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Prof Jean-Pascal van Ypersele , Vice Chair of the Intergovernmental Panel on Climate Change
Prof Jean-Pascal van Ypersele. Credit: Greenweek/Flickr ©EC/CE
8 April 2015 8:50

The Carbon Brief interview: Jean-Pascal van Ypersele

Roz Pidcock


Roz Pidcock

08.04.2015 | 8:50am
InterviewsThe Carbon Brief interview: Jean-Pascal van Ypersele

Jean-Pascal van Ypersele is professor of climatology and environmental sciences at the Universite catholique de Louvain in Belgium. He has held the position of vice-chair of the Intergovernmental Panel on Climate Change (IPCC) for seven years and is now running for the role of chair, to succeed Dr Rajendra Pachauri who  stepped down in February.

As part of his campaign for the IPCC chair, van Ypersele discusses….

Greater transparency: “I think the IPCC would benefit from opening in an organised way its work to more media scrutiny.”

The two-degree target: “The IPCC doesn’t say that fossil fuels â?¦ need to be phased out, it will say that emissions need to be brought to zero â?¦ which is different”.

The IPCC’s new carbon budget: “Confronts policymakers with numbers that some have a difficulty to accept”.

Climate risks increasing with temperature: “This is coming from the carbon cycle laws, the laws of nature which you cannot negotiate.”

The first rule of climate science is honesty: “There is absolutely, absolutely no gain, I believe, in exaggerating anything.”

IPCC authors: “[Authors from developing countries] have not always felt a perfect team spirit and respectful atmosphere in their work for the IPCC.”

‘Himalayagate’: “Now, did we learn enough about the lessons of the mistakes in the past? I think the answer is no.”

The lack of women in senior IPCC roles: “I would most welcome having more women in the IPCC leadership â?¦ I’m very hopeful that we will have that in the next round”

Climate skeptics on Twitter: “I don’t block any of them, contrary to some of my colleagues”

His rivals for the IPCC chair: “There are some good people who have in their capacity as co-chairs, for example, done a good job. But the position of chair at the IPCC is different”

CB: With the 5th assessment report done and dusted now, how do you look back on it, and how do you feel it was received?

JY: Well, I really think this was the best report ever for the IPCC, the fifth in a series that started in 1990. So, there is a lot of experience from past reports built into it. There is a lot of quality, a lot of material, because the literature has literally exploded since the beginning of the IPCC. So, it’s a very nice synthesis, and not only synthesis but also assessment of the state of knowledge, about all dimensions of climate change. So, I think it was very well-received. We, and I say we, [my] colleagues in the IPCC leadership, spent a lot of time talking to a number of different audiences: governments, of course, the UN, the UNFCCC [United Nations Framework Convention on Climate Change], the business community, NGOs, the media, of course, citizens in public lectures. There was a lot of interest, and I think it was very well received.

CB: The IPCC has decided to continue producing big assessment reports every six or seven years or so. Would you have preferred to see smaller more frequent reports focused on more specific regions, as has been suggested?

JY: Well, it’s important to maintain the quality of the products of the IPCC, and you cannot have quality without spending some time. I mean, the cycles of review and rewriting of the drafts of the reports by the authors are very important to achieve the level of quality we have. So yes, I’m in favour of having products that are matching better the cycle of the negotiations process but the quality level absolutely needs to be maintained, that’s really essential. So, maybe we can compress a bit the production cycle but we cannot divide it by two in terms of length because quality comes with labour, labour takes time.

CB: Looking ahead to AR6 then, will the RCPs [Representative Concentration Pathways] stay the same? Will there be any fundamental differences with the scenarios in AR6?

JY: Well, that’s a bit early to say. There is an expert meeting on scenarios in May, in Austria. That meeting will assess the situation, discuss the advantages of the present set of scenarios but also what they are missing and how they can be updated. So, we are well on schedule actually because six months before the beginning of, the official beginning of, the AR6 cycle, there is that reflection on future scenarios. But what will come out of that meeting is something I don’t know yet. And of course, in the scoping process of AR6 itself, this issue will receive a lot of attention, but the basis is there. What’s important when you look at scenarios, is to have a range of scenarios. I mean, not to have one scenario but to really have a range of scenarios covering the different possibilities: business as usual, different kind of business as usual maybe but also mitigation scenarios, simulating the concentration of greenhouse gases at different levels. The RCPs are doing that, so to have something fundamentally different for the next cycle is probably not going to happen. But there might be improvements here and there.

CB: It’s understood that the next special report that the IPCC undertakes will be on food security. Is that going to be the case? Or will it be something else?

