̽��ֱ�� of Cambridge - David Hodell

Ten Cambridge scientists elected as Fellows of the Royal Society 2024

Anonymous — Thu, 16 May 2024 08:51:02 +0000

̽��ֱ��Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering and medicine.

̽��ֱ��Society’s fundamental purpose, as it has been since its foundation in 1660, is to recognise, promote and support excellence in science and to encourage the development and use of science for the benefit of humanity.

This year, over 90 researchers, innovators and communicators from around the world have been elected as Fellows of the Royal Society for their substantial contribution to the advancement of science. Nine of these are from the ̽��ֱ�� of Cambridge.

Sir Adrian Smith, President of the Royal Society said: “I am pleased to welcome such an outstanding group into the Fellowship of the Royal Society.

“This new cohort have already made significant contributions to our understanding of the world around us and continue to push the boundaries of possibility in academic research and industry.

“From visualising the sharp rise in global temperatures since the industrial revolution to leading the response to the Covid-19 pandemic, their diverse range of expertise is furthering human understanding and helping to address some of our greatest challenges. It is an honour to have them join the Fellowship.”

̽��ֱ��Fellows and Foreign Members join the ranks of Stephen Hawking, Isaac Newton, Charles Darwin, Albert Einstein, Lise Meitner, Subrahmanyan Chandrasekhar and Dorothy Hodgkin.

̽��ֱ��new Cambridge fellows are:

Professor Sir John Aston Kt FRS

Aston is the Harding Professor of Statistics in Public Life at the Statistical Laboratory, Department of Pure Mathematics and Mathematical Statistics, where he develops techniques for public policy and improves the use of quantitative methods in public policy debates.

From 2017 to 2020 he was the Chief Scientific Adviser to the Home Office, providing statistical and scientific advice to ministers and officials, and was involved in the UK’s response to the Covid pandemic. He was knighted in 2021 for services to statistics and public policymaking, and is a Fellow of Churchill College.

Professor Sarah-Jayne Blakemore FBA FMedSci FRS

Blakemore is the Professor of Psychology and Cognitive Neuroscience, Department of Psychology, and leader of the Developmental Cognitive Neuroscience Group. Her research focuses on the development of social cognition and decision making in the human adolescent brain, and adolescent mental health.

Blakemore has been awarded several national and international prizes for her research, and is a Fellow of the British Academy, the American Association of Psychological Science and the Academy of Medical Sciences.

Professor Patrick Chinnery FMedSci FRS

Chinnery is Professor of Neurology and head of the ̽��ֱ��’s Department of Clinical Neurosciences, and a Fellow of Gonville & Caius College. He was appointed Executive Chair of the Medical Research Council last year, having previously been MRC Clinical Director since 2019.

His principal research is the role of mitochondria in human disease and developing new treatments for mitochondrial disorders. Chinnery is a Wellcome Principal Research Fellow with a lab based in the MRC Mitochondrial Biology Unit and jointly chairs the NIHR BioResource for Translational Research in Common and Rare Diseases. He is a Fellow of the Academy of Medical Sciences.

Professor Rebecca Fitzgerald OBE FMedSci FRS

Fitzgerald is Professor of Cancer Prevention in the Department of Oncology and the inaugural Director of the ̽��ֱ��’s new Early Cancer Institute, which launched in 2022. She is a Fellow of Trinity College.

Her pioneering work to devise a first-in-class, non-endoscopic capsule sponge test for identifying individuals at high risk for oesophageal cancer has won numerous prizes, including the Westminster Medal, and this test is now being rolled out in the NHS and beyond by her spin-out Cyted Ltd.

Professor David Hodell FRS

Hodell is the Woodwardian Professor of Geology and Director of the Godwin Laboratory for Palaeoclimate Research in the Department of Earth Sciences, and a Fellow of Clare College.

A marine geologist and paleoclimatologist, his research focuses on high-resolution paleoclimate records from marine and lake sediments, as well as mineral deposits, to better understand past climate dynamics. Hodell is a fellow of the American Geophysical Union and the American Association for the Advancement of Science. He has received the Milutin Milankovic Medal.

Professor Eric Lauga FRS

Lauga is Professor of Applied Mathematics in the Department of Applied Mathematics and Theoretical Physics, where his research is in fluid mechanics, biophysics and soft matter. Lauga is the author, or co-author, of over 180 publications and currently serves as Associate Editor for the journal Physical Review Fluids.

