Was there a Little Ice Age (LIA)?The Little Ice Age (LIA) was a heterogeneous climatic cooling that predominantly effected Europe. The

exact dates of this cooling fluctuates throughout the literature but the Fifth Assessment Report by the IPCC

(2013) defines it as occurring between mid-14th to mid-19th century (Fig. 1). From solar variability to

increased agriculture and afforestation; some suggested causes and mechanisms of climatic change during

the last millennia are introduced and discussed. Contemporary research is presented that deals with

drawing a link between these causes and the onset of the LIA. The majority of this research has been

conducted in the higher latitudes of the northern hemisphere. Resultantly, as evidence on the LIA is

predominantly based from European and northern hemispheric research; this essay presents

contemporary research that is geared towards developing the LIA-related palaeoclimatic record for

regions in the southern hemisphere and outside of Europe.

The first cause of the LIA to be discussed is orbital forcing. This external forcing is essentially a fluctuation

in Total Solar Irradiance received by Earth due to long-term changes in its oscillation and orbital patterns

(the Milankovitch cycles) (Smithson et al., 2008). The contributions of orbital forcing to the onset of the

LIA (and climate of the last millennia) are stated to be very minimal (Servonnat, 2012). However, evidence

does suggest that there appears to be a general trend of orbital-forced-cooling occurring and the LIA is

testament to this (Kaufmann et al., 2009). Although, Esper et al. (2012) stated that published preindustrial

GEG358: Climate of the Last 1,000 Years Page 1

Fig. 1. The simulated and reconstructed climate of the past millennium. MCA, Medieval Climate Anomaly; LIA, Little Ice Age. . (IPCC AR5, 2013, Chapter 5, Information from Palaeoclimate Archives, p.413).

climatic reconstructions may have missed the orbital forcing signals in their records, and that their

palaeoclimate reconstructions may be erroneous due to imperfect proxies used. Although there are

arguments for and against it, the consensus is that orbital forcing has had relatively little influence in

causing the Little Ice Age.

Solar variability (SV), the fluctuation in the Sun’s radiative output, has recently been attributed to being

one of, if not, the most dominant causes of recent climatic change on Earth. Although, as with most

suggestions in science; there is some disagreement to this. However, there appears to be some convincing

evidence when Total Solar Irradiance is attributed to the LIA (Fig. 2.). The Paleoclimate Modelling

Intercomparison Project (PMIP3) (Schmidt et al., 2011) is one of the principal models used in

reconstructing palaeoclimate; using a plethora of gathered archives and data, this model featured heavily

in the IPCC’s Fifth Assessment Report. Bard and Frank (2006) concluded that SV’s effect on climate

remains unproven. Alternatively, Miller et al. (2010) examined Arctic ice-cores for a relationship between

volcanism and the onset of the LIA. They suggest that TSI was not predominantly responsible for the LIA;

rather it was due to explosive volcanism that induced and sustained colder temperatures due to

atmospheric sulphur loading. This volcanism coupled with orbital forcing encouraged Arctic sea-ice

expansion; generating sea-ice ocean feedback, suppressing summer temperatures.

Volcanism and climate have been intimately linked by a vast quantity of studies. Eruptions eject large

quantities of sulphur dioxide into the atmosphere; and depending on their atmospheric residence time,

they can have a substantial net-cooling effect on (potentially) global climate and temperature. For example

McCarroll et al (2013) and Gao et al. (2008) found a distinct pattern between of volcanic eruptions and

decreases in summer temperature. Furthermore, this effect is particularly exacerbated if there’s a series of

simultaneous eruptions.

GEG358: Climate of the Last 1,000 Years Page 2

Fig. 2. Total Solar Irradiance (TSI) reconstructions. The Little Ice Age is dated as c.1450 – c.1950; TSI begins to noticeably decrease from around ~1400 onwards until ~1750. There’s 300 years in which the defined LIA and TSI correspond. (IPCC AR5, 2013, Chapter 5, Information from Palaeoclimate Archives, p.390).

As shown, there are various arguments for and against how solar forcing, orbital forcing, and volcanic

forcing influenced the climate of the LIA. However, there are further causes attributed to this cooling.