JY: Well, it’s a bit early to say. It’s an important subject, but they’ll be other subjects suggested by governments. There have been proposals made in the Nairobi plenary in February to have a special report on the oceans, on the oceans and climate change, that’s another proposal, climate change and desertification. So, there will be a number of proposals. It’s clear that the IPCC will not be able to handle all suggestions in terms of special reports. We will have to prioritise and see how the special reports can best be integrated in the production of the AR6, as a whole, as a package, as a coherent package. And we’ll see, of course, food security is a very important subject, but there might be other subjects as well.

CB: The summary for policymakers (SPM) has been criticised as being quite hard to read.

JY: I agree [chuckles].

CB: So, what do you think of the suggestion to seek the advice of science writers and graphic designers – I think that was under discussion in Nairobi – do you think that’s a good idea?

JY: It’s a very good idea. I mean, I’ve been pleading for that kind of thing for a long time, but it’s not easy to implement also. I mean, one should also realise it’s not easy to implement because it is key for the summary for policymakers that the authors who prepare the report have the last word of the scientific content of what’s in there. It’s also important that governments – because the IPCC is an intergovernmental body – have a say in the way the issues are framed. In the way that scientists should not use jargon, for example, and be very clear about the uncertainties about certain statements, etc. And so, those two communities are very important. If there is a third actor in terms of professional writers, and to a lesser extent graphic designers, it shouldn’t create additional difficulties to reach a conclusion because as you know, IPCC plenaries to approve summaries for policymakers are usually very long, very intensive, and we have to see how the help of professional writers can be incorporated. I think it probably needs to be done as upstream as possible, so that the product, the text that is discussed in the plenary, is already in the best shape in terms of the quality of the writing. But it is important to leave the last word to scientists and to governments.

CB: Because, of course, it’s too simplistic to think that if the SPMs were written more accessibly the message would get through to policymakers. What else is getting in the way?

JY: Well, of course. I mean the information deficit model is known not to be an accurate description of the reasons why the international community is not acting more on climate change. I mean, it’s not an issue of lack of information. The information has been there, the information was even there to a large extent before the IPCC even existed. You can find in reports published more than 40 years ago a discussion on the danger of having 2C warming, for example. You also have very important political statement made decades ago about the importance of reducing emissions of greenhouse gases. So, it’s not an issue of lack of information. But, on the other hand, if the messages in the SPM, in the summary for policymakers, are clearer, it can only help. But I’m not naive enough to believe that this way will magically transform the dynamics of the climate negotiations. Of course, they have many other aspects than simply the clarity of the IPCC reports.

CB: And on that question of clarity. Looking back, what more do you think could have been done to make the IPCC’s findings more media-friendly? Perhaps a related question is: how much of a priority will improving communication be if you got the job?

JY: It would be a top priority. I think improving communication and improving relations with media is really important. The IPCC needs to be more transparent, explain better what it’s doing, and be even more responsive. I think a lot of progress was made over the last three or four years; the framework of that communication, the IPCC communication strategy which I really helped to implement and define. But still much more progress can be done. The engagement of professional writers, as we discussed a minute ago, in the preparation of the summary for policymakers would certainly help media, the media community, as well because it would have less work to do to rewrite in an understandable language some of the IPCC jargon. So, there is much to do in this area. Also, I believe in the usage of social media, for example, and the IPCC can be more active, more responsive, more modern in a way. Also, I think that in a way facilitating access to the IPCC products under embargo, for example, which is a recent evolution in IPCC, is a step in the right direction, because it helps the media community to do its job with more time and then to understand better what is done. I think we need to increase overall the transparency and access by media to the work of the IPCC, and that will help the understanding of what the IPCC is doing.

CB: Would that extend to the plenary sessions? Would they ever be open to the media, or do you think the process needs to stay closed to the media?

JY: It’s a very interesting question. It has been discussed a little bit over the years, within the IPCC, with no clear desire up till now by the plenary. I mean, you should realise that the power lies with the governments, and it’s not the views of the chair. The bureau members are somewhat interested, but the power lies with the governments. So, if the international community represented in the plenary doesn’t want to open the plenaries to media, to other observers, then that will not happen. Now that being said, I think the IPCC would benefit from opening in an organised way its work to more media scrutiny. I mean, if you look at UNFCCC – and I’ve observed the climate negotiations for 20 years now, I was at the first COP [Conference of Parties] in ’95 which was 20 years ago, and attended almost all COPs since – there, the media don’t have access to the most sensitive negotiation sessions. And I think that’s good because sometimes things are difficult enough, you don’t want in addition to have observers looking at every detail and reporting immediately through Twitter or otherwise what is happening on the spot. I mean, you need to have the time to build trust between the negotiators, etc.

