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Drivers of the Little Ice Age and the onset of the Anthropocene

By Ignacio Jara

The profound and permanent anthropogenic imprint on the planet and the accelerated rate of environmental change has opened a lively debate about establishing a new human-made geological epoch: the Anthropocene. Widely covered in by the public media, the Anthropocene Working Group has officially recognized that human impacts on the environment are of sufficient scale to be considered as a new geological time and agreed that such time started at AD 1950 with the global-wide spike of radionuclides resulting from atmospheric nuclear bomb testing.

blog-15-figure-1-jpgFigure 1. The beginning of the Anthropocene at AD 1950 as proposed by the Anthropocene Working group. Figure modified from Waters et al (2016)6. For more information regarding the Anthropocene Working Group visit:

Significantly for Quaternary scientists, recent paleoclimate investigations proved to be important in defining the onset of the Anthropocene epoch. At the end, these investigation provided evidence to refute proposed pre-instrumental dates as the starting point for this new epoch, helping to tip the balance towards AD 1950 as the best candidate. Early last year, Lewis and Maslim (2015) reviewed the history behind the concept of an Anthropocene epoch in the Journal Nature1. Considering the formal criterion for defining a geological epoch; that is, the existence of a global-scale signature in stratigraphic material, the authors proposed two specific dates or “golden spikes” for the initiation of the Anthropocene: AD 1610, associated with the collision of the old and new worlds; and AD 1964, associated with the great acceleration of industrial production.

In favor of AD 1610, Lewis and Maslim (2015) listed a series of evidence for global environmental change at around that time, including minimal atmospheric CO2 concentrations in Antarctic ice cores and the presence of exotic fossils markers in sediment sections as new crops and animals started to be exchange between continents. Furthermore, based on a series of articles published between 2008 and 2011, the authors suggested that the drop in atmospheric CO2 recorded in Antarctic ice cores between AD 1580 and 1650 (Figure 2) was caused by an increase in the terrestrial CO2 uptake resulting from a large-scale forest expansion in previously cultivated lands across the Americas. This reforestation followed the dramatic decline of indigenous populations due to socio-political upheaval, famine and disease, brought about by European colonization and exploitation. In other words, Lewis and Maslim (2015) suggested that human activities were behind the CO2 and temperature decline during the coldest part of the Little Ice Age.

A human-driven cooling during Little Ice Age turned out to have wider implications because recent studies have shown that changes in atmospheric CO2 over the last millennium were sourced in the terrestrial biosphere and not in the oceans2. This evidence further opened the enticing possibility that major events in human history over the last 1,000 years could have produced minor -albeit global- variations in atmospheric carbon dioxide3. All these events occurred several centuries before what it is generally accepted as the onset of global anthropogenic impacts, and certainly well before AD 1950.

However, it has long been noted that the net flux of CO2 between the atmosphere and the terrestrial ecosystem is not only controlled by the rate of vegetation uptake (termed primary production), but also by the emissions of CO2 from animals, fungi and some microorganisms (termed terrestrial respiration). Thus, any drop in Atmospheric CO2 could be caused either by an increase in primary production or by a shutdown of the terrestrial respiration.

Bearing these principles in mind, an article published in Nature Geosciences this month4 challenged the suggestion of a human-induced drop in CO2 during the Little Ice Age. Interestingly, this new study did not focus directly in carbon dioxide but on Carbonyl Sulfide (CAS), an organic molecule also present naturally in the atmosphere. Like CO2, CAS is removed from the atmosphere by the terrestrial vegetation. Yet, unlike CO2, CAS is permanently incorporated into plant metabolism and not emitted back to the atmosphere. In other words, atmospheric CAS is a direct measurement of the primary plant production. Rubino et al (2016)4 shows that low concentrations of CO2 during the Little Ice Age are contrasted by an increase in the concentrations of CAS (Figure 2). These opposite changes are a strong indication that a reduction –not an increase- in plant uptake occurred during the Little Ice Age. A CO2 decrease induced by large-scale forest regeneration is therefore unlikely because vegetation re-growth would have dropped CO2 and CAS simultaneously. Instead, the results are consistent by a proportionally larger decrease in the terrestrial respiration (which reduce CO2 emission but does not affect CAS concentration).

The new study of Rubino et al (2016) points to the fact that cooling in the earth system rather than human activities were behind the CO2 decline during the Little Ice Age. In other words, this new study provides evidence against the proposition of AD 1610 or any previous date as the “golden spike” for the beginning of the Anthropocene, adding indirect support to AD 1950 as the best date for the beginning our current epoch.


