Global Climate Change : Reflection#3: Was Medieval Warming Global? (2004)

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Reflection#3: Was Medieval Warming Global? (2004)

topic started 1/10/04; 11:07:08 AM
last post 5/6/05; 12:56:06 PM

Dr. Hays Cummins - Reflection#3: Was Medieval Warming Global? (2004)

1/10/04; 11:07:08 AM (reads: 43000, responses: 42)

Was Medieval Warming Global?

You know the drill!

Reflection Essay Format: -Title
-What was "Done" (methods. true source of data)
-What was learned (results)
-What it means (what did I get out of it.)
-How did/will this article change my thinking.

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pudgemobile@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

1/31/04; 11:07:03 AM (reads: 44390, responses: 0)

Wallace S. Broecker uses reason and references to convince us that the medieval warming period was a global event and not limited to Northern Europe.

As his first arguement, Broeckner suggests that the modern day rise in temperature that started in 1860 can not be attributed completely to greenhouse gasses because the industrial revolution did not get into full swing by then, and there could not be a large enough increase in CO2 etc. to warrent the inc. in temp. Broeckner does not give data or references to back his inference.

Broekner then states other researchers have found that dating rusty vs. clean particles found in ice indicate an oscillation of warm to cold climate every 1500 years. Broeckner says 1860 is the end the cold era, but writes the little ice age only lasted 510 years (1350-1860) and the warming period before the little ice age only 400 (800-1200). Is it me, or does this not add up?

Broeckner states that there are only two data types capable of providing reliable historical temperature data: reconstruction of temps from historic snowlines and borehole thermometery. He first references that the retreat of glaciers around the world from their maximum extent began in 1860. Because of this, Broekner summerizes there must have been a Little Ice Age ending in 1860.

A study of Holocene glaciel retreats referenced by Broeckner finds warm perionds detected by radiocarbon dating of exposed larchwood stumps at 1500 and 2400ybp. A second similar study of wood and peat fragments indicate warm periods around 8600, 6600, and 4300ybp. Broeckner himself says the dates don't lineup with his position, but are encouraging.

Mr. Broeckner then attempts to use borehole thermometry references to strenghthen the medeival warming theory. His convolutions about comparisons among time, temperature, and, ice thickness do nothing but make it difficult to understand his correlations. Perhaps a graph or table would make this easier to understand.

He again references a study, Huang et al. whose borehole temp. data does not jive with the timing of his theory. Also, how do you dig down 200 years and not have temperatures be affected by seasons?

His evidence from the U.S. is just as poor. Broekner infers that because lake Tenya in the high Sierras had a lower pool level over 600 years ago that it must have been warm. All this means is that it was dry! If this were the case wouldn't the warm temps of today make it dry there now as well?

Finally, Broekner writes about how the transfer of water vapor from the Atlantic to the Pacific is enough to change the salinity of water in the North Atlantic. This supports the increase of circulation from north to south on a episodic basis of 1500 years, changing the climate of both hemispheres. Broeckner has no evidence of this behavoir of water but says he believes this to be the case. No studies have ever been done to indicate this.

In my opinion, this article uses conjecture and hope as much as scientific data in an attempt to get people to agree with his theory. Perhaps, more explicit data would have been helpfull in convincing me he is correct. Cetainly, this article was not peer reviewed. Mr. Broekner may be correct in stating the medeival warming period was global, but this article comes far from swaying me into believing it is true.

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hamannmm@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/04; 2:15:29 PM (reads: 44293, responses: 1)

What was done?

Wallace S. Broecker makes the argument that the post-1860 warming was part of other warmings that have been at 1,500-year intervals during the Holocene. He sounds almost bitter in his angst that many people have cited that the 20th century warming was unique during the last millennium. Therefore, Broecker attempts to cite 22 people to prove that the Medieval Warm Period was a global event rather than a local event.

-Methods:

Because of their accuracy to .5 degrees C over multiple centuries, Broecker uses the reconstruction of temperatures from the elevation of mountain snowlines and borehole thermometry. The snowline evidence he uses is from the Swiss Alps while the borehole records come from polar ice and wells from all continents. He also explores the duration of 2 lengthy droughts that happened is the western United States at the same time.

-True Sources of Data:

First off- He cites his own work 4 times in the article; that's nearly 20% of the citations. That worries me that he builds his "suspecions" on his own published work.

Broecker uses the data from other scientists around the globe to make the argument that this is a global problem. Please see methods (above) for the global position of this data points.

What were the results?

"I consider this evidence sufficiently convincing to merit an intensification of studies aimed at elucidating Holocene climate fluctuations, upon which the warming due to greenhouse gases is superimposed." - This statement, I believe, is the only real result from this article.

Broecker cites many of the findings of other global studies on the Holocene and Medieval Warming Period. All in all, the only representation of data that he has was on page 2. The annotation that went along with this graph stated that the correlation was "encouraging" but offered no numerical comparison between the data of Alpine warm phases and the Bond's North Atlantic ice-rafting record.

What was learned?

Based on thermometry, snowline, and drought records, Broecker "suspects" that the Medieval Warm Period was global in nature and a part of the natural oscillations that occur every 1,500 years.

What did I get out of this article?

I was unaware that there has been a distinct pattern of oscillations in weather patterns from the past 100,000 years and that they are on a periodic cycle of 1,500 years. The use of historical aqueduct documents was rather compelling to me; it sounded like an anthropology experiment that was undertaken by a paleontologist- a rather interdisciplinary endeavor.

How did/will this article change my thinking?

I think that I might have given this author more of a chance if he would have explained things better and worded himself differently. Wallace uses a rhetoric that is both vague and one that makes his argument weaker. Words/phrases such as suspect, simple considerations, an encouraging correlation, and admittedly do not help his cause used in the context of this article.

Point blank, Broecker has an interesting point that might catch my attention more if he rephrased his writings and organized the data in an easy-to-read, concise manner.

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nagyrc@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/04; 7:13:20 PM (reads: 44378, responses: 1)

Broecker attempted to use reconstructions of global temperatures over the last 100,000 years to suggest that there are periodic fluctuations about every 1500 years. Further, he was trying to support the claim that the Medieval Warm Period was a global affair. He used a variety of data in his research, but stated that "only two proxies can yield temperatures that are accurate to .5 degrees C: the reconstruction of temperatures from the elevation of mountain snowlines and borehole thermometry".