But they have access, media have access in UNFCCC, to many parts of the events. Some events in the UNFCCC are closed to media but some are quite open. I think in the IPCC we might think in the future about opening some additional parts of the IPCC work, not all, because I think it’s important to be able to negotiate some difficult issues at some point in full confidence and in a very calm as possible atmosphere, and in a closed way. Maybe some parts could be open but this needs to be done with the agreement of governments, with the confidence of governments that this wouldn’t disrupt the process. It also needs to be done with the agreement of the authors, because it is important that the authors, who are doing voluntary work, don’t have an additional layer of difficulty to deal with if they had to do their work under permanent scrutiny. So yes, opening, yes, but in a controlled way but with the agreement of all those who would be observed.

CB: So, the media coverage of AR5 was different across the working groups – working group one got quite a lot more media attention than working groups two and three. Interestingly, working group one was the only one to spend all of the money allocated in the budget to communications. Do you think that had an impact, and do you think that suggests a difference in priorities between the working groups?

JY: Well, it probably played a role. But on the other hand, if you look at past reports, the pattern was similar I think. I mean, I didn’t do a very detailed assessment but from what I remember of the past reports, the media attention was also much larger on the first and to a lesser extent the second part then on the third part, the mitigation part.

CB: That’s interesting, isn’t it? Because you might think that the more policy-relevant areas came in working groups two and three?

JY: Yes, on the other hand maybe it relates less directly to people and to what is interesting to the media. If you can talk about, you know, extreme events: floods, heatwaves, effects of climate change in terms of storm intensity or whatever, it gives you quite vivid images and it’s easy to illustrate, for example, on TV. If you talk about the importance of energy efficiency to decrease emissions of greenhouse gases, that’s much more abstract. Or if you talk about carbon markets and the importance of having a price on carbon, how do you communicate those in an attractive way? in terms of interest, that’s probably more difficult. But let’s work on that challenge as well because if there is much more attention on the problems than on the potential solutions, which the IPCC spends a lot of time on, both in the area of adaptation and mitigation, well [chuckles] those solutions will not receive the same impetus, the same momentum to be implemented, and people will continue to be depressed by the evolution of climate without realising enough that there are so many options to deal with the problem.

CB: Do you think that’s an argument for more focus on the synthesis report? And a related question: do you think it’s still a good idea to have a synthesis report as a separate product? Or would you like to see better linkages between the working groups as you go through? So, perhaps linking specific impacts in a particular country with the physical hazard. Do you see that as a possibility?

JY: The synthesis report is certainly a very important part of the IPCC work. I mean, on the one hand you have 5,000 pages in three parts and on the other, you have a 50-page document. Of course, policymakers and most readers and also media members will probably look more at the synthesis report, which is not only shorter but it also – it’s key of course – it integrates information in a policy-relevant way without being prescriptive from the three working groups, matching – indeed, as we’ve suggested – the description of the problem to the elements of solutions, so that’s a very good way to communicate.

Now, can we produce a synthesis report without the underlying report? I don’t think so, I mean we need both, we need the underlying report and we need the synthesis report. Now there is also that wish to have more frequent information, because there is a strong request by many countries, and also on the side of UNFCCC to have more regular IPCC information than just one big report every five or seven years. And there might. Maybe there is a way but this reflection needs to be integrated in [the] preparation of AR6 – to prepare synthesis reports on a more regular basis, intermediate synthesis reports that will be fed, by the evolution of the IPCC report. I mean, for example, after a special report there could be a synthesis report bringing that new information from that special report together with some older information that would be still quite relevant from previous IPCC reports. That way, there might be a way. It’s something to explore with the governments and with the plenary. This might be a way to provide more regular information in the future.

CB: We hear a lot that the IPCC’s job is to assess the science in a policy-relevant but not policy-prescriptive way, and you’ve just mentioned it there. With climate science so much more political than it was a couple of decades ago or more, when the IPCC formed, and with the understanding of the risks so much greater now – is it still possible or desirable for the IPCC to be policy neutral? Or have those definitions changed do you think?

