Nebojsa Nakicenovic is the  deputy director of the International Institute for Applied Systems Analysis (IIASA) and a former professor of energy economics at the Vienna University of Technology. He has been involved in the IPCC since the first assessment report, serving as a convening lead author of the  Special Report on Emissions Scenarios. He is now running to succeed Dr Rajendra Pachauri as IPCC chair.

On producing shorter, more accessible reports: “It would be very desirable to have products that can be produced at a shorter scale, that can more reflect the concerns that are there.”

On the workload for IPCC scientists: “I think there are scientific rewards…But the burden is large, I have no doubt about it that the burden is very large.”

On the Sustainable Development Goals (SDGs): “Clearly climate is connected strongly to almost all of the facets of sustainable development.”

On assessing countries’ INDCs: “I think there is a role the IPCC and the scientific community to look at how consistent they are with some of the long term pathways.”

On the feasibility of BECCS: “There is nothing automatic about it, removing such large amounts of carbon from the atmosphere is a real tall order.”

On meeting the 2C target: “Most important is the social changeâ?¦Without that, I think scenarios like 2C and below will be out of reach.”

On a low carbon transition: “One shouldn’t look at this transformation into a low emissions world as something one have to fear, it could be a huge opportunity for humanity, if we do it right.”

On the IPCC’s mandate to be policy-relevant but not prescriptive: “I think the definition is evolving with time.”

On scientists as advocates: “Science definitely needs to speak and I think the views of scientists…can benefit our collective views about the future and what needs to be done”

On social media: “I think that the IPCC has to keep up with the times, the world is changing. There are other ways of communicating and this should not be ignored.”

 

CB: With the 5th assessment report [AR5] done and dusted, how do you look back on it? How do you think it has been received?

NN: Well, first of all let me thanks you for this, for taking this interview. To come to your question about the fifth assessment report, I think it has been received quite well. The fifth assessment report was a significant advance. In particular, I’m not just referring to the substance, but also to the outreach functions and the way it has been presented with the regional workshops. I think this all has helped, and let me also say that I think things have changed in the world. I think the fifth assessment report came out somehow just at the right time because this year, 2015, is a very special year. We will have, next week in New York, the sustainable development goal summit and end of the year, Paris. This is all putting much stronger emphasis on the need for action and I think climate is an important part of the overall transformations ahead for our society. In addition to the substantive contribution of the IPCC, I think it is coming at the right time and these messages are very relevant for these processes that I think many people are concerned about.

CB: The IPCC has, of course, confirmed that there will be an AR6 [sixth assessment report]. How do you think its scope or function might differ, then, from AR5? Or how might it signal a move forward for the IPCC?

NN: I think it is definitely decided the structure will stay the same. There was talk before the Nairobi plenary of perhaps restructuring the working groups, the three important pillars of IPCC working groups one, two and three – and the decision is quite firm that that will stay as it is. I’m not aware that a definite decision has been made about the structure of AR6, but I’m quite certain that eventually there will have to be an assessment report. So, from my point of view, one of the biggest challenges for the new assessment, AR6, would be to have even more integration than we had in AR5. AR5 went beyond AR4, but I think for AR6, a major challenge is to try to link climate change together with vulnerabilities and impacts, together with loss and damage notions, and together with economic and social aspects of mitigation and adaptation. I think this is where the big challenge is. And the reason is this year in New York, the sustainable development goals will be adopted, goal number 13 is on climate; in Paris, we will know roughly how the commitments look by various countries. I think IPCC is the main scientific body to look into those areas, those issues in an integrated fashion. Therefore, my view is that the sixth report, whatever form it takes, might be one of the most important ones because one could argue that the world has changed. Since Kyoto, there has been quite a lot of talk about the possible action, and there has been some action; even in the private sector, but certainly by many governments. But the big, let’s call it, heavy lifting; the big efforts are still ahead of us and I think that’s why the sixth report is so important.

CB: The IPCC has decided to continue producing big assessment reports every 5-7 years. Would you have preferred to see smaller, more frequent reports on specific regions or specific topics, as some people were suggesting?

NN: Well, let me just first say that I don’t think all of these issues are something that the chair can decide. The function of the chair is a catalytic one, it’s one of leadership. At the end of the day, it’s a scientific community and the governments decide that. But if it were left to my own devices, I would think precisely because of what I said in a comment to your previous question, it would be very desirable to have products that can be produced at a shorter scale, that can more reflect the concerns that are there. Because as we go beyond Paris, I think we will see development and the science will need to be there to inform the decision makers. Let me try to be specific: I would imagine that the tool of the workshops would be an excellent instrument to try to address those kind of questions. I would imagine even longer workshops that we had in the past with the reports, I think that would also give an opportunity to engage a broader scope of scientists and experts, in particular, more from developing countries. I think we have to work on that. But also, social sciences and other disciplines that will be required for understanding the way forward in a world that has to mitigate and at the same time adapt and deal with the loss and damages. I think it’s a really tall order. So, those kind of expert workshops would be a good idea. I would also like to see the instrument of dialogues with various groups deepened. I think that has worked really well at the COPs, with the UNFCCC. I think that has shown the expert dialogues to be quite a good vehicle. I would imagine that could be expanded also to other communities, and perhaps also expanded at a regional level. But while I’m saying all of that, I think one also has to worry a little bit that the scientists who are contributing to the IPCC do all of that pro bono, so one should not make the task more difficult. It is difficult as it is. So, it won’t be easy to find a middle way, but I would argue strongly that there are products that are more adaptive on the short term.

