In 1993, Harvey Weiss and colleagues published a paper in the journal Science setting out evidence that the urban site at Tell Leilan had been abandoned at the end of the Early Bronze Age as the result of an unprecedented drought event. It was possible to link this rupture at 2200 BC to the end of one of the world's first empires—the Akkadian. Their study attracted wide interest, not least because of the ‘salutary lesson’ it supposedly offered, namely that our modern civilisation could equally collapse in the face of rapid climate change. Although not the first person to postulate a link between climatic instability and the end of the Early Bronze Age world system, Weiss set in motion what has become something of a 4.2 kilo-year (ka) industry. This has included a NATO workshop on third-millennium BC climate change and Old World collapse (Dalfes et al. Reference Dalfes, Kukla and Weiss1997), and a study of cores from the Gulf of Oman (Cullen et al. Reference Cullen, Demenocal, Hemming, Hemming, Brown, Guilderson and Sirocko2000).

The edited two-volume work reviewed here is the latest offering in the burgeoning 4.2ka production line. It results from a workshop meeting held in 2014 at Halle Museum, and includes no fewer than 42 separate papers, some with appendices containing radiocarbon date lists or other raw data; most are written in English, with nine in German. The first volume centres on the Mediterranean basin, while the second volume moves the geographic focus into Central and Northern Europe. The books, which weigh in at over 4kg, are beautifully produced, with high-quality colour plates, and they are admirably free of typographic, language or other mistakes—except, that is, for the book cover. On this there is a bizarrely distorted map of Europe, apparently on fire, and a misspelling of ‘cause’ as ‘couse’! Cover notwithstanding, it is very much to the editors’ credit that they have produced and published these volumes so quickly to such a high standard.

The books start with a helpful preface by the editors (three archaeologists, one palaeoclimatologist), which sets out key research questions for the subsequent regional syntheses. These questions include whether or not there is evidence for climatic change between 2300 and 2100 BC and, if so, whether or not there is archaeological evidence that this change had consequences for the societies in each region. As Jung and Weninger put it in their chapter, if the primary evidence is not compelling, “many of the archaeo-climatological interpretations [. . .] may well be built on sand” (p. 206). So, how does the evidence stack up? The answer, almost inevitably, is mixed. There are certainly a few records, such as Renella Cave in Italy, that show an abrupt, short-lived (i.e. multi-decadal) climatic anomaly at some point between 2300 and 1900 BC. Most of the 52 sites from the Mediterranean–Near East listed by Weiss in his chapter, however, do not show such a clear pattern, and many show no pattern at all. That is not to say that the 4.2ka climate event did not occur, but rather that in some environmental settings its signal was amplified, as Arz et al. clearly demonstrate in their study of cores from two contrasting settings in the Red Sea. The palaeoclimatic evidence for a distinct and unique climate event at 2200 BC looks even less convincing for Northern Europe. In the very last paper in Volume 2, Baillie and McAnaney show that no less than six cool-wet ‘events’ can be identified in the north-west European tree-ring datasets between 2350 and 1900 BC, so take your pick!

What about the archaeological record? 2200 BC undoubtedly represented a turning point for many Euro-Mediterranean cultures. It marked the end of a period of supra-regional networks and connections, corresponding to the final Neolithic in most of Europe, and a reversion to smaller, regional entities, often with distinctive Early Bronze Age material cultures. They include the ‘Cetina’ expansion across the Adriatic, Sicily and southern Greece (chapters by Pacciarelli et al., and by Fiorentino and Recchia), and the Argaric culture of south-eastern Iberia (Lull et al.). Nine of the chapters in Volume 1 are syntheses that integrate both palaeoenvironmental and archaeological data in specific regions from Anatolia to southern France. Most are excellent and conclude that climate change probably played a role in prompting cultural evolution, but that societal responses and adaptations were not pre-determined. Eight further archaeological studies in the first (Mediterranean) volume include no direct reference to climate, but in some cases (e.g. Levant, Egypt, Aegean) invoke a shift in Early Bronze Age chronologies that removes potential synchronicities with the 4.2ka event, and therefore appear to falsify a hypothesised climatic causation.

Disappointingly, Volume 2 largely loses the climatic thread, with 13 out of 19 chapters being straightforward archaeological accounts of the late third millennium BC in temperate Europe, mainly Germany. A few of the authors, however, do conclude that there was no cultural crisis during this transition that needs to be explained by climate or anything else. Overall, one is left with the sense that climate probably acted as a pacemaker for major societal restructuring in much of the Mediterranean during this time, but that the case for a similar role north of the Alps has yet to be made convincingly. So the 4.2ka climatic event remains enigmatic. It has no convincing cause. Marie-Agnès Courty, for example, who provided the original scientific data for drought at Tell Leilan, has subsequently re-interpreted the evidence and now points towards an extra-terrestrial impact, a view supported in this volume by Mike Baillie. This explanation, however, seems no more probable than the proposal for a change in El Niño as advanced by Frank Sirocko in his chapter, even if he is surely correct in ruling out either a solar or a volcanic explanation. But if the cause remains obscure, its human consequences were not pre-ordained. As researchers such as Jason Ur (Reference Ur, Kerner, Dann and Bangsgaard2015) have demonstrated, individual Bronze Age communities adapted in different ways to the 2200 BC climatic crisis. In the face of climatic adversity, the fate of these societies was ultimately in their own hands, and so is ours.