According to François E. Matthes, the little ice age began around 1300 and ended in 1850 at the advent of the Industrial Revolution.

When Sporer, Dalton and Maunder minimum sunspots periods appeared.

From a glaciological point of view, the first LIA advance that reached levels similar to those of the late LIA maxima (17th and 19th century) occurred between the late 13th century and the mid to late 14th century. This advance was triggered by harsh climate conditions starting in the second half of the 13th century, with a temperature drop around 1270 AD in the Alps. This later date could thus be considered as the onset of the LIA. This timing can be evidenced at a number of Northern hemisphere locations (Alaska, Canada, Alps, Russia) based on tree ring dated subfossil finds and also in the Himalayas based on 10Be dating (see e.g. the review by Rowan 2016, The Holocene). The second half of the 13th century can therefore be considered as the onset of the LIA glaciation in the Northern Hemisphere.

Thanks, Melaine! This is very useful. But I also have a question for you. Has the glaciological record changed since the publication of Jean Grove's updated book? Compared with the first edition, the most important change was that Grove was unable to keep up a synchronous dating of the LIA. -- By the way, the same has happened more recently with temperature reconstructions, particularly since we've been able to compare NH with SH multi-proxy reconstructions (Neukom et al. 2014). Neukom et al. (2019) found "no evidence for a globally coherent warm and cold periods over the preindustrial Common Era" (already stated in the title). -- Is the glacial record more coherent than it was back in the early 2000s?

Dear Franz

The LIA is obviously an interesting climate phenomenon but attempts to define the exact onset and termination, particularly from a global (or even hemispheric) perspective, are tricky and could even be seen as a futile exercise. Again from a glaciological perspective (following on from Melaine's reply), regional differences in timing of glacier advances (even in NW Europe/Alps) are such that trying to pinpoint overall start and end dates is arguably not very helpful (tail wagging the dog?). Whilst cooler temperatures clearly play a role, there have also been suggestions that regional increases in (winter) precipitation may have played a considerable role (although the jury is still out on that one...).

John

Hi all,

Franz Mauelshagen Since Grove's work (even the update) a lot has been done about this question. We now have tree ring dates (instead of 14C ages at that time) for a fair amount of glaciers in the northern hemisphere. It shows that 'interstadial forests' that established in the forefields during the Medieval warmth peak (~900-1100 AD) started to be crushed by glaciers in the second part of the 13th century. For sites so far apart and glaciers so different (e.g. 5,000 km2 Bering glacier in Alaska vs few km2 glaciers in the Alps)... quite remarkable. With respect to the Neukom's paper I would say that the glacial record seems to be more coherent for the LIA, as the main peaks of glacier advance are visible at different locations.

John F. Hiemstra The more trees are dated, the more it appears that some synchronous features do emerge. Don't know if it's futile exercise, but quite exciting to see that pattern though... Clearly no other method than dendrochronology can help us with establishing such (inter) hemispheric comparisons in the timing of glacier peaks at sub-decadal resolution.

'Regional differences' : do you talk about differences Alps/Scandinavia ?

Because within the Alps, the LIA timing of glacier advances show no differences that could be linked to other factors than slope/size/response times of the different ice bodies.

Cheers

Melaine

Hi Melaine Le roy and John F. Hiemstra ! Thanks to both of you for participating in this conversation. Dendrochonology has certainly helped the problem of more precise dating. Good point. It may well be that the shift in standards -- from the original glacial record (Matthes started with) to temperature reconstructions — may not have helped the issue of dating the LIA. I don't think it is futile to have a dating discussion, while it may be difficult to come to terms with it.

Melaine Le roy -- Is there a recent summary of the global glacial record? Or is it perhaps time to write one? What do you think?

There are indeed reviews of the global glacial record... Most recent by Solomina et al (2015, 2016). But not yet that integrate tree ring dates for most of the Holocene glacial events...

Hello, thank you for the discussion,

We are curently analysing samples of LIA moraines in Central Asia - Tien Shan - Pamir Alay. We are expecting a local LIA maximum expansion that could be pretty early - 1200-1400 AD, with glacier expansion close to the local LGM... Still a lack of data.

Best.

Thanks, Gabriel Béra ! This sounds very interesting. Please, keep me posted about this.

Hello all!

