The Medieval Warm Period - Essay Example

?MEDIEVAL WARM PERIOD al Affiliation) Introduction The Medieval Warm period could also be referred to as Medieval ClimateOptimum. It’s the period which occurred from about 1000-4000. During this time, the global temperatures were few degrees warmer than those of the preceding and following periods (Villalba 2004, p. 13). The period corresponds to temperatures that occurred in the span of 950 to 1250 AD in certain regions in Europe and North Atlantic (Bianchi 2009, p 43). During this period the temperature was believed to have even extended compared to those of the late 20th century. The Medieval Warm Period idea was discovered by an English Climatologist known as Hurbert H. Lamb for the first time in 1965. He also founded the (CRU) UK Climate Research Unit where he estimated that the High Middle Ages temperatures were 1-2 degrees above the normal (Bianchi 2009, p.87). This period impacted most part of the North Atlantic and the regions surrounding it. The Little Ice Age period followed after the occurrence of High Middle Ages Period. During earlier Medieval Period, Europe experienced the mild climate conditions where agriculture was practiced in the higher latitudes (Scott 2004, p. 21). The medieval Warm Period could be regional other than global but some traces shows that the period existence in other parts of world (Bradley 2003, p. 13). In attempt to provide evidence for the occurrence of medieval warm climate as a global element, the Holocene, interglacial and the bond argued on the basis of ratio of iron-stained present in ice –rafted debris in North Atlantic (Bradley 2003, p.18). The objective was to reconstruct Holocene temperature fluctuation but the problem encountered was that the yield temperature was less than one degree percent (Scott 2004, p.30). The optimum temperature needed for the reconstruction could have been 0.5 degrees Celsius. Some of the records that tried to explain the existence of medieval warm period include the mountain glaciations record, the tree ring records, the corals and the remains of flora and fauna found on the sediments in lakes and bogs. Some of the papers that supports that the High Middle Ages could be global include the tree-ring reconstruction in the Southern Hemisphere. The records shows that above average temperatures were received in the New Zealand during the summer temperatures. The period was also experienced in the pacific basin where sea level rose reaching a maximum that exceeded the normal sea level. In Asia, evidence of medieval warm Period was characterized by the cultivation of citrus fruits which was never as far as to the north. The extreme warmth resulted to the existence of some insects such as the Heterogaster urticae beetle that was detected during the Roman Optimum (Bradley 2003, p.22). A case study in the northern part of the United States on the icy crystal known as Ikaite by geochemist Zunli Lu of Syracuse shows evidence of existence of Medieval Warm Climate. The case was 10,000 miles south of northern Europe (Mann 2003, p.85). The mineral forms in cold waters and constitutes water and calcium carbonate. The crystal could be found in Green land and off the coast of Antarctic Peninsula. The two climates were important because temperature variation resulted into the formation of the Ikaite. The hydrated water from the bottom of the ocean holds the crystal structures together hence during cooling; the ice sheets would expand as the bottom ocean water accumulates heavy oxygen isotopes (Goose 2006, p.223). Melting of glaciers causes mixture of the bottom water with the enriched light oxygen fresh water. When the ratio of oxygen isotope in calcium carbonate and that o hydrated water was taken, a correction of oxygen was determined between rises and fall. A conclusion in the Antarctic Peninsula was that the crystal Ikaite could build oscillations around the globe especially during the High Middle Ages (Peterson 2005, p.116). The Mediaeval Warm Period in South China The medieval warm period was generally reported from the North Africa and the Equatorial East Africa as a period of drought. This was later replicated in the Lake Huguangyan in South China during the past 1400 years. Lake Huguangyan could be located on the coordinates of 29o 9’ N and 110o 17’E which lies on the Leizhou Peninsula. The site would be influenced by the regime climate of the North Pacific Ocean which could be seasonal. It also experiences 90% of the annual rainfall comprising of 1567 mm which occurs between the month of April and October. The climate within the site would be controlled by variation in intensity and position of the West Pacific Ocean. The site would also be exposed to an annual average temperature of 23o C which most of the time would be experienced in the month of November. This usually was regarded as the dry season. Figure 1. The figure shows the Huguangyan Crater Lake location in the tropical South China with its coring sites (Goose 2006, p.24). The study involved collection of various sediment core approximately seven of them at different location between 14 and 22m depth. Historical document were used to reconstruct and evaluate the rainfall relation and the cold winters from the Lake Huguanagyan proxy records (Kuijpers 2009, p.23). Due to wide variety of climatic regimes, the pas information would be restricted to the tropical plains of the site. The historical information was the most important original source of the palaeoclimate study due to the quality of quantification and interpretation. To provide distinction between the different degrees of fleet, snow and frost in the tropical plains of South China, development of cold winter index was enhanced (Kaufmann 2003, p.204). The cultivation of perennial herb and citrus trees in china from the records collected clearly shows the existence of medieval warm period in other parts of the word other than the Europe. The citrus tree and perennial herb were used in the twelfth, eighth and thirteenth century to produce maps to show the distribution of these plants (Kaufmann 2003, p. 213). The boundary to the north of the citrus trees cultivation was the site for modern distribution which was established in the thirteenth century. This century was almost northern most