JY: Personally, I think it’s essential to maintain that. The IPCC has become the respected body it is, accepted and having its products accepted by everybody, by all countries of the world. There is no single government who has a dispute with this agreement, with the content of the IPCC report, which is a remarkable achievement, because it provides a sound, solid basis for the climate conversations. It leaves the options open, and that’s what governments want. Because an option in the area of adaptation or mitigation that would be appropriate in one country, in a particular context, may be totally inappropriate in another country, in a different context. And so the political priorities, and the political choices between options to cope with climate change, both in the adaptation and in the mitigation area, are really in the domain of policymakers and governments, and if scientists were starting to cross that boundary between policy-relevance, which is very important, and which can be improved, and policy-prescriptiveness, the IPCC would very quickly lose its credibility. So I think it’s essential to maintain that boundary. But it’s a subtle boundary, and its a boundary across which a dialogue is needed and that’s very important. I mean, it’s not a war. It is a boundary across which discussions can take place. That will improve the relevance, while keeping options open for policymakers to decide.

CB: The last report talked about how the science is very strong and that, to be consistent with a 2C pathway, unabated fossil fuel use needs to be phased out, and emissions need to reach net-zero. And at the same time low-carbon energy needs to be phased in. So, that isn’t policy-prescriptive?

JY: Actually the IPCC, if I may correct you a second, didn’t say that. It didn’t say that fossil fuels need to be phased out, it did say that emissions need to be brought to zero or even go negative by the end, before the end, of the century, which is not the same. Because you can still use fossil fuels if you use carbon capture and storage. So, it’s a very important nuance. The IPCC doesn’t say that fossil fuels – it will never say it – that fossil fuels need to be phased out. It will say that emissions need to be brought to zero, or even to be become negative, which is different.

CB: OK, and so on that then, the IPCC scenarios for 2C do rely quite heavily on CCS and BECCS [Bio-energy with Carbon Capture and Storage] specifically. Is that realistic? And, if so, what are the risks?

JY: Well, the answer to your question could involve some value judgement, but if it is something realistic or not depends on many things, including value judgement in terms of priorities, etc. So I couldn’t – certainly on behalf of the IPCC – give a straight answer to that question. But that being said, the IPCC report discusses the advantages and the disadvantages of the different options, and mentions that there are some significant challenges associated to BECCS. For example, in terms of potential conflicts between food production and biofuels production or biomass production for BECCS, and that these needs to be addressed. But again, that’s a matter of political choice. And also, this is related to choices that might be made differently in different parts of the world, depending on the geographical possibilities. I mean, when you have very large areas where you can produce biomass without conflicting with food production, or very little, it is a very different situation than in a country where the area, cultivation area, is limited and where conflicts would be much, much more severe. So again, the IPCC is cautious. It says the laws of the carbon cycle are such that if the concentration needs to be stabilised, the emissions need to be brought down to zero, and this is not something you can negotiate with. But how to achieve that, whether it’s with carbon capture and storage and with BECCS, or with other techniques, that’s something to be left to policymakers. But the IPCC discusses all the options, and also the combination of options, and also highlights that the choice is constrained by the fact that if some options are eliminated, are not chosen, that can be done for one or two options. But you cannot do everything with one technique. There is no silver bullet to solve climate change, no single technology is going to solve all the problems.

CB: Carbon budgets were a new concept in the last IPCC report. Why do you think they were introduced for this last report, and how important or how useful do you with they are for expressing perhaps the scale of the challenge, or just to sort of visualise where we are? When you talk to policymakers and the public and you talk about carbon budgets, do you see that message getting through?

JY: Well, first of all, why is it receiving more attention in this report than in previous reports?  Simply because the literature has evolved between the Fourth Assessment Report and the Fifth Assessment Report. There weren’t many articles on the notion of carbon budgets and so the IPCC, assessing the scientific literature, the peer-review literature, mostly reflects that. It’s understandable that this [has] received more attention [now]. I mean, it’s not a wish to present things in that way, it’s because the literature evolved that way that the IPCC uses that concept more in this report.

Now, is it useful? Well it’s certainly useful for some and it’s a difficulty for others. It confronts policymakers with hard numbers, which are not always well understood, by the way. Because, for example, it’s very often mentioned that the remaining carbon budget is 1000 gigatonnes [billion tonnes] of CO2 to stay under 2C warming. What is often not reminded is that this is with a probability of achieving the target of two-thirds. Which means there is one chance out of three to be above the 2C objective, even with 1000 gigatonnes of CO2 budget. So it’s, I think, a useful way to communicate the urgency of the action because we know when we emit approximately 40 billion tonnes of CO2 per year, if the budget is 1000 it means that at this level, it’s only a few decades that’s left. So, the sense of urgency has probably been increased by using those carbon budgets.