CB: Do you think the burden is too high on scientists taking part in the IPCC already? Or do you think it is a fair task, perhaps given what the scientists and their institutions get from it?

NN: I find it absolutely amazing that, actually, this very unique process of science together with policy is working the way it is and that the scientific community has approached it with lots of enthusiasm. I think there are also big rewards for the scientific community, in terms of integration of different disciplines together – let’s say, climate science together with economists, sociologists. I think this is something that in AR6, might even come more in the foreground. I think there are scientific rewards of identifying the future research questions, helping to publish the relevant material. But the burden is large, I have no doubt about it that the burden is very large. I think in the long run, maybe that’s not immediately relevant for AR6, but certainly beyond, as I hope this process will continue, one has to think about other different models. In particular, I would say for colleagues from developing countries, where there is huge expertise, but because of the lack of funding and lack of opportunities, colleagues are not empowered enough to always be able to devote the time that would be required. I am very much impressed, I would say, and proud that the scientific communities have been providing this and I think my expectation is that it will work well in the sixth report, but all along we have to think of different mechanisms. And the reason why I’m saying that is because the scientific reality has changed. Many scientists work on specific projects where they have to account for their time. I had the privilege of coordinating two other assessments, one is a global energy assessment and the other one was the Austrian climate assessment, that was basically rooted and based on the IPCC. And, in both cases, we had those issues. I know that also within the IPCC, many accept those issues. So, I am very hopeful for AR6, but we shouldn’t lose that out of our attention.

CB: In terms of specific topics of interest, one suggestion for next special report has been food security. Would that be your preference, or is there something that is more urgently needed, such as Monaco’s suggestion for a focus on the oceans?

NN: I would argue that both topics are important and there might be others. I have mentioned the loss and damage topic as well, also in the context of mitigation. The scientific communities have joined forces to produce new scenarios for the IPCC. I think this is another important topic, and so on. I think also, how does the IPCC respond to the INDCs [Intended Nationally-Determined Contributions], to the commitment governments are making. What role IPCC or science can play in those? I think these are all important topics. I think the problem is related a little bit to the earlier question. I personally wonder whether it would be feasible to do more than two special reports and since there are so many of these important topics, from oceans to food security, but think about water, these are all cross-cutting themes that concern all of the three working groups and need to be handled in an integrated way. There may be other tools, workshops. The IPCC also has the tool of the policy papers. However, those are usually limited, the terms are usually limited to the already completed assessment reports but they might be new forms of those that could be also talked about. And let me mention one more topic that is not in this portfolio that might become important. There is, as we look at sustainable development, clearly climate is connected strongly to almost all of the facets of sustainable development. And there might be a need to strengthen even more the idea of how does one link climate to the other development goals. I think this is very important. AR5 has made a step forward in that direction by looking at the multiple benefits and co-benefits of mitigation and avoiding catastrophic climate change. But perhaps that needs to be even broader in the sixth report. That might yet another topic to be added to the portfolio that we discussed.

CB: You mentioned INDCs there. The former chair, Rajendra Pachauri, suggested the IPCC could have a role to annually assess INDCs and progress towards targets. Do you think that’s a role that the IPCC could play?

NN: I think that is an important potential role. I know that Dr Pachauri suggested that, and I think it’s a very good suggestion. But one needs to discuss how that could be done. Because in my view, it’s clear that the initiative would have to come from the convention, if it were something that would be done on a more regular basis. However, as one thinks about it, I think for sure it would be my view that the IPCC should not look at the individual national INDCs. I think there are other bodies that will do that, including the convention and also many other independent, scientific groups. So, my take would be that the potential role for the IPCC is to look at the aggregate of all the INDCs and then look in particular beyond the current timeframe, beyond the short term. What does it mean for 2050? How consistent are the aggregate of the INDCs to the long term trajectories of where one could end up in the long run? So it is very much connected to the scenarios but also to other notions that I have discussed before. I think it would require an integrated approach. So, I hope it is clear what I am trying to say – I think looking at all of the INDCs together – and they might evolve over time, because there’s no doubt there could be adjustments – I think there is a role the IPCC and the scientific community to look at how consistent they are with some of the long term pathways. There is yet another scientific dimension that I would like to mention. The convention primarily assesses the commitments of the greenhouse gases. But many of the INDCs, in particular in developing countries, put quite a lot of priority also on air pollution, in particular on particulate matter emissions. Those substances are also closely linked with climate and with emissions of greenhouse gases, and I see that as another potential role of the scientific community, to provide answers to how those also look at the aggregate [level]. So, to look beyond greenhouse gases because the INDcs will include also adaptation but they will include, as I mentioned, mitigation of air pollutants that could have a positive effect on emissions of greenhouse gases, because that’s the highest immediate priority in many of the countries.

CB: The summaries for policymakers [SPMs] have in the past been criticised as being too hard to read. What do you think of the suggestion to seek advice from science writers and graphic designers, for example, to help make them more accessible?