When studying the relationship between past rockfall occurrence and past climate in the Mont Blanc massif (Western European Alps) I had to solve the "when did the LIA started and finish?" problem, because dates changed depending to the source, and to the method used to study the climate in the past. My conclusion was that there is not an easy answer to the question, and that (at least in the Alps) we cannot propose only one single date. In my 2020's paper (Gallach et al, 2020), published on ESPL I had to give a LIA starting date, so I introduced the following sentence:

"Glacier advance in the Alps during the early LIA may not have been driven by a cooler climate but by an increase in precipitation (Vincent et al.,2005). Matthews and Briffa (2005) distinguished a LIA glacierization (c.1300-1950 CE) associated with a period of glacial advance, from a LIA climate (c.1570-1900 CE) characterized by lower temperatures. The observed drop in rockfall probability after c.1600 CE may result from the cooling effect of the LIA climate".

I hope it helps.

Thanks, Xavi Gallach ! I am surprised to read about a connection between the LIA and rockfall frequency in the Alps. Very interesting! I have looked at a few single cases myself, that is: historical reporting about rockfalls, e.g. the one in Piuro 1618, but never quite considered a connection with the LIA, although it is quite plausible. Heavy rainfall preceded the Piuro case in 1618. -- In any case, we are back in the Alps there. From the point of climatology, wee need a more global perspective in order to define a starting date for the LIA. What do you think?

Franz Mauelshagen, the link between slope processes and glacial activity is quite well-known; this may be coincident, but one could also see a lag between glacial debuttressing (upon glacier retreat) and an increase in slope activity, including rockfalls. I am sure Xavi Gallach can confirm. In a way, this could be considered a 'paraglacial' period, in this case after the LIA maximum.

By the way, Melaine Le roy , I agree that dendroglaciology is promising in this context. In fact, we are just finishing a little paper looking at tree records in southern Norway to try and explain regional LIA and post LIA glacier fluctuations. Watch this space..

John F. Hiemstra Really looking forward to read that !

Thanks for your comment, Franz Mauelshagen.

My team (Deline, Ravanel, etc) is doing a wondeful work trying to understand the link between climate and rockfall occurrence in the Mont Blanc massif. They are doing it on a short timescale (since systematic observation of rockfalls started in 2007), but have done some work at the medium timescale as well (since the end of the LIA); my mission was to study it at a longer timescale, so my PhD work focused on the Holocene (the last 12 kyr).

For the LIA, we had to focus on the effects of the LIA in the Alps, but I totally agree that what is evident in one massif, it may be different in another one (even within the Alps), so more studies are needed.

Yes John F. Hiemstra , the link between glacial retreat and increase in slope processes due to debutressing is evident and well studied in the glacier's ablation zone.

Our work focuses on the glacier accumulation zone (>3000 m a.s.l. in the Mont Blanc massif), where debutressing is almost non-existant because of the lack of glacial erosion: ice density is still too low (at the base of the rock walls we can consider that the first tens of meters of thickness are more "hard snow" than "ice"), and the ice flows towards the center of the valley, not parallel to the valley slopes. On that conditions, permafrost thawing (caused by climate warmings) is considered to be the main cause of the increase in rock falling. On permafrost altitudes, the evolution of rockfall frequency is more related to air temperature changes than to changes in glacial extension or thickness.

Thanks, Xavi Gallach, for the explanation of the >3000 m a.s.l. glacial / rock / climate interaction you + team are looking at.

Hi Franz. I tend to use 1560 or so. Actually I usually describe the LIA as three cold periods, roughly 1560-1620, 1660-1700 and 1800-1830. There were of course earlier cold periods around 1300 and 1450. But these were interspersed with period that weren't particularly cold. The colder periods between the mid-16th and mid-19th centuries were close enough together that they could be considered at 'age', and of course there was a very cold year in Europe in 1740. But I tend to remind students that the 18th century as a whole wasn't particularly cold, although of course colder than today.

Yes, George Adamson , that is also what we tell our students on fieldwork in the Austrian Alps: the 'regional' LIA can be seen to consist of three 'peaks'. Excuse the pun.

Hi George! Thanks for your reply. This looks like a very practical approach, which I like. In my recent course on LIA climate history, which just finished with the end of this semester, I did something similar: I focused on those cold periods and tried to connect as best as possible with global trends in external forcing, mostly solar and volcanic. With regard to the latter, my "timing" is just somewhat diverging from what you suggest, 1590-1645 (to include the Ming-Qing transition), 1660-1700 (same as yours) and 1780-1850 (from the Laki eruption 1783 to the last glacial maximum in Europe). That said, medievalists won't be too happy with leaving out the "Great Transition" or "Crisis of the 14th Century", as some have called it. In the last two decades or so some of them were happy to claim a piece of the LIA for themselves, and with the traditional, European-focused datings questioned, quite understandably so... The problem hasn't been solved yet. But I believe, we need a debate.