Most of his results were inconclusive. He kept saying that they suggested support for his argument, nothing that he found could prove that it was indeed a global phenomenon. Specifically, he stated, "Evidence for the Medieval Warm Period from other parts of the world exist but is spotty and/or circumstantial".

From this article alone, I was not convinced that the Medieval Warm Period was global, or that because of this global warming might be part of the normal 1500 year temperature fluctuations. I feel that his findings did not adequately support his side of the "story" that he was trying to convey. I was impressed however that he attempted to use data from a very long-term scale to support his ideas. He obviously realized the importance of looking over a long period to see the greater picture. I was surprised that he denounced the use of ring counting as a practice for precise data over long time periods and then used a study that included it to support his hypothesis.

I feel that it is important when reading an article to make sure that you analyze what they present to you. Because he admitted that most of his data only suggested support of his theory, I feel that this was not a very convincing article. Perhaps more graphs would have been helpful to better understand his findings.

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Brad Shumaker - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/3/04; 1:41:42 AM (reads: 44297, responses: 0)

Reflection#3: Was Medieval Warming Global?

This article written by Broecker explains the conclusions derived from several tests that were conducted by other people that try and prove there was a Global Warming episode following the little ice age. Several tests that were conducted include the study of glacial retreat, the study of snow cap elevation all over the world, Borehole Thermometry, and radiocarbon dating of various substances. No actual data sets were presented, and much like the articles we have previously read Broecker simply researches research and then puts together an article based on the collaboration of others material.

The tests discussed in the article, when looked at individually, have large margins of error and seem to be generally inconclusive, but when one looks at and analyzes several different tests that come out with the same conclusion the magin of error becomes less and less of a factor with every addition test. Throughout all the discussed conclusions there seems to be a constant trend that there was a period of global warming following the little ice age. All the tests that were conducted were done so throughout the globe and all came up with relatively similar conclusions. The evidence discussed in this article suggest that the warming that took place was not regional and was infact a global climate warming.

In my opinion the evidence sounds rather convincing, but I would like to get a hold of the data sets and graph and interpret the graphs and come to my own conclusions. After reading this article I moderately convinced that there was a global warming. The evidence was however not totally conclusive, and though all the tests met a common trend there was a lot of margin for error. The question is still up in the air.

This article met my expectation for articles that are trying to prove something that is extremely difficult to prove 100%. The evidence was seemingly strong yet overwhelming inconclusive. I personally wasn't aware there were so many ways to measure global climate change. The snow cap elevation test was interesting, and leads me to believe that there is a way to test almost anything.

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miller43@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/3/04; 10:24:13 AM (reads: 44242, responses: 0)

Was the Medieval Warm Period Global?

Broecker seems largely convinced by Bonds arguement that over the last 100,000 years, there have been a series of oscillations in natural warmings approximately every 1500 years that can be inferred from data of iron-stained to clean grains in ice-rafted debris in North Atlantic sediments. In trying to determine whether or not temperature fluctuations as of recent are natural occurences or not, Broecker used data collected from boreholes and mountain snowlines to predict what temperatures were like more than a century or two ago being accurate to approximately plus or minus .5 degrees Celcius. Other methods were mentioned, but it was noted that they could not provide data from the period of interest to the degree of precision that the author was interested in. Also, the well-documented findings that glacial retreat is occuring everywhere with some exceptions in Antarctica provides evidence that warming is occurring on a global scale.

As of recent, studies of glacial retreating within the Swiss Alps, along with radiocarbon dating of organic material from these retreating glaciers, find that there appeared to be warming trends around both 2400 and 1500 years ago. These findings, although not exactly in tune with the Bonds North Atlantic ice-rafting record, are similar to a degree that they encourage one another. Boreholes from Greenland appear to show temperature fluctuations during periods from around the Medieval Warming Period to the Little Ice Age of approximately 2 degrees Celcius, and are also consistent with the temperature fluctuation findings from the Swiss Alps. Moisture records of lodgepole pine trees in the Western United States reflect that roughly 1000 years ago, areas of the west received many decades of drought as noted by carbondating and ring counting of the long-standing lodgepole pine trees.Broecker also feels that the buildup of salt within the Atlantic builds up to a point until conveyor circulation begins and reduces the salt content thus contributing as a source to the warming fluctuations.

Although the range of studies and the degrees to which data from them is inferred is quite large, by and large, there is an extensive amount of speculation taking place. In stating this, I must also point out that although there is much speculation, the general answer sought is not exact, it is broad; simply whether or not a cycle of warming trends have and will continue to occur. No conclusive evidence was suggested, although consideration for a number of new studies helped broaden the extent to which researchers can rely on in the future to study warming trends.

I was interested in seeing that there are so many variable methods and material from which information pertaining to past temperatures can be deduced. Also, I have trouble seeing the relevance to which some of these seemingly small temperature fluctuations have on prior global conditions, partly due to the fact that globally, the impact of such a change cannot be quantified, and if it can be, then reflect that in the article to give weight to the findings.

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caritymr@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 9:08:49 AM (reads: 44270, responses: 0)

What was done? (methods, true source of data):

The author of the article is attempting to illustrate how the Medieval Warm period was on the global scale rather than just the regional scale. Only two methods of gathering data have enough accuracy and dependability, the author states. Those two methods are borehole thermometry (what I assume is coring) and reconstructing temperature from mountain snowlines. Apparently studying tree rings gives an accurate depiction of climate, but not a good enough picture of the larger temperature trends. Corals also are not good enough to obtain past temperature readings from because not many of them go back a thousand years. Moreover, plant and animal sediments from a bog or swamp-like area will not work either because their temperatures are not accurate to give or take 1.3 degrees Celsius.

Using mountain snowlines to support his claim the author suggests that at the "Last Glacial Maximum" mountain snowlines were about 900 meters lower (down the mountain) than they are today. This suggests that warming temperatures have had some impact on moving that snowline up in altitude. According to today's temperature change rates this would require a 5 degree Celsius change in temperature to move the snowline 900 meters. The author then goes on to say that the snowline dropped 300 more meters during the "Younger Dryas (typo?)". This cold spell lasted for 1200 years. After the Little Ice Age, Swiss glacier retreat has resulted in a 90 meter rise in the snowline. If air temperature could account for all of this rise, the temperatures would have to have warmed between .5 and .6 degrees (C). Other evidence, though, suggests precipitation may be effecting this data. This post-1860 glacial retreat is not confined to Switzerland. The snowline rise has been documented everywhere (except Antarctica). Moraines and glacial deposits suggest where the glacial advances have stopped and started to retreat. Using these methodologies, though, has proved difficult.

