And back to history! Unfortunately we will have to skip two subseqent Bond events as this blog is not really about the impact of climate change on human activity. However, as a closing note I could not resist the topic that well be pretty familiar for most of you - the Little Ice Age.
Those who have never heard about LIA might think that I'm implying that just a few centuries ago Europe once again had 3-4 km of ice on top of it. In reality this term, intoduced by F.Matthews in 1939, describes a period of cooling that took place roughly between the 16th and 19th centuries. Saying that, there is actually no consensus on the exact timing of the Little Ice Age onset, and as you will see later, the proposed dates start from the mid-13th century.
Since this is the most recent abrupt cooling event, there is actually plenty of evidence for its occurrence. Mann (2002) points out multiple documentary accounts of dramatic mountain glacier retreats and advances during past centuries, as well as widespread historical documentation of weather conditions and even a handful of several centuries-long thermometer measurements. For example, in London the freezing of the Thames River became a rather common occurrence and each time it was celebrated with a winter carnival, which was depicted in many paintings:
The Little Ice age brought colder winters to large regions of North America and Europe. Mann (2002) points out many farms and villages, that were lost to the advancing glaciers in the mid-17th century. He also gives a mention to increased reports of famine, disease and child mortality in Europe during that period. Further illustrating this point, here is the graph of rye prices in Germany, where we can observe some very pronounced peaks, possibly atributing them to years of low agricultural productivity:
However, Mann (2002) believes that in Europe The Little Ice Age may have been more pronounced in terms of variability of the climate, rather than changes in the average climate itself. Thus, a severe winter preceded the hot summer that precipitated the Great Fire of London in 1666.
Finally, deteriorating climatic conditions during the Little Ice Age have frequently been blamed for the demise of Norse population in Greenland (e.g. Brown, 2000). However, although the LIA cooling has definitely created additional pressure for the Viking colonies in Greenland, it is very likely that the collapse of the Norse Greenland can also be attributed to the complex societal dynamics (Brown, 2000). If this topic seems interesting to you, my friend has a great blog about the fate of Nordic settlements in Greenland.
But was the LIA really a global phenomenon?
Mann (2002) highlights the fact that outside the North Atlantic region the large-scale signature of the Little Ice Age becomes rather unclear. In general, available evidence suggests generally colder conditions anywhere from the 13th through 19th century, quite variable in timing from region to region, and in most cases punctuated with intermittent periods of warmth. There are some long instrumental climate records in North America going back to the mid 18th century, nonetheless, Mann (2002) believes they provide a mixed signal. Thus the 17th century, the coldest century in Europe, does not appear to have been unusually cold in North America. By contrast, during the 19th century, as Europe was recovering from Little Ice Age conditions, North America was experiencing some of its coldest temperatures. The paper also points out the evidence of receding glaciers, left by the position of moraines, which suggests increased glaciation in certain regions of the world outside Europe prior to the 20th century, including Alaska in North America, and New Zealand and Patagonia in the Southern Hemisphere. However, the precise timing of glacial advances in these regions differs considerably from region to region, leading Mann (2002) to conclude that they possibly represent roughly coincident, but independent regional climate changes, rather than globally synchronous increased glaciation.
The existence of the Little Ice Age (whether deļ¬ned by the particularly cold conditions in Europe during the 16th–18th centuries, or the more modest large-scale cooling of the 15th–19th centuries) invites questions as to what factors may have led to such a cooling. I have already given an overview of the suggested triggers for Bond Cycles, but let's see what event-specific mechanisms have been proposed...
In terms of volcanic forcing, many scientists give a particular mention to the 1815 eruption of Tambora in Indonesia, when the following year came to be known as a Year Without a Summer. However, a recent paper by Miller et al. (2012) presents the evidence of precisely dated records of ice-cap growth from Canada and Iceland, arguing that LIA ice growth began earlier than thought between 1275 and 1300 AD, followed by an intensification 100-150 years later. The authors use the results to conclude about the link between the onset of the LIA and an unusual 50-year-long period with four large sulfur-rich explosive eruptions. The same paper states that "large changes in solar irradiance are not required".
Nevertheless, a group of scientists does not share this opinion, as there has been a continuous effort to link the LIA cooling event to a period of low solar activity, known as the Maunder Minimum (e.g. Ineson et al., 2011). Other proposed causes include orbital forcing, a slowdown of the thermohaline circulation, possibly attributed to the preceeding Medieval Warm Period (e.g. Broecker, 2000) or even decreased human populations. Thus, Ruddiman (2003) identified the Black Death and the colonisation of the Americas as one of the main causes of reduced human populations, which he links to the decreased carbon dioxide levels and lower temperatures.
And finally, a pretty amusing fact about the Little Ice Age... I am sure you have all hear about Antonio Stradivari, the famous violin maker, who lived in the 17th century and whose instruments still sound superior to their modern analogues. The popular opinion was that the musician had some sort of a "secret ingridient", giving the violins their unique sound. However, recently two American scientists suggested the climate was to blame. They say that lower temperatures during the LIA made the trees grow slower and therefore their wood was denser than today, contributing to the tone of Stradivari's instruments (Whitehouse, 2003).
List of references:
Broecker, W. (2000) 'Was a Change in Thermohaline Circulation Responsinle for the Little Ice Age?', Proceedings of the National Academy of Sciences of the United States of America, 97, 4, 1339-1342.
Brown, D. M. (2000) 'The Fate of Greenland's Vikings' (WWW), Archaeological Institute of America (http://archive.archaeology.org/online/features/greenland/), 7/01/2013.
Ineson, S., A. Scaife, J. Knight, J. Manners, N. Dunstone, L. Gray and J. Haigh (2011) 'Solar Forcing of Winter Climate Variability in the Northern Hemisphere', Nature Geoscience, 4, 753-757.
Mann, M. (2002) 'Little Ice Age' in T. Munn (ed.) Encyclopedia of Global Environmental Change, Wiley & Sons Ltd: Chichester, 504-509.
Miller, G., A. Geirsdottir, Y. Zhong, D. Larsen, B. Otto-Bliesner, M. Holland, D. Bailey, K. Refsnider, S. Lehman, J. Southon, C. Anderson, H. Bjornsson and T. Thordarson (2012) 'Abrupt Onset of the Little Ice Age Triggered by Volcanism and Sustained by Sea/Ocean Feedbacks', Geophysical Research Letters, 39, 2.
Ruddiman, W. (2003) 'The Anthropogenic Greenhouse Era Began Thousands of Years Ago', Climatic Change 61, 261–293.
Whitehouse, D. (2003) 'Stradivarius' Sound due to Sun' (WWW), London: BBC News (http://news.bbc.co.uk/2/hi/science/nature/3323259.stm), 06/01/2013.
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