[Podcast] Imprints: Lake and archive diving with Atreyee Bhattacharya

  • Atreyee Bhattacharya’s work takes her to lake beds and libraries. She analyses sediments drilled from old lakes and scours archival records to reconstruct past rainfall changes, understand variabilities, in order to work with policy makers to mitigate the effects climate change.
  • Bhattacharya says that using paleoclimate research to inform policies is very important. These evidence-based policies will help frontline workers and improve the food security of the country.
  • This is the first episode of ‘Imprints’, a new podcast series in which the host talks to five paleoclimate scientists to understand how unearthing old data helps us to mitigate climate change.

Exploring the geological history of Earth is fascinating work. That is what paleoclimatologists do. In order to understand climate change or to recognise it, we need to first understand what the planet was like before. This will help us gather what has changed and how. Paleoclimatology uses different methods and technology to obtain data from corals, treeI rings, sediments, ice sheets and more.

Paleoclimatologists sift through abundant geological evidence develop the context for understanding recent climate change. This aids in predictions of future climates and helps shape policy for climate mitigation.

In the first episode of the podcast Imprints, Mongabay-India Contributing Editor and podcast host, Sahana Ghosh speaks with paleoclimatologist Atreyee Bhattacharya, Research Faculty at the University of Colorado, Boulder in the United States, to understand the world of paleoclimate, the significance of paleoclimate research, challenges in the field and how the research can inform policy.

Listen here:



Full transcript

Sahana Ghosh (SG): You are listening to Everything Environment by Mongabay-India.

Welcome to our show, Imprints. I am Sahana Ghosh, Contributing Editor at Mongabay-India. In this episode, we hear from Atreyee Bhattacharya, a paleoclimatologist.

Paleoclimatologists look back at past climates to develop the context for understanding recent climate change. This aids in predictions of future climates. Using this knowledge, they can work with policymakers to mitigate negative outcomes. Atreyee’s work takes her to lakebeds and libraries. She analyses sediments drilled from old lakes and scours British archival records to reconstruct past rainfall changes.

Peering through hundreds of pages of archived, digitised British records, letters and maps, never seen by anyone before, Atreyee looks at past instances of disasters such as floods, droughts, famines. She is excited as new information on records of famines in Maharashtra, going back to the last 200 years, come up because this record will help her reconstruct what happened in the past as rainfall fluctuated.

But despair cuts through her excitement – we have not learnt any lessons from the past. Maharashtra has always been water stressed. Despite that, it’s been intensively farmed, and more and more thirsty crops are being grown.

But there are reasons to hope. With these time capsules, Atreyee is able to partner with economists to shed light on policies that can turn a climate variability into a climate disaster. Her recent research in collaboration with natural resources economist Gaurav Arora, has shown that famines in southern India in 18th to 20th centuries, were caused by not extreme, but minor rainfall fluctuations. This kind of research, she hopes, will act as a guidebook to influence policy so that people who produce our food – farmers and fisher community – are protected from climate shocks.

Let’s hear from Atreyee.

SG: So, Hi Atreyee. Welcome to Imprints. I introduced you as a ‘paleoclimatologist’ and that’s quite a mouthful. Now, let me ask, what do you do as a paleoclimatologist? Why do you call yourself as such? How did you end up being a paleoclimatologist? Was it a conscious career choice?

Atreyee Bhattacharya (AB): Sahana, thank you for having me. It’s a great pleasure doing a podcast. It is the first time I’m actually doing a podcast.

How did I become a paleoclimatologist? I just don’t know this. I have no idea how I ended up here, except that I know this thing — that I was trained as an earth scientist, and then I was doing my masters and at that time, you know, this was early 2000s. I was really not motivated by the skill-based approach of learning that was there like you learn this, you learn that. And most of the time, I didn’t really know ‘why’ I’m supposed to learn this, and ‘how’ this matters. And this was true in Presidency College and IIT, Kharagpur, for the longest possible time. And I was doing my Masters and really not feeling very motivated. In fact, I was going to be a journalist after that. And then, we were forced to basically listen to seminars. There was a seminar at IIT, Kharagpur, by a very eminent scientist – Dr. SK Acharya from Physical Research Laboratory. He spoke about using isotopes to reconstruct monsoon strength over the last millennia or something like that.