Firstly, internal variations are overviewed: multi-proxy reconstructions of the El Nino Southern Oscillation

(ENSO) found that it was very inactive during this period of cooling (Hereid et al., 2013; Fowler et al.,

2012; Gergis and Fowler, 2009). However, McGregor et al. (2010) states that there are great uncertainties

with the assumptions that ENSO activity and the LIA are related. Additionally, it’s a fair suggestion to say

that ENSO activity is vulnerable to the external forcings previously discussed. Furthermore, by an analysis

of Fennoscandian stable carbon isotopes Loader et al (2013) interpreted the LIA as changes in the Arctic

Oscilliation.

There is a concerted effort within LIA-research to understand the relationship between the multi-

centennial cooling and the variations in ocean circulations. Schleussner et al. (2015) found with the

CLIMBER-3 simulations that a there’s an observant non-linearity in the North Atlantic Ocean (NAO)α

circulation that may have had a significant contribution to the onset of the LIA in the northern hemisphere.

Interestingly, it has been suggested that the NAO circulation may have been influenced by previous

volcanic eruptions (Schleussner and Feulner, 2013; Goosse et al., 2012). This epitomises the complexity of

palaeoclimatic reconstructions as volcanic eruptions not only have a direct influence upon the climate,

there is evidence to suggest they also indirectly influence it by causing alternations to various circulation

mechanisms (Kinnard et al., 2010). Finally, Zou and Xi (2014) simulated that the heat-transfer

mechanisms of the Gulf Stream were detrimentally altered due to a 180-260km southward displacement

of the ITCZ during the LIA – exacerbating the cooler conditions evident in northern Europe.

It is agreed that internal variations in the Earth’s climatic systems, such as ENSO and other atmospheric

circulation mechanisms, have a substantial influence upon palaeoclimate and are key in explaining spatial

variations for palaeoclimate reconstructions (Trouet et al., 2009).

The final two causes attributed to climatic change of the last 1,000 years are anthropological influence and

the greenhouse gases. Pre-industrial (before ~1750AD) greenhouse gases experienced low variability

(Crawley et al, 2000). Fig. 3. (from the IPCC’s AR5) shows there’s compelling evidence to support this

suggestion: the relationship between these greenhouse gases and the LIA appears to be non-existent.

GEG358: Climate of the Last 1,000 Years Page 3

There are also suggestions that the LIA was caused by various anthropological factors such as agriculture,

afforestation and disease-induced population decrease (Ruddiman, 2011). Although there are suggestions

and theories as to the cause of the Little Ice Age; the general consensus is that no singular cause can be

attributed to inducing the heterogeneous cooling present between ~1500 - ~1800. From the variety of

proxies used (ice cores, tree-rings, marine sediments etc) to reconstruct the palaeoclimate of the last

millennium, the exact dates of this cooling are disputed. This proxy variety also relies on differing signals

to infer palaeoclimate, resulting in the disagreements on the cause of the LIA.

There is an overwhelming hemispheric bias to the location of where palaeoclimatic records have been

obtained (Fig. 4.). Beginning in the Andes, there has been considerable work examining its glaciers. By

analysis of O2 isotopes in glacial ice from the Quelccaya ice in Peru, Thompson et al. (2006) discovered

evidence for a significant period of cooling that coincides with the Little Ice Age. Furthermore, Espizua and

Pitte (2009) reconstructed the advancement of 4 Argentinian glaciers and found that they reached their

GEG358: Climate of the Last 1,000 Years Page 4

Fig. 3. The Greenhouse Gases (CO2, Carbon Dioxide; CH4, Methane; N2O, Nitrous Oxide) show relatively little variance during the past millennium. In general, all three gases begin to significantly increase from ~1700AD – roughly coinciding with the beginning of the industrial age. (IPCC AR5, 2013, Chapter 6, Carbon and Other Biogeochemical Cycles, p.485)

maximum between 1550-1720AD. However, the maximum advancement of the Glaciar Rio Manso in the

north Patagonian Andes occurred much later: between the late-1700s to mid-1800s (Masiokas et al.,

2010). By dating glacial moraines, Xu and Yi (2014) found that 22 glaciers on the Tibetan Plateau reached

their maximum extents during the ~1450AD – remarkably earlier than those in the Andes. Several of these

began to advance during the late-18th to early-19th century but have since begun to extensively retreat

(Loibl et al., 2014). Understanding how variations in palaeoclimate influence precipitation enables

scientists to quantify how precipitation may fluctuate both regionally and globally in the near-future (Chen

et al., 2014). This is of a particular importance to China, whose northern region is water scarce. Zeng et al.