NN: I think that’s a very difficult question because the summaries for policymakers are negotiated documents. I would definitely see, perhaps, a stronger role of scientific writers to work with the drafting teams of the SPMs, so that the initial draft that’s submitted to the governments is perhaps already in a more readable form. But at the end of the day, it is a negotiated document and some terse language is bound to pop up. On the other hand, the big benefit of that is even if it might not be readable, it gives you exactly the information of where governments and the scientific community can agree on. I think that’s exceedingly important information and probably shouldn’t be given out of hand. So, perhaps one has to look for other mechanisms and I think there are already some ideas in that area of other groups interpreting what’s in the SPMs. It doesn’t necessarily need to be only in the form of language, there are other media possibilities as well. But I just wonder whether that would be the job of IPCC. I think it should be part of the outreach and, hopefully, that outreach will also then lead to the broader interpretation. I think uniqueness of the IPCC, of science working together with governments, should not be eroded. On the contrary, it needs to be strengthened while at the same time making products that are easier to understand and easier to read. So, it’s a tough challenge, but I think if one looks in the literature, there are examples of how that has been done. Some leading science articles allude to the results of the IPCC and try to interpret them, so I think we should see more of that.

CB: Looking back then, do you think more could have been done by the IPCC or other groups to make the IPCC’s findings as a whole more media-friendly?

NN: I’m sure that one could improve that and I think we are already doing, in AR5, the outreach in an attempt to reach a broader audiences, including media . I think there should be more attention to press conferences, the IPCC does hold press conferences and I’m sure after the next plenary there will be a series of press conferences. So, I have no doubt that the outreach function needs to be further strengthened and I think this is very important, also because of what we discussed before – I think the world has changed and I think the role of the IPCC could be significantly larger in the future and it should not be kept as a scientific secret. So dissemination is very important and some media outreach, for me, would be one of the top priority areas, to work together with governments and writing teams to improve the outreach functions.

CB: How do you think the IPCC process could be made more transparent? Particularly the SPM plenaries. For example, do you think they will ever be open to the media?

NN: First of all, I think this is a very good point because the IPCC process is exceedingly unique and has been copied many times. For example, I participated in the Millennium Ecosystem Assessment that was modelled to a large extent after the IPCC process, the two assessments that I mentioned that I had the pleasure of coordinating – the global energy assessment and the Austrian national climate change assessment – were also modelled after the IPCC. And I would argue the new process, the IPBES [Intergovernmental Platform on Biodiversity and Ecosystem Services], is also modelled after IPCC. So, in some ways, the IPCC process is the shining example of how one can bring science for policy or work together between the government and science. And this process is very intricate and I don’t think it is really well understood. And so, I think transparency of the process should be enhanced. Of course, there are documents on the IPCC website, everybody can read about the process. But it’s another thing if somebody can interpret it and make it a little bit easier to understand and more comprehensive. I think it would be good to also involve various stakeholder groups, including social science, to try to articulate the processes in such a way that is more understandable for the broader communities. Because I think there may be quite a lot of value in thinking that similar processes could be started in the context of the sustainable development goals. Also initiated at the regional and local level, I think that’s also important. When we talk about IPCC, the IPCC does lots of assessments that refer to the regional level but there is an incredibly high value of doing assessments that are based on the IPCC in specific regions. These are just some of the examples. But to answer your question about whether media should be in the meetings, I’m a little more reserved about that. That’s also related to the question that you asked me before, whether the ambition level is too high for authors. I think that the authors should have a right to communicate with each other according to what’s called Chatham Rules – they’re not necessarily quoted until the drafts are ripe enough, and this is the function of the review process. However, that should not exclude the possibility of doing media and other outreach functions as the process is being developed, and that’s another reason why I was arguing also for a higher role of expert dialogues and expert workshops because that would be another channel of disseminating the ideas, and the special reports that you mentioned at the beginning. I think one has to look at this holistically. But right now I am a little bit skeptical whether it would make sense to include explicitly the media in the early stages of the work.

CB: It’s been suggested that the different working groups work too independently of each other. Do you think there’s a need to better integrate the three groups?

NN: For me, that’s the highest priority. In fact, I would say I have two highest priorities: one is even stronger involvement of colleagues from developing countries, to bring in local knowledge and other perspectives, especially as we’re talking about adaptation and mitigation. The other is to strengthen the connections between the working groups. But please do not misunderstand me: I think a lot has already done in AR5 to do that. This is a very difficult job and that’s why I think it deserved the utmost attention from the bureau and the executive committee of the IPCC. In my personal experience, I’ve been working in [an] interdisciplinary [field] for most of my scientific career, and my experience is that interdisciplinary work is perhaps the most difficult thing we have to do as scientists, it’s difficult to cross those barriers. At the end of the day, each of the working groups is an important pillar, so I would not argue for softening those pillars but I would argue for building a new superstucture on top of them. Not just on top, but perhaps also across. To be specific, one can imagine chapters and certain topics that are even taken more extensively across the working groups, sharing the authors. One of the examples I mentioned before was loss and damage. I think all three working groups need to contribute to that topic, it’s one of the most important issues coming up. But I would also say that at the level of the bureau and executive committee, one has to think much harder of how to integrate the three working groups because the challenges ahead of us, in my view, will be of an integrated nature.

