The Bronze Age climate and environment of Britain

Abstract

Over the last twenty years there have been tremendous advances in our knowledge of climate change in later British prehistory from a wide variety of proxy-climate sources. This chapter will summarise our present understanding for the period 2000-500 BC and highlight the areas in which further research is required. A secondary aim is to review how much we can infer from these proxy-climate records concerning the wider environment, including the day-today environment of Bronze Age peoples and the stresses imposed upon their societies. This area is far more subjective but lies at the heart of serious, i.e. non-superficial, attempts to relate aspects of change in Bronze Age society to environmental change.

Full text

A
Bronze Age Review
The international journal of research into the archaeology
of the British and European Bronze Age
Volume 1, November 2008

BROWN BRONZE AGE REVIEW VOL. 1 NOVEMBER 2008
Creating a research agenda for the Bronze Age in Britain
For the first volume of the Bronze Age Review, the editor invited senior scholars to draw on
their experience and expertise and write on what they would like to see happening in Bronze
Age research in Britain in the future. They were asked to look as broadly as they can and
explore issues and areas of study that they feel are currently missing or underdeveloped. The
aim is to provide a period of open consultation until 31 January 2009 with suggestions,
comments and proposed new chapters to the editor who can be contacted at
broberts@thebritishmuseum.ac.uk. The authors will subsequently revise their articles for
inclusion in a volume published by the British Museum Press.
Contents
1-6 A canon for the Bronze Age? Anna Brindley
7-22 The Bronze Age climate and environment of Britain Tony Brown
23-33 Prospects and potential in the archaeology of Bronze
Age Britain Joanna Brück
34-47 The agenda gap? Approaches to the Bronze Age in
current research frameworks Jonathan Last
48-56 Information, interaction and society Ben Roberts
57-78 Towards a fuller, more nuanced narrative of
Chalcolithic and Early Bronze Age Britain 2500–1500 BC
Alison Sheridan
79-96 Bronze Age pottery and settlements in southern
England Ann Woodward

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The Bronze Age climate and environment of
Britain
Tony Brown
(University of Southampton)
Abstract
Over the last twenty years there have been tremendous advances in our knowledge of climate
change in later British prehistory from a wide variety of proxy-climate sources. This chapter
will summarise our present understanding for the period 2000-500 BC and highlight the areas
in which further research is required. A secondary aim is to review how much we can infer
from these proxy-climate records concerning the wider environment, including the day-to-
day environment of Bronze Age peoples and the stresses imposed upon their societies. This
area is far more subjective but lies at the heart of serious, i.e. non-superficial, attempts to
relate aspects of change in Bronze Age society to environmental change.
Bronze Age Proxy-climate records
This period of the Holocene c. 4000-2500 BP has long been regarded as a period of decreased
average temperatures following after the Holocene maximum and before the Roman-early
Medieval warm periods (Lamb et. al., 1966; Godwin, 1975; Houghton et al., 1996). The most
reliable, and therefore most used, terrestrial proxy-climate sources of data for the Bronze Age
of Britain are derived from raised (or ombrogenous) mires. This work has its origins in the
climatic stratigraphy of mires used to formulate the Blytt-Sernander climatic scheme (Sub-
Boreal to Sub-Atlantic covering the Neolithic and Bronze Age) and in modern times from the
overturning of the autogenic theory of bog-regeneration by Barber in 1981. Barber’s work
produced the first bog surface wetness (BSW) curve for the UK from Bolton Fell Moss in
Cumbria (Figure 1a) and has provided the stimulace for many studies of increasingly higher
temporal resolution which culminated in the recently completed ACCROTELM Project
(Charman, et al., 2007) and ISOMAP-UK Project (part of the NERC Rapid Programme). The
method of using macrofossils of Sphagnum spp. and peat humification has been applied in
environmental transects across Europe (Barber et al., 2000) and combined with other proxies
such as pollen, Testate amoebae (Hendon and Charman, 1997; Charman et al., 1999) and
most recently ∂18O and ∂D from plant macrofossils (Brenninkmeijer et al., 1982; Barber, 2007;
Daley in prep.). Testate amoebae have proved to be very valuable as they have allowed a
complimentary method of calibrating the fluctuations in the water table estimated from plant
macrofossils and humification (Hendon and Charman, 2004). Temporal resolution, has been
improved by both wiggle-matching and the use of in-situ tephra deposits (Mauquoy et al.,
2004; Plunkett, 2006) and at the best sites a decadal resolution is claimed (Mauquoy et al., in
press) which is as fine, if not finer, than the dating of most archaeological sites within the
Bronze Age. One of the reasons for placing a considerable amount of faith in these climatic
reconstructions is the correlation between them and a vast array of other proxies, including
written records from the Post Roman period. Well known historical climatic ‘events’ often
derived from soft-data such as the Late Medieval Climatic deterioration (or Crusader Cold
Period cf. Lamb, 1977), the Medieval Warm Period and the Little Ice Age, are also clearly