Another method the author cites is radiocarbon dating of larchwood. It seems a little odd to me that he just cited the works of many researchers then moved on without really drawing any significant conclusions. Specifically with the Larchwood dating, it seems as if he just wrote about the study and how it was done, then presented a graph and moved on, not really making any conversation about the findings.

Borehole thermomtery (not coring, like I thought prior to this article) is a method by which a researcher measures the geothermal heat produced by the Earth. In short, the evidence from boreholes supports the findings from the Alps. I wonder if the medium through which the hole was cut would effect temperatures. It seems to me that would have an impact somehow. The author did not really mention anything about that.

Data from the U.S. comes from a lodgepole pine study showing how growth results in the trees given certain circumstances. Gee, that's funny. I thought at the beginning of the article the author said that tree ring growth wasn't a good indication for long term studies?!

In his final section he mentions that they still need data from the Southern hemisphere and continued data from Northern hemisphere glacial retreat. Yet, somehow he draws the conclusion that the Medieval Warm was in fact global. ....interesting...

What was learned? (results):

The author suggests that the Medieval Warming was in fact global in scope, rather than regional. Although, he also mentions that the studies are not concluded yet and there is still more data to obtain.

What it means (what did I get out of it?):

For some reason with this article I really thought about the sources and amount of references you make in your study. This guy's argument sort of seems flimsy to me. I just don't feel right about how he presented his information. There was one graph in the reading and it was sort of a stand-alone. When he did cite references he more or less just talked about the methods of their work and not the implications. I feel like this research was pretty superficial.

How did/will this article change my thinking?:

I feel like I will be more inclined to look at reputable facts and figures and be leary of early conclusions based on seemingly superficial facts.

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maikutdl@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 1:24:57 PM (reads: 44301, responses: 0)

What was done?
Wallace S. Broecker states that the post-1860 natural warming is the most recent of many warmings that are occurring in a 1500-year interval. He then say he will try to make a case that the Medieval Wam Period was not regional, but global. Assuming that the temperature fluctuations were probably less the 1C, the reconstruction of temperatures from the elevation of mountain snowlines and borehole thermometry wer ete ony two proxies that could yield accurate to .5C.

What was learned?/What does it mean?
After gathering many observations/sources from other people's data, we are unable to determine whether the Medieval Warm Period was global or not. There has been some information that may suggest a certain percentage of certainty that it may have been global, but there is not enough data to form a 100% certiainty. As Broecker points out that as the mountain glaciers continue to retreat, more information will be revealed. This may be when we find out the hard evidence and begin to create theories.

How did/will this article change my thinking?
I don't believe this article has had much of an affect on me. I have become aware of this situation that seems to be occurring but I don't believe I can really base anything off of it other that assumptions due to the lack of data/evidence presented. Just as Broecker did in this article, I can base my own assumptions/hypotheses off of the data that we do have but this is not a theory. We are not certian that this information if telling the whole truth and we may not know for a very long time (way past my time).

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smithdb1@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 9:40:36 PM (reads: 44360, responses: 0)

The author of this article, Wallace S. Broeker, claims that global temperatures have fluctuated within the last 10,000 years between warming and cooling. He states that between 900 and 1,200 years ago, that global temperatures were warmer than they were during the Little Ice Age, which supposedly occured from around 1350 to 1860. Now he believes we are now in a natural warming period of the Earth's global climate cycle. His evidence however, does not seem very detailed or conclusive. Most of the sources for his figures are his own and many figures are taken from one region of the world, not the planet as a whole.

It is undeterminable whether global fluctuations in temperatures have occured within 1500 year periods based on the evidence put forth by Broeker. For example, Broeker only shows climate conditions in few select regions of the planet. He states that the glaciers in the Swiss Alps were retreating around 1,000 years ago, but he does not really show any other examples of similar occurences taking place elsewhere on the planet around the same time. Also, the margin of years that the warming could have occured is very large. Broeker does not show enough evidence to show that a warming period occured within a certain time frame.

I think with more evidence, that Broeker's theory might have some validity, but right now, more evidence needs to be found to support global fluctuations in temperatue within the last 1000 years. It just might be plausible however, that global climate conditions do operate on cycles. For instance, Broeker talks about the salinity of oceans and how it fluctuates and mixes, depending on the melting or freezing of polar ice. Perhaps there are certain planetary cycles and changes in the path of the planet through space relative to the sun, that might affect fluctuations in global climate periodically. More evidence should be collected to determine if frequent fluctuatinos in global temperatures do take place and to what scale.

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carveykn@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 10:01:33 PM (reads: 44405, responses: 0)

Broecker states his hypothesis of the medievil warming was in fact a global event rather than in only certain areas. He does so by studying glacial melting, retreating/building, borehole thermometry, mountain snow amounts, and other various factors and methods that can complie information about the past temperature averages.

Results? Unfortunately, his data and his argument were weak. Broecker uses methods such as borehole thermometry to support his ideas, but I had trouble finding connections nor did I find the argument strong enough to believe it. The conclusion was not definate; while it still remains a possibility of that global warming during that time, this article certainly does not make that solid truth. However, he did use several interesting approaches to make his argument, and I give him props for effort.

What I gained from this article was another "twisted" opinion, much like what we talked about in class. One of many who take data and attempt to find a different response than what was provided into the system; ie, stretching or skewing data so that it appears different than it actually is. While I am not surprized, this is definately one of the more obvious articles I have seen.

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murphyj4@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 10:11:15 PM (reads: 44216, responses: 2)

What was done? (methods, true source of data)

The author of this article bring in numbers sources in an attempt to prove that the the period of medieval warming that those alive europe and the surrounding areas was experienced on a global scale. This warm up followed the little ice age which ended the viking stay on Greenland. He sites numerous sources, including himself several times. he concentrates on two methods to gather data, which he states that to be the only reliable methods, those were glacial records and bore-hole thermometry. He describes 1500 year fluctuations in temp, it was on one of these fluctuations that this warm up occurred.

What was learned?/What does it mean? Even after siting numerous sources and data points, the author of this article is still unable to confirm one way or another if the period of medieval warming was global in effect. He us uses several studies in his argument that are on going, so he is presenting an argument on incomplete data.