CB: Do you support having a separate synthesis report, then? Or do you think it would be better to make linkages between the working groups throughout the process?

NN: I would say both. I think these are interactive processes and I would imagine that much more focus on the synthesis upfront would also enhance this cross-collaboration in the working groups. Because in some ways it is the fact – and I think it could stay so for a long time – the really hard work will occur at the level of the working groups because one has to assess the literature, make judgements about the literature, look at the uncertainty, what do we know, what we don’t know, what are the future research questions. That still needs deep disciplinary insights in various areas of the IPCC. But going beyond that, I think talking about these broader issues, for example, sustainable development and its relationship to climate mitigation and adaptation, I think this is an overarching issue that has to be considered across all three working groups. I’m suggesting stronger scoping on the synthesis before, probably much stronger emphasis on the synthesis but still allowing enough elbow room for working groups, who are an important pillar of the IPCC, to focus on their own topics. I would see that more as an interactive process. I think it would be a chance lost if one would leave the synthesis at the end so that it’s more a summary of what happens in three different worting groups, rather than an integration of the three working groups.

CB: What is your own background and how does your experience make you well-suited for the job of IPCC chair?

NN: [Smiles] Well, that’s really not for me to judge. That’s really for the others to judge, I can just say what I’ve been working on. My scientific interests are largely in the area of how do we achieve a developed world while not interfering with what’s nowadays called planetary boundaries, that is essentially not going beyond the limits of our relatively small planet. Economic development is at the centre of my issues. In particular, those who are left out of the economic development. To illustrate it, we live today in an economy that’s on the order of $100 trillion for 7 billion people. The average of that is not so bad, it’s about $50,000 for a family of four and yet we have three billion people who do not benefit from that, that live in relative poverty. Three billion people do not have access to sustainable energy. That access is very important, it is also something that has to be looked at in the context of climate change. I would say development is one of the big interests of mine. It has also to do with my background. I was born in a developing country [Montenegro], so I have lots of sympathy with the challenges that many countries are facing. At the same time, however, it is clear that we need to deal with the environmental problems, and climate might be one of biggest challenges that humanity is facing. It is a tall order, we need to develop. In particular, connect those who are not part, who have not benefitted from the industrial revolution, while at the same time ramping down the negative impacts through a reduction in emissions and increasing the adaptive capacity. That has been my interest throughout my working career and with some focus on technology issues in a broader social and institutional context.

CB: What’s the right balance to strike between adaptation and mitigation? Do you think that the IPCC reports, given their three working group structure, is clear enough that it’s not an either-or situation?

NN: It’s definitely not either-or, the two things go together. I would say they also go together across the wide spectrum of possible future development pathways and I think we have to see that in that context. It’s clear that we also need to analyse the current situation because climate is changing as we are speaking and one needs to adapt also to the changing climate. But I think as we go further into the century, the challenges might become bigger. So the more we mitigate, the easier adaptation will be. The less we mitigate, the more adaptation will have to be done. The new scenarios that our community has developed – and that have been partially available for AR5 and that will be fully available for the AR6 – provide a kind of a backbone or an organising mechanism to look exactly at those trade offs. While there are are trade-offs and there are mutual benefits, we will need to do both. Because we are definitely beyond the phase where adaptation can be considered to be a marginal issue, it isn’t. It is as important as mitigation.

CB: What would you say is your biggest frustration with current research direction? Or put another way, what specific questions would you like to see answered more than any others?

NN; I wouldn’t call it frustration, but I think there are issues that the scientific community is facing that I think need to be somehow resolved. Let me just give you an example from AR5, so that it’s not all totally abstract. AR5 has looked at the consequences of short-term decisions on long-term outcomes. In particular, in working group three and the synthesis report that comes out quite strong. I think we have a little bit of that problem today in the world, when we deal with climate and many other similar issues. The solutions require immediate action and the outcomes of that immediate action is very long term. In other words, our current decisions that are made for many different reasons – not climate alone, for sure not, and that’s how it should be, there are other priorities – but they do cast a very long shadow into the future. To bridge that gap is a very important topic for the scientific community to deal with and, therefore, provide information to the policymakers about how some of the short term decisions, what kind of consequences they might have in the long run.

CB: If I can ask you a very topical question. NOAA just announced last night that there is a 97% chance that 2015 will be the hottest year on record. What do you think the significance of things like that are? What should we take from that, do you think?

NN: Let me just give you my personal view. It’s not surprising the way this year has looked. We still have to wait till the end of the year to have higher certainty, but it does look like it’s one of the warmest years on record. Certainly, for example, in central Europe we had one of the hottest, the hottest ever July on record. So let me put it this way, an important finding of the IPCC AR5 is that with high certainty, we know that the climate is changing. Attribution of single events, shorter term events, to climate change continues to be very difficult and uncertain. But the other way around, we have quite a lot of certainty. As the climate changes on average, we can also expect to be hitting lots and lots of records on the upper end of the scale in the coming decades. For that, I think there is quite a high certainty and the problem is that many of those events might be very extreme and this is why I think the consequences of extreme events and the risk perception that the IPCC already started in the AR5 are so important. My conclusion is one shouldn’t be surprised, if there are phases like the “hiatus” when we are below the trend and we should not be surprised that there are phases when we are above the trend. I think what is very significant is that the trend is going upwards unless we can implement immediate mitigation of climate change, namely, of greenhouse gases and other substances.

