course, in the scientific literature, it looks like the fabled MWP was neither global nor particularly warm.

Heres the last thing I saw on it. Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement | Science Advances

I think the general scientific consensus is last stated in the last IPCC report, which states:

Of course, the 2012-2016 data has only moved the average of the last 30 years higher, which would probably give more confidence that the NH is warmer now than in the past.

Bad science begets unfounded conclusions.

Baffin Island study disappoints: The illusive ‘coup de grace’ on the Medieval Warm Period

Guest essay by Sebastian Lüning Big news on 4. December 2015 by the Earth Institute of Columbia University. In a press release the institute claimed that climate and human history has to be re-written and climate had no major influence on Viking settlement on Greenland: Study Undercuts Idea That ‘Medieval Warm Period’ Was Global Vikings…

January 18, 2016 in MedievalWarmPeriod, Paleoclimatology.

". . . A research team led by the glaciologist Nicolás Young claimed in a new paper in Science Advances that there actually was no Medieval Warm Period (MWP) in Greenland. Instead, they propose that a cold phase occurred 1000-1250 AD in the region which even triggered glacier advance. Interestingly, Young and colleagues base their model on a study of a single local glacier on Baffin Island which they generalize for the entire region. . . ."

Threegoofs · Jan 3, 2017

Jack Hays said:
Bad science begets unfounded conclusions.

Baffin Island study disappoints: The illusive ‘coup de grace’ on the Medieval Warm Period

Guest essay by Sebastian Lüning Big news on 4. December 2015 by the Earth Institute of Columbia University. In a press release the institute claimed that climate and human history has to be re-written and climate had no major influence on Viking settlement on Greenland: Study Undercuts Idea That ‘Medieval Warm Period’ Was Global Vikings…

January 18, 2016 in MedievalWarmPeriod, Paleoclimatology.

". . . A research team led by the glaciologist Nicolás Young claimed in a new paper in Science Advances that there actually was no Medieval Warm Period (MWP) in Greenland. Instead, they propose that a cold phase occurred 1000-1250 AD in the region which even triggered glacier advance. Interestingly, Young and colleagues base their model on a study of a single local glacier on Baffin Island which they generalize for the entire region. . . ."

Yes, I'm not surprised there is a differing opinion on denier websites.

Thats pretty much what they do.

Jack Hays · Jan 3, 2017

Threegoofs said:
Yes, I'm not surprised there is a differing opinion on denier websites.

Thats pretty much what they do.

Pacific Ocean Heat Content During the Past 10,000 Years | Science
Pacific Ocean Heat Content During the Past 10,000 Years
Yair Rosenthal, Braddock K. Linsley, Delia W. Oppo
Abstract:
Observed increases in ocean heat content (OHC) and temperature are robust indicators of global warming during the past several decades. We used high-resolution proxy records from sediment cores to extend these observations in the Pacific 10,000 years beyond the instrumental record. We show that water masses linked to North Pacific and Antarctic intermediate waters were warmer by 2.1 ± 0.4°C and 1.5 ± 0.4°C, respectively, during the middle Holocene Thermal Maximum than over the past century. Both water masses were ~0.9°C warmer during the Medieval Warm period than during the Little Ice Age and ~0.65° warmer than in recent decades. Although documented changes in global surface temperatures during the Holocene and Common era are relatively small, the concomitant changes in OHC are large.

Jack Hays · Jan 3, 2017

Threegoofs said:
Yes, I'm not surprised there is a differing opinion on denier websites.

Thats pretty much what they do.

Medieval Warm Period confirmed via cave study of 3000 years of climatic variations

Remote cave study reveals 3000 years of European climate variation From the University of New South Wales: SYDNEY — University of New South Wales Australia-led research on limestone formations in a remote Scottish cave has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman…

The paper: http://www.nature.com/srep/2015/150611/srep10307/full/srep10307.html

Abstract:

Annually laminated stalagmites can be used to construct a precise chronology, and variations in laminae thickness provide an annual growth-rate record that can be used as a proxy for past climate and environmental change. Here, we present and analyse the first composite speleothem annual growth-rate record based on five stalagmites from the same cave system in northwest Scotland, where precipitation is sensitive to North Atlantic climate variability and the winter North Atlantic Oscillation (NAO). Our 3000-year record confirms persistently low growth-rates, reflective of positive NAO states, during the Medieval Climate Anomaly (MCA). Another persistently low growth period occurring at 290-550 CE coincides with the European Migration Period, and a subsequent period of sustained fast growth-rate (negative NAO) from 600-900 AD provides the climate context for the Viking Age in northern and western Europe.