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shown in the mire-derived data sets (Barber, 1981). For the prehistoric period BSW data has
been correlated with a variety of both global and regional proxies including the European lake
level record (Magny, 2004), ice drift records from the North Atlantic (Bond et al., 2001) and
ocean core proxies for the North Atlantic Deep Water circulation (Chapman and Shackleton,
2000). In terms of the causal mechanism most interest has focussed around solar forcing with
comparison of BSW with the 14C relative production rate/solar activity including solar events
such as the Homeric minimum (850-550 cal BC) which has been correlated with a major wet
phase across North West Europe (van Geel et al., 1996; Mauquoy et al., 2004). Mauquoy et al.
(2008) have shown that at two sites, one in northern England the other in Denmark, BSW
appears to lag changes in 14C production in the historical period by between 0 and 50 years.
However, solar activity does not appear to explain the entire record and it is likely that it has
been moderated by other factors, particularly ocean circulation especially in the west of
Britain, Scotland and Ireland. Most studies have shown a statistical periodicity to climate
variability (Aaby, 1976; Langdon et al., 2003; Blundell and Barber, 2005; Swindles et al., 2007)
with values of; 200 years (Chambers and Blackford, 2001; Plunkett, 2006), 265 and 373-423
years (Swindles et al., 2007), 550 years (Hughes et al., 2000), 560 years (Blundell and Barber,
2005), 580 years (Swindles et al., 2007); 600 years (Hughes et al., 2000) and 1100 years
(Langdon et al., 2003). These can be compared with periodicities in other proxy data such as
210, 400, 512 and 550, 1000 and 1600 years in tree rings and ocean core-data (Chapman and
Shackleton, 2000; Raspopov et al., 2001).
Taking the major studies together (Figure 1a and 1b) it can be seen that there is a large
degree of agreement in relation to the major trends. Indeed the noise which appears to be
fairly equally if not normally, distributed over time is typical of that which might be expected
due to differences in dating, different site sensitivity, and in regional variation. The trend is
relatively clear. There is stability or a slight reduction in BSW from c. 2000 BC to 1800-1500
BC as reconstructed from multiple proxies in northern Scotland (Anderson et al., 1998). After
which there is an increase in BSW, or rise in bog water tables, which persists for 200-300
years and ends
c
. 1200 BC when bogs go into a dry phase. This dry phase is short lived and at
c.
800-750 BC there is an increase in BSW which is seen right across Europe and is probably
the most profound climatic shift of the Holocene prior to the Little Ice Age (the so-called 2.7
Ka event; Van Geel, 1996; Yeloff et al., 2007). Most records show this phase lasting for
between 200-400 years before a return to drier conditions before a wet shift again
c
. 400 BC.
The Bronze Age is preceded by the so-called 4.2 Ka event which has been identified from the
ocean and ice cores (Bond et al., 1997), from a severe drought event in eastern Africa and
increased sand movement in coastal dune systems along the eastern Atlantic coast
(Gilbertson et al., 1999; Knight and Burningham, in press). In the UK it has been identified as a
cool/wet phase from BSW record in a number of sites in Northern England (Chiverrell, 2001;
Charman et al., 2006 and Barber and Langdon, 2007) and Scotland (Barber and Langdon,
2005) and from combined BSW and chironomid data from Talkin Tarn (Barber and Langdon,
2007).