He is a recipient of three awards from the American Physical Society: the Andreas Acrivos Dissertation Award in Fluid Dynamics, the François Frenkiel Award for Fluid Mechanics and the Early Career Award for Soft Matter Research. He is a Fellow of the American Physical Society and of Trinity College.

Professor George Malliaras FRS

Malliaras is the Prince Philip Professor of Technology in the Department of Engineering, where he leads a group that works on the development and translation of implantable and wearable devices that interface with electrically active tissues, with applications in neurological disorders and brain cancer.

Research conducted by Malliaras has received awards from the European Academy of Sciences, the New York Academy of Sciences, and the US National Science Foundation among others. He is a Fellow of the Materials Research Society and of the Royal Society of Chemistry.

Professor Lloyd Peck FRI FRSB FRS

Peck is a marine biologist at the British Antarctic Survey and a fellow at Wolfson College, Cambridge.

He identified oxygen as a factor in polar gigantism and identified problems with protein synthesis as the cause of slow development and growth in polar marine species. He was awareded a Polar Medal in 2009, the PLYMSEF Silver medal in 2015 and an Erskine Fellowship at the ̽��ֱ�� of Canterbury, Christchurch in 2016-2017.

Professor Oscar Randal-Williams FRS

Randal-Williams is the Sadleirian Professor of Pure Mathematics in the Department of Pure Mathematics and Mathematical Statistics.

He has received the Whitehead Prize from the London Mathematical Society, a Philip Leverhulme Prize, the Oberwolfach Prize, the Dannie Heineman Prize of the Göttingen Academy of Sciences and Humanities, and was jointly awarded the Clay Research Award.

Randal-Williams is one of two managing editors of the Proceedings of the London Mathematical Society, and an editor of the Journal of Topology.

Professor Mihaela van der Schaar FRS

Van der Schaar is the John Humphrey Plummer Professor of Machine Learning, Artificial Intelligence and Medicine in the Departments of Applied Mathematics and Theoretical Physics, Engineering and Medicine.

She is the founder and director of the Cambridge Centre for AI in Medicine, and a Fellow at ̽��ֱ��Alan Turing Institute. Her work has received numerous awards, including the Oon Prize on Preventative Medicine, a National Science Foundation CAREER Award, and the IEEE Darlington Award.

Van der Schaar is credited as inventor on 35 US patents, and has made over 45 contributions to international standards for which she received three ISO Awards. In 2019, a Nesta report declared her the most-cited female AI researcher in the UK.

Ten outstanding Cambridge researchers have been elected as Fellows of the Royal Society, the UK’s national academy of sciences and the oldest science academy in continuous existence.

Royal Society

̽��ֱ��Royal Society in central London

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Prolonged droughts likely spelled the end for Indus megacities

cmm201 — Wed, 26 Apr 2023 09:42:35 +0000

̽��ֱ��beginning of this arid period — starting at around 4,200 years ago and lasting for over two centuries — coincides with the reorganisation of the metropolis-building Indus Civilization, which spanned present-day Pakistan and India.

̽��ֱ��research identified three protracted droughts — each lasting between 25 and 90 years — during this arid period. “We find clear evidence that this interval was not a short-term crisis but a progressive transformation of the environmental conditions in which Indus people lived,” said study co-author Prof Cameron Petrie, from Cambridge’s Department of Archaeology.

̽��ֱ��researchers charted historic rainfall by examining growth layers in a stalagmite collected from a cave near Pithoragarh, India. By measuring a range of environmental tracers — including oxygen, carbon and calcium isotopes — they obtained a reconstruction showing relative rainfall at seasonal resolution. They also used high-precision Uranium-series dating to get a handle on the age and duration of the droughts.

“Multiple lines of evidence allow us to piece together the nature of these droughts from different angles — and confirm they are in agreement,” said lead author of the research Alena Giesche, who conducted the research as part of her PhD in Cambridge’s Department of Earth Sciences.

Giesche and the team identified distinct periods of below-average rainfall in both the summer and winter seasons. “ ̽��ֱ��evidence for drought affecting both cropping seasons is extremely significant for understanding the impact of this period of climate change upon human populations,” said Petrie. He adds that the droughts during this period increased in duration, to the point where the third would have been multi-generational in length.

̽��ֱ��findings support existing evidence that the decline of the Indus megacities was linked to climate change. “But what’s been a mystery until now is information on the drought duration and the season they happened in,” said Giesche. “That extra detail is really important when we consider cultural memory and how people make adaptations when faced with environmental change.”