during the past 100 years. The indication of this situation was claimed as the warmest period of all time. Climatic conditions knowledge was regarded useful especially during the plantation these species, for example it was estimated that the average annual temperature required would be 0.9-1.0oC for the plants to blossom. This was in the thirteenth century in Henan Province (Kaufmann 2003, p.241). The Glacial Geological Evidence for the Medieval Warm Period Glacial expansion would be known to have occurred in Europe and some other parts of the world between 800 A.D and 900 A.D. During this period, glacial expansion remained more advanced in the mid twentieth century and later it was found to have occurred within six centuries between 1250-1300 A.D and 1850-1900 A.D. This led to the emergence of the Little Ice Age which within the last four centuries. The hypothesis that the medieval warm climate could be preceded and followed by the deposition of glaciers would act an evidence for the occurrence of the medieval warm period. The glaciers in the hemispheres both northern and southern would usually expand in few hundred years after their formation. The existence of the glacial genesis as a result of anomalous warm temperatures due to medieval warm climate could be determined by the remain of moraines within the or a few miles away from the present ice fronts. Formation of the moraines could be favored by circumstances such as the organic material which provide a maximum age for its formation. The medieval warm period could be traced between the formations of the moraine during the periods of enlargement and the current dates (Hunt 2009, p.25). Evidence for a ‘Medieval Warm Period’ in a 1,100 year Tree-ring Reconstruction of past Austral Summer Temperatures in New Zealand The medieval warm period could have been first identified in Europe which later triggered the debate concerning the existence at a global level. The high middle ages was detected in the Southern Hemisphere due to high-resolution, well-dated and paleo-temperatures records that could have covered last 1,000 years. This resulted to emergence of tree-ring reconstruction from South Island from New Zealand which entails Austral summer temperatures (Hunt 2009, p. 39). The reconstruction covered the past 1,000 years where it emerged the longest record that could have been kept in New Zealand for such a long time. The evidence shows that the persistent above average temperaratures existed resulting to the period assigned as the medieval warm period. This period, when compared with some of the selected proxies temperatures from Southern and Northern Hemisphere, clearly shows that the period was highly variable in space and time (Hunt 2009, p. 43). The tree-ring reconstruction in the Southern Hemisphere of New Zealand could be dated back to the proposed A.D 1000-1300 when the tree species were known as dendroclimatic potential. The anomalous warm period could also be found in the Northern Hemisphere. An example of tree-ring site in New Zealand would be the Oroko Swamp with coordinates lat. 43_ 140S, long. 170_ 170E, elev. 110 m.a.s.l.). The site could be located in the west coast of South Island and supported variety of tree species that was necessary for the dendroclimatic studies in New Zealand. One of the tree species that include the silver pine that could be impervious to decay and it could also live up to a maximum of 1,000 year. The crew made a concerted effort in utilization of the dendroclimate resource which included the sub-fossil logs that were extracted at the swamp for four years (Hughes 2004, p. 3). This resulted to the tree-ring reconstruction during the Austral Summer that was between January to March in New Zealand. The intensive use of sub-fossil wood resulted to the silver pine chronology that had greater sample depth as compared to that of sub-fossil wood. The ring width series that were up to 260 which enabled the crew to establish the Regional Curve Standardization that covered the period A.D. 700-900, this resulted to the development of annual tree –ring chronology (Goni 2004, p. 86). Tree-ring information could not be relied on or be able to capture changes in climate for a long term period like 100+. The reason would be due to the tree size, genetic climate adaptation, the roots or shoots ration and also the forest density that could shift due top prolonged changes in climate. Most of the tree-ring reconstruction the response of tree ring width could e due to temperature (Goni 2004, p. 104). This could not be always the case since sometimes the tree rind with would decrease with further temperature as well as increase to an optimal level of temperature. The response of the tree ring width could be due to the inadequate water supply at higher temperature since the evaporation rate would be high at high temperature resulting to increases in tree ring width (Crowley 2000, p. 43). Holocene Periodicity in North Atlantic Climate and Deep Ocean Flow South of Iceland The Holocene climate occurred in the Northern Atlantic Ocean and the cause was probably changes in solar flux. In a normal situation it would be expected involvement of water masses from the Atlantic Ocean that would cause the Holocene climate changes but in this case its yet to be established. The grain size sediments information would be used to reconstruct the changes occurred in the ice land basin (Crowley 2000, p.55). The site where the study took place was determined by the Scotland-Iceland Overflow water which moderated the European climate through thermohaline circulation. The changes of the climate coincided with the existence climatic condition which includes the medieval warm period and the little ice age (Grove 2004, p. 76). The information from the grain size sediments would indicate the rate of flow of the Iceland Scotland Overflow Water that shows when the European climate from the north would be warmer. The Atlantic Northern Ocean would be very useful due to the North Atlantic Current in the modification of the Holocene climate. The heat would be lost to the atmosphere as the current move to the Norwegian Sea in the deep water that accelerated the formation of northwestern Europe temperate climate (Crowley 2000, p. 65). The waters of the Atlantic would