CB: You mentioned the “hiatus” there. What do you think when people say that a record 2015, and, indeed, a record 2014, signals an end to the so-called “hiatus” in surface warming? Do you engage with conversations like that?

NN: To be honest, not all that much because I think there is not scientific clarity completely on why we had this lull in the temperature increase, let’s put it this way. But, as I said before, I do expect large volatility around the trend and so I have not been surprised that we do not have every single consecutive years as a record. But I think it is a topic for future research that we have a little bit higher certainty. Predictability – I would be very cautious with that word. Nobody can predict the future, it depends on our actions. I think this is why this interface between science and policy is so important, is actually to have a view of what humanity can do for this large problem and at the same time continue developing.

CB: Talking of the interface between science and policy, one very policy-relevant and new introduction into the last IPCC report is the concept of carbon budgets. How effective do you think the concept of carbon budgets is? Do you see the message getting through in terms of a finite limit for a particular temperature target?

NN: I do believe so. I think that the concept is exceedingly important and, let me just say, I was delighted to see that AR5 has taken that on board. It is also kind of an integrative concept so one shouldn’t underestimate that dimension. I would say in the research of climate change, the idea of a budget has been present for a long time. What is really significant is that the IPCC has taken that on board and has based it on the most recent findings and literature. The reason why it’s important is – basically what the IPCC says – that in the first approximation, climate change will be a function of cumulative emissions. I think it’s also important the finding that we have already emitted roughly two thirds of the emissions for the budget for stabilising at roughly 2C, there are 1000 billion tonnes or so left. I think this is a very powerful notion, independently of which level one might stabilise climate, the budget is always limited. It’s an endowment for the whole of humanity, it’s an endowment to achieve what is ahead of us, to achieve development, to meet other social and human needs. So, I think this notion is very important, that using the endowment rationally needs to be communicated really well. That it’s not an open ended horizon.

CB: The IPCC scenarios that keep the world below 2C of warming above pre-industrial levels, which is, of course, the internationally agreed limit, rely heavily on BECCS [Bioenergy with Carbon Capture and Storage]. Is that risky?

NN: This is yet another of the topics that I would say for the scientific community continue working, as we speak there are very large efforts around the world to understand a little bit better from all dimensions, starting from the climate and earth systems going all the way to the mitigation options that would be required. The scenarios in the literature indicate, as you have mentioned, that stabilising at 2C or below, most of them rely on net negative emissions, not just negative emissions. Many scenarios in the literature include negative emissions, but they include net negative emissions. The more we overshoot over such a target, the larger the amount of net negative emissions might be required. So, if you go back to the number of thousand billion tonnes of carbon left, if we emit 1,300 we would have to remove 300, and this is a real tall order from the current perspective. My view on that is that we do have all of the component technologies. That means that, technically, one can think how that could be done. There are component technologies for carbon capture and storage. Biomass is also a technology that can be done sustainably. Afforestation as well, because that would also result in net negative emissions. Or think of the Brazilian ethanol programme when you ferment sugar into ethanol, CO2 could be in principle collected and stored. There are options that could be done. The problem, and this is really the big problem, is that we know how to do that at the level of millions of tonnes of carbon or so per year. But thinking about the cumulative need to remove a hundred billions of tonnes, that means scaling up by more than a factor of a thousand. This is not known. We cannot know today whether there will be negative consequences of such a large scale up of those technologies, whether they would be socially acceptable, how to control the risks – because they will have many risks, as we know already today. There are many, many questions there, but I would also like to add the question on the Earth systems side. I don’t believe that we have a high certainty now that as we overshoot the target and remove carbon to go down to whatever the level might be, that we know exactly how the earth system will be reacting to that. It’s a different dynamic than what we have until now. In the past, we have been thinking how to approach a certain target from below, namely, by limiting emissions. Now we are talking about approaching from above, namely, overshooting the target and removing greenhouse gases to go back to that target. And so I think this is a topic for future research. There is nothing automatic about it, removing such large amounts of carbon from the atmosphere is a real tall order.

CB: A lot of countries that are already seeing the effects of climate change are calling for 1.5C instead of 2C. Given how ambitious 2C is and everything you’ve just explained, have we missed our chance for 1.5C? Is it off the table now?