According to Petrie: “ ̽��ֱ��archaeological evidence indicates that over a 200 year period, the ancient inhabitants took various steps to adapt and remain sustainable in the face of this new normal.” During this transformation, larger urban sites were depopulated in favour of smaller rural settlements towards the eastern extent of the area occupied by Indus populations. At the same time, agriculture shifted towards reliance on summer-crops, especially drought-tolerant millets, and the population transitioned to a lifestyle that appears to have been more self-reliant.

Megadroughts have recently become a popular cause to explain a number of cultural transformations, including the Indus Valley, explains David Hodell, study co-author from Cambridge’s Department of Earth Sciences. “But the links are generally fuzzy because of difficulties involved in comparing climatic and archaeological records.” This is now changing because, “Palaeoclimate records are becoming progressively better at refining changes in rainfall on a seasonal and annual basis, which directly affects people's decision making,” said Hodell.

̽��ֱ��team are now looking to expand their climate reconstructions to western parts of the Indus River Region, where the winter rainfall system becomes more dominant than the Indian Summer Monsoon. “What we really need are more records like this, from a west-east oriented transect across the region where the summer and winter monsoons interact — and, crucially, capturing the beginning of this arid period,” said Giesche.

“Currently, we have a huge blind spot on our maps extending across Afghanistan and Pakistan where the Indian summer monsoon and the Westerlies interact,” said Prof. Sebastian Breitenbach, co-author and palaeoclimatologist at Northumbria ̽��ֱ��. “Sadly, the political situation is unlikely to allow for this kind of research in the near future."

“There’s more work to be done by both palaeoclimatologists and archaeologists,” said Hodell. “We are fortunate in Cambridge to have the two departments next door to one another.”

Tracking down how interacting rain zones influenced the Indus Civilisation has been one of the questions at the centre of the TwoRains Project, a collaboration between Cambridge and Banaras Hindu ̽��ֱ��, which was funded by the European Research Council (ERC).

Giesche, A, Hodell, D A, Petrie, C A, Haug, G A, Adkins, J F, Plessen, B, Marwan, N, Bradbury, H J, Hartland, A, French, A D, Breitenbach, S F M. 2023. Speleothem evidence for recurring summer and winter droughts post-4.2 ka in the Indus River Basin, Nature Communications Earth & Environment (2023), https://doi.org/10.1038/s43247-023-00763-z.

New research involving Cambridge ̽��ֱ�� has found evidence — locked into an ancient stalagmite from a cave in the Himalayas — of a series of severe and lengthy droughts which may have upturned the Bronze Age Indus Civilization.

Over a 200 year period, the ancient inhabitants took various steps to adapt and remain sustainable in the face of this new normal

Cameron Petrie

Alena Giesche

A section through the Dharamjali stalagmite that the authors studied.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Carbon dioxide ‘pulses’ are a common feature of the carbon cycle

cmm201 — Thu, 20 Aug 2020 18:00:00 +0000

Ice cores from Antarctica show that, in the span of less than two centuries, atmospheric levels of carbon dioxide jumped repeatedly at the end of the last ice age, when the Atlantic was continuously disturbed by melting ice sheets.

Whether these CO₂ jumps might occur in today’s conditions, when we are already seeing the impact of human-driven CO₂ emissions and rapidly melting polar ice sheets, has remained unknown.

̽��ֱ��study, published in the journal Science and by researchers from the Universities of Cambridge, Bern and Grenoble Alpes, reveals that rapid CO₂ jumps also occurred during a period from 450,000 to 330,000 years ago, a key time in Earth’s history covering more than a full glacial cycle.

“By looking back further in time, to previous glacial and interglacial conditions, we find the same CO₂jumps - irrespective of whether the climate was cold or warm,” said first author Dr Christoph Nehrbass-Ahles from Cambridge’s Department of Earth Sciences, who conducted the research while based at the ̽��ֱ�� of Bern.

These rapid CO₂ rises seem to be a common feature of the carbon cycle in the past. But, said Nehrbass-Ahles, human activities are releasing carbon a rate ten times faster than during CO₂ increases in the past. “What is unclear is how a future jump in carbon may interact with or exacerbate anthropogenic carbon emissions,” he said.

Central to the team’s finding was their detailed analysis of Antarctic ice from the EPICA ( ̽��ֱ��European Project for Ice Coring in Antarctica) Dome C ice core.