Threegoofs · Jan 3, 2017

LOL.
One study defines the MWP as year 0-1000AD. https://marine.rutgers.edu/pubs/private/yair_2013.pdf

The other study defines it as 900-1400 AD. Stalagmites preserve 3,000 years of northern hemisphere climate

Thats an overlap of 100 years between them, with one starting 900 years before and the other ending 400 years later.

But I'm sure the denier blogs you cribbed the last two studies from didnt mention that.

Jack Hays · Jan 3, 2017

Threegoofs said:
LOL.
One study defines the MWP as year 0-1000AD. https://marine.rutgers.edu/pubs/private/yair_2013.pdf

The other study defines it as 900-1400 AD. Stalagmites preserve 3,000 years of northern hemisphere climate

Thats an overlap of 100 years between them, with one starting 900 years before and the other ending 400 years later.

But I'm sure the denier blogs you cribbed the last two studies from didnt mention that.

Different research, different time scales. You won't dodge this with lawyerly arguments.

Threegoofs · Jan 3, 2017

Jack Hays said:
Different research, different time scales. You won't dodge this with lawyerly arguments.

LOL.

The Black Knight loses another limb!

Jack Hays · Jan 3, 2017

Threegoofs said:
LOL.

The Black Knight loses another limb!

As you wish. The bankruptcy of your position is apparent. The OP stands thus far unchallenged.

Quaestio · Jan 6, 2017

Threegoofs said:
LOL.
One study defines the MWP as year 0-1000AD. https://marine.rutgers.edu/pubs/private/yair_2013.pdf

The other study defines it as 900-1400 AD. Stalagmites preserve 3,000 years of northern hemisphere climate

Thats an overlap of 100 years between them, with one starting 900 years before and the other ending 400 years later.

But I'm sure the denier blogs you cribbed the last two studies from didnt mention that.

The timing of the 'medieval warm period' seems to be moving target for science deniers. It's almost like there were local regions where the temps were warmer at different time periods. oh wait.

Quaestio · Jan 6, 2017

Threegoofs said:
LOL.

The Black Knight loses another limb!

'The Black Knight' lost his mind long ago it seems.

Lord of Planar · Jan 6, 2017

Quaestio said:
The timing of the 'medieval warm period' seems to be moving target for science deniers. It's almost like there were local regions where the temps were warmer at different time periods. oh wait.

You guys are the science deniers.

Different studies using different methods yield different results. People who do not deny science understand such things. We also understand that the science is never actually "settled."

There are two sensitivity studies I read in the past few years that yield different results than what is considered settled. That is because the methodology was different. That is how science works.

Quaestio · Jan 6, 2017

Lord of Planar said:
You guys are the science deniers.

Different studies using different methods yield different results. People who do not deny science understand such things. We also understand that the science is never actually "settled."

There are two sensitivity studies I read in the past few years that yield different results than what is considered settled. That is because the methodology was different. That is how science works.

I don't actually care what your unqualified poorly informed ideologically biased layperson's opinions are. They're irrelevant to science.

I'll stick with the evidence-based opinions of scientists and their published research thanks. Published in reputable Journals that is, not fly-by-night "Journals" operated by predator publishers, or 'published' on someone's blog.

Lord of Planar · Jan 6, 2017

Quaestio said:
I don't actually care what your unqualified poorly informed ideologically biased layperson's opinions are. They're irrelevant to science.

I'll stick with the evidence-based opinions of scientists and their published research thanks. Published in reputable Journals that is, not fly-by-night "Journals" operated by predator publishers, or 'published' on someone's blog.

LOL...

Yo have things 180 degrees!

You are funny. I didn't know the were taking auditions for the Forum Jester.

Threegoofs · Jan 6, 2017

Lord of Planar said:
You guys are the science deniers.

Different studies using different methods yield different results. People who do not deny science understand such things. We also understand that the science is never actually "settled."

There are two sensitivity studies I read in the past few years that yield different results than what is considered settled. That is because the methodology was different. That is how science works.

I guess you agree with JH then.

When one study defines the MWP as year 0-1000, and another defines it as 900-1400, it's pretty much the same thing, right?

Lord of Planar · Jan 6, 2017

Threegoofs said:
I guess you agree with JH then.