partly be maintained and counterbalanced due to the dense, deep and the return flow of the Ice –Scotland Overflow Water that trespasses to the Iceland basin through the Iceland-Scotland ridge. The thermohaline that controls the circulation in the Iceland –Scotland Overflow water would be sensitive and unstable due to salty water balance (Crowley 2000, p.76). The results show that the stable Holocene would generally have temperature fluctuation. The climate change in the Northern Europe had been presented by the history documentary as marked by alteration of warmer and cooler period. Currently, the records show that the northern Europe would be recovering from the cold period of Little Ice Age that coincided with the Iceland-Scotland Overflows water. The medieval warm periods perked in the European region at different times and the regions surrounding the North Atlantic Basin (Grove 1994 p. 83). The emergence of the medieval warm period was between 750 and 1,050 A.D. And between 900- 1250 A.D. The history of this warm climate would be dated back to the existence of the Roman Warm Period where the glaciers and cooling effects advanced to the Dark ages which existed during the 500-1000 A.D. The figure below illustrates the comparison of the Little Ice Age and the Medieval Warm Period and their recurrent feature of the Holocene Climates history. The warm period intervals coincide with the faster near bottom flow of water in the southern Ice basin (Huffman 2006, p.97). Figure 2 Adaptation and Human Migration, and Evidence of Agriculture Coincident with Changes in the Indian Summer Monsoon during the Holocene The evolution of climate and ecological interaction has resulted to the change of the human societies. The change in climates has led to the migration, mitigation and adaptation of the intimate relationship among the human societies (Huffman 2006, p.113). The evidence existed in the northwestern part of India where the civilization of the human societies flourished during the early Holocene when the rainfall was much higher and the Indian summer much stronger. This occurred over the Indian land masses in the past 7000 years during the intensification of the earlier Holocene (Hughes 2004, p. 5). The palaeo records show that the Holocene climate was marked by the millennial scale variability. The changes in climate resulted to adaptation of the human society to migration due to the extreme weather condition such as the medieval warm climate and the little ice age (Huffman 2006, p.123). The proxy records indicate that earlier Holocene 10000-7000 was marked by warmer and wetter interval conditions. The records of the earlier Holocene South West monsoon changes in rainfall and the intensification raises the question about the rise and fall of the human society civilization during the establishment of agriculture in the Indian subcontinent (Cook 2002, p. 23). The Medieval Warm Period, the Little Ice Age and Simulated Climate Variability The existence of medieval warm period which could be followed by the Little Ice Age could be determined by the multi millennial simulation. The two climatic conditions existed in the Northern Hemisphere through the regional temperature reconstruction. This would be the Scandinavia north of 60oN, the warm season for the northern Siberia and the Greenland which had warm temperature season (Cook 2002, p.34). In this case the global climatic model would be used to determine in approximation the experience of the settlers in Greenland in relation to the medieval warm period (Goni 2004, p. 106). The objective was to evaluate the replication of natural climate variability in order to counteract the experienced global warming (Favier 2006, p. 66). In attempt to refute the occurrence of carbon dioxide induced in the global warming, the media expressed the views to the public (Cook 2002, p.47). The millennium simulation identified above average temperatures for the year period of 291 and another one of 41 year of the cooler period. This was followed by subsequent analogue that represented the conditions of the Norse settlement period (Favier 2006, p.75). The two would be identified by the inter-annual variability where positive and negative anomalies of the temperatures were noted. This resulted to the warm period disregarded as the benign conditions (Favier 2006, p.87). The warm period would be associated with above average precipitation which would enhance growth of pasture land and production of hay thereby satisfying the livelihood of the Norse Greenlanders (Goni 2004, p.123). The survival prospects of the settler would be limited by the occurrence of climatic condition associated by the cold period. The proxy data of the climatic conditions would be similar to that of the anomalies of temperature replicated in the simulation only that those would be smaller in size (Favier 2006, p.98). This temperature would appear to be more than enough for the viability of the Norse Greenlanders. The climate mechanism of warm and cold periods generated by the nonlinear processes could be as a result of the stochastic influences. The simulation would not offer a basis for the argument that the current global warming would be as a result of conditions manifested during the settlement of Norse Greenlanders (Ding 2001, p.57). Figure 3. Show the two climatic conditions due to temperature change between 1000- 1900 A.D. Conclusion The existence of medieval warm period information has been extracted mostly from Southern Hemisphere. This would be due to the warm southern ocean in the 14th and 15th centuries where paleoclimatic proxies clearly indicate the existence of high middle ages. The northern hemisphere on the other hand would be associated with the occurrence of the cold period hence the Little Ice Age period (Holmgren 2001, p.57). The above mechanism provides basis of models for the change in climate during the lags of 150 years in the Southern Hemisphere and the Northern Hemisphere. The climatic evolution would result to the understanding of the future climatic changes. The evidences provided for the existence of medieval warm period would imply that the southern ocean would continue to influence the climatic conditions in the southern hemisphere. 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