AB: I think that was the moment that I decided that ‘oh! this was very cool’. Then I wanted to understand past climate and understood that it is these kinds of studies (learning the past climate) that tells us what ‘the present’ is in the context of the larger history of Earth is. So, I think that would be the pivotal moment when I decided that I would study Earth’s climate, and much later did I realise that it was paleoclimate.

So that’s how I became a paleoclimatologist, at the brink of wanting to leave the discipline. This is what has kept me going for at least more than a couple of decades. As paleoclimatologists, we reconstruct past climate; paleo means past, climate means climate. So, we reconstruct at different resolutions, the past climate history of the earth. And that’s broadly the discipline of paleoclimate scientists. We use different kinds of tools, different scientists use — some of us use measurements, different types of geo-chemical primarily but also biological proxies. To reconstruct climate history and there is also the modelling component that people use to reconstruct past climates. So, all of these would fall under the larger paleoclimate.

SG: Tell me something, why do we need this? Why do we need climate research? And the reason why I am asking this question is, how does it tie in with what should we do as human beings on this earth so that we make our existence and our environments also stable? How does paleoclimate research link to what we are currently doing, and our actions on this planet?

AB: I think it’s a very good question. I would almost argue that, without paleoclimate research, we just wouldn’t know that we are in a climate crisis. Paleoclimate research is sort of the cornerstone, the backbone, the spinal cord, however, you want to call it, that first and foremost told us that we are in unprecedented times.

So, without the study of the past about 4.6 billion years… paleo climate record goes back to almost 540 million years, and that encompasses the entire pharmacological and environmental history of the earth. And it is only in that context do we know that today is an aberration in all of that time. Without paleoclimate research, this would be we would not know where we are. I would say that climate research started as such, that the start that much before the word paleoclimate came into being is how we know under what conditions different kinds of life evolved, under what conditions different kinds of life went extinct (mass extinction events). We know about evolution, but we also know about the climate background under which these things happen.

So, I would argue that you know, without paleoclimate research, there is no climate change. It is only climate change, because we know that it is a change of unprecedented magnitude and unprecedented pace. So, Warren, the famous American poet, said that history cannot tell us what to do, but it can give us a blueprint of ‘what are some of the risks associated?’ I’m paraphrasing him. And I think this is what paleoclimate research does. It doesn’t tell you that ‘do this’ or ‘don’t do this’, but it does give you a very good idea about conditions under which human society has progressed, conditions under which human society has not progressed. And it also tells you what are the environmental triggers we need to be aware of as human societies because these are long-running variables. They don’t happen. They’re not like pandemics. They take forever. In human imagination, it’s forever but it’s quite quick in nature. So, I think this is the most important, I would think of all climate sciences. Yes, it doesn’t have predictive power, but it tells you under what conditions, what are the suitable conditions under which human society has prospered, and under what conditions society has not prospered; under what life has evolved. It’s a sort of a guidebook I would say to the future rather than the sort of what to do and what not to do, which is the realm of climate predictions. So that’s what we do.

SG: Now I want to know – what are the questions that you are trying to ask? What is it that you are trying to get a response to in paleoclimate research?

AB: The primary goal of my research is to understand and reconstruct rainfall variability and using that, we can also reconstruct whether there were phases when rainfall was lower than a certain threshold value for X number of years. So, those are the things that we can get from the kind of work that I do with natural systems, particularly, lake sediments and geochemical analysis of lake sediments.

When we think of disasters, disasters are not natural phenomena. Disasters are only words that we use in the context of some kind of negative impact on human society. So, a drought is basically low rainfall, when that becomes a disaster or whether that becomes a disaster and in what capacity is really about how our socio-economic system, and eventually cultural and political systems, are associated with the expectation of a certain amount of rainfall every year at a certain time.

So, one part of my research, which is based on natural archives, geochemical analysis, basically reconstructs the variation of rainfall and weather, and also in that process, we can find out whether there were periods of a long time when rainfall was lower than a certain amount or lower than the average.

Disasters are something that we don’t find in natural archives. To understand that we go to human archives, I study British archives – British institutional documents, to reconstruct a record of disasters, independently. We record disasters of all kinds. Sometimes disasters can be because of a war. Sometimes disasters can be precipitated by rainfall reduction but become a disaster only when certain policies continue to operate without taking into account the reduction. So, that’s the human archival data. In my case, I look at British administrative documents. And then when we lay that information on top of this very independent record, of rainfall variability, and we start seeing interesting information about ‘is there a threshold below which of rainfall reduces our current or, the past economic, socio-economic policies, did they become a disaster because they were not cognizant or did not quite appreciate the degree of rainfall variability. So, the disasters would be slightly different but rainfall and drought and whether at what point that rainfall and drought variability becomes a disaster is something that I study by combining two sets of independent information.