(2012) analysed lake sediments across southern China and concluded that during the LIA, precipitation

rates were increased. However, this was due to a displaced East Asian summer monsoon, resulting from

global temperature imbalances as the northern hemisphere was colder - causing northern China to

experience periods of drought. Lee and Park (2015) suggest that this climatic imbalance and drought was

a residual effect of the Medieval Climate Anomaly.

The spatial variety of LIA-related palaeoclimatic reconstructions is ever-expanding: the ITCZ was

displaced southwards over the Caribbean during the LIA – causing severe aridity (Lane et al., 2011, and

references thereon in). By examining pollen in laminated sediments, Heusser et al (2014) found that

GEG358: Climate of the Last 1,000 Years Page 5

Fig. 4. The distribution of palaeoclimatic records concerned with the Little Ice Age. Note the obvious bias to records constructed in the Northern Hemisphere; furthermore, the sheer volume of reconstructions based from tree-rings is evident, particularly from Fennoscandia and western USA. Edited from: Mann et al., 2009.

during the LIA, mesic vegetation was abundant throughout southern California. Kaniewski et al (2011)

also examined pollen-laden sediments and found that, unlike southern California, the LIA caused much

drier conditions in Syria – even more so than its climate at present. Evidence for the LIA has also been

found in Antarctica (Bertler et al., 2011).

Concluding, the Little Ice Age was not a globally synchronous period of cooling; most reconstructions

generally agree that climate was cooler between the mid-15th to the mid-18th centuries (Ahmed et al.,

2013). There have been a variety of causes attributed to inducing this period of cooling which lasted for

~4 centuries. Aside from the vast array of scientific evidence that supports the presence of the LIA;

various works of art and literature also document this period of cooling. From the multitude of studies

using various proxies, predominantly tree-rings and ice cores; it’s evident that there was a global cooling

that took place during the Little Ice Age. Further developments in southern hemispheric palaeoclimatic

reconstructions will enable for a greater understanding of climatic variations during this period.

Word Count: 1,548

References1. Ahmed, M. et al. 2013. Continental-scale temperature variability during the past two millennia. Nature Geoscience. [Online].

6(5), pp.339-346. [Accessed on 24th April 2015]. Available from: http://www.nature.com.openathens-proxy.swan.ac.uk/ngeo/journal/v6/n5/full/ngeo1797.html

2. Bard, E. and Frank, M. 2006. Climate change and solar variability: What's new under the sun? Earth and Planetary Science Letters. [Online]. 248(1-2), pp.1-14. [Accessed on 18th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0012821X06004328

3. Bertler, N. A. N. et al. 2011. Cold conditions in Antarctica during the Little Ice Age — Implications for abrupt climate change mechanisms. Earth and Planetary Science Letters. [Online]. 308(1-2), pp.41-51. [Accessed on 18th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0012821X11002925

4. Chen, J. et al. 2015. Hydroclimatic changes in China and surroundings during the Medieval Climate Anomaly and Little Ice Age: spatial patterns and possible mechanisms. Quaternary Science Reviews. [Online]. 107(Jan. 2015), pp.98-111. [Accessed on 28th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0277379114003990#

5. Crawley, T. J. et al. 2000. Causes of Climate Change Over the Past 1000 Years. Science. [Online]. 289(5477), pp.270-277. [Accessed on 20th April 2015]. Available from: http://www.sciencemag.org/content/289/5477/270

6. Esper, J. et al. 2012. Orbital forcing of tree-ring data. Nature Climate Change. [Online]. 2(2012), pp.862-866. [Accessed on 21st April 2015]. Available from: http://www.nature.com/nclimate/journal/v2/n12/abs/nclimate1589.html

7. Espizua, L. E. and Pitte, P. 2009. The Little Ice Age glacier advance in the Central Andes (35°S), Argentina. Palaeogeography, Palaeclimatology, Palaeoecology. [Online]. 281(3-4), pp.345-350. [Accessed on 28th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0031018209001345

8. Fowler, A. M. et al. 2012. Multi-centennial tree-ring record of ENSO-related activity in New Zealand. Nature Climate Change. [Online]. 2(2012), pp.172-176. [Accessed on 21st April 2015]. Available from: http://www.nature.com/nclimate/journal/v2/n3/full/nclimate1374.html