On the other hand, if you go to the previous report, AR4 in particular, you can see the emissions scenarios that were compatible with the 2 to 2.4C warming range that was discussed in AR4. Those emissions curves were crossing the zero line, as I have been explaining in many of my lectures, well before AR5. They are crossing the zero line well before the end of the century and this was, on a picture, on a diagram, included in the IPCC report published in 2007. So, the information is not fundamentally new. It’s a different way of presenting it and overall, I think it’s useful. But it confronts policymakers with numbers that some have a difficulty to accept.

CB: Do you think that staying below 2C is enough or should we be aiming for 1.5C, as many countries have argued?

JY: You probably know that’s not a question that the IPCC can answer, and I can only speak on behalf of the IPCC.

CB: Do you have a personal opinion?

JY: My personal opinion doesn’t matter. The IPCC has been very clear in its report in trying to show, first, that there are impacts already affecting many people, particularly poor people, and also affecting ecosystems and infrastructure, with the present warming, the warming of 0.9C – let’s take a round number – we’ve had since the beginning of the 20th century. It has also been very clear in explaining that with increasing warming, the severity of the impacts, the pervasiveness of the impacts would only increase with higher temperature levels. It has also tried to give marks and reference points showing the kind of increasing impacts, mostly negative impacts, that would occur at different warming levels: 1.5, two, three, four degrees.

But, again, the IPCC puts those facts on the table in its reports and it is then for policymakers to choose. That is actually what happened in Copenhagen, and confirmed in Cancún in 2009, in 2010. Then, the government leaders, the heads of states, having read, presumably, at least the summary of the IPCC report, decided in their wisdom that 2C, with the possibility to revise that down to 1.5, was the political compromise around which a consensus could be formed around that time. But it’s not for the IPCC to take the job of policymakers and to say we think, as scientists that this or that, because we don’t have a mandate for that. We actually have a mandate not to do that, not to say as an organisation what would be an appropriate target.  But I think we have been very clear in highlighting the potential consequences, the differential impacts for different warming levels. Then it’s for policymakers to decide. Once they have decided, then we can say – because this is coming from the carbon cycle laws, the laws of nature which you cannot negotiate – if you want to achieve this temperature level, or this acidification level, or this particular objective, then the carbon budget is approximately that number for a given probability level of achieving it, and here are the options to achieve it. That, the IPCC can do. But to choose between two and 1.5C, we can’t.

CB: So, climate science still has a very important role to play in countries deciding what level of risk they’re willing to expose themselves to?

JY: Yes, absolutely. I mean, I think the IPCC’s job is essential to highlight and to inform the decisions to be taken by policymakers, or the positions taken by policymakers. And I’m aware that dozens of countries are willing, are pleading for a lower target than 2C, but that’s something to negotiate under the UNFCCC.

CB: So, risk is obviously a very important framing, a very important issue, and the UN has just very recently agreed a new disaster risk framework. How prominent is climate change in that disaster risk framework? And do you think that marks a growing recognition of the role that climate change plays in vulnerability or exposure to extreme weather?

JY: Well it’s present in the Sendai text and the reverse would have been strange to say the least, especially after what had happened just before the Sendai conference opened in Vanuatu and in the region. But, on the the other hand, the disaster risk reduction strategy is not a climate change only related strategy. It also deals with geophysical events like earthquakes and tsunamis, etc. So, it is normal that climate change doesn’t receive large prominence in that text, because this is not the main body to deal with climate change impacts. But of course it’s mentioned and taken on board by the strategy.

CB: It’s interesting that framing climate change as a risk, and a risk that needs to be managed, features heavily in IPCC reports and in UN language, but that doesn’t seem to carry over to the media. Do you think policymakers or the general public have a difficulty understand probabilities and risk, or do you think that’s an issue that lies with journalists?

JY: No, no it doesn’t rely on journalists. It’s a much broader issue. It’s also a very abstract concept, I mean it’s at least as abstract as globally averaged temperature, which is a very abstract concept. We know that, for example, driving faster increase the risk when we drive. I mean, we never drive a little faster than what the limit is, even if we know that the risk increases if we go above the limit? I’m not sure. So, it’s not easy to make a risk level, something very clear, very precise. I’m not surprised that the concept doesn’t flow very well.  I mean, it’s also related inversely to the question that always comes after a particular weather extreme – is this weather extreme, whether it’s a flood or heat wave or a particularly intense tropical storm, related to climate change? And we climate scientists always have to say maybe the probability, the risk of that happening, has been increased by climate change. But to attribute that specific event that you are mentioning right now and that happened today or this morning to climate change is something that cannot be done. In the same way, if I can use an analogy, if for example a government had been increasing its speed limits by 10 miles an hour or 10 km per hour on highways, if there is a terrible accident just after that decision is implemented can you say that it is because the speed limit has been increased? Maybe not, it may be because the driver was drunk, or because of other factors. So, to attribute a specific event to a change in context, in risk level, is something that we need to be very cautious with. It’s not surprising, then, that the concept is hard to relay in media as well. But it’s not only a media-related problem.