Figure 2. Upper: atmospheric CO2 concentration recorded in during the little Ice Age in the ice core record of Law Dome, Antarctica4. Lower: Carbonyl Sulfide (CAS) concentration anomaly relative to pre-industrial values4. Figure modified from Rubino et al (2016)4

All these recent studies highlight how important paleoclimatic and paleoecological research is to our overall understanding of the current trends of the earth systems. As showed in a recently published revision of the industrial-era warming this month5, the entire instrumental time series are immersed into a long-term warming ramp, making instrumental data too short to fully investigate the drivers and structure of the current warming trend.

Formal definitions do not change tangible anthropogenic impacts; neither do they change future scenarios of environmental change, and therefore a debate over when did precisely the Anthropocene began may not be of any significant relevance for the general public. However, the footprints of human activities are now undeniably global and certainly will be detectable for thousands of years to come. Establishing a starting date for the Anthropocene not only has scientific relevance but also social and political implications for the way we understand our relationship to the environments around us – which we invariably depend upon. For example, agreeing that the Anthropocene starting point occurred earlier than the 19th industrial revolution would have effectively dismissed the accelerated modern industrial scale of greenhouse gas emissions since AD 1950, and their associated global warming impacts. The proposed definition of the Anthropocene will need to be ultimately recognized by the International Commission on Stratigraphy (ICS), a process that might be argued over several years.


  1. Lewis, Simon L., and Mark A. Maslin. “Defining the anthropocene.” Nature 519.7542 (2015): 171-180.
  2. Bauska, Thomas K., et al. “Links between atmospheric carbon dioxide, the land carbon reservoir and climate over the past millennium.” Nature Geoscience 8.5 (2015): 383-387.
  3. Kaplan, Jed O. “Holocene carbon cycle: Climate or humans?.” Nature Geoscience 8.5 (2015): 335-336.
  4. Rubino, M., et al. “Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake.” Nature Geoscience 9.9 (2016): 691-694.
  5. Abram, Nerilie J., et al. “Early onset of industrial-era warming across the oceans and continents.” Nature 536.7617 (2016): 411-418.
  6. Waters, Colin N., et al. “The Anthropocene is functionally and stratigraphically distinct from the Holocene.” Science 351.6269 (2016).

AQUA Conference 2016 update

Aqua 2016 in Auckland update: 9 session proposals being decided on, abstract and registration forms will be sent out shortly.

Keep 5-9 December free, and the following week if you plan on going on one of the extended field trips!

Next AQUA conference: “Quaternary in the City of Sails”, Auckland, NZ, 5-9 December 2016

The next AQUA biennial conference will be held in Auckland New Zealand, from the 5-9 December 2016!


Topic sessions will be held on the 5-6 & 8-9 December, with calls for session themes and registration details to be sent out in February 2016.

At this stage, two mid-conference field trips will be held on the 7th December, with options to head to the buried OIS7 forest on the tidal flats and temperate rainforest walk or Rangitoto shield volcano excursion and Motutapu Island in the Hauraki Gulf.

A Conference dinner will be held on the 8th December (venue being discussed), with a Quiz nite and BBQ on the 9th December.

Two post conference field trip options (6 days each) are currently being planned, and will be run according to level of interest.

The post conference field trips would depart Auckland 10 December and end 15 December 2016.

Trip 1: The Quaternary of the winterless North (a loop around the sub-tropical Northland/Far North region starting and ending in Auckland; Three nights in Bay of Islands, two nights at Kai Iwi Lakes). The trip will focus on ancient kauri, changes in ecology as seen in pollen records over interglacial-glacial scales, and coastal barrier evolution from OIS5-present.

Trip 2: Quaternary volcanism and environmental change

(excursion south from Auckland through the Waikato, the central North Island and ending in Wellington; Three nights in Taupo, two nights in Palmerston North). There will be a focus on Quaternary volcanism, tectonism, sedimentation, and climate. Stops will include the Taupo and Rotorua volcanic centres, glaciation in the Tongariro National Park, Napier/Hawkes Bay and the Kapiti- Horowhenua / Wanganui Basin sequences.

A PDF flyer is available here to begin advertising within your organisations. More information will be published on the AQUA website and Facebook as it becomes available.

Travel grants available for Australian and New Zealand ECR Geoscientists

The Academy, together with the Australian Geoscience Council, has opened a call for applications for a travel grant scheme for Australian and New Zealand ECR Geoscientists. This is a new fund that offers annual grants of up to $5000 for career-enhancing travel, established with the proceeds of the 2012 Brisbane IGC.

For conditions and criteria head to the Australian Geoscience Council Website.

Applications close on 31 October 2015 for travel beginning in 2016.

The advent of the Anthropocene in Australasia

We’d love your opinion on this article!! Please head to and choose your preferred definition of “The Anthropocene”.
If you choose the option of “other” then please email with your other.Votes close at the end of September.
First published in Quaternary Australasia, July 2015. – PDF version
Helen C. Bostock1, David J. Lowe2, Richard Gillespie3, Rebecca Priestley4, Rewi M. Newnham5, Scott D. Mooney6


As early as the late 19th Century, several scientists had suggested that humans were starting to influence the physical environment of planet Earth (e.g. Marsh, 1864; Stoppani, 1873; Arrhenius, 1896; Chamberlain, 1897). This idea was resurrected and expanded in 2000 by Paul Crutzen, a Nobel Prize-winning chemist, and the late Eugene Stoermer, a professor of biology specialising in diatoms, who suggested that we had left the Holocene and entered the “Anthropocene” (Crutzen and Stoermer, 2000). As summarised by Steffen et al. (2011) and Wolfe et al. (2013), these iconoclastic scientists were referring to the Anthropocene as the interval of demonstrable human alteration of global biogeochemical cycles, beginning subtly in the late 18th Century following James Watt’s invention of the coal-fired steam engine, and accelerating markedly in the mid-20th Century (termed “The Great Acceleration”). Thus Crutzen and Stoermer (2000) argued that the Anthropocene should be an epoch, and for a starting date at the beginning of the Industrial Revolution (Monastersky, 2015).

The term Anthropocene is now regularly used in the geological/environmental literature, appearing in nearly 200 peer-reviewed articles in 2012, and three new journals have been launched over the last few years specifically focussed on this topic, namely The Anthropocene Review, Anthropocene, and Elementa: Science of the Anthropocene. In 2014, the Geological Society, London, published A Stratigraphical Basis for the Anthropocene (Waters et al., 2014), a 321-page volume devoted to the subject. The problem is that the Anthropocene has not yet been formally defined and different disciplines (and even scientists within the same discipline) have different viewpoints as to when the Anthropocene began, if at all (Table 1). In addition, most perspectives on this issue are derived from the Northern Hemisphere, although Brown et al. (2013) and Ellis et al. (2013) and some others have taken a more global viewpoint. Continue reading

AQUA t-shirts for sale!


Super stylish AQUA t-shirts are now available to purchase!

T-shirts are light blue and feature an AQUA logo on the front, and a quaternary-inspired design by Emily Field on the back.

T-shirts are only $39, including postage within Australia and New Zealand!

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Currently, we only have sizes L, XL, and 2XL available, however smaller sizes will be available to purchase soon.


If you would like to order a t-shirt, or would like to put in a request for a smaller size, please contact Scott Mooney ( to double check sizing availability. You will then be given AQUA’s bank details to pay via direct deposit.

Congratulations to Matt Ryan

PhD student Matt Ryan from Victoria University in Wellington, NZ was awarded a Student Poster award at the recent INQUA congress in Japan. With many hundreds of posters presented at the conference, this is an excellent achievement for Matt.



Blog 15: Two weeks in Patagonia – A fieldwork diary

By Ignacio Jara

26 January

It is somewhat symbolic that the initial stop of my field season in Chile is the very same place where, one year ago, Brent Alloway and I finished Victoria University, Wellington, School of Geography, Earth and Environmental Sciences first international field trip with a traditional Patagonian asado (spit barbeque)… but this summer the mission is different.

Last night Brent showed me satellite images depicting what looks like an unrecognized volcanic dome right next to Chaitén volcano. Based on the geochemical analysis of ash layers found in road cuts around Chaitén, Brent is convinced that this previously unrecognized dome has erupted at least once in the last millennium. The plan is try to get to the dome, have a look and take some rock samples to analyze and compare. Looking at the maps, we agreed that it will be a difficult objective since the area is covered by dense temperate rain-forest without any visible tracks. But we are optimistic.

27 January

For now, my field trip has been about planning and enjoying the hospitality of Brent which includes good food and of course the marvelous Chilean Carménère wines. However, tonight this enjoy-without-working scenario will change when we meet a fieldwork team from Universidad de Chile to embark on the Don Baldo ferry for an overnight trip that will take us down south to the Chaitén province, the northern gate of Patagonia.

Photo 1. “The arrival to Chaitén could not have been more beautiful”

Photo 1. “The arrival to Chaitén could not have been more beautiful”

28 January

Our arrival to Chaitén early this morning couldn’t have been more beautiful (photo 1). From the Ferry’s deck the greenness of the forest, the calm of the waters and the mountains on the background reminded me the Marlborough Sounds after crossing the Cook Strait. While the ferry slowly made its final way trough a narrow channel before arriving at the small landing platform, greeted by a couple of tourists waiting on the shore to take the same ferry back to mainland Chile. A calm tranquil morning in the small town of Chaitén.

29 January

With Brent and two other students we spent the whole day trekking up the Chaitén valley trying to reach the newly discovered lava dome. The devastation in Chaiten township and up the valley produced by the ashes and pyroclastic flow during the 2008 eruption is simply overwhelming. Tramping around burned trunks, strong smelling sulfide orange-coloured streams and being completely surrounded by tons of white ashes evokes a special feel of devastation and remind us that nature is both powerful and deadly (Photo 2).

At the end of the day we were unable to reach the dome. It was just too difficult to get to. We traversed the river valley as much as we could but we were impeded by a massive waterfall which prevented us from progressing further. Obviously we are bit disappointed and frustrated but trying to get around the waterfall through the impenetrable forest and vertical terrain would undoubtedly have been too risky.

Photo 2 “Tramping around tons of white ashes from the 2008 eruption evoked a special feel of devastation and remind us that nature is both powerful and deadly”. Prof. Brent Alloway, the steaming Volcán Chaitén and the devastated Chaitén valley with Volcán Corcovado on the background.

Photo 2 “Tramping around tons of white ashes from the 2008 eruption evoked a special feel of devastation and remind us that nature is both powerful and deadly”. Prof. Brent Alloway, the steaming Volcán Chaitén and the devastated Chaitén valley with Volcán Corcovado on the background.

31 January

Despite our failure in trying to reach the volcano, Brent still wants to have a closer look. He has contacted a local pilot to fly a small 1969 Piper Cherokee monoplane over the crater. A bit scary considering the size of the airplane was not bigger than Mini Cooper with wings (Photo 3)!

Luckily, we enjoyed a stunning sunny day without any of those gusty winds that I usually experience in Wellington. Only one of those winds would have made the monoplane shake like a scared dog (Photo 3)!

Leaving all those concerns aside, the views were simply fantastic! The mountains, the endless coastline and the Chaitén volcano with all of its ash from the 2008 eruption mantling the surrounding area, created a wonderful visual experience. But more importantly, the views from the aircraft confirm that there is now a new satellite dome just a stone throw from Chaitén Volcano.

Photo 3 “We enjoyed a stunning sunny day flying the tiny 1969 Piper Cherokee monoplane, nothing compared with those gusty winds usually experienced in Wellington”. The Patagonian coastline, the Volcán Chaitén crater and the narrator posing with the 1969 Monoplane.

Photo 3 “We enjoyed a stunning sunny day flying the tiny 1969 Piper Cherokee monoplane, nothing compared with those gusty winds usually experienced in Wellington”. The Patagonian coastline, the Volcán Chaitén crater and the narrator posing with the 1969 Monoplane.

2 February

After our flying adventure we have now rejoined the group from Universidad de Chile in Futaleufú, a small town 80 kilometer inland from Chaitén. Over the next few days we will be on a raft coring two small lakes in the surroundings. Despite their small size, the access to the lakes is always a main issue and that wasn’t an exception during this fieldtrip. It turned out that one of the lakes was actually on the top of a small hill and there wasn’t any nearby road allowing for vehicles to get the coring platform to the lake edge. We therefore needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track. …..the Patagonian way (photo 4)!

Photo 4. “We needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track.  ...the Patagonian way”. The narrator in the middle of a coring day, the bow yoke with our field equipment and our second lake next to Futaleufú township.

Photo 4. “We needed the assistance of a bow yoke with two old oxen to bring all our equipment up to a steep farm track. …the Patagonian way”. The narrator in the middle of a coring day, the bow yoke with our field equipment and our second lake next to Futaleufú township.

5 February

After 3 days of pretty intense coring work are we now finished with our first lake and moving on to another lake, just on the outskirts of Futaleufú town (Photo 4). Very hot, dry, sunny days working on the raft and as a result I got a little sunburnt. I am tired and I miss all the comforts of the city, but I am also very excited with our progress as we retrieved a lot of core containing sediments that will be the final part of my PhD thesis. There is an impressive variety of layers preserved in the lake sediments, including countless volcanic ash layers (to keep Brent happy!), wood fragments, glacial silts and nasty black charcoal layers inter-fingered. So much work to do reconstruction the history of the lake!

8 February

Another three days working in our second lake and now we have even more sediment to analyse (I am not that sure how lucky I am now!) Our field trip is coming to an end. Tomorrow we will drive back to Chaitén and then board the overnight ferry that will take us back to mainland Chile. In Santiago, I will spend the next two months sampling and processing the sediment we got in the field.

For me this has been a great time to reconnect with the people I worked with during my Masters. Hard work? For sure. Rewarding? Absolutely! Now I must get to work in the lab – lots of samples to process, pollen to count and a PhD to finish!

Ignacio wants to thanks Dr. Patricio Moreno and all the members of Laboratorio de Palinologia Quaternaria at Universidad de Chile for all their support during the field and laboratory work described in the column above.