How did/will this article change my thinking? I did not feel that Broecker made a very convincing argument, partly do to the lack of evidence and the need to collect more data and include more through graphs of his arguments. I for one had trouble interpreting his arguments and some of the terminology he used. Such as his mentioning of iron-stained grains and how they were used to in the graph.

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greenerr@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/4/04; 10:32:47 PM (reads: 44221, responses: 0)

What was done:
The author recreated temperatures by looking at different types of models from glacier cycles to data from bore-hole thermometry. It is the attempt to understand why there was a small ice age and then a sudden warm up during the year 1500. It is interesting to note that this period they are looking at is known as the dark ages, a period known for gloom and cold weather. One such theory that Broecker does not look at is one that I find likely and also find more convincing. There is a theory that a massive eruption from the volcano, Krakatoa. It is believed to hold an important key in causing a global cooling during such a small time period.

What was learned:
Though none of the theories has predominately taken over as the cause for this little ice age, it would seem that the ice core's should hold a more concrete answer or at least present a partial explaination to this mystery. There is strong evidence that Krakatoa did play a major part from the evidence gather from historical accounts from China to the actual layers around the surrounding area. I agree with some of the other responses that Broecker presents a weak case, but it would seem that he is proposing a question than actually stating hard facts. At this point it will be hard to determine the truth.

What I got from it:
As one who focuses on the Krakatoa theory, he was unable to present anything that would make me think other wise. I suppose it did allow new insight into the other arguements and theories as to what might have happened.

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dormancs@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/5/04; 12:22:40 AM (reads: 44272, responses: 0)

What was Done?

Brockner looked at evidence of temperature to show that there are 1500 year cycles of global warming and cooling. By looking at glacier levels, boreholes, and moisture levels he argued that specifically the most recent Little Ice Age and following warming were experienced not just in Europe, but globally. While he makes a somewhat convincing arguement, it is also clear that there is not very much reliable data on this topic. He states that there are very few accurate records that extend back past 1000 years ago.

What was learned?

Brockner makes the arguement that the most recent cooling and heating of the earth that was documented in Europe was also experienced around the rest of the world. However, the evidence presented is inconclusive as Brockner admits that the amount of data on the topic is incomplete.

What it means?

I was not previously aware of any patterns in the heating and cooling of the earth. Given the lack of evidence, I am still not convinced of this conclusion.

How did this article change my thinking?

This article really did not change my thinking at all. The hypothesis taht Brockner presented is only supported by what seems to be a small amount of weak data. It seemed that he was really stretching the availible data to prove his point, and I did not always completely understand his points. Until I see further results showing that Brockners hypothesis may be valid, this article will not change my thinking.

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Gattje@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/5/04; 1:04:55 PM (reads: 44198, responses: 0)

Wallace S. Broecker compiled data to prove the idea that the Midieval warming period was a global event and did not just occur in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place>Northern Europe</st1:place>. He refutes many arguments that it was a local event, and he uses data from other scientists to make his arguement that it is a global problem.

Broecker looks at the differences in snowlines in the Swiss Alps and borehole thermometry from ice wells from all the continents. He also compared drought periods in the <st1:country-region><st1:place>United States</st1:place></st1:country-region> that occurred at the same time as the warming period. Though he did have a lot of data it was very inconclusive though it did add to his idea of a global warming period after the little ice age.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

<o:p> </o:p>

From this article I learned that based on the data presented, it is suspected that the midievil warm period was a global occurance. Also the warming trend could be attributed to natural oscillations that occur every 1,500 years. This means that the warming we are experiencing could be a natural occurance and not due to greenhouse gasses.<o:p></o:p>

<o:p> </o:p>

I found it very interesting that these types of warming cycles happen every 1,500 years. I would love to look into it more and maybe study the causes. We could be going through a warm period right now, and people are fearing global warming for nothing because if nature follows its course, we will cool and return to cooler temperatures eventually.<o:p></o:p>

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panzake@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/5/04; 2:59:39 PM (reads: 44288, responses: 0)

Broeker attempts to prove in his paper that the medieval warming period was a global event. He used information taken from many areas, but the two most important were mountain snow lines and borehole thermometry. These were believed to be the most convincing and accurate sets of data.

I don't believe anything was really learned from his work. This is one of several articles we have read so far on this issue and I feel more substantial evidence was seen in the other papers. His information was jumbled and not to the point. The style that he wrote it in makes him come off as less knowledgable.

What I gained from this article is a sense of how to write these kinds of papers. If you want people to listen to you, you need to be more to the point and precise with your writing.

This article has not changed my thinking at all. I think that Broeker needs a little more clear cut evidence for his point to be believed.

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Headenln@m... - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/5/04; 3:21:11 PM (reads: 44284, responses: 0)

The author cites 21 other people to try and proof that there was a global medieval warming period and that it is part of a 1500-2000 year cycle which included the little ice age. He divided his article into four topics: The Mountain Glaciation Record, Borehole Thermometry, Far Field Evidence and The Case for a Global Event. In the first three topics he presented evidence of localized temperature changes. Then he uses the third section to tie them together and show that the temperature change was global.

I learned that the medieval warming period seems to be global based on a variety of data. There is not enough data currently to determine for sure that it was global but the data seems to be pointing in that direction. As the retreating glaciers reveal more information we may be able to get a clearer picture of how wide spread the medieval warming period was.

This article shows that reconstruction temperature data is really difficult. There are many things which could affect the projected temperature reading found from the various methods. Overall I feel like the data presented was rather convincing and although I knew of this warming trend before I didn‚t have the facts that I got from this article.

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Doug - Re: Natural Temperature Cycles are Not Enough

2/2/05; 2:25:26 PM (reads: 43433, responses: 0)

Amy

Wallace Broecker states that the reconstruction of global temperatures can provide many clues on how the climate may change in future years. Temperatures have been fluctuating at roughly 1500 year intervals throughout the Holocene. Broecker feels the warming that is currently occurring is part of that fluctuation. Also, it is commonly believed that the warming that occurred during the Medieval Period was regional rather than global. Broecker thinks otherwise, and uses data collected by others in an attempt to show that this warming was in fact global.

Only two proxies (the elevation of mountain snowlines and borehole thermometry) were able to be used to yield temperatures that are accurate to .5 degrees C. The elevation of mountain snowlines was used to suggest that the retreat in glaciers represent a rise in snowline, thus suggesting a warming period. The amount of warming that would need to occur for this glacial retreat is between .6 and .7 degrees C. Broecker explains that the glacial retreat occurred everywhere on Earth except Antarctica and at approximately the same time. Boreholes in Greenland show temperature fluctuations, and if one interprets this data broadly then matches can be made to temperature fluctuations that occurred in other parts of the world. Broecker states that "other evidence for the Medieval Warm Period from other parts of the world exists but is spotty and/or circumstantial."