NN: It depends what you mean by chance. I think that the scientific community is already working on scenarios that limit the temperature increase to 2C, or well below 2C. This is already ongoing work as we speak and one would have to analyse those new scenarios as they become relatively large. If we think about likelihood in terms of what kind of properties those scenarios have, that’s one thing. The other one, if you’re talking about the likelihood of occurrence, I would say that is in the beholder’s eye. There is no doubt that the lower we go, the more difficult it is going to be. However, in view of our discussion in the previous question, if you are approaching a future climate target from above, in principle, there is no limit to how low does one go. It’s an issue of more effort, instead of removing 100 gigatonnes, maybe you have to remove 200 gigatonnes. That’s more on the technical side, but what I would like to put forward is the fact that this is not just a technical issue. Losses and damages in some parts of the world are already high today and are likely to increase. So clearly the lower targets from that point of view are very much more attractive. At the same time, we will need more technologies to achieve those and for that we need upfront investment, which is very difficult nowadays. Perhaps most importantly, and it’s something to consider for the AR6, most important is the social change, and changing the human behaviour. Without that, I think scenarios like 2C and below will be out of reach. Behavioural changes – and, hopefully, that is good news, not negative news – hopefully behavioural change will bring many things that are positive for our society. One shouldn’t look at this transformation into a low emissions world as something one has to fear, it could be a huge opportunity for humanity, if we do it right. And, again, this is the value of the assessments, to understand where the possible benefits and where the possible trade-offs are.

CB: Looking at the very short term, what would success in Paris later this year look like, do you think? What are you hoping for from those negotiations?

NN: I think one can put a very positive spin to that. I would say that the INDCs that we have already seen from some of the larger emitters, like the European Union, the United States and China in particular, are quite ambitious. They’re very ambitious, so I think that is the good news. I know that people are looking at the aggregate of the INDCs and, as many more come in, we will by the time of Paris know roughly what kind of future they’re consistent with, those short term commitments. Are they more consistent with 3C stabilisation, or in which area they are. I have no doubt that more needs to be done, but my optimism is based on the ambition level. These are national commitments, so, hopefully, that also means that the nations will be implementing them. And if it turns out that it’s not enough and a little bit late, that more has to be done – because we are truly late with mitigation for low stabilisation levels – then I hope that will also be ramped up. So, I am quite optimistic about Paris. Let me put it another way, it is the main chance we have, the Paris meeting. So, in some ways Paris has to be a success and I hope it will be a success.

CB: So is it 2C or nothing? Do you think we would have failed if the INDC’s don’t add up to 2C?

NN: No, no. We are talking about a range of future outcomes. It is impossible to pick one single number. I think 2C is a symbolic number because in some ways it represents a balance between not having to do impossibly too much adaptation and not having to do impossibly too much mitigation. It’s a high degree of ambition, but I think it is one of the more doable futures. The deeper one goes, the more difficult it goes. The higher one goes, the higher the need for adaptation. I think, particularly, that will be very difficult for vulnerable areas. So that’s exactly what the IPCC needs to continue doing, I think ramp up the assessment of the knowledge in those areas. But I don’t think that one can say 1.9C is much better that 2C and 2.1C is much worse. At the end of the day, many of the scenarios that stabilise at those different levels are also associated with a likelihood. We shouldn’t forget that dimension of the problem as well.

CB: There’s a lot of momentum building before Paris, from lots of different angles. So, you have the IPCC report, the Papal encyclical, the divestment movement, for example. How important do you think the international UNFCCC process still is?

NN: Well, I think it is a crucial process. I mentioned before that the sustainable development goal 13 is on climate. It needs to be filled with substance, and I think that substance will come from processes like IPCC and UNFCCC. In particular, after Paris, I think we’ll understand a little bit better how the relationship between various climate targets and the other sustainable goals, where are the mutual co-benefits. Let me just mention one thing that the IPCC has done really well, I think. It’s a huge contribution to assess the literature on what are the benefits of climate mitigation for example for air pollution or energy security, and vice versa. I think this is a very important finding for the IPCC. Connecting these processes together will bring lots of value and make the transformation to a more sustainable future even more feasible than I think it looks today, once one has connected the various independent pillars, as we talked about, the three working groups. I think that’s true for other areas of transformation that are ahead of us, be it water or be it food. So I am hopeful there will be many synergies if one take a more holistic approach to the transformation ahead.

CB: We hear a lot that the IPCC’s job is to assess the science in a policy relevant but policy neutral way. With climate science a lot more political issue than it was 20 years or so ago and the understanding of climate risks much stronger now, is it still possible, or indeed desirable, that the IPCC should remain policy neutral? Have those definitions changed at all?

NN: I think the definition is evolving with time and I think as one involves more social science in IPCC, that fine line will be even more difficult to draw. Nevertheless, I think it is crucial that the IPCC remains non-prescriptive. The ideal situation is that certain questions would be posed to IPCC that the IPCC can ask, even if they are hypothetical questions. I don’t think it is the role of the IPCC to be prescriptive. I think this is different for individual scientists, I think scientists can have a view. I think scientists should express a view, this is the notion of co-production and codesign of science along with society and stakeholder groups in general. But I think for this particular process, it is quite important not to be prescriptive. But I am aware of the fact that the notion of what is prescriptive and what’s not prescriptive might be changing. Just take a trivial case, after Paris, we will have national commitments, so that is no longer prescriptive. This is what the governments have decided, and then you can look at it in a positive way from the climate side.

CB: Do you think an IPCC chair can be free to act and comment from a personal perspective, or would you see yourself as representing the IPCC at all times?

NN: I would tend to go for the latter, but I think this is also something that the bureau and the IPCC has to decide. As I said before, I think individual scientists in the IPCC have the right to have their own view. I think that is slightly different with the chair because it that be misinterpreted, personal statements. In any case, in an official capacity, the chair, and I would also include the co-chairs and the whole leadership of IPCC, should speak with one voice. But I also don’t think there should be any censorship. Science cannot be censored. All I’m trying to say is that their personal views need to be very carefully separated from the findings of the IPCC and need to be associated with very strong caveats if they are very personal. As I said before, if one does that there is always the risk that it would be misinterpreted.