I think a paper that draws together these different lines of scientific evidence with the intellectual history of the term would be very valuable (if it doesn't already exist).

George Adamson Again from a glacier perspective (which is at the origin of the term) and also based on moraine stratigraphy, it's all matter of the threshold you choose, but over the last millenium glaciers were never as retracted between the late 13th-mid-19th c .interval, as they were before and after... Despite less cold periods in the 15th and early 16th century as you mentioned. This calls to consider this period as 'homogeneous' enough, with respect to glacier extent, to deserve the term of 'age'.

The three peaks of similar magnitude we observe in glacier reconstruction are 1300-1350, 1600-1650, 1820-1850 (http://www.co2science.org/data/mwp/images/l2_greataletsch.gif). Of interest, last pre-LIA advance of similar magnitude was around 850 AD (not shown on the Aletsch curve)

Some interesting further readings about the LIA :

https://www.historicalclimatology.com/features/the-good-bad-undefined-little-ice-age

And also about the nomenclature of Holocene glacier advance (see especially the section 4 about the LIA)

http://facultyweb.kpu.ca/~jkoch/qsr_2009.pdf

Thanks, José, and apologies for a late response! I am familiar with Grove's article from 2001, while the 2017 article is new to me. That said, I think both these texts have a specific regional focus. The problem I was trying to address with my initial question is, how do we handle the quest for globality? Or do we not care at all about the global dimension of the LIA? The latter, I believe, we cannot afford, because we need to develop some criteria for defining historical epochs of climate variability, some standards that might stand the test of time. At this point of the long debate that started as early as the 1950s we have reached a state of chaos and avoidance of robust definitions. At least, that is my impression.

George, Franz, the core time period of the LIA also had rather warm periods/decades (if we consider temperature as a main factor; e.g. early 18th century) - just like the period between the late 13th-early 16th century. So, I do not think one can really use this distinction as a main reason for excluding the 14th-15th centuries from the LIA. At least I do not think many late medievalist climate historian would agree with George on that... As for both documentary and non-documentary proxies, it depends what criteria we want to use as indicators and especially what is the limitation (and its criteria) we consider as already LIA (and not MWP). It is not an easy question. I think it is the combination of several factors (and not just based on the experience of one-one discipline), i.e. a combination of causativ factors (i.e. external+internal), atmospheric consequences, temperature, precipitation, cryospheric impact and the frequency and intensity of (weather-related) extreme events, but I would also include the societal impact and consequences of and while peak periods can be defined easily, the method of limitation should be defined first. We are talking about a starting point, a boundary, but we do not tell what are the criteria of defining this boundary as such. Until there is no kind-of objective/consensus on the evaluation critera and how we define the boundary, all disciplines and regions will have their own criteria of this limitations. As far as I see that while trying to define the beginning of the LIA, the main question is usually what to do with the late medieval transition period. I go for roughly calling the period between ca. 1300-1550 as LIA transitional period in general, and when one talks about regional/local variations one can mention/distinguish any difference from this dating, keeping in mind that this is a flexible timing anyway. Other possibility is calling it as MWP-LIA transitional period (less good, in my opinion). To start the LIA from 1450 I think the least reasonable option in my opinion - at least from a European/Eurasian point of view.

George, Franz, the core time period of the LIA also had rather warm periods/decades (if we consider temperature as a main factor; e.g. early 18th century) - just like the period between the late 13th-early 16th century. So, I do not think one can really use this distinction as a main reason for excluding the 14th-15th centuries from the LIA. At least I do not think many late medievalist climate historian would agree with George on that... As for both documentary and non-documentary proxies, it depends what criteria we want to use as indicators and especially what is the limitation (and its criteria) we consider as already LIA (and not MWP). It is not an easy question. I think it is the combination of several factors (and not just based on the experience of one-one discipline), i.e. a combination of causativ factors (i.e. external+internal), atmospheric consequences, temperature, precipitation, cryospheric impact and the frequency and intensity of (weather-related) extreme events, but I would also include the societal impact and consequences of and while peak periods can be defined easily, the method of limitation should be defined first. We are talking about a starting point, a boundary, but we do not tell what are the criteria of defining this boundary as such. Until there is no kind-of objective/consensus on the evaluation critera and how we define the boundary, all disciplines and regions will have their own criteria of this limitations. As far as I see that while trying to define the beginning of the LIA, the main question is usually what to do with the late medieval transition period. I go for roughly calling the period between ca. 1300-1550 as LIA transitional period in general, and when one talks about regional/local variations one can mention/distinguish any difference from this dating, keeping in mind that this is a flexible timing anyway. Other possibility is calling it as MWP-LIA transitional period (less good, in my opinion). To start the LIA from 1450 I think the least reasonable option - at least from a European/Eurasian point of view.