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(a)
(b)
Figure. 1a-b. Climate proxy records for northern England and Ireland. (a) Climatic records derived from
the Detrended Correspondence Analysis (DCA) scores of macrofossil data from cores from Bolton Fell
Moss, northern England, Mongan Bog, central Ireland, and Abbeyknockmoy Bog, western Ireland,
plotted against age. Peaks reflect dry conditions, troughs reflect wetter conditions. Dashed lines pick
out changes which are mainly at two of the sites (ca. 4400, 4000, 1750, 1400 and 1000 cal. BP) and
changes which are coincident at all three sites (ca. 3200, 2750, 2250, and 700 cal. BP). Shaded zones
emphasize two major phases of change, which are apparent in many other records, around 4400–4000
and 2750–2250 cal. BP. From Barber et al., 2003, with permission.(b) The composite record of water
table variability from northern Britain (top) compared with the lake level records of Magny (2004) as
dark blue shaded bars. The water table record shows original data points (yellow) and 100-year
moving average (thick red line). Redrawn with permission from Charman et al. (2006).
This chronology will probably be further refined in the next few years with the increasing use
of tephra layers but the broad pattern is unlikely to change. Far more of a problem is what
these shifts mean in climatic terms and how these bog-proxies relate to other hydroclimatic
variables. The water table of a raised mire is in theory simply the result of cumulative
moisture deficit (precipitation-evapotranspiration) with perhaps a small marginal loss to the
surrounding area due to throughflow, at least prior to extensive bog drainage. Theoretically at

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least either changes in precipitation or evapotranspiration could cause a bog water table to
vary over the period of moisture deficit – the summer. Under present climatic conditions in
the UK bog water tables during the summer are probably most sensitive to precipitation
(Charman, 2007). However, it is probably not possible to entirely deconvolve the effect of
temperature and precipitation from the BSW palaeo-series, although it maybe possible in
contemporary hydrological studies. As Barber (2007) has emphasised - the BSW proxy is a
composite measure of past climate. There are two principle reasons for this. Firstly a change
to a more continental climatic regime is likely to alter the relative importance of precipitation
and temperature, and secondly even for the present oceanic climate of the British Isles there
is a correlation between temperature and precipitation at least at the mean annual scale
(Barber, 2007). Even for the site studied by Charman (2007) the driest years on record such as
1975 and 1976 were also two of the hottest. The reason is that anticyclonic conditions and
high pressure cells draw in relatively dry air from Europe and Siberia, although augmented by
convectional precipitation, whereas cyclonic conditions draw in warm wet air from the
Atlantic. At the annual scale the linking factor is the correlation between summer
precipitation and the winter NAO index (Kettlewell et al., 2003) which is also correlated
strongly with changes in mean annual temperature. This climatic coupling with North Atlantic
sea surface temperatures is strong enough to be used in forecasting by the Meteorological
Office (http://www.metoffice.gov.uk/research/seasonal/regional/nao/index.html); Rodwell et
al., 1999 and Rodwell and Folland, 2002). This was pointed out by Barber et al., (1994) and is
why there is a strong correspondence between the record of bogs like Bolton Fell Moss and
both the summer wetness and winter severity indices of Lamb (1977), the NAO, and on the
longer term the Thermohaline Circulation (THC) as discussed by Barber (2007). The inclusion
of summer temperatures as one of the drivers of BSW is confirmed by chironomid data as
reported for Talkin Tarn by Barber and Langdon (2007). Given these complications it is best to
regard the BSW record as principally a response to north Atlantic sea surface temperatures
mediated through prevailing synoptic regimes and the resultant summer water deficit and
perhaps more attention should be paid to the dry shifts which may also have significant
archaeological implications as discussed later in this article.
Two other palaeoclimatic techniques which are probably more closely related to variations in
precipitation and are applicable to the Bronze Age in the UK are speleothem luminescence
and palaeohydrological interpretation of river valley sediments. Long-term variations in
speleothem luminescence intensity can be related to climate and especially precipitation
(Baker et al., 1999) although it is also sensitive to local vegetation change (Baldini et al.,
2005). Using data from both mires and speleothems from Sutherland in northwest Scotland
Charman et al. (2001) have shown a correlation between peat humification and speleothem
luminescence emission wavelength and ice accumulation from GISP2. The use of speleothems
has further potential to produce regional data in areas lacking ombrotrophic mires such as
southwest England and the Mendip Hills. At present there is an examination of both the UK
and Irish speleothem record to detect and measure the duration of the 2.7 Ka event as
discussed above (McDermott in press). A geologically related method - stable isotopes from
travertine/tufa deposits may also have potential in southern England (Davies, et al., 2006).
The second technique is to use the proxy record of river discharge from river valley sediments.
Unfortunately in the UK and Ireland hydrological conditions don’t exist to allow the
estimation of flood magnitude series from slack-water sediments which record individual
flood events. Instead event series are inferred from river activity in alluvial reaches based on
the frequency of 14C dates from various sedimentary contexts as illustrated in Brown (1997, p
53) and Lewin et al., (2005). In practice this has involved the analyses of the probability
density function of alluvial 14C dates after calibration effects have been removed (Macklin et
al., 2006). Macklin and co-workers have improved the technique and been able to sub-divide
the series by UK regions (Johnstone et al., 2006). It is still not a quantitative measure of
variations in precipitation, or even catchment discharge, but it is argued that it is a qualitative