CB: What about for climate scientists more widely, not necessarily part of the IPCC? There are a few different opinions about whether scientists can be advocates. Would you encourage scientists to voice their views, political or otherwise?

NN: Well, scientists are part of society and science is an official stakeholder group as well in the UN process. So, yes, science needs to speak. Science definitely needs to speak and I think the views of scientists can be really well-informed and can benefit our collective views about the future and what needs to be done. So, I do think scientists need to be active. But it is also, as I said before, exceedingly important that when scientists do that to distinguish what’s based on the vetted scientific knowledge and what is a derived personal view. That distinction is important.

CB: Many people might see the new chairmanship as an opportunity for a fresh start, a re-energising for the IPCC. Is there anything that you think could mark the start of a new chapter?

NN: In many ways, it is the start of a new chapter. And I would say not just because of the IPCC, but because of what is happening in the world; that we have these important processes and an ever higher awareness that business-as-usual will be associated with difficulties, so that we have to find a new development pathway in the world and climate, in my view, is an important part of that. I would say the perception in the world has already changed. In some way, the IPCC may have influenced that through the five assessment reports by providing ever more robust scientific findings. So there is that dimension. There is also an internal dimension, that essentially the whole leadership of the IPCC will be changing. There will be a new chair, there will be new co-chairs, there will be a renewed secretariat in Geneva, a new technical support unit building up on the great achievements of the past reports. I think there is an opportunity for a new direction and as I mentioned previously in reaction to some of you other questions, I think it is something that can be tackled now, because I think we have sufficient knowledge now. So I do see it as a chance for a fresh start, indeed.

CB: What do you think Pachauri’s biggest achievements in his 12-year stint as chair have been? And, equally, what lessons have been learned in that time?

NN: Let me say that all three previous chairs made great contributions, but also co-chairs. One should not single one person. But of course Pachauri’s role was very important, also significantly because he was the chair in two cycles of the IPCC. If one goes through the list there are many achievements, and I think he deserves quite a lot of praise for many of those that the IPCC has achieved. As number one, I would say ever greater contribution from colleagues from developing countries. That has to be further strengthened, but I think he had worked very hard on that. I think the outreach and visibility of IPCC has improved a lot. We discussed how one can further that in the future, but I think that has been another improvement. One of the things Dr Pachauri did well is to find a balance between giving enough freedom for the co-chairs and for the working groups and providing overall leadership, in particular, in AR5 on the synthesis report because at the end of the day the synthesis report is very important, it’s the glue that puts all of the working groups together. I think these are some of his great contributions to the IPCC.

CB: Do you think the IPCC has done enough to learn from the mistakes made in AR4? Following the interacademy council recommendations, do you think enough progress has been made around transparency and an error protocol? Or do you think there’s more to be done there?

NN: I think these are all important steps and it was very good that the IPCC did react to the interacademy report and has improved the structure. Also a conflict of interest policy is very important and, as we discussed before, I think one can do a little bit more on the transparency, but it’s going on the right direction. Dealing with errors is clearly important. Another quality of IPCC is that it is exceedingly comprehensive, therefore, for most people, too much to read. With such large reports, there will always be errors. It is important to have an error protocol in place to distinguish trivial errors like typos from more substantive errors that are both corrected and communicated. I think the IPCC has taken steps in the right direction after AR4 and I think in AR6 that needs to be further strengthened as one goes along. Because in the series of drafts, it’s very easy that something falls under the carpet and more attention needs to be given to the error correction, it’s essential.

CB: You mentioned it will be a priority for you to increase representation in the IPCC from developing countries. Do you think gender diversity is an issue as well? For example, do you think it sends a sign that there are no female candidates for the IPCC chair position?

NN: Yes, that is in many ways disappointing. There are four very good candidates – my other colleagues who are offered the candidacy and have been nominated for chair. Unfortunately, no women. I hope that there will be women co-chairs and many, many authors. I think the IPCC has to work on that. Who knows, we’re not in the plenary yet. Maybe somebody will put a candidate forward. But if not, I wish that next time around there will be much more focus on gender equality in the leadership of the IPCC.

CB: Anyone who’s been to a plenary session knows it can be tense, there is vigorous debate between countries and political sensitivities need careful handling. What characteristics do you think a chair needs to do that side of the job?

NN: I think an important function of the chair is, first of all, to make sure the due process is observed. I think that’s very important. Reaching compromise is very important, finding the right language and catalysing the governments that are participating in the plenary to find the right language. I think in particular crucial when it comes to negotiations of the SPM’s and the synthesis report. I would say the role of the chair is a mediating chair, at a couple of levels. One is at the plenaries, but also I would not underestimate the importance of doing that also with the writing teams. Both of those dialogues are important, the dialogue with the government and the science but also the dialogue between different scientific communities. Last but not least, I think there is also a motivational function of the chair. We talked in the beginning of the interview that it’s a tall order that so many people are putting in free time. I think there is a benefit of that and many are enthusiastic about doing it. But also, I think it’s a function of the IPCC leadership to make the job easier and even more rewarding.