Before I read this article I was unaware that warmings similar to the one we are now experiencing have been occurring at 1500-year intervals throughout the Holocene. However, I was not convinced that the Medieval warm period was global. While the author did gather a variety of data, I do not think that the data presented was conclusive or that there was enough data gathered from around the world to convince me that warming during the Medieval period was global.

This article presented another opinion or reason for the increase in temperature that is currently occurring. I was unaware of this warming cycle that has presented itself for many years. While I do not think that the current warming can only be explained by the cycle as the author suggests, the natural cycle combined with greenhouse gas emissions is a very convincing reason why the global climate is changing.

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Zach Moning - Re: More Than Just Emission

2/2/05; 2:26:27 PM (reads: 43326, responses: 1)

What was Done

In response to a study by Bond et al., who published an article arguing that the Medieval Warming event was regional rather than global, Wallace Broecker analyzed data from such sources as glacial history, borehole thermometry, and the study of tree rings to suggest otherwise.

What was learned

Broecker's sources seem to indicate that the warming event in Medieval times was, indeed, global. During the time period in question, there were widespread glacial retreats, droughts in areas as far from the region in question as California, and suggestions of a global temperature oscillation in boreholes drilled in Greenland. Broecker concludes that, while there is not enough evidence to say for certain, the Medieval warming seems to have been global.

What it means

Broecker's conclusion from the limited data he studied is that global warming has been occuring (off and on) for thousands of years. If Medieval Warming was global, it may give some credibility to the atrocious "scientific" studies funded by oil corporations that claim humans are not causing climate change. However, it might not.

How did/will this article change my thinking

If anything, this article will make me more wary of how humans may be affecting the climate. It occured to me while reading the article that Carbon Dioxide, one of the most prevalent greenhouse gases, is utilized by plant life (i.e. trees) constantly. During and in the years leading to Medieval times, agriculture and early industry and engineering required the deforestation of massive land areas. Is it not feasible that by taking away plant life, humans allowed more greenhouse gases to reach the atmosphere? Rather than attempting to shake the blame from our species for peace of mind, I find myself discovering new reasons to try to find a solution.

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Doug - Re: All that and a big of chips

2/2/05; 3:58:21 PM (reads: 43421, responses: 0)

What was done:

The author has compiled several studies of temperature data (gathered from different means) and created a rudimentary timeline of temperature trends on Earth. Some of the methods were more successful than others and all did contain significant margin of error. The goal of this study was to prove the existance of a Medieval warming period and equate previous climate trends to future ones. The author feels that the data does indeed support that there was such an event.

What was learned.

The data showed that there has repeatedly been warming events every 1500 years or so. This has apparently been prevalent over the past 100,000 years (therefore cementing it as a fairly constand earth process), and is likely to continue as long as human interactions to not severely alter it. As far as the Medieval warming period is concerned, the data seems to be problematic. Most of the dates provided have a deviation of 200-300 years. This hardly seems adequate when deducing conditions for a period that only slightly longer than one of these deviations. On the other hand, the data supporting the Little Ice Age were more convincing.

What is means:

If the author's claim is to be accepted, this would mean that Global Warming is a natural trend. This would alleviate all human liability if this were true. I felt that many of the collection techniques were too flawed to be trusted and the data does not show how rapidly these trends occur (i.e. is it evenly distributed over the 1500 years or does it happen very quickly?). I would like more data before I draw any conclusions about such an event.

What I learned from this article:

I learned about the 1500 year interval between these temperature events. I also had never heard of the Medieval warming period. Also (as this class goes on) I am learning about how data can really be skewed. It never ceases to amaze me how people can use science to back-up two completely different and opposing viewpoints. Although I certainly do not like the idea of being super-critical, I am beginning to realize its necessity in science. Finally I realized that I can easily be confused by the overwhelming inclusion of values, years, studies, places, and gathering techniques with no logical structure(this article made my head hurt).

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Jason Fox - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/05; 8:45:58 PM (reads: 43325, responses: 0)

Method: In this paper, Broecker looks at previous fluxes in the temperature to see if there was previous global warming in medieval times. The period in question is the Medieval Warm period from 800 to 1200 AD, which was then followed by the well-documented Little Ice Age. The main problem in trying to document this was the difficulty in constructing what the rest of the world would be like at the same time of the Medieval Warm Perioud. A number of different methods were used to try and see what the condition was at the other parts of the world. These included looking at glaciation records of mountains, climate oscillations of the time, and other ways. The data was collected from many different sources, all to help Broecker with his hypothesis.

Result: While Broecker could not directly say whether the Medieval Warm Period was truly a global phenomenon, the evidence does seem to point into that direction. Unfortunately, there is still not enough data on the subject, but when there is, there could very well be a good indication that there was a time of global warming in the past. This information could be very important, because it could show what could be ahead in our future. Could there be a possibility that Earth could experience another mini Ice age?

I got more out of this article than I have for the other articles that I have read for this class. Rather than looking at the global warming we are experiencing right now, this article tries to put this trend into a bigger historical perspective. I really think that if there is conclusive evidence that there was a trend of global warming in the past, that our perspective of what is really going on will change. We will also be able to possibly look ahead and see what is coming.

This article has changed my perspective on global warming. This is a viewpoint that really has not been discussed that much. Whether it is true or not, it is still something that most people hadn't really thought hard about. Because of this article, I have a fuller perspective of what really could be the cause of global warming. It may be something we hadn't thought of before.

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Adam Brule - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/05; 8:56:38 PM (reads: 43324, responses: 0)

What was "Done" (methods. true source of data)?<o:p></o:p>

The author of this article, Wallace S. Broecker, investigated Global Warming episodes that followed the Little Ice Age by studying mountain glacial records, climatic oscillations, thermometry, and borehole thermal records. He reconstructs and analyzes these global temperature phenomenons over the last 100,000 years to study temperature fluctuations. He was also trying to prove that the Medieval Warm Period was not just local, but rather a global affair.