When one study defines the MWP as year 0-1000, and another defines it as 900-1400, it's pretty much the same thing, right?

It just proves science doesn't settle without a fight.

Deuce · Jan 7, 2017

Jack Hays said:
As you wish. The bankruptcy of your position is apparent. The OP stands thus far unchallenged.

I'm not sure what you think the OP brings to the table that is new. The existence of a warmer period about a thousand years ago, followed by cooling to the "little ice age?" Uhh, yeah, we all knew that already.

Jack Hays · Jan 7, 2017

Deuce said:
I'm not sure what you think the OP brings to the table that is new. The existence of a warmer period about a thousand years ago, followed by cooling to the "little ice age?" Uhh, yeah, we all knew that already.

Watch out. You may be called a "denier" now. The AGW advocates have been trying to erase the MWP since 2001.

[h=1]Relative Homogeneity of the Medieval Warm Period (MWP) and The Little Ice Age (LIA)[/h]Guest Opinion: Dr. Tim Ball The 2001 Intergovernmental Panel on Climate Change (IPCC) “Hockey Stick” graph produced solutions for three facts challenging the claims of key IPCC climate scientists at the Climatic Research Unit (CRU). The problems appeared in Figure 7c in the 1990 First Assessment Report (FAR) (Figure 1). The three problems it created…

March 22, 2015 in Climate News, IPCC.

Jack Hays · Jan 7, 2017

Deuce said:
I'm not sure what you think the OP brings to the table that is new. The existence of a warmer period about a thousand years ago, followed by cooling to the "little ice age?" Uhh, yeah, we all knew that already.

[h=1]When the IPCC ‘disappeared’ the Medieval Warm Period[/h]IPCC changed viewpoint on the MWP in 2001 – did this have effect on scientific results? Guest post by Frank Lansner Latest News (hidethedecline) A brief check indicates a “warm MWP-consensus” before IPCC published the Mann hockey stick graph in 2001. But after 2001, results on MWP seems to approach the IPCC viewpoint. In April 2009…

Deuce · Jan 7, 2017

Jack Hays said:
Watch out. You may be called a "denier" now. The AGW advocates have been trying to erase the MWP since 2001.

[h=1]Relative Homogeneity of the Medieval Warm Period (MWP) and The Little Ice Age (LIA)[/h]Guest Opinion: Dr. Tim Ball The 2001 Intergovernmental Panel on Climate Change (IPCC) “Hockey Stick” graph produced solutions for three facts challenging the claims of key IPCC climate scientists at the Climatic Research Unit (CRU). The problems appeared in Figure 7c in the 1990 First Assessment Report (FAR) (Figure 1). The three problems it created…

March 22, 2015 in Climate News, IPCC.

Ahh, so I take it you're not aware of the origin of the first image in that post.

Threegoofs · Jan 7, 2017

Jack Hays said:
Watch out. You may be called a "denier" now. The AGW advocates have been trying to erase the MWP since 2001.

[h=1]Relative Homogeneity of the Medieval Warm Period (MWP) and The Little Ice Age (LIA)[/h]Guest Opinion: Dr. Tim Ball The 2001 Intergovernmental Panel on Climate Change (IPCC) “Hockey Stick” graph produced solutions for three facts challenging the claims of key IPCC climate scientists at the Climatic Research Unit (CRU). The problems appeared in Figure 7c in the 1990 First Assessment Report (FAR) (Figure 1). The three problems it created…

March 22, 2015 in Climate News, IPCC.

You mean the MWP that started in year 0 and continued to year 1000, or the one that was from 900AD-1400AD?

Or is it just whatever period fits in with your preconceived notions?

Jack Hays · Jan 7, 2017

Deuce said:
Ahh, so I take it you're not aware of the origin of the first image in that post.

It's an IPCC image, IIRC, pre-2001.

Jack Hays · Jan 7, 2017

Threegoofs said:
You mean the MWP that started in year 0 and continued to year 1000, or the one that was from 900AD-1400AD?

Or is it just whatever period fits in with your preconceived notions?

Those whose basic claim has been that the MWP was only a regional phenomenon are in a weak position to protest when its timing varies region by region.

Deuce · Jan 7, 2017

Jack Hays said:
It's an IPCC image, IIRC, pre-2001.

Right, but I mean any detail about it other than that. What it was, what dataset it represents, etc.

Anyone who thinks that image needed to be "disappeared" is clearly not very familiar with its details.

Documenting the Global Medieval Warm Period[W:196]

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