Why is there such a debate in the scientific community about the existence of the Medieval warm period?

Question

when historical records prove otherwise. http://www.archaeology.org/online/features/greenland/

If the hockey stick graph is correct, how can such a colony survive?

Trevor:

Many studies shows that the medieval warm period was warmer than today.
In typical fashion you danced around the issue without answering it.
Second paragraph "As the archaeologists dug through the permafrost and removed the windblown glacial sand that filled the rooms, they found fragments of looms and cloth." Settlements in permafrost suggest a time when Greenland was warmer than today.

"Greenland's climate began to change as well; the summers grew shorter and progressively cooler, limiting the time cattle could be kept outdoors and increasing the need for winter fodder."

No wonder they are calling global warming junk science. In the science community historical records are given preference to proxy studies. You give greater weight to the proxy study than historical records.

Bob:

They are finding settlements in what is now permafrost. This suggest that the glaciers were further north during the medieval warm period.

Tomcat, you hit the nail on the head. If the glaciers were further north, there was a greater melting of Greenland ice, and we should have seen some historical record of coastal flooding, but we do not.

Enraged Parrot. You are right it is not a proxy study. But it is an indication of which proxy studies are more accurate. The ones that say that the Medieval warm period was an event or Man's study that say it was not.

Answer 1

"There has been much discussion of late about the magnitude and geographical extent of the Medieval Warm Period and Little Ice Age. Soon et al. (2003) review a wealth of paleoclimatic data from around the world that suggest these relatively warmer and cooler epochs were of global extent and that the Medieval Warm Period was at least as warm as - and, in many places and times, even warmer than - the current Modern Warm Period.
On the other side of the debate, Mann et al. (2003) stridently claim these several-hundred-year climatic episodes were not nearly as dramatic nor as widespread as what Soon et al. (2003) suggest. Why? Because if they were, there would be nothing unusual about what climate alarmists, such as themselves, typically describe as the unprecedented global warming of the past century, which characterization makes the temperature increase of the past hundred-plus years appear so unusual they can further claim it must have been caused by something unnatural, such as the concomitant increase in anthropogenic CO2 emissions."

There is a whole section on the MWP at co2science that has many studies by many scientist. By far, more studies say the MWP was warmer.

http://www.co2science.org/scripts/CO2ScienceB2C/data/mwp/mwpp.jsp

Answer 2

There isn't any debate. Denier websites claim some scientists don't accept the MWP, which is false.

No one in the scientific community claims the MWP didn't happen, although there is some question as to whether it occurred worldwide, or was concentrated in limited locations. In any event global temperatures went up a bit,

Mann's original graph was overly smoothed (averaged) and obliterated the MWP. Bad idea. It doesn't really change the basic idea, though.

Since then studies have done with less aggressive statistical methods. They clearly show the MWP, that the present warming looks nothing like that, and that we're now warmer.

http://www.globalwarmingart.com/wiki/Image:2000_Year_Temperature_Comparison_png

The article you cite supports that:

"it was once the site of a Viking colony founded along the island's grassy southwestern coast that stretches in a fjord-indented ribbon between the glaciers and the sea"

"that stretches", present tense. The coast of Greenland has some ice free places (and they're getting larger). The colony didn't go away because it got colder. "The disappearance of the Greenlanders has intrigued students of history for centuries."

It was no doubt a hard life, then and now.

co2science cites Soon. Soon's paper was so bad that the editor of the journal published it admitted it was a mistake. When the publisher refused to print an apology, half the editorial board, including the editor, resigned. Typical use of bad science by global warming deniers.

http://cfa-www.harvard.edu/~wsoon/1000yrclimatehistory-d/Sep5-CHEarticle.txt

EDIT - "In the science community historical records are given preference to proxy studies. "

Flat wrong. Quantitative (numerical) proxy studies are considered far more reliable than qualitative (descriptive) historical studies. Science is about numbers, not descriptions. Which is why:

"There's a better scientific consensus on this [climate change] than on any issue I know... Global warming is almost a no-brainer at this point. You really can't find intelligent, QUANTITATIVE arguments to make it go away."

Dr. Jerry Mahlman, NOAA

Answer 3

Eric, Vikings in Greenland are not proxies for global temperatures. No one's ignoring historical records, this one just doesn't tell us anything about global climate. It's as simple as that. Although, despite what you seem to think, the Vikings farmed the exact same areas in greenland that are farmed today.

Also, the Hockey stick graph you have your panties in a wad over is mostly irrelevant nowdays. First, the controversy that surrounded the graph was far more complicated than you realize, in fact, if you aren't a scientist, I promise you you don't have the foggiest idea what it was about. Second, the graph is ancient history now. It was a single study done over a decade ago. There have been dozens of reconstructions done since then which all show the same thing.