What was learned?<o:p></o:p>

<>He reported the results from Huang et al. that from about 500 to 1000 years ago the Earth‚s temperatures were warmer than today. Furthermore there was cooling that occurred 200 years ago. The borehole records from wells and polar ice from many different continents suggest the existence of a Medieval Warming Period. When the data and evidence is looked at, the margins of error separately the data is rather conclusive. But with many tests coupled together they really make a statement of a constant trend of the Medieval Warming and then followed by a Little Ice Age.<o:p></o:p>

What does this mean?<o:p></o:p></>

Personally, this article did not show any very conclusive results or significant evidence for a global Medieval Warming Period. With statistical differences of over .5C its had to say anything about warming because the Little Ice Age was only a .2C to .7C difference. The 1500 year temperature fluctuations show very strong evidence for climate change, but if this data were blown up to look at say a 10 year temperature fluctuation I am positive that there would be fluctuations between the years. However, he did do a good job pulling data and resources from a variety sources to make claims about global climate changes.<o:p></o:p>

How did/will this article change my thinking?<o:p></o:p>

This article really opened up the seemingly impossible methods and tests to study and measure global climate changes. Snow cap elevation tests and borehole records were just a sample of the means of testing. This article, if anything, presented the many ways to show and manipulate data. Although the testing is interesting, it just seems like its coming from way too many sources. If something does not fit, they just through the data away, or didn‚t except the results. Researchers and reporters are being bias because they only present the evidence that supports their claims.<o:p></o:p>

<o:p></o:p>

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Jacob Schober - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/05; 9:02:40 PM (reads: 43327, responses: 0)

-What was "Done" (methods. true source of data)
This article was written by Wallace S. Broecker, who is at Lamont-Earth Observatory at Columbia University. A number of different sources or 'proxies' were referred to in the article. Of whom the author mentions has varying views on the subject of global warming periods. The author admits that really none of these proxies are able to estimate the global temperature to lower than within 1 degree celcius.

-What was learned (results)

It was learned that the evidence which may suggest a global warming period during the medieval times is a bit suspect and is for alot of reasons inconclusive. Different methods as using snow retreats on mountains, tree rings, borehole theometry were all used to develop these theories. But all of this data is still incomplete and cannot possibly be reasonably used to inferred that there was in face a 'global' warming, because there just isnt that much of it.
-What it means (what did I get out of it.)

I learned how this type of data from centuries ago is collected and by what means it is. I also learned how many collective theories somewhat counter each other. And alot of times alot of things have to be inferred from the data we have instead of the data we would want to have, frankly just because there is enough data that exists to do more than infer. I also found it interesting that one proxy said that the global warming that started after the industrial revolution in fact started before the industrial revolution.
-How did/will this article change my thinking.
this article changed my thinking because i basically just didnt know how determining the world temperature thousands of years ago was determined. I also didnt realize how many different sources and varying opinions there are on topics like this. Also the possibility of the global warming thats been going on the last centruy and a half being possibly not caused by the industrial revolution is also new to me because i always thought it was caused by the revolution. Not that i no longer do, but the possibility of it being natural is now in my head.

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Emily Barcelona - Re: ben and rasheed are way better wallaces

2/2/05; 9:45:18 PM (reads: 43264, responses: 0)

What was Œdone‚:

Wallace (not as cool as either of the Pistons) S. Broecker presents his argument that global warming can be chalked up to natural fluctuation in global weather. He claims, based on several foggy data sets, that this fluctuation occurs on a 1,500 year interval and that it can be supported by data from the Swiss Alps and New Zealand Alps.

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What was learned/results:

Wallace uses many data sets and points, which confused me and left me thinking that he used so many numbers to lose his reader. It seems to me that the believed temperature differences and changes are small, small enough in fact, to be almost negated by their by the uncertainty associated with such readings. The warming episodes of 2400±300 and 1500±200 calendar years ago give large uncertainties for the bold statement the author attempts to support. I have a hard time getting behind his theory with this shady data.

<o:p></o:p>

What I got out of it:

Yeah, I don‚t think that global warming is entirely fossil fuel created. I do think that the earth changes temperature regularly and cycles through different stages. HOWEVER, this Wallace didn‚t really give me any information that I feel like I could actually rely on or use to defend my thoughts. It seems to me that statistically, most of his presented data (granted its not all his) doesn‚t hold any water. I think that he‚s on the right track with showing that it‚s not just one factor, but I would like to see solid data to back up his theory.

<o:p></o:p>

How‚d this article change my thinking:

Well, now I know who my least favorite Wallace isΣand that again, data can be manipulated to say ANYTHING the author wants. I also felt like he skimmed through the data and the support, or maybe he skimmed cause there wasn‚t much there, either way, I felt confused at the end and not very supportive of an idea I think is causable. I do not think that human causes are the soul reason the globe is warmer, but I think we are the ones speeding it up and making it go crazy. Plus, who else calls it Medieval Warm Period?

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David Emerman - Re: Why even write the article if your conclusion is that yo

2/2/05; 10:42:03 PM (reads: 44750, responses: 0)

What was "Done" (methods. true source of data)

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In the article Wallace Broecker examines the theory that a time period called „the Medieval Warm Period‰ was a regional increase in temperature, not a global increase. Broecker also investigates the theory that before 1860 the earths changing temperature was cyclic, with a period of around 1500 years. Broecker gathered information from pervious studies of glacier advances, snow cap heights, borehole thermometry, tree ring dating and analyzing the composition of ice-rafted debris. He focuses of borehole thermometry and glacier advances, claiming these are the most accurate systems of measure.

-What was learned (results)

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The author reports that the snow line on the caps of mountains in the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place>Alps</st1:place> has risen 210 meters since 1860. This indicates a rise in temperature. Based on the percent of iron-stained grains in samples taken in the <st1:place>North Atlantic</st1:place>, the author claims that the warm phases found by this method support the 1500 year cyclic global temperature change theory. The author also finds evidence that <st1:place>Antarctica</st1:place> was colder during the Medieval Warm Period then it was during the Little Ice Age, suggesting that the Medieval Warm period was regional.

-What it means (what did I get out of it.)

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The author concludes that there is not enough information to tell whether or not the Mediaeval Warm Period was regional or global. He states that more studies of glaciers advances need to be done in the southern hemisphere. The author does however claim he has found enough evidence to say that global temperatures are cyclic with a period of 1500 years.

-How did/will this article change my thinking.

<o:p> </o:p>

It did not change my thinking a whole lot. I thought his examples were a little hard to follow because I did not fully understand the studies he used as evidence. In the end he does, however, make a number of speculations that could make sense. Although, he presents no evidence to support them.

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David Emerman - Re: Why even write the article if your conclusion is that yo

2/2/05; 10:42:07 PM (reads: 44867, responses: 0)

What was "Done" (methods. true source of data)

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p> </o:p>

-What was learned (results)

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-What it means (what did I get out of it.)

<o:p> </o:p>

-How did/will this article change my thinking.

<o:p> </o:p>

Add your comments here!

Laura Jones - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/05; 11:00:08 PM (reads: 43225, responses: 0)

What was "Done" (methods. true source of data)

The author uses evidence from various studies to support his claim that the Medieval Warming period, which is supposed to have allowed Vikings to go to Greenland, was actually a global trend, not just local. He mostly uses European and American evidence, stating that there is little evidence available from the Southern hemisphere. He cites studies involving glacial retreat in the Swiss Alps, and various dating methods on debris found there, and in tree rings in CA.

-What was learned (results)

While a lot of evidence was cited from various studies, and the author suggested that it supported his hypothesis, this seemed to be a weak connection. It seems more like a collection of related data than a strong argument for scale of the Medieval Warming Period.

-What it means (what did I get out of it.) It doesn‚t seem like this article has a significant amount of meaning, other than that the author really believes in his own hypothesis. I don‚t understand how he can make a claim for the global nature of this warming period if he doesn‚t have strong evidence from the southern hemisphere as well- it seems like more of a guess than an argument.

-How did/will this article change my thinking.

One of the problems I had with this article is that I had to take the authors word on the validity of the data he used. I feel like I can better judge an article when I know more background about the subject. I guess the lesson here is to do my homework before buying into a theory.

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Bryan Glosik - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/2/05; 11:40:04 PM (reads: 43324, responses: 0)

What was done

This goal of this paper was to figure out whether or not the medieval global warming period was infact global or just regional. The author studied things such as glacial history, tree rings, and borehole thermal records to look into the past climate to help determine the likelihood of such an event. The data that was gathered in the end according to the author supports the idea that the medieval warm period was global affair or at least inconclusive.

What was learned

Overall the the author did say his results were inconclusive however the data does seem to lean toward that the medieval warming period was a global event. The data says over the past 100,000 years about every 1500 years or so the temperature does in fact warm up.

What it means

What this article means is that past heating of the climate since the industrial revolution may just be coincindence and that the globe is warming up naturally. If it is warming up naturally then we may be facing another ice age in the future. I don't feel that the data was all that convincing. I would like to see more data that indicates that the warming is not due to anthropogenic activity.

How did it change my thinking

The article did not change my thinking all that much. Although it was interesting to learn about the various ways of gathering data. But this article seemed to have too many sources of data. I was confused a lot.

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willis okech - The Case for Medieval Global Warming.

2/3/05; 12:02:56 AM (reads: 44808, responses: 0)

Wallace Broecker argues against an article concerning global warming by Bond et al. In the article, Bond et al reconstructed global temperatures during the last millennium and implied that the 20^th century warming was unique during the last millennium. Bond et al also stated that the Medieval Warm Period (from around 800 to 1200 A.D.) was local. Broecker on the other hand argues against this and believes that the oscillations in the earth≠s paleoclimates are spaced out at intervals of roughly 1500 years and that the Medieval period was global as opposed rather than local. In this article, Broecker uses data from other authors. Broecker analyzes from past authors who had looked into glacial retreat history, tree ring analysis and borehole thermometry as evidence of past warming or cooling temperatures.

From his reconstruction of past climates (using research from other authors), Broecker states that it is unreliable to use tree rings and coral reefs to document past climates over 1000 years therefore disputes past data that have claimed so. Using data from an aqueduct in the Swiss Alps Broecker asserts that radio carbon dating of Larchwood stumps and peat found at the bottom, suggests warming periods in 8600, 6600, and 4300 years before present. From research on borehole thermometry, Broeckner links the deconvolutions of thermal records from ice cores drilled to state assert linkages with colder global temperatures and also periods of warming during the Medieval Warm Period to Little Ice Age oscillation, he finds this to correspond with the eventual abandonment of the Viking colonies in southern This he finds to parallel the warming of the Swiss Alps as well. Broeckner also suggests that the advancement of the Little Ice Age ends around 1860 as this is when glacial advance seemed to end. From this he seems to infer that the advent of the industrial revolution may not be to blame for the global warming and that it is just a natural cycle.

From the reconstruction Broecker concludes that global warming has been in cycles of on and off. He asserts that the cycles are in intervals of roughly 1500 years even though he admits some inconclusive data, e.g. the data from the aqueduct in the Swiss Alps which does not tie to his intervals. However he believes that Medieval warming was global.

My stance is that there needs to be more data to convince the reader that indeed Medieval warming was global. Broeckner≠s inference that the current warming is just part of a cycle does not correspond with his intervals of every 1500 years. He seems to be suggesting that anthropogenic causes are not to blame especially since the industrial revolution (he states the ice age retreat in 1860). I believe that anthropogenic effects play a major role especially within the last 100 years. Broeckner is not convincing when he links droughts of Western California and drying up of lakes in the Sierras to a warming period, while dismissing tree rings and coral reef data. This seems to me like a bias. Indeed he admits lack of conclusive and convincing data for his assertions. The data is mainly from the northern hemisphere and merely mentions other parts of the world. I think that some data from other parts of the world would be more convincing for his claim that Medieval Warming was indeed global.

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Sophia Turczynewycz - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/3/05; 12:20:02 AM (reads: 43340, responses: 0)

In this article, Wallace S. Broecker predicts that the post-1860 natural warming was the most recent within a 1500 year interval. He agreed with past authors that the "swing from the Medieval Warm Period to the Little Ice Age was the penultimate of these oscillations" and presented the case that the Medieval Warm Period was global rather than regional. He attempted this by present all sorts of data and observations that he, along with many other sources, collected. He addresses glatial melting, borehole thermometry, tree ring records, etc.

After all the research and data collected, he was unable to confirm that the Medieval Warm Period was indded global instead of regional. Evidence of this hypothesis exists, as he presented, but it is still circumstantial. Much of the data came from snowlines, retreating glaciers, mountain glaciers... There was a lot of data presented but I don't feel like it was strong enough to back up his claim. I had never heard of the Medieval Warm Period before, or borehole thermometry, so everything in the article was pretty new to me.