CB: How can scientists strike the right balance between talking about areas of uncertainty  that the media tend to pick up on – attribution is one, also perhaps things like the surface warming slowdown, climate sensitivity and Arctic amplification – and more established areas of climate science that are important for policy?

JY: Well, I would say that the first thing that should guide climate scientists – and the IPCC also by extension when it talks to the media or the public about climate science or its report – is absolute honesty. I mean, there is absolutely, absolutely no gain, I believe, in exaggerating anything. I mean, I would say the situation is dire enough not to need to exaggerate things, even by focusing only on the most extreme projections, for example. I think it’s important to be honest, to describe the situation as it is, to try to communicate the nuances that are around. Also to communicate, to accept, that we don’t know everything. I mean, there are issues for which there are still question marks. I mean, in limited areas, and it doesn’t affect at all the main elements of the consensus. But still, there is still a lot of research to be done, a lot of question marks to address and so I think the first thing is to be honest about the state of knowledge. And the IPCC actually – it’s not always understood – is not there only to describe the consensus, it’s also there to highlight, to recognise, where there are gaps in knowledge, and where there are different scientific interpretations of some observations. Again, if you take the 5,000 pages of the last report, the bulk, the thrust, of that report is very clear. Human activities are the main factor explaining the warming for the past 50 to 60 years, for example. So the question marks don’t affect that main conclusion, which is the foundation for climate action and the UNFCCC. But to communicate about climate science, the first guiding principle I think should be honesty and transparency about where there are still difficulties and problems.

CB: So, as a climate scientist, what areas of new research excite you the most, which questions would you like to see more than any others?

JY: Probably one of the key questions is the role of clouds. I mean, the main reason behind, let’s face it, the large range in the climate sensitivity, the equilibrium climate sensitivity – sorry for using jargon here, but probably the readers of this will know what we’re talking about – climate sensitivity is simply the amount of warming that you get at equilibrium when you double the amount of CO2 in the atmosphere. But the range for the number has been basically [the same] for the last 40 years; 1.5 to 4.5C with some fluctuations. It’s a situation with nuances, but basically it’s a large range – it’s a factor of three. It would make a big difference to reduce that range and to know better if, for a doubling of the concentration, the warming would be 2C, 3C, or 4C. It would make a big difference for policymakers as well when they discuss risk management because the risk would be better known. And the main factor behind that is cloud microphysics and the way clouds interact with other elements in the climate system. And relatively little progress has been made actually. When Charney published in 1975 his first assessment of the range of climate sensitivity, it was 1.5 to 4.5 and it’s still the same today. So little progress has been made, and the main factor is the uncertainties around clouds.

CB: So, my understanding of clouds – cloud feedbacks – is that there’s quite a lot of evidence that there is a positive feedback, which means it would amplify the warming that you would get just purely for a doubling of carbon dioxide. There are suggestions that it might be a negative feedback, but there isn’t a lot of evidence to support that, in fact I’m not sure of any. Having identified clouds as an issue, does that lessen the possibility that’s it’s at the lower end of that range?

JP: Things are even a little more complicated than that. Because it’s true that overall water vapour – and clouds is one of the manifestations of water vapour – increase the warming for an increase in the CO2 concentration, so overall the feedback is positive. But inside that big envelope there are different behaviours for different kinds of clouds. I’m not a cloud expert, but still, I know that, for example, high-level clouds like cirrus, have a warming effect if there’s an increase in their number. Low-lying clouds, low in the atmosphere, on the contrary, have a cooling effect because they reflect more sunlight to space, while the upper clouds have a larger greenhouse effect by trapping heat radiation. So, when you talk about clouds, clouds is not just a large cloud – let’s use that word! – of water vapour in different forms. The altitude and type of clouds and the microphysics is quite different for different levels in the atmosphere. And to understand the overall effects of clouds and changing cloudiness in warming climates depends on the understanding, the detail of the understanding, of the microphysics of those individual layers of clouds at different layers. For some layers, it’s a positive feedback and for some layers it’s a negative feedback. And the balance is positive indeed, but how positive? How to quantify that depends on the details of the microphysics of clouds, and there there is still much progress to do. One difficulty being that it’s very hard to observe what is happening inside clouds at their level, and the other difficulty – or one other difficulty – is the difficulty to model with high resolution – the high resolution that would be needed to resolve clouds. It’s very difficult to do that in climate models because we are limited by computer power, and that’s one of the difficulties.