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measure of the changing frequency of moderate and large floods. The pattern for the Bronze
Age is again relatively clear with a rise in alluvial activity from
c
. 4300 to 4000 BP then a
sharp fall
c
. 3500 and a period of lower alluviation until a pronounced peak around 2700-
2800 BP lasting under 100 years and then a fall - but to levels higher than before (Figure 2).
Figure. 2 The probability density function for upland and lowland river catchments in Great Britain
during the Bronze Age. Adapted from Johnstone et al. (2006).
Using the aggregate data (all dated units) this peak is the highest in the entire Holocene
alluvial record with the exception
c.
600-700 BP (Lewin et al., 2006). Its co-incidence with the
dramatic wet shift seen in mires at
c.
2600-2700 BP is strong and it suggests that it is
primarily the result of increased river discharges and soil erosion caused by a solar-forced
climatic event under boundary conditions of a large proportion of the landscape under arable
cultivation. Indeed the climatic instability of the later Bronze Age is revealed in many studies
of floodplain alluviation, such as the Thames (Needham and Longley, 1980), the Trent (Brown
et al., 2007; Howard et al., in press) and in tributaries of the Severn (Brown, 1988). The lack of
this peak in the database record for southwest England is almost certainly due to a lack of
previous studies and recent work in the Exe Basin has confirmed hydrological fluctuations in
this period (Bennett et al. in press; Brown et al. in prep).

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All British
Rivers
Upland rivers Lowland rivers Climatic deteriorations
from mires (Hughes et
al., 2000)
4030
4000
3830
3580
3540
3510
3500
3150
2900
2800
2730 2730
2550 2560
2600
Table 1. Episodes of major flooding in Great Britain and mire wet shifts from Macklin et al. 2005 and
Hughes et al. 2000. All dates in rounded years cal BP.
From the combination of these methods it is possible to postulate climatic phases with
dominant or stable synoptic conditions during the Bronze Age, which would have resulted in
alternations of periods with higher frequency of wet years to periods with a higher frequency
of dry years or summer droughts (Table 2).
Approximate
Period BC
Bog Record (BSW) Alluvial Record
2300-2000 cold/wet (4.2 Ka
event)
high activity
2000-
1800/1500
reduction in BSW
1800/1500-
1200
increase in BSW
1200-850 warm/dry phase
low activity
850-650/550 cold/wet phase (2.6
Ka event)
sharp rise in activity
650/550-400 reduction in BSW fall in activity but to levels higher then previous
low activity periods
400-100 cold/wet phase increase in activity
Table 2. A summary of Bronze Age (shaded) climatic trends derived from bogs and the alluvial record
for Britain from sources references in the text.
Additionally taken together the mire-derived and the alluvial data suggests that there have
been some major climatic events including severe storms and prolonged serious droughts.
Whatever the climatic cause, the wet periods such as the late Bronze Age, must have
contained large floods which would have caused localised damage and disrupted everyday life
especially along floodplains. There is also evidence from both stratigraphical studies of small
catchments (Shotton, 1978; Brown and Barber, 1985; Smith et al., 2005; Brown in prep.) and
14C inventory studies that these storms were responsible for an acceleration of soil erosion
from arable fields which could have imposed stresses via temporary reductions in agricultural
productivity. What is also clear from the alluvial 14C data is the regional variation in