Lastly, it is possible that temperatures during the medieval warm period were as warm as today's. The level of uncertainty surrounding any past climate reconstruction mean we can't exclude the possibility. However, probabilistically speaking, it's likely that today's temperatures are warmer.

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Edit: No, you misunderstood what I said. You are attempting to use Vikings in Greenland as a proxy for global climate. I was pointing out the flaw in this method.

Answer 4

There isn't a debate. The scientific evidence shows it existed, peaked approx 1000 years ago when average global temps reached 14.03°C, warmer than they had been for a long time, the same as the global temp was in 1972 but 0.4°C cooler than they are now.


The whole issue about the MWP is something that has been blown out of all proportion. The Hockey Stick graph showed a lesser MWP than more recent research has shown to be the case, similarly it showed a lesser Little Ice Age (approx 400 years ago).

When you compare the 'Hockey Stick Graph' with all the other and more modern graphs they're almost the same apart from one warmer and one cooler period. The crucial thing is that they all show current temps rising faster than ever and reaching record levels.

There are 'colonies' on Greenland now, far many more than there were in the Viking Era. Survival on Greenland is easier than it's ever been. The ice cover has shifted to expose some parts that were previously covered by ice (one or two isolated spots) but more importantly it's now shrinking at the rate of 220 cubic kilometres per year.

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Some further points. The figure of 14.03°C is a 'best estimate', it's the average of several studies, the figure could be out by as much as 0.1°C.

The MWP wasn't global warming in the way we understand it to be today, it was an event that was primarily confined to some parts of the northern hemisphere. The global temperature model provides a graph more similar to the famous 'hockey stick graph'.

In recent years the methods available for recreating historical temps have advanced greatly, existing methods have been improved and new techniques developed. 20 or 30 years ago few people bothered what the temp had been in the past so this is effectively a new science. As progress is made more accurate figures come to light and existing data is re-evaluated; inevitably some temps are revised upward and some are revised downward.

If you're interested in Greenland or history then a good book to read is The Saga Of Eric The Red. It's the biography of the infamous Viking, it explains his voyages to Greenland, establishment of a community and the hardships they faced due to a lack of fertile land and very short summers. It was Eric who gave the country it's name in a piece of Viking propaganda designed to lure Icelanders to his new settlement (he'd been exiled from Iceland for murder after having already been exiled from his native Norway for the same thing).

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RE: YOUR ADDED DETAILS

I didn't dance around the issue. If you want a direct answer then it's glaringly obvious... People survived there 1000 years ago for precisely the same reasons that the Evenks, Innu, Eskimos etc survive today. Just because a place is cold doesn't mean people can't or don't exist there.

Compared to some environments, the former habitations of Greenland's southwestern coast were positively balmy, for millennia people have survived in much colder conditions.

It's pointless eluding to the fact that people only survived in Greenland because it was warmer 1000 years ago.

The historical records you refer to do not prove anything - they're archaeological records, not climatic ones. They tell us about the people that lived in one location, not what the global climate was like. Glaciers and ice caps periodically advance and retreat, that’s normal.

If we apply non-scientific logic then the fact that remains of settlements have now emerged from the ice is proof that global temperatures are rising and are now as warm as, or warmer than, the MWP.

Answer 5

Tomcat got it right. If it doesn't fit the scare agenda, it is discredited or ignored. I thought the hockey stick was so thoroughly discredited that no one except the uninformed used it. I personally would be somewhat surprised if the Medieval warm period was as warm as today since we have been coming out of a glacial period and there has been a general warming for several thousand years. It seems to indicate a great variability in the climate even as it is generally warming. This certainly provides reason not to get too alarmed over temperature variations of a degree or two. Telling a GW alarmists that they shouldn't get alarmed is a little bit like telling my wife she shouldn't shop.

Answer 6

It is my opinion the debate is because the Medieval warm period tells a story about how a warm climate is beneficial for the human race. This downplays the gloom and doom projections by alarmists, hence negatively impacting their funding and their ego. There is no doubt that the onset of the LIA was directly responsible for the demise of the Viking colony on Greenland, contrary to what some propagandists say.

Answer 7

There's almost no debate in the scientific community.

What's happening here is that those who want to deny global warming are taking their case to the media which gives them way too much air time compared to how good their arguments are or how many of them there are making a small discredited fringe group look like a large respectable group.

Answer 8

Because the MWP shows that the Earth was warmer than it is today without cars or industry.

This negates the theory that man causes warming, as the MWP was a world wide warming period caused naturally by the Sun.

People who are invested in man made warming must dismiss any notion that the Earth warms and cools naturally, as they would be out of a job.

Answer 9

There isn't. The archeologic record really doesn't prove anything except that they were there (as they have been since, and are today). Some people want to use it as evidence to support outlandish theories about climate change, but it doesn't. As with Global Warming, the only "debate" is in their minds.