All the very good replies in this discussion show that there is no definite answer to the question. It might be beneficial to view the LIA rather as a period of "Little Ice Age Type Events" (LIATE). To my knowledge, that term was introduced more than 20 years ago by Wanner et al. (2000) but it was rarely picked up. The LIATE consists of three main periods with significant European Alpine glacier expansions. The advantage of using glacier expansion for the LIATE definition is that their advance (or shrinking) represents a low-pass-filtered integrated signal for profound climate changes leading to significant anomalies.

However, it is important to acknowledge differences regarding the importance of winter vs. summer season and precipitation vs. temperature changes that define these events. Because seasonal changes or precipitation vs. temperature changes are of different importance spatially and for a given proxy, the heterogeneous picture of LIA or LIATE is rather a key characteristic of that period than a problem of definitions or proxy-uncertainty.

Wanner et al. 2000: https://www.researchgate.net/publication/250190940_Interannual_to_century_scale_climate_variability_in_the_European_Alps

Re: Andrea. Thanks so much! I think all of these are valid and important points: inclusion of late medieval historians, particularly with regard to what you call the "transitional period", c. 1300-1550. I am particularly curious to hear more about your ideas regarding the, in my view, critical point of defining the boundary / starting point of the LIA. Probably, the interdisciplinarity of historical climate studies to this point has made it more difficult to find common ground on the criteria you are asking for, but rather than continue to avoid a discussion we should enter it. How would we do this? Form a committee? Or a society first (or reactivate the society we founded in 2013), then form a committee with interdisciplinary participation? Geologists have developed standards for defining geological periods to include in the Geological Time Series. Obviously, it would make little sense for people involved in historical climate studies to look gor similarly strict criteria. However, I do believe we can learn from geologists how to organise a process of definition -- perhaps one that also keeps us flexible enough to make changes and adapt to the advancement of research. Hence my follow-up question to you: What do you suggest?

Thanks also to you, Frederik, for reminding us of the LIATIMP concept! Maybe it is even quite close to Andrea's idea of combining criteria for definition including impacts on societies. That said, how do we handle the problem that LIATIMP is a concept well-suited to regional impacts, while the definition of a lower boundary / starting point of the LIA requires a global level. This raises the question of regional vs. global definitions? Do we want to do without a global definition and just have a multiplicity of regional LIAs? Or the contrary, no regional definitions, just a global perspective? Or do we want to combine global and regional definitions? -- Personally, I tend towards the latter, because of the lack of homogeneity and perhaps even globality of most of the pre-Global Warming historical periods in the last 2 ky. -- What is your take on this?

Frederik Schenk I agree to promote the use of 'LIATE'. This term has been regularly used since its introduction but mainly in the 'Holocene glacial chronology field' as an alternative to 'glacier pulse' to better highlight the complexity of previous Holocene cold periods - likely as complex as the LIA (e.g Article The 'Little Ice Age': Re-evaluation of an evolving concept

Article Holocene glacier chronologies: Are ‘high-resolution’ global ...

Article Recurrent transitions to Little Ice Age-like climatic regime...

Franz Mauelshagen From a glacier perspective, imprint of the LIA is quite clear globally. It is recognized and dated everywhere. Only the magnitude differs between northern and southern hemisphere (it is one of the (late) Holocene maximum advance in NH, but not as prominent in SH). So, this is a global phenomenon, even if from a climate perspective cold peaks are not exactly synchronous (https://www.nature.com/articles/s41586-019-1401-2). More, I would say that glacier advances over the last 2 kyr are synchronous, at least in the northern hemisphere.