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alluviation particularly between upland glaciated-catchments and lowland unglaciated-
catchments (Johnstone et al., 2006, and Fig. 2). Given the lower stream powers of the lowland
catchments this cannot be an autogenic effect instead it is due to greater supply of sediment
to stream channels almost certainly due to arable agriculture from the late Neolithic onwards.
Whilst climate supplied the ‘power’ it was Bronze Age agriculture that supplied the sediment.
Recent work on ombrotrophic mires has suggested that factors other than climate may have
influenced their ecology during the Holocene. Studies by McClymont et al. (in press) and
Hughes et al. (in press) suggest that the decline in
Sphagnum austinii
at Butterburn Flow is
associated with changes in nutrient status in the bog and could be the result of pollution
particularly of Ti and Si. If pollution events from agricultural, mining or metallurgical sources
are associated with shifts in the balance of the ombrotrophic communtities this could have
implications for the use of peat bog climate proxies at the time of major changes in land use
(Hughes pers. com.).
Climate, environment and culture
Since neither the proxy-climate data nor the archaeological data are, or probably ever will be,
resolvable to the event or even year, it follows that correlations between climate and cultural
change will either be highly localised and an ‘event effect’ (e.g. abandonment or repair due to
a flood event) or more commonly an approximate temporal coincidence of a climatic trend
and a some change in the cultural series. If we refer to this as an ‘aggregated effect’ then the
chances of observing it and its being meaningful are maximised in situations of marginal
habitation or agriculture although it must be remembered that marginality is still
fundamentally defined by particular economic and social systems (Brown et al., 1998). This
approach underlies studies of farming at the margins of cultivation or in environmentally
sensitive locations. It is also necessary to at least postulate the mechanisms by which a
climatic change results in cultural actions. The reason for this is that it is not always clear
which way climate-culture correlations should operate in temperate environments. An
example is upland arable cultivation which is susceptible to both a reduction in temperatures,
especially in the growing season, and to drought, a factor rarely considered but likely to be
important especially on the lower and dryer of British Uplands (e.g. Dartmoor or the North
York Moors). This may not have had immediate effects but been cumulative through stressing
the agricultural system with lower productivity and increasing time taken to obtain adequate
water for stock, domestic use and horticulture. Indeed although masked by imported food,
climatic factors, such as variations in summer rainfall, still have significant effects on present
day wheat production (quantity and quality) which can be linked to the North Atlantic
Oscillation (Chmielewski and Potts, 1995; Kettlewell et al., 2003), Therefore a chain of
causality is essential as the chances of finding correlations between climatic fluctuations of all
types and cultural changes by chance is almost certainly very high and increases with the
increasing number and precision of proxy climate records. For example using the BSW data
already discussed for Scotland (Langdon et al., 2003) and given realistic temporal precision,
even with tephras of ±25 years, the chances of having a correlation between a cultural change
and a wet shift registered at one or more of the sites studied is 52%. As the number of sites
studied increases this figure will rise and it could be argued that, just as there are lags in the
proxy-climate record, there are also potential larger lags in the cultural record. It follows that
correlation may be a necessary prerequisite but it is not sufficient to prove causality which
should primarily be based upon a mechanistic explanation or theory which can be tested using
independent data. In a recent study attempting to correlate proxy-climate data with
“enhanced archaeological visibility” from databases of Irish 14C dates by Turney et al (2006) it
is far from clear how the claimed causality is supposed to operate with shifts to wetter
conditions being related to an increase in crannog and settlement dates and in some, but not

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other wet periods, an increase in dates from forts. Since the enhanced 14C duration identified
in this study is approaching 50% of the Holocene, especially in later prehistory, and having
regard to taphanomic factors such correlations may have little archaeological value.
Later Bronze Age climatic change
The problem of assigning climatic causality to cultural changes has been highlighted in
connection with the well-known, and noted above, climatic change registered across Europe
at c. 700 BC (2.7 Ka event, Barber et al., 2004) by Coombes and Barber (2005). Van Geel and
co-workers have related this climatic event to a variety of archaeological changes across
western Eurasia and even globally at
c
. 2650 BP although the date of this event has still to be
tracked with sufficient resolution and varies considerably from study to study. Van Geel et al
(2004) have also proposed that this abrupt climatic change in the form of increased humidity
around 850 BC caused an expansion of population in the Altai region of Central Asia which
was a stimulus for outward migration of the Scythian culture with repercussions for Europe
and eastern Asia. However, this hypothesis has received archaeological criticism (Riehl and
Pustovoytov, 2006), and is at odds with some data suggesting colder, and therefore drier,
conditions (Andreev and Klimanov, 2000). In the British Isles this climatic event has been
correlated with increases in BSW at many sites especially in northern Britain (Charman et al.,
2006) and as discussed above in the alluvial record. However, what effect it had on late
Bronze Age society although frequently speculated upon remains unclear, as has been
emphasised by Dark’s (2006) unusually comprehensive analysis of 75 pollen diagrams across
Britain which on aggregate show no evidence for “wholesale” land use change at
c
. 850 BC
indeed in many cases there is increased agricultural activity. Similarly Tipping et al.’s (2008)
analysis of proximal upland and lowland pollen sites in north east Scotland “posits a
restructuring of agricultural activities” (Tipping et al., 2008 p.2379) rather than abandonment
of settlement or agriculture due to late Bronze Age climatic deterioration.
In alluvial environments it is occasionally possible to observe directly the ‘event effect’. An
example comes from Argosy Washolme, Aston-upon-Trent (near Shardlow), Derbyshire where
a large log boat was stranded by a flood and wedged against several large oak logs on a gravel
bar in an unstable reach of the River Trent (Howard et al., 1999). The stranded log-boat which
was radiocarbon dated to 1440 - 1310 cal BC was carrying several large blocks of locally hewn
Bromsgrove Sandstone which, given the absence of monumental construction in stone at this
time in this area, were most likely destined for the construction of a causeway, wharf or
landing hard. The boat was found 22m from a linear structure of oak, brushwood and stones,
one of two structures interpreted as a causeway (Knight and Howard, 2004). Since then
another log-boat has been found at Shardlow which is within a kilometre of Argosy
Washolme and illustrate how important the Trent was for ‘goods transportation’. Also at
Aston 12 metal objects have been recovered dating to this period (Knight and Howard, 2004).
Whilst such events can provide important evidence of Bronze Age cultural activities, which
might otherwise have been archaeologically invisible, they cannot reveal climate change as a
contributory factor in wide societal or cultural change.
The most commonly used aggregate effect is data concerning the abandonment or
extensification of upland farming due probably as much to soil acidification as to climate
change, and a corresponding re-organisation of lowland landscapes (Bradley, 1978; 2007). In
the case of the well known of Dartmoor Reaves this process appear to have started earlier in
the middle Bronze Age with the extension of the co-axial field system down onto lower slopes
(Fleming, 1988). In the first palaeoclimatic reconstruction from Dartmoor, Amesbury et al.
(2008) have shown using testate amoebae and peat humification that a major shift to cooler
and/or wetter climate occurred c. 1395-1155 cal BC which is coincident with the period
believed to include the abandonment of the reave system. However, as this study ably shows