“Our previous understanding of rapid CO₂ changes has been hampered by a lack of detailed data over this interval – so these events were often missed,” said Nehrbass-Ahles. Thanks to a new gas extraction method and detailed sampling campaign, the team was able to identify subtle changes occurring at centennial timescales.

̽��ֱ��study marks an important step in understanding what causes such abrupt increases and possible feedbacks in the Earth’s climate system. “Scientists are uncertain as to the mechanism behind the CO₂ jumps, but think a combination of factors, including ocean circulation, changing wind patterns, and terrestrial processes, are likely responsible,” said co-author Professor David Hodell, also from the Department of Earth Sciences.

̽��ֱ��researchers combined the new ice core data with detailed information on ocean circulation from marine sediments collected off the coast of Portugal. ̽��ֱ��site, which was drilled as part of the International Ocean Discovery Program (IODP), is unique for its high accumulation of sediments and is ideally situated for monitoring the changes in ocean circulation triggered when ice sheets collapsed.

̽��ֱ��isotopic signal of the marine sediments showed the same pattern as the ice cores. “ ̽��ֱ��abrupt changes are clearly represented in both the marine and ice records, telling us that they must be connected to major changes in the surface and deep circulation of the Atlantic Ocean,” said Hodell.

According to Nehrbass-Ahles, the key is the high resolution of the ice and marine sediments records, making observations of these rapid changes in both records possible. “Understanding these centennial-scale changes is crucial because they operate at a similar pace to the anthropogenic changes altering our planet,” he said.

Reference:
C. Nehrbass-Ahles et al. ‘Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions.’ Science (2020). DOI: 10.1126/science.aay8178

Researchers have found that pulse-like releases of carbon dioxide to the atmosphere are a pervasive feature of the carbon cycle and that they are closely connected to major changes in Atlantic Ocean circulation.

Understanding these centennial-scale changes is crucial because they operate at a similar pace to the anthropogenic changes altering our planet

Christoph Nehrbass-Ahles

Thibaut Vergoz, Institut polaire français

Concordia research station in Antarctica

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Scientists measure severity of drought during the Maya collapse

sc604 — Thu, 02 Aug 2018 18:00:00 +0000

Researchers from the ̽��ֱ�� of Cambridge and the ̽��ֱ�� of Florida developed a method to measure the different isotopes of water trapped in gypsum, a mineral that forms during times of drought when the water level is lowered, in Lake Chichancanab in Mexico’s Yucatán Peninsula where the Maya were based.

Based on these measurements, the researchers found that annual precipitation decreased between 41% and 54% relative to today during the period of the Maya civilisation’s collapse, with periods of up to 70% rainfall reduction during peak drought conditions, and that relative humidity declined by 2% to 7% relative to today. ̽��ֱ��results are reported in the journal Science.

“ ̽��ֱ��role of climate change in the collapse of Classic Maya civilisation is somewhat controversial, partly because previous records are limited to qualitative reconstructions, for example whether conditions were wetter or drier,” said Nick Evans, a PhD student in Cambridge’s Department of Earth Sciences and the paper’s first author. “Our study represents a substantial advance as it provides statistically robust estimates of rainfall and humidity levels during the Maya downfall.”

Maya civilisation is divided into four main periods: the Preclassic (2000 BCE – 250 CE), Classic (250 CE – 800 CE), terminal Classic (800 - 1000 CE) and Postclassic (1000 CE – 1539 CE). ̽��ֱ��Classic period was marked by the construction of monumental architecture, intellectual and artistic development, and the growth of large city-states.

During the 9^th century however, there was a major political collapse in the central Maya region: their famous limestone cities were abandoned and dynasties ended. And while the Maya people survived beyond this period, their political and economic power was depleted.

There are multiple theories as to what caused the collapse of the Maya civilisation, such as invasion, war, environmental degradation and collapsing trade routes. In the 1990s, however, researchers were able to piece together climate records for the period of the Maya collapse and found that it correlated with an extended period of extreme drought.

Professor David Hodell, Director of Cambridge’s Godwin Laboratory for Palaeoclimate Research and the senior author of the current paper, provided the first physical evidence of a correlation between this period of drought at Lake Chichancanab and the downfall of the Classic Maya civilisation in a paper published in 1995.

Now, Hodell and his colleagues have applied a new method and estimated the extent of this drought. Using a new geochemical method to measure the water locked within gypsum from Chichancanab, the researchers have built a complete model of hydrological conditions during the terminal Classic Period when the Maya collapsed.