CB: What’s your own background in climate science? And how does your experience make you well-suited for the job of IPCC Chair?

JP: Actually, that’s two quite different questions…

CB: [laughs] OK!

JP: I’ll answer both. Your first question -, I am a physicist, I studied at University of Louvain. I wanted to become an astronomer, actually, I had a passion – I still have – for astronomy. I wanted to become a professional astronomer when I was a teenager, and I started to study physics. Just before switching universities in Belgium after my bachelor degree and going to another university that is more specialised in astrophysics than the University of Louvain, I discovered two things. One, that I was as much interested by human issues and development issues than by scientific issues such as astronomy and physics. And that at the time, there was a research lab – a new research lab – being built by Professor André Berger that was dealing with climate change and climate modelling. And so, just before I was about to direct my career towards astrophysics I decided not to switch universities and to specialise myself on climate change instead.

So, my first degree was obtained doing a thesis on the effect of CO2 on global climate with simple climate models, very simplified climate models. Then I specialised myself in the study of sea ice and the ocean circulation around Antarctica, and went to the US National Centre for Atmospheric Research – a very important research laboratory, with large computer power and a lot of expertise and scientists – and did my PhD thesis on the effect of CO2 warming on sea ice and ocean circulation around Antarctica. Then I came back to Belgium, worked on Antarctica for a few more years, got a permanent position at the University of Louvain, and then became interested before the Rio conference in ’92 by the interaction between climate change and sustainable development, and also the outreach of climate change and sustainable development issues. So, I spent a lot of time giving public lectures, giving advice to the government in the arena of climate change and sustainable development.

I participated, for that reason, to not only the Rio conference in ’92, but also to all – except two – Conference of the Parties under the UNFCCC. Which means – and now I’m getting to your second question – that I’m very, very aware, because I talk to many policymakers, including heads of state and heads of government, I know what ‘policy-relevant’ means. I know what are the needs of policymakers and climate negotiators in particular. I also interacted a lot with the media, I gave probably hundreds – maybe thousands – of interviews and public lectures overall, so I think I could project the image of [the] IPCC and the IPCC products in a powerful manner. But I think, as we discussed earlier, that the IPCC needs to communicate better and to interact better with those who are interested by the issue. I also have a very strong capacity in chairing meetings, which are difficult. I have learned that when I was a student. I studied for a few days the art of managing meetings when people disagree at the beginning, but need to find some way of agreement by the end. And I’ve practised that for the past more than 15 years now – almost 20 – chairing a working group in the Sustainable Development Council in Belgium. It is an energy and climate working group where you have the electricity producers, you have the trade unions, you have the federation of the industry, you have the NGOs, you have Greenpeace, you have development NGOs, you have as observers the ministries. You can imagine that those people have very different views on many of the issues, and still, we have managed in that working group to produce dozens – literally dozens – of advices to the governments on sustainable development and climate change issue and interface of both, where most of the recommendations are consensus recommendations. And we also recognise when there is disagreement, but this has been done in a cordial atmosphere, in a respectful atmosphere.

I would like to do that in the IPCC as well, to make the different members of the communities – and they are different communities, let’s face it. My background is in Working Group 1 but I have been Vice Chair between 2002 and 2008 of Working Group 2, so I know that community as well. And I have published in the three working group areas, I have had papers in AR3 – the Third Assessment Report – quoted in the three working group volumes. So, I know the different communities. And let’s face it, they are different. They have a different scientific culture, different vocabulary, different habits, and they don’t always collaborate easily, and interact easily. I would really like to instil – in the way I did in the many meetings and the many institutions I have worked with – a better team spirit and collaboration spirit so that everybody feels respected. That’s also something important between authors from developed countries and authors from developing countries, who have not always felt a perfect team spirit and respectful atmosphere in their work for the IPCC. I would really like to instil a better team spirit and better, more-respectful atmosphere so that everybody collaborating to the IPCC – let us remind us this is a volunteer job that the authors are doing – so they shouldn’t face any difficulties and any uneasiness in doing that.  I would really like to contribute to instilling that team spirit in the work of the IPCC.

CB: Picking up on your climate science background on Antarctic sea ice. What’s your understanding of the slight increase in Antarctic sea ice that we’re seeing? And how would you explain how that fits into global trends?