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the problem with such a correlation is the poor dating constraint on the abandonment of the
reaves rather than the proxy-climate record and the authors correctly caution that
deteriorating climate may have been only a contributory factor in abandonment. What is
required in this situation is better dating of the abandonment of the reave system and
archaeological or palaeobotanical data revealing stress through changes in productivity, crop
type or farming practices.
Other aggregate effects in this period mentioned by Bradley (2007) may have been increased
construction of wooden trackways in wetlands such as the Somerset levels (Coles and Coles,
1986), the Fens and across parts of floodplains such as the Thames (Sidell et al. 2004) and
even the construction of the first Bridges (Bradley, 2007) such as that excavated at Testwood
in Hampshire (Brown, 2008). However, the chain of causality is not clear in all cases as for
example with bridges, as it is arguable that societal factors such as trade, power, prestige and
territoriality as well as technological changes in wood working are more likely the key drivers.
Likewise the middle-late Bronze Age increase in the deposition of hoards in rivers and lakes
(Bradley, 1990), the renewal of ‘water cults’, the use of riverine islands (Brown, 2004) or the
start of crannog construction in Ireland (Fredengren, 2002) cannot be taken as direct evidence
of any change in the environment. They maybe related to a changing perception of the
environment or a rise in intra-societal conflict which itself could be an aggregate effect of
environmental stress although this is far from being proven. What is certain is that during this
period there are major changes in the structure of society involving a concentration of power
in the hands of elites, increased long-distance trade and changing ritual activity (Bradley,
2007) which may have been associated with changing belief systems – and that all these
forces lead to a change in the monumentalisation of natural places. Although largely
concerned with the collapse of complex societies Coombes and Barber (2005) emphasise that
in order to avoid crude correlation-based determinism, environmental change must be
identified as the ‘critical factor’ in cultural change rather than being just one of a number of
factors influencing change in what are socio-economically complex systems which show
many of the characteristics of self-organising systems (Dearing and Zolitscka, 1999). This
applies as much to the British Bronze Age as classical civilisations and in any attempt to
understand such complexity a critical parameter will always be some derivative of population
density or its proxy.
Conclusions
Through the serendipitous nature of archaeological excavation there will no doubt be further
remarkable sites which reveal event effects on the material record such as site destruction or
the rare preservation of a catastrophy, and no doubt these will provide valuable insights into
Bronze Age life and possibly cognition. However, it is unlikely, and indeed axiomatic, that
there will never be enough of these rare events to allow the geographical delimitation of such
climate-induced change on society at large. Archaeologists are therefore likely to continue, or
indeed increase (due to changes in research funding) attempts to match aggregate events to
the increasingly detailed and complex palaeoclimatic record – the increasing complexity of
which may further in turn weaken such correlations.
Several research needs are clear; firstly there is an inevitable disparity between our
palaeoclimatic knowledge from northern and western Britain in comparison with southern and
midland Britain. As has been pointed out many times this is unfortunate as the majority of
the British population in later prehistory was located in the midlands and the south. Research
into alternative sources of proxy-climate data is therefore potentially valuable. Secondly a
more subtle and meteorologically meaningful description of past climate is required from the

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proxy-climate data which could be matched with archaeological data and particularly
archaeobotanical data. Whilst reductions in temperature and increasing rainfall during critical
periods of the year have been emphasised these may not have been critical and lowland
England and other stresses such as drought should be considered. At the heart of most
scenarios of climatic forcing there is some squeeze on resources, be it by drought or
deteriorated growing conditions. This will then act on society through one or more of several
mechanisms including; changes in health, the birthrate and mortality (particularly neo-natal),
emigration and eventually the population density, but also resource substitution and societal
change including social differentiation and conflict. What is required is regionally delimited
studies in areas with high proxy-environmental potential which focus on these aspects of the
archaeological record over a critical period such as the two or three centuries before the
eruption of Hekla 3. Just as there has to be continued improvement in the modelling of
climate forced environmental change (such as relative productivity) there also have to be
improvements in the conversion of the archaeological record from site narratives, or
databases of site types, to resource related parameters which can be related to changing
environmental conditions rather than cultural dynamics. At the heart of aggregate effects of
climate change remains demography and it is advances in this area that are most likely to
clarify rather than further muddy our view of environment-human interactions in the Bronze
Age.
Acknowledgements
I must thank all the PLUS team (Keith Barber, Pete Langdon and Paul Hughes) for their
invaluable help in the writing of this chapter. I must also thank John Dearing, Andy Baker,
Mark Macklin and Richard Chiverrell for additional material and discussion.

BROWN BRONZE AGE REVIEW VOL. 1 NOVEMBER 2008
www.britishmuseum.org/bronzeagereview/1 17
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