Global
Climate
ENV 250.001
Isatta
Musahson
October 24,
2014
Due to the increase in the global temperature
during the twentieth century, there have been many scientific research carried
out to determine what was responsible for global warming. According to the Intergovernmental
Panel on Climate change Fourth Assessment Report, the global mean surface
temperature increased by 0.74 = 0.18 degree Celsius between the year 1906 and
2005. Based on this observation gathered many previous studies argue that
global worming has been continuous. Researches believed that the increased
concentration of the greenhouse gas like carbon dioxide and methane plays a key
role to increase in the global mean surface temperature since the industrial
period.
It is known
that this abnormal warm climate occurred around AD 950-1250, which is called
the medieval warm period. The concentration
of greenhouse gases during this period was relatively low and fixed during
those periods in comparison with the present warm period ( Lim, Yeh, Kim, Park,
Song P. 72). The medieval worm period is somehow similar to the present warm
period except the concentration of greenhouse gas.
Evidence
suggests that the Medieval Warm Period may have been warmer than today in many
parts of the globe such as in the North Atlantic. This extreme warming cause
Vikings to travel further north than had been previously possible because of
reductions in sea ice and land ice in the Arctic.
The Little Ice
Age was a period of cooling that occurred after the Medieval Climate
Optimum. This period has been defined as
a period from the 16th to the 19th centuries, or from
1350 to about 1850.
However, evidence
suggests that some places were very much cooler than today including the
tropical pacific. The Little Ice Age can only be considered as a modest cooling
of the Northern Hemisphere during this period of less than 1°C relative to late
twentieth century levels. There were several cause proposed for this change in
temperature: the cyclical lows in solar radiation, volcanic activity, changes
in the ocean circulation, an inherent variability in global climate, or
decreases in the human population.
During the
period of the Little Ice Age, it brought colder winters to parts of Europe and
North America. Farms and villages in the Swiss Alps were destroyed by glaciers
during the mid-seventeenth century. Canals and rivers in Netherlands and Great
Britain were frequently frozen.
Sources
Hughes, Malcolm K., and Henry F. Diaz. "Was there a ‘Medieval Warm
Period’, and if so, where and when?." Climatic change 26.2-3 (1994):
109-142.
Harrison, Stephan, et al. "Little Ice Age glaciers in Britain:
Glacier–climate modelling in the Cairngorm mountains." The Holocene 24.2
(2014): 135-140.
Lim, Hyung-Gyu, et al. "Contributions of solar and greenhouse gases
forcing during the present warm period." Meteorology and Atmospheric
Physics 126.1-2 (2014): 71-79.