SG: When does ‘variability’ become a ‘disaster’? That is what is the crux of what you are doing. You have a substantial amount of fieldwork. About these semi-arid landscapes, where you do your fieldwork, especially in Maharashtra. Could you take us through your fieldwork experience? Where is it that you go exactly? How do you select these places in the first place? If you’ve got a toolbox? What are the tools in your toolbox, while you’re on the field?

AB: So yes, the field which I have not been able to go to for the last two years, thanks to the pandemic. So, I look at lakes – I look at old lakes. Sometimes these are natural depressions, sometimes they are natural depressions that have been walled off to make reservoirs. So, these are old techniques of harvesting and using water in semi-arid landscapes, not just in Maharashtra or southern India, but across most of the Indian Ocean region. I look at lakes, I find out lakes that are mentioned in historical documents, both British documents and older and we go there and do a combined  – so these kinds of studies where you want to understand, you know how the lake system evolved over time. It’s not one tool that can give you any of these answers. They’re incomplete by themselves. Because these are systems that are not just natural or manmade, they’re composition of both.

So, what we do is first deploy remote sensing to see what the recent history of the lake is. Then we also deploy geophysics. A colleague of mine Sudipto Sarkar is in IISER, Pune. He works in remote sensing and lake geophysics. We also map the bottom using different kinds of geophysical tools. And we understand the sediment pile and then we go and take out the cores. These are tubes of sediment, the top one being the youngest, the bottom one being the oldest. We take out these one to one-and-a-half metre cores, using different kinds of coring techniques, gravity coring, and micro-coring depending on how much they can penetrate and what can be recovered. And then we take these to the lab back in the US, at the University of Minnesota that specialises in these kinds of core analysis, and we split it right down the middle. And once we split it down the middle you can sort of see history visually that the top of the core, was the day we collected it. And as we go down, it goes basically back in history, so then we go ahead and date these cores. We have three different kinds of radiometric dating carbon dating, Caesium-137.

So that’s what we do and when we then compile all of these to understand when did the sedimentation rate change, whether it was climatologically controlled, whether it was biologically-controlled, whether it was human-controlled. And then can we construct not just a climate history, but a landscape history which is modulated both by climate as well as human activity.

This is the kind of fieldwork which we do. The other kinds of fieldwork that I do, it’s also archival work, in which we go and look into documents, the British documents, institutional documents, in regional and national archives, and we look at minute papers all the way to reports and extract information related to mention of floods, droughts or disasters.

SG: But in addition to Covid-19 impacting fieldwork, what are the other challenges in paleoclimatology? Is there something that is really bothering paleoclimatologists when they are working in India?

AB: I think several, for example, currently getting international, collaborative work funded is usually challenging. And that is making scientists of different countries work on their own … domestically and that changes how effectively we can collaborate across different disciplines across different countries. So, that’s a major game changer. I think, what do we mean by collaborative science? Can we do field sciences? A lot of times people in it used to be a field-going in paleoclimate scientists, but currently, a lot of my focus is sort of on modelling and statistical modelling, because I’m not able to go out in the field. So, with these kinds of… as COVID 19 sort of evolves and stabilises and impacting things is that this has been a major problem in this field. The past two years, I don’t think people have been able to go out in the field and do any meaningful work. The repercussions of this are going to continue. So, I don’t know what the solution to this but I think in the next five to 10 years, we’re going to see severe impact on fieldwork, on at least international teamwork.

I mean, over the last two years, we have hardly been able to go to any of the archives. Because earlier we used to be able to go to the archives and work long hours and go into the map room and see what maps are there. During the pandemic we have not been able to access the archives at all. We rely on digitisation by archivists, to do these things. And while there are several archivists who have made documents available for your course, very easy to access. I do think that one thing that needs to be done is that archives can basically you know, digitise everything and make it available. Because currently, last two years, we have not been able to go to the archives either. So, all of the work, basically all the data collection has stopped. Right now, it’s gazetteers or secondary information that we are mining, which is in a way fantastic because it’s comprehensive, but it’s not raw data.