JY: Well, I wish I had a perfect explanation. But as you are aware, there are actually a number of possible explanations. Some of which are quite coherent with the warming, for example – though this is probably not the place to give a lecture on Antarctic sea ice! The melting of the ice sheets, which is happening, and which has been happening for the last ten or 20 years, as the GRACE satellite has shown, is changing the salinity of the ocean around Antarctica. And we know that the freezing point of water is lower when the water is more saline. Now, if there is melting from the ice sheets – which is pure water, no salt – it means that the water freezes more easily on top of the ocean around Antarctica. So, the melting of the ice sheets facilitates the freezing of the water around Antarctica, to give you just one example of a process that might – that is probably contributing – to the slight increase we are seeing in the amount of sea ice – at least in extent – around Antarctica. There are other theories involving changes in ocean currents, wind patterns, etc. But it’s probably not the place to cover that today.

CB: What do you think the former chair Rajendra Pachauri’s biggest achievements have been in his 12-year stint? And, a related question is, do you think the IPCC has done enough to learn from AR4 – things like, you know, the ghost of ‘ Amazongate‘ and ‘ Himalayagate‘ do still pop up from time to time. Do you think the IPCC has learnt enough from the mistakes it’s made?

JY: Dr Pachauri led the IPCC at the time that the IPCC got a Nobel Peace Prize, so this should be acknowledged as part of his achievement and part of his heritage. He led the IPCC for a long time, almost 13 years, I would say in overall in a successful way. It doesn’t mean an improvement cannot still be made in the future. The former chair of the IPCC led the IPCC in a strong way, and also succeeded in instilling a certain team spirit in the plenaries and in the organisation as a whole.

Which again, does not mean that more cannot be done. I certainly intend to do more in that area. One way I intend to do more is by being full time on the job. Dr Pachauri wasn’t. I am very lucky, he did not have that luck that I am in a university position that allows me to work full time, that would allow me to work full time, for the IPCC, while the University would continue to pay my salary. While Dr Pachauri was at the same time chair of the IPCC, he was leading a research institution in India, and being a professor in a US University. And so, therefore it’s difficult to be fully available for the IPCC.

Now did we learn enough about the lessons of the mistakes in the past? I think the answer is no. We’ve not been enough, we have not reacted and it’s a collective ‘we’. I mean, I was part of the leadership when those events took place, and I think we have not been reacting fast enough and strongly enough to what happened and we should have acknowledged quicker the mistakes. But we didn’t have procedures. The error correction protocol was a procedure that was designed after those [events]. So, it’s part of the lessons taken from what happened, and also in terms of communication at the time. We had no communications strategy, nobody to help in the IPCC secretariat to explain our goodwill. Actually, the IPCC was full of goodwill but couldn’t express it. So, we were quite naive at the time on how to deal with the media around those questions. We are now in a much better position I think. We have a communications strategy, we have excellent people in the IPCC secretariat to deal with communications and be much more responsive. So if something similar happened today, the IPCC would probably be much more reactive and the errors would be corrected much faster, also. But we have procedures today which we didn’t have then.

CB: Hopefully, are there procedures further upstream to prevent those sort of errors creeping in as well?

JY: Yes, absolutely. That’s an avenue that also needs to be emphasised more in how to prevent mistakes. Because, of course, it’s good to have error correction protocol but it’s even much better to prevent mistakes. Now, as I’ve said many times, the IPCC is a human institution, so to avoid mistakes totally is not possible. But what we can do – and it’s a risk management issue again – is to reduce the risk of having mistakes. And to reduce the risk, we need to have the best author teams, so we need to select the authors in the best manner. We also need to empower and increase the importance of the role of the Review Editors because they can help in that process, to prevent mistakes. And we also need, still, to improve the review process. Not enough countries participate in the review process, not enough scientists participate in the review process. And even though we had 140-something thousand comments on the last report, still they did not prevent some small mistakes to appear here and there. In the AR5 we have corrected a number mistakes already.

CB: What kind of mistakes do you mean there?

JY: Well, you know, mistakes in labelling some diagrams, in some numbers. Some numbers have been corrected. I mean, there were a number of small mistakes but they were corrected swiftly with a very transparent process, and with a very clear procedure – the procedures we didn’t have in 2010, when the Himalaya problems occurred, for example. So what we need to do is, indeed, to prevent those mistake to happen if possible, and improving the review process. Having more participants in the review process, a better more important role for the Review Editors will help in that perspective, but to avoid mistakes completely is probably not possible.

CB: A suggestion that Pachauri has put forward for the future of the IPCC is perhaps that it could have an annual role in assessing countries’ INDCs. