The historicity of the Medieval Warming Period is a minor controversy these days. Almost everyone accepts the data from the 20th Century which shows that global average temperature has increased by about 1.0 degrees Celsius since about 1908. By the same token, there is only a minor embarrassment that the temperature rise leveled off from about 1946 through 1975, and that once again the temperature rise has slowed since 2002. This data is not in serious dispute, or at least it is not disputed by the Village Elliot.
Given that global temperatures have risen, the next question is whether human activity has been the primary cause. Conventional wisdome is that human activity is absolutely implicated, based on the presumption that the average temperature of the earth has remained constant, plus or minus about 0.5 degrees Celsius, for thousands of years (referred to as the Climate Statis hypothesis; i.e., that climate change is definitely not natural or at least not on the timescale of "only" 100 years or so). Hence a temperature rise of 1.0 degrees Celsius is too much to attribute to non-anthropogenic causes, and thus the CO2 Greenhouse Effect can safely be identified as the sole cause for the temperature rise. Moreover, many mainstream climatologists argue that the world is headed for a climate catastrophe, and major changes are required in the global hydrocarbon economy in order to avert disaster.
The Village Elliot is not on board with some of these key principles, despite the fact that the persons making these assements are much better qualified and well studied in these matters. In particular, I suggested in my last blog that historical climatology is basically blind as a bat if it could not see much unusual about 1816, the Year Without a Summer, in which snow fell year round. It is thought that tree ring data provides information about the temperature in any given year, which I find amazing, given that on three continents trees reportedly failed to even grow rings that year because they stayed dormant. The cooling of 1816 was caused by a massive volcanic eruption at Tambora, Indonesia and does not directly affect the CO2 Greenhouse hypothesis. It does call into account whether the historical records of the 19th century are worth a darn, and specifically whether they allow us to rule out climate change caused by factors other than carbon dioxide.
Let us then turn our attention to the Medieval Warming period. As is the case with the Year Without a Summer, the Medieval Warming period used to be a historical fact. Eric the Red colonized Greenland at the end of the 10th century. The Vikings flourished there, so that by the 13th century there were over 3000 colonists in 300 farms.
Some historians have suggested that Eric named Greenland simply as a propaganda ploy to attract new residents. Maybe so, but someone had to convince crops to grow in a short growing season, and people and livestock to not freeze to death once they did settle there. These seem close to being historical facts which can not be easily overturned.
Some historians have suggested that Eric named Greenland simply as a propaganda ploy to attract new residents. Maybe so, but someone had to convince crops to grow in a short growing season, and people and livestock to not freeze to death once they did settle there. These seem close to being historical facts which can not be easily overturned.
Yet, according to conventional wisdom, global average temperatures changed only slightly during this period, and even the localized temperatures in the North Atlantic were cooler than they are today.
The Village Elliot wonders how this could be true. Even with today's agricultural technology, it is very difficult to farm in Greenland. To think that thousands of Vikings could be farming in a wintry wasteland does not make sense. Morever, Antactic Ice core data supports the notion that this period was indeed warmer than the later period. This, plus the general dominance of the Vikings during those centuries, strongly implies that the temperatures were much warmer during that period.
Moreover, the Vikings were not the only group that settled Greenland. It turns out that the aboriginal Tuniit and Inuits also greatly expanded their territory in Greenland coming from from the northwest, and thrived for a time before receding significantly during what historians can the Little Ice Age (but which most climatologists call a 0.5 degree temperature dip).
Moreover, the Vikings were not the only group that settled Greenland. It turns out that the aboriginal Tuniit and Inuits also greatly expanded their territory in Greenland coming from from the northwest, and thrived for a time before receding significantly during what historians can the Little Ice Age (but which most climatologists call a 0.5 degree temperature dip).
Why it Matters
The existence or nonexistence of the Medieval Warming period does not contradict the reality of the CO2 Greenhouse effect. Rather, the reality of absorption of thermal energy by carbon dioxide is pretty much undisputed. The advancement of the Climate Stasis hypothesis, or the notion that the climate never changed much prior to the 20th century. mainly serves to confuse the modelers and perhaps impart some errors into the assumptions that go into current climate models. Namely, we may be left with a model of a robust terrestrial climate, which suggest that the earth's average temperature is not strongly affected of volcanos such as Tambora. The models further suggest that the Year Without a Summer and the Medieval Warming Period never happened, or at least that they were greately exaggerated. Hence this might lead to understimation of effects other than carbon dioxide. Moreover, most climate historians seem content with the view that recent climate has been fairly static.
The Village Elliot, however, is a habitual contrarian. Certainly I do not have the tools to prove or disprove the consensus views of professional climatologists. Nevertheless, in my opinion--and it's just an opinion--future more objective reviews of history will lead probably climatologists to conclude that there are indeed other factors worth worrying about in addition to carbon dioxide. From the standpoint of politics, however, this is a heretical prediction, as we've pretty much settled on a policy of reducing carbon emissions even if it retards economic growth.
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Oct 30, 2012 Post Script: It turns out that at least one recent peer reviewed study in fact has in fact vouched for a warmer Warming Period and a cooler Little Ice Age. You may read about it here:
http://elliotkennel.blogspot.com/2012/10/post-script-medieval-warming-period-and.html
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Oct 30, 2012 Post Script: It turns out that at least one recent peer reviewed study in fact has in fact vouched for a warmer Warming Period and a cooler Little Ice Age. You may read about it here:
http://elliotkennel.blogspot.com/2012/10/post-script-medieval-warming-period-and.html
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Additional Reading
Check out the present average monthly temperatures in Greenland, and tell us how Vikings were able to grow crops there if the temperatures were lower in the 10th century than they are now... http://www.greenland.com/en/about-greenland/natur-klima/vejret-i-groenland/gennemsnitstemperaturer.aspx
Kim, B.;
Yoon, Ho Il; Kang, Cheon Yun; Bahk, Jang Jun (2002). "Unstable Climate
Oscillations during the Late Holocene in the Eastern Bransfield Basin,
Antarctic Peninsula". Quaternary Research 58 (3): 234
J. Fabres et al., Branfield Basin fine-grained sediments: Late Holocene Sedimentary Processes and Antarctic Oceanographic Conditions, The Holocene September 2000
vol. 10
no. 6
703-718 http://hol.sagepub.com/content/10/6/703.abstract
http://elliotkennel.blogspot.com/2012/04/significance-of-year-without-summer.html
http://en.wikipedia.org/wiki/Medieval_Warm_Period