SG: While the problem of a pause in data collection/data mining efforts, sounds serious. But, on a lighter note, I was curious, did you have any ‘aha’ moments when you are going through these archives? When you’re going through these documents that are hundreds of years old? You come across some information, and you think ‘Oh Wow! this is really cool. ‘What I have is, something really cool, which I need to understand more.’ Do these ‘aha’ moments come in your work?

AB: The ‘aha!’ moments come when you actually create both these records and superimpose them on one and then the ‘aha’ moments come when you analyse, but also these documents are really cool. I mean, some of these have been written 200 years ago, never seen by anyone. And then you’ll see that you know, people are talking about the same thing that you’re talking about now. I think working in the archives has been quite fascinating for me. It’s not been an area where I was trained formally as a graduate student. I learned that later. And I think archives are digging into the past and looking at letters and, minutes, reports, and maps. And then you see the problems that we’re talking today. We’re not just today there were 200 years ago as well. And you’re almost saying that we have not learned any lesson at all. There are cool moments and there are also despairing moments, I would say.

SG: As you said, working in these archives has been really fascinating. Could you give us a glimpse of what was so fascinating in terms of your findings? What were these interesting findings? You’ve been able to uncover during these decades of work, these interesting things. Could you give us a summary of what these findings mean and what these findings exactly are?

AB: What has been sort of a deeper understanding is that today we know that semi-arid regions are water-stressed, and we think that it is present-day climate change, when in fact, it used to be far more water-stressed 200 years ago, simply because we are in a different climate regime altogether. Even what we call the Little Ice Age. And today when we you know if we think of western India, southern India, the monsoon doesn’t arrive on the first of June or the 5th of June or whenever that is, we start panicking.

But in these documents, you often see instances of failed monsoons for two seasons. And those are ‘Eureka’ moments. You’re like, people survived somehow, and you know, but they didn’t survive, there were widescale social disruptions and deaths. As soon as that famine would be over in the next five years, things would go back to the same old-same old. But I often find that you know, all of the problems that we talked today have been around not just for 50 years, but for 200, 300 or 400 years. And we somehow tend to think of these problems as problems of the ‘past’ because we changed the language of discussion around it.

For example: Maharashtra. The state today is water-stressed, but it has always been water-stressed. In the last 1000 years, it has always been water-stressed. And yet every time you see, every epoch, you’ve seen it more intensively cultivated more and more water…thirsty crops being grown, simply because Maharashtra is connected via Bombay as an important port, and therefore, trade commerce and economic decisions have always sort of driven the market in a direction which is front-loaded. In the sense that, there is rainfall variability here, rainfalls do fluctuate quite often. And every time it fluctuates, there is a famine. You have 200-year records of famine, and you see nothing changes it only becomes worse. So, these are some Eureka moments that nothing that we are seeing today is new, but yet we continue on this path of sort of market-driven decision making which ultimately makes any variability into a disaster far more quickly, and far more effectively.

SG: You’ve made a very important point about this path that we are on, where our decisions are so market-driven right? Which in a way, transforms variability into a disaster far more quickly. What I am trying to get at now, is, taking off from all this research, how does your work inform policy? And in addition to policy, can it inform planning? So that, we understand the impacts of climate variability better, so that we can adapt to climate variabilities better.

AB: That’s the point where I feel actually better about things, because I work very closely with the natural resources economist Gaurav Arora at IIIT Delhi. This is where we basically take the recent past and sort of the contemporary and see what sort of the main drivers are. What it was 200 years ago is very different today. I mean, there were very different kinds of technology, then, very different kinds of technology today, different policies then, and different policies today. But what we do is basically try to understand the pivotal components of problems of today.

And we have found out that, you know, water stress, food security, access to ports, whether that’s a port today, or whether there was a port 200 years ago, has been sort of the most important issues driving famines and disasters. So, in this way, when you when you develop methodologies, pretty much analytical methodologies (In fact, we’re currently drafting a paper on this methodology) is that when you’re able to not just say this is not a contemporary problem, this has been around for 200 years. And these are sort of the systematic and institutionalised issues that cause climate variability to become a climate disaster. And when you do that, then you start influencing policy, hopefully. So, we are more inclined to basically think about sustainable policies and implementation because these are too big for farmers to do on their own.

Farmers will obviously want to sow a crop that fetches them more money in the market. It is up to the policymaker and the administrator to come up with policies that are more sustainable and protect farmers, rather than asking farmers to make a change in direction that doesn’t give them the money that they need.