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Caitlin - Re: Maybe Medieval Knights Werent the Only Ones Sweat'n It

2/3/05; 11:36:54 AM (reads: 43244, responses: 0)

The author Wallace S. Broecker states that the warming during the medieval Period was not local but rather a more global warming for that time period. He uses mountain glacial records, climate oscillations, borehole thermometry, as well as other evidnece to state his case against a localized Medieval warm period. He also suggests that the that the post-1860 warming was rather a part of other warmings that have been at 1,500-year intervals during the Holocene than a seperated case due to the Industrial Revolution.

He uses many other scientist's cases to prove his own on what seems to be a wild goose chase to prove somebody wrong. He takes evidence from the the Swiss and New Zealand Alps using snow lines and glacial retreats, polar ice caps, Antartica, and droughts from the United States in the last few sentences of argument. This gave a wide variety of evidence removing the localization from just Europe.

I dont really know what I got out of it. He seemed very jumpy in his work and it seemed put together from chunks of different articles to rationalize his own case. It was also very hard to follow with so many numbers, I had to go back and forth to sorta understand what was going on. It sounded like different facts strung together that didnt all fit at once. I dont know?

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Kate Echement - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/3/05; 12:00:13 PM (reads: 43256, responses: 0)

What was done:

Broecker, a professor at Columbia University, looked at past records of a warming trend in the Middle Ages, and Little Ice Age to discover if they were a global or local trend. He used two proxies that can yield temperatures sufficiently sensitive for Holocene thermometry: the reconstruction of temperatures from the elevation of mountain snowlines and borehole thermometry.

What was learned:

From the snowline analysis they found significant drops of snow level in the Swiss and New Zealand Alps during the Little Ice Age. During the Medieval Warm Period, the Grosser Aletsch Glacier in the Swiss Alps caused an aqueduct to be rerouted after the glacier advanced in 1370 A.D. Composites of debris left behind also mark the extent of the glacier. Radiocarbon dating of larch wood stumps, wood, and peat fragments taken from the Grosser Glacier and the Swiss glaciers respectfully also show a correlation between the Alpine warming and the warming of the North Atlantic ice-rafting record. From the borehole thermometry, holes from the polar ice caps reflect the colder temps during glacial times; where as ones from Greenland had narrower maxima, which requires a temperature oscillation occurrence. This swing matches that of the Medieval Warm Period to Little Ice Age oscillation. Studies done in Lake Tenaya in the Sierra Nevada show the lake went through a several decade-long periods of drought. Due to circulation, changes in Antarctica would be opposite in phase to those in the North Atlantic; as such was the case, further supporting the idea that the warming period and mini ice age were global events.

What it means:

This study shows that there is cause to further study whether or not the warming period and mini ice age were global events. Thus far the data supports this claim, but there is much more information to be gathered. If in fact the events were global, it further shows how we are all connected and we do have an impact on the planet and its weather.

How did this article change my thinking:

It brought to my attention a theory I had never heard of before. I was unaware of a previous warming period and mini ice age. It aroused my attention to the possibility that the warming we are experiencing is just part of the earth's cycle, but also raises new questions. Such as, will the system recover as it did before, or will this change be more permanent? More research definitely needs to be done before any conclusions may be reached.

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Drew Ruther - Bring on the fossil fuels

2/3/05; 12:39:59 PM (reads: 43357, responses: 0)

What was done?

This man, Wallace Broecker, is saying that their are oscillations in the Earth's average temperatue that take place every 1500 years. So the medieval warm period was followed by the little ice age in the 15th-18th centuries. Now we are in the midst of the warming period following that mini ice age. Broecker is using evidence from around the world to support his theory.

What was learned?

I wasn't even aware that there was such a thing as a medieval warm period. I had recently heard of the little ice age of the 15th-18th centuries. I believed that was caused by reduction of solar energy in the form of less sunspots and also increased volcanic activity on the earth which blocked out solar radiation. I'm not sure if either or those tow phenomenom have been known to be cyclic or not.

What does it mean?

It means that we can proceed to leave the lights on when we leave a room. We are not the masters of the universe.

How did this article change my thinking?

This article has not changed my thinking much. I still am as confused as ever about what is happening to the Earth's climate. All I know is that things are very complex and will probably never be figured out conclusively. Welcome to science. But I did enjoy this article very much.

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Justin - Blah Blah Blah

2/3/05; 1:23:42 PM (reads: 43301, responses: 0)

What was done?

Wallace Broecker uses mountain glacial records, climate oscillations, and borehole thermometry, to look at past temperature changes and to figure out if the middle ages and modern times warming periods are global or not.

What was learned?

Using his data from the Swiss Alps he concludes that temperture oscillations have occured regularly in Earth's past.

What it means?

He is trying to argue that human changes haven't and don't cause global temperature changes. He says that the industrial revolution didn't do this and that we aren't doing it today.

How did this article change my thinking?

Well, it didn't really. This guy didn't use all of the data available saying it wasn't good. What a jerk.

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jason - Re: Reflection#3: Was Medieval Warming Global? (2004)

2/3/05; 1:55:45 PM (reads: 43227, responses: 0)

What was done?
Wallace S. Broeker, who does work at the Lamont-Doherty Earth Observatory at Columbia University, analyzes the relationship between various experiments to record historical fluctuations in global temperatures from different geographic locations on earth. Broeker argues that the Medieval warm period, like the Little Ice Age, is global in extent not just some regional phenomenon. Broeker uses multiple experiments such as: data found from mountain snowline retreating, tree ring analysis, borehole thermometry, and data from the thermohaline circulation to correlate these two findings.

What was learned?
Levels of the mountain snowline at the last glacial maximum was on average around the globe 900m below the present day levels, meaning that a 5 degree decrease in temperatures needed to take place. Thereafter, the level during the Little Ice Age in the Swiss Alps was 90m above, giving rise to an increase in air temperature. This kind of evidence is found on all mountains during this time period. Broeker also argues that radiocarbon dating of tree rings exposed by the retreating glaciers in the Swiss Alps correlates to ice-rafting record in the North Atlantic. Greenland boreholes also give evidence of a temperature swing that correlates with the Midieval warming period and the Little Ice Age that made the Vikings immigrate elsewhere. Broeker goes on to use Stine's study of lodgepole pines to conclude that there was a massive drought in the western United States about 70 years before 1033 A.D. He also argues that based on ice-rafting debris in the Atlantic shows a cooler trend in the Antartic during the Medieval warm period and a warmer period during the Little