CB: It’s probably fair to say the IPCC is a much-hated institution among climate sceptics. How, if at all, would you address this as chair?

NN: One of the important features of IPCC from its beginning and the first chair of IPCC, Bert Bolin, always stressed – and it is imprinted in my memory – that a crucial function is to understand the full scale of uncertainty. Maybe the IPCC clips the tail of the uncertainty, if you understand what I’m trying to say. That the most extreme views might be excluded, but it still needs to have a representative range of the views. Given that notion, it is also important to include skeptics to the extent those skeptics actually have scientific foundation and are really working in the science sphere and have peer-reviewed published literature. I think it would be important to include those people in the wide range of opinions in the IPCC. But those skeptics who are working outside of the range of the scientific community, I see difficulties in including them directly in the work of the IPCC. One has to work on it, on both sides of the scale. But let me just stress again, it’s just important that nobody who works in the IPCC has a conflict of interest. This is why that policy is so important.

CB: In terms of including those other views, how would that be done? Do you mean through the review process, or are you suggesting something extra?

NN: No, no. Both. I mean there is a review process and there is an expert review. I think one needs to work harder on enlarging our portfolio, even though authors have quite a lot of work to deal with 50 or 60,000 of reviews. Sometimes the reviews are longer than the chapter itself. So it is a challenge. Nevertheless, I would argue that one should enhance the review process, to try to have even broader participation. That’s also related to the earlier discussion about the outreach: the more people who are involved, the more people will understand what’s in the report. One of the suggestions I have is thinking to develop – and I don’t have the right expression for it – but let’s call it a facility, an inventory of names and people who work in the broad area of the IPCC, where they are, what their expertise is. I think that would not only be useful for choosing the authors, reviewers and review editors, and other very important functions in the IPCC, but it might also help with various focal points and other places in the government just to have information of who to nominate for those functions of the IPCC. So, I think the review process of the IPCC is very important. Strengthening it is definitely beneficial in the long run.

CB: A question about social media. Do you use Twitter or Facebook, or things like that? If not, how have you or noticed it being used by the IPCC or by other scientists to communicate the IPCC’s work?

NN: Personally, I don’t participate much in social media directly. But my home institution does; we put quite a lot of emphasis on that. The IPCC is doing that as well, it is doing much of the outreach to social media. So there is no doubt that is very important. One thing we didn’t discuss until now that’s connected to that is how to involve younger generations, early career scientists, in the work of the IPCC. That’s important, and it’s not completely independent from your question because I think new generations have different ways of communicating and the IPCC has to embark in there. This is why it’s also important to involve young people not just in the work of IPCC but also, for example, in the TSU and to put even more chances for young people to be authors, contributing authors and lead authors, where appropriate, but also in the outreach function. I think that the IPCC has to keep up with the times, the world is changing. There are other ways of communicating and this should not be ignored. On the contrary, I think more effort has to be put in that direction. Even at the local level. We should not forget that even though IPCC reports are translated into the main UN languages, it is important that this information is spread in terms of the local reference, other languages, to have even broader dissemination of the IPCC findings.

CB: What other advice would you give young people thinking about a career in climate science? What challenges do you think they’ll face that you didn’t?

NN: My impression at least from the students – because until last year I was a professor. I retired last year, which is also one of the reasons I feel I have time for such a challenging job should I get elected. But let me get back to your question. I have an impression among the student that the young generation is very much motivated by making a difference. The IPCC for young scientists is a place where one can make a big difference. But not only that, even before the difference comes, before you’re empowered enough to make a difference, it’s important to connect to the communities. Thousands of people are working behind the scenes for the IPCC, the IPCC rests on the huge pool of knowledge. I think for young people it’s a huge opportunity to interconnect, have access to the latest knowledge. Then for whatever career they choose afterwards. Hopefully, in research. I think the best people should stay in research. In my view, we should try to motivate them to stay in research – this would establish a wonderful jumping board for dealing with important questions in the future. Climate and development issues are century scale issues, they will not go away tomorrow. It is actually something for future generations to solve. I hope that we will leave the planet in a situation where they can make a big difference. But it’s important to involve them in this work as early as possible.

CB: Final question: If you weren’t running yourself, which of the other candidates would get your vote?

NN: [Smiles] This is perhaps a little bit of an unfair question. I am not voting, I don’t think in those terms. The other four candidates are extremely qualified top scientists who have devoted lots of their time to the IPCC. At the end of the day, it is a community effort so I think they all are qualified for the position. I am actually quite happy I am not in the position of voting as it is a difficult choice that the governments have to face. Put it this way, I think the really good news for the IPCC is that there are five very good candidates and there are lots of candidates if you go to the IPCC website for the other important positions in the IPCC. I think this is another illustration of the fact that the climate and the IPCC as an organisation, or rather as a process, is becoming much more visible and there is an increasing awareness of how important it is. Otherwise, all these people would not put their names forwards.

CB: Brilliant. Thanks very much.

NN: Great, thank you.

Image: Professor Nebojsa Nakicenovic speaks at the International Symposium & Public Lecture “Science-Policy in a Global Context”. Credit: IIASA/Flickr.