̽��ֱ��researchers analysed the different isotopes of water trapped within the crystal structure of the gypsum to determine changes in rainfall and relative humidity during the Maya downfall.

They measured three oxygen and two hydrogen isotopes to reconstruct the history of the lake water between 800 and 1000 CE. When gypsum forms, water molecules are incorporated directly into its crystalline structure, and this water records the different isotopes that were present in the ancient lake water at the time of its formation. “This method is highly accurate and is almost like measuring the water itself,” said Evans.

In periods of drought, more water evaporates from lakes such as Chichancanab, and because the lighter isotopes of water evaporate faster, the water becomes heavier. A higher proportion of the heavier isotopes, such as oxygen-18 and hydrogen-2 (deuterium), would indicate drought conditions. By mapping the proportion of the different isotopes contained within each layer of gypsum, the researchers were able to build a model to estimate past changes in rainfall and relative humidity over the period of the Maya collapse.

This quantitative climate data can be used to better predict how these drought conditions may have affected agriculture, including yields of the Maya’s staple crops, such as maize.

̽��ֱ��research was supported by the European Research Council.

Reference:
Nicholas P. Evans et al. ‘Quantification of Drought During the Collapse of the Classic Maya Civilization.’ Science (2018). DOI: 10.1126/science.aas9871

Inset image: Lake Chichancanab, the site of the study. Chichancanab means “Little Sea” in Yucatec Maya, reflecting its relatively salty water composed dominantly of calcium and sulfate. (Credit: Mark Brenner)

̽��ֱ��severity of drought conditions during the demise of the Maya civilisation about 1,000 years ago has been quantified, representing another piece of evidence that could be used to solve the longstanding mystery of what caused the downfall of one of the ancient world’s great civilisations.

̽��ֱ��role of climate change in the collapse of Classic Maya civilisation is somewhat controversial, partly because previous records are limited to qualitative reconstructions.

Nick Evans

Edzná ruins, Campeche

Yes

Decline of Bronze Age ‘megacities’ linked to climate change

lw355 — Thu, 27 Feb 2014 12:57:09 +0000

Scientists have demonstrated that an abrupt weakening of the summer monsoon affected northwest India 4,100 years ago. ̽��ֱ��resulting drought coincided with the beginning of the decline of the metropolis-building Indus Civilisation, which spanned present-day Pakistan and India, suggesting that climate change could be why many of the major cities of the civilisation were abandoned.

̽��ֱ��research, reported this week in the journal Geology, involved the collection of snail shells preserved in the sediments of an ancient lake bed. By analysing the oxygen isotopes in the shells, the scientists were able to tell how much rain fell in the lake where the snails lived thousands of years ago.

̽��ֱ��results shed light on a mystery surrounding why the major cities of the Indus Civilisation were abandoned. Climate change had been suggested as a possible reason for this transformation before but, until now, there has been no direct evidence for climate change in the region where Indus settlements were located.

Moreover, the finding now links the decline of the Indus cities to a documented global scale climate event and its impact on the Old Kingdom in Egypt, the Early Bronze Age civilisations of Greece and Crete, and the Akkadian Empire in Mesopotamia, whose decline has previously been linked to abrupt climate change.

“We think that we now have a really strong indication that a major climate event occurred in the area where a large number of Indus settlements were situated,” said Professor David Hodell, from Cambridge’s Department of Earth Sciences. “Taken together with other evidence from Meghalaya in northeast India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.”

Hodell together with ̽��ֱ�� of Cambridge archaeologist Dr Cameron Petrie and Gates scholar Dr Yama Dixit collected Melanoides tuberculata snail shells from the sediments of the ancient lake Kotla Dahar in Haryana, India. “As today, the major source of water into the lake throughout the Holocene is likely to have been the summer monsoon,” said Dixit. “But we have observed that there was an abrupt change, when the amount of evaporation from the lake exceeded the rainfall – indicative of a drought.”

At this time large parts of modern Pakistan and much of western India was home to South Asia’s great Bronze Age urban society. As Petrie explained: “ ̽��ֱ��major cities of the Indus civilisation flourished in the mid-late 3rd and early 2nd millennium BC. Large proportions of the population lived in villages, but many people also lived in ‘megacities’ that were 80 hectares or more in size – roughly the size of 100 football pitches. They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East. But, by the mid 2nd millennium BC, all of the great urban centres had dramatically reduced in size or been abandoned.”