So, we tend to focus on using such research to draft or inform policies that are more sustainable in the regional context, and we hope that that method might be helpful for/ protective of frontline workers, farmers, and fishermen who provide our food. This is where I think a new kind of research is emerging. Climatologists who look into the past, partner with economists interested in not just 10 years of data, but a long-term running variable. And use that to say, well, here is the evidence, and we need to come up with policies that are cognisant of this and protective of our frontline workers and our food security. That’s the place where I feel hopeful that if we know these things, can we work with policymakers, and governments so that we do not encourage policies that have only backfired every time and it’s going to backfire severely, as climate variability increases … more droughts become common, and there’s more pressure on the natural system and natural ecosystem services. Does that make sense?

SG: Yes, that absolutely makes sense, what you are trying to emphasise here. You’re saying that climate mitigation needs to be fair and just. But, can you give us a few examples of how this ‘just’ pathway is? Are there examples of inequity in climate mitigation and on the other end, what a sustainable policy or a pathway could look like? Could you give us an idea of what that might be?

AB: Today, Maharashtra gives subsidies for solar-powered ways of extracting water. That’s great, and the argument often is this is going to mitigate against climate change, climate change. True, maybe from the energy aspect, but given that this allows farmers to extract water from a limited supply, and that availability is also marked by caste, gender, age, position, society, all of that. What ends up happening often is rich farmers become richer and poor farmers become poorer. So this is the kind of policy well, on one hand, yes, solar-powered pumps are great. You can get water. But again, this policy is not working for poorer farmers. And when they cannot farm the land, they basically go out to the city which is sort of a migration. So, Gaurav and my work is to understand climate migration and the role of policy and climate impact. So, this is just one example that we are looking into currently, but there are several such examples across the country, the northern part in the southern part, and sort of even desert areas. If we are to solve this problem, the policy is really the only way to solve this. There is no other way.

SG: And one thing that I want to go back to, is in our earlier conversations, you’ve spoken to me about a paleoclimate research database that is coming up. You’ve been talking about a group of people coming together to create a database, in addition to you. Now, how is that going? Can we access that database? At what level is the work now?

AB: We are hopeful that this database… the thing is first of all in our country, we don’t have access to data. Say an anthropologist wants to compare oral history against an independent report of rainfall, that person will not find that data anywhere or will have to go through great trouble trying to locate the author, request the data, and so on and so forth. One of the things that are not true in many other countries. What we wanted was a beta database, which has a section for scientists, and people like me, who need other data to benchmark their own new data against and the other one is for stakeholders and eventually for teaching, that we want to create products that different kinds of people need.

A planner will not look at isotopes, but they may want to look at what is the rainfall history of the region, so they may want to know in millimetres, but all data is available in very different metrics. So, there is a job in converting all of this data into what we call usable measures. So, the database first will give access to researchers which enhances their research output. We also expect to use the database to create products that are usable by planners, decision-makers, policymakers and even farmers. And then we also hope that we create teaching modules that NGOs working at the interface of community and science can access and use that to work with their own community members. We call it teaching modules, but it’s not necessarily classwork teaching. It’s more about addressing that… there’s a lot of good data science, that scientists produce, that use that is not just for entertainment, but creating modules that allow people to get trained in how to use the data and the information. These are the three aspects of that database. The first aspect is currently what we are working on, but we are also sort of developing methodologies to see how we can convert existing data. So it’s a mammoth work. The first part is done. The second part is in progress and the third part is a dream so far, but hopefully, we’ll get funding to make that dream possible.

SG: Thanks Atreyee for helping us make sense of our current challenges and also for explaining, for unpacking, how this kind of research can contribute to effective solutions and how we can take it ahead for implementation on the ground. Thanks for spending time with us on Imprints.

In our next episode, we will hear from someone who finds clues in mollusc shells. Please subscribe and share our podcast, Everything Environment by Mongabay-India, with your friends and family.

This episode of Imprints was hosted and produced by me – Sahana Ghosh. Co-produced by Kartik Chandramouli and edited by Tejas Dayanand Sagar. Cover art by Kartik Chandramouli. Copy edits by Sapna Verma and Priyanka Shankar.

Read more: Most famines in south India under British rule due to minor rainfall fluctuations, rather than extreme events


Banner image: A lake near Lohgad in Maharashtra. Photo by Karthick/Wikimedia Commons.

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