9. Gao, C. et al. 2008. Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models. Climate Dynamics. [Online]. 113(D23). [Accessed on 25th April 2015]. Available from: http://onlinelibrary.wiley.com/doi/10.1029/2008JD010239/abstract

10. Gergis, J. L. and Fowler, A. M. 2009. A history of ENSO events since A.D. 1525: implications for future climate change. Climatic Change. [Online]. 92(3-4), pp.343-387. [Accessed on 17th April 2015]. Available from: http://link.springer.com/article/10.1007%2Fs10584-008-9476-z

GEG358: Climate of the Last 1,000 Years Page 6

11. Goosse, H. et al. 2012. The role of forcing and internal dynamics in explaining the "Medieval Climate Anomaly. Climate Dynamics. [Online]. 39(Feb. 2012), pp.2847-2866. [Accessed on 17th April 2015]. Available from: http://pubs.giss.nasa.gov/abs/go06500y.html

12. Hereid, K. A. et al. 2013. Coral record of reduced El Niño activity in the early 15th to middle 17th centuries. Geology. [Online]. [Accessed on 18th April 2015]. Available from: http://geology.gsapubs.org/content/early/2012/10/18/G33510.1.abstract?papetoc

13. Heusser, L. E. et al. 2014. Vegetation response to southern California drought during the Medieval Climate Anomaly and early Little Ice Age (AD 800–1600). Quaternary International. [Online]. [Accessed on 29th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S1040618214006806

14. Kaniewski, D. et al. 2011. The medieval climate anomaly and the little Ice Age in coastal Syria inferred from pollen-derived palaeoclimatic patterns. Global and Planetary Change. [Online]. 78(3-4), pp.178-187. [Accessed on 27th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0921818111001123

15. Kaufman, D. S. et al. 2009. Recent Warming Reverses Long-Term Arctic Cooling. Science. [Online]. 325(5945), pp.1236-1239. [Accessed on 20th April 2015]. Available from: http://www.sciencemag.org/content/325/5945/1236.short

16. Kinnard, C. et al. 2011. Reconstructed changes in Arctic sea ice over the past 1,450 years. Nature. [Online]. 479(Nov. 2011), pp.509-512. [Accessed on 19th April 2015]. Available from: http://www.nature.com/nature/journal/v479/n7374/full/nature10581.html

17. Lane, C. S. et al. 2011. Oxygen isotope evidence of Little Ice Age aridity on the Caribbean slope of the Cordillera Central, Dominican Republic. Quaternary Research. [Online]. 75(3), pp.461-470. [Accessed on 19th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0033589411000135

18. Lee, K. E. and Park, W. 2015. Initiation of East Asia monsoon failure at the climate transition from the Medieval Climate Anomaly to the Little Ice Age. Global and Planetary Change. [Online]. 128(Feb., 2015), pp.83-89. [Accessed on 30th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0921818115000582

19. Loader, N. J. et al. 2013. Stable carbon isotopes from Torneträsk, northern Sweden provide a millennial length reconstruction of summer sunshine and its relationship to Arctic circulation. Quaternary Science Reviews. [Online]. 62(Feb. 2013), pp.97-113. [Accessed on 23rd April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0277379112004854#

20. Loibl, D. et al. 2014. Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line altitude calculation. Geomorphology. [Online]. 214(Jun. 2014), pp.22-39. [Accessed on 28th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0169555X14001457

21. Mann, M. E. et al. 2009. Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science. [Online]. 326(5957), pp.1256-1260. [Accessed on 21st April 2015]. Available from: http://www.sciencemag.org/content/326/5957/1256.short

22. Masiokas, M. H. et al. 2010. Little Ice Age fluctuations of Glaciar Río Manso in the north Patagonian Andes of Argentina. Quaternary Research. [Online]. 73(1), pp.96-106. [Accessed on 28th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0033589409001021

23. Matthews, J. A. and Briffa, K. R. 2005. THE ‘LITTLE ICE AGE’: RE-EVALUATION OF AN EVOLVING CONCEPT. Geografiska Annaler: Series A, Physical Geography. [Online]. 87(1), pp.17-36. [Accessed on 10th April 2015]. Available from: http://onlinelibrary.wiley.com/doi/10.1111/j.0435-3676.2005.00242.x/abstract

24. McCarroll, D. M. et al. 2013. A 1200-year multiproxy record of tree growth and summer temperature at the northern pine forest limit of Europe. The Holocene. [Online]. 23(4), pp.471-484. [Accessed on 22nd April 2015]. Available from: http://hol.sagepub.com/content/early/2013/01/18/0959683612467483.abstract

25. McGregor, S. et al. 2010. A unified proxy for ENSO and PDO variability since 1650. Climate of the Past. [Online]. 6(2010), pp.1-17. [Accessed on 16th April 2015]. Available from: http://www.clim-past.net/6/1/2010/cp-6-1-2010.html

26. Miller, G. H. et al. 2012. Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks. Geophysical Research Letters. [Online]. 39(2), [page no. unavailable]. [Accessed on 27th April 2015]. Available from: http://onlinelibrary.wiley.com/wol1/doi/10.1029/2011GL050168/abstract

27. Ruddiman, W. F. et al. eds. 2011. The early-Anthropocene hypothesis. The Holocene. 21(5). [Accessed on 28th April 2015]. Available from: http://dial.academielouvain.be/handle/boreal:94483

28. Schleussner, C. F. and Feulner, G. 2013. A volcanically triggered regime shift in the subpolar North Atlantic Ocean as a possible origin of the Little Ice Age. Climate of the Past. [Online]. 9(Jun. 2013), pp.1321-1330. [Accessed on 18th April 2015]. Available from: http://www.clim-past.net/9/1321/2013/cp-9-1321-2013.html

29. Schleussner, C. F. et al. 2015. [Post-print]. Indications for a North Atlantic ocean circulation regime shift at the onset of the Little Ice Age. Climate Dynamics. [Online]. [Accessed on 14th April 2015]. Available from: http://link.springer.com/article/10.1007/s00382-015-2561-x

30. Schmidt, G. A. et al. 2011. Climate forcing reconstructions for use in PMIP simulations of the last millennium (v1.0). Geosci. Model Dev. [Online]. 4(2011), pp.33-45. [Accessed on 19th April 2015]. Available from: http://pubs.giss.nasa.gov/abs/sc07400c.html

31. Servonnat, J. 2012. Influence of solar variability, CO2 and orbital forcing during the preindustrial part of the last millennium in the IPSLCM4 model. Quaternary Internation. [Online]. 279-280(Nov. 2012), p.442. [Accessed on 24th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S1040618212024883#

32. Smithson, P. et al. 2008. Fundamentals of the Physical Environment. 4th Ed. London: Routledge.33. Stocker, T. F. et al. eds. 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the

Fifth Assessment Report of the Intergovernmental Panel on Climate Change. [Online]. Cambridge University Press: Cambridge. [Accessed on 15th April 2015]. Available from: http://www.ipcc.ch/report/ar5/wg1/

GEG358: Climate of the Last 1,000 Years Page 7

34. Thompson, L. G. et al. 2006. Abrupt tropical climate change: Past and present. PNAS. [Online]. 103(28), pp.10536-10543. [Accessed on 16th April 2015]. Available from: http://www.pnas.org/content/103/28/10536.full

35. Trouet, V. et al. 2009. Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly. Science. [Online]. 324(5923), pp.78-80. [Accessed on 27th April 2015]. Available from: http://www.sciencemag.org/content/324/5923/78

36. Xu, X. and Yi, C. 2014. Little Ice Age on the Tibetan Plateau and its bordering mountains: Evidence from moraine chronologies. Global and Planetary Change. [Online]. 116(2014), pp.41-53. [Accessed on 20th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S092181811400040X#

37. Zeng, Y. et al. 2012. The wet Little Ice Age recorded by sediments in Huguangyan Lake, tropical South China. Quaternary International. [Online]. 263(2012), pp.55-62. [Accessed on 19th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S1040618211007087

38. Zou, Y. and Xi, X. 2014. The possible role of Brazilian promontory in Little Ice Age. Dynamics of Atmospheres and Oceans. [Online]. 67(Sept. 2014), pp.29-38. [Accessed on 29th April 2015]. Available from: http://www.sciencedirect.com/science/article/pii/S0377026514000207

GEG358: Climate of the Last 1,000 Years Page 8