Many possible causes have been suggested, including the claim that major glacier-fed rivers changed their course, dramatically affecting the water supply and the reliant agriculture. It has also been suggested that an increasing population level caused problems, there was invasion and conflict, or that climate change caused a drought that large cities could not withstand long-term.

“We know that there was a clear shift away from large populations living in megacities,” said Petrie. “But precisely what happened to the Indus Civilisation has remained a mystery. It is unlikely that there was a single cause, but a climate change event would have induced a whole host of knock-on effects.

“We have lacked well-dated local climate data, as well as dates for when perennial water flowed and stopped in a number of now abandoned river channels, and an understanding of the spatial and temporal relationships between settlements and their environmental contexts. A lot of the archaeological debate has really been well-argued speculation.”

̽��ֱ��new data, collected with funding from the Natural Environment Research Council, show a decreased summer monsoon rainfall at the same time that archaeological records and radiocarbon dates suggest the beginning of the Indus de-urbanisation. From 6,500 to 5,800 years ago, a deep fresh-water lake existed at Kotla Dahar. ̽��ֱ��deep lake transformed to a shallow lake after 5,800 years ago, indicating a weakening of the Indian summer monsoon. But an abrupt monsoon weakening occurred 4,100 years ago for 200 years and the lake became ephemeral after this time.

Until now, the suggestion that climate change might have had an impact on the Indus Civilisation was based on data showing a lessening of the monsoon in Oman and the Arabian Sea, which are both located at a considerable distance from Indus Civilisation settlements and at least partly affected by different weather systems.

Hodell and Dixit used isotope geochemical analysis of shells as a proxy for tracing the climate history of the region. Oxygen exists in two forms – the lighter ¹⁶O and a heavier ¹⁸O variant. When water evaporates from a closed lake (one that is fed by rainfall and rivers but has no outflow), molecules containing the lighter isotope evaporate at a faster rate than those containing the heavier isotopes; at times of drought, when the evaporation exceeds rainfall, there is a net increase in the ratio of ¹⁸O to ¹⁶O of the water. Organisms living in the lake record this ratio when they incorporate oxygen into the calcium carbonate (CaCO3) of their shells, and can therefore be used, in conjunction with radiocarbon dating, to reconstruct the climate of the region thousands of years ago.

Speculating on the effect lessening rainfall would have had on the Indus Civilisation, Petrie said: “Archaeological records suggest they were masters of many trades. They used elaborate techniques to produce a range of extremely impressive craft products using materials like steatite, carnelian and gold, and this material was widely distributed within South Asia, but also internationally. Each city had substantial fortification walls, civic amenities, craft workshops and possibly also palaces. Houses were arranged on wide main streets and narrow alleyways, and many had their own wells and drainage systems. Water was clearly an integral part of urban planning, and was also essential for supporting the agricultural base.

At around the time we see the evidence for climatic change, archaeologists have found evidence of previously maintained streets start to fill with rubbish, over time there is a reduced sophistication in the crafts they used, the script that had been used for several centuries disappears and there were changes in the location of settlements, suggesting some degree of demographic shift.”

“We estimate that the climate event lasted about 200 years before recovering to the previous conditions, which we still see today, and we believe that the civilisation somehow had to cope with this prolonged period of drought,” said Hodell.

̽��ֱ��new research is part of a wider joint project led by the ̽��ֱ�� of Cambridge and Banaras Hindu ̽��ֱ�� in India, which has been funded by the British Council UK-India Education and Research Initiative to investigate the archaeology, river systems and climate of north-west India using a combination of archaeology and geoscience. ̽��ֱ��multidisciplinary project hopes to provide new understanding of the relationships between humans and their environment, and also involves researchers at Imperial College London, the ̽��ֱ�� of Oxford, the Indian Institute of Technology Kanpur and the Uttar Pradesh State Archaeology Department.

“It is essential to understand the link between human settlement, water resources and landscape in antiquity, and this research is an important step in that direction,” explained Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.”

Inset image upper: one of the snail shells collected for the study.

Inset image lower: Cameron Petrie in the field.

Climate change may have contributed to the decline of a city-dwelling civilisation in Pakistan and India 4,100 years ago, according to new research.

They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East. But, by the mid 2nd millennium BC, all of the great urban centres had dramatically reduced in size or been abandoned

Cameron Petrie

Amir Taj

Indus script

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