In the northern hemisphere the onset of the LIA killed 400 year-old forest stands that established into glacier forefields thanks to Medieval climate. No trees were able to establish later at these sites at any time during the LIA. See for example this poster (Poster Glacier advances and summer temperature variability at the o...

Thanks, Melaine! Interesting referencces.

Hi Franz, with breakpoint detection. A rather simple way of doing that you can see in my book, with my regional database (Floods and long-term water-level changes in medieval Hungary). Of course, it is just about one region, and I tried to identify breakpoints for general purposes to understand general variability, and only and speicifcally for determining the starting point of LIA.

Franz, for breakpoint detection (for a slightly different purpose, but with a large-scale database), for example, see our paper, also available on researchgate:

Current European flood-rich period exceptional compared with past 500 years. I recommend this because I saw how useful it is at the hydrologists.

Interesting discussion. Since there is not yet a consensus on the causative factor of the LIA, and different regional climate variations are observed over a broad time period proposed for this cold spell (a time interval between mid-13 to mid-19 century), it is not easy to define an exact beginning for the LIA. Among the proposed causatives for the LIA, if just the grand solar minimums were essential, we should see relatively more homogeneous regional climate responses over the LIA, as it is an external forcing that affects the entire Earth's climate. Unlike solar activity, volcanic activity is a more regional phenomenon and can increase the heterogeneity of the regional climate responses over the LIA. That is why some researchers consider the year AD 1257, in which the Samalas volcano erupted, as the beginning of the Ice Age. While the climate variations induced by this volcano are found only in some and not all paleoclimate records of the world. Thus, as climate records around the world show, some regions seem to be more sensitive to total solar irradiance variability and some to volcanic activities. Further, possible chronological problems and errors in paleoclimate archives contribute to increasing heterogeneity in regional climate responses to the global cooling over the LIA. Therefore, defining the beginning and termination of the LIA in the world using proxy data seems very challenging and unlikely. For this reason, I agree with Frederik Schenk about using the term Little Ice Age Type Events (LIATE).

Thanks, Reza, for this valuable comment, which is a strong statement in favour of the LIATE approach. — There are a few things I would like to add: 1) solar forcing during the LIA: this must always be seen in context with other forcing factors. It is simply that the "grand solar minima" during the LIA are not particularly significant in terms of radiative forcing. None of them! It is kind of logical that if the factors that can lead to globally synchronous patterns are weak, they cannot be determinants. -- 2) Volcanic activity: I am not sure about your statement that "volcanic activity is a more regional phenomenon". That depends... Large tropical eruptions do leave a global climate signature, which is indirectly discernible in the ice core record from both poles. During the LIA though, the global effects are limited to 1-3 years. So the predominant factor that limits the effect of volcanism during the LIA seems to be time, although right next there is also regional variability to be seen in the climatic effects of large eruptions.

Our study concerning the fluvial cycles of the Sakarya River at NW Turkey revealed

2 distinct erosional and depositional periods since 2 ka. We determined the initiation of the most recent depositional period to 1219-1284 calCE and related with the hydrological regime change due to LIA. More precise dates are on its way as we have started a new study focusing on the HEX events during this period.

https://www.researchgate.net/publication/330113205_Fluvial_response_to_rising_levels_of_the_Black_Sea_and_to_climate_changes_during_the_Holocene_Luminescence_geochronology_of_the_Sakarya_terraces

https://www.researchgate.net/project/Investigation-of-palaeo-hydrological-extremes-HEX-and-climate-changes-using-fluvial-archives

Thanks a lot! This looks very interesting. This is, however, new territory to me. So I need some more time to look into your research!

We also should look into the historical events as Ottoman empire flourish and reign during the LIA. This is a very nice and interesting discussion, thanks Franz!

Agreed! The question is very interesting, but the answers are probably quite complex. Can you suggest literature on the Ottoman Empire and the LIA? My knowledge is more or less limited to Sam White's book and the debate on it.

I don't think there is a directly related literature. Official Chronicles rarely record natural phenomenon (however Ambrasseys and Finkel successfully built a historical earthquake catalogue). I will keep you updated as we advance.

@ Melanie Le Roy's and Frederik Shenk's contributions add value to the discussion.

The Chinese possess climatological records going back centuries, so this might be a further useful source.

In England, from studying economic geography over the past eight centuries, there may be a correlation between LIAs and the decline and rise of rural agriculture and associated population changes; prior to the Industrial revolution on the 1750s.

It was little late than 1300s. Three sunspots fases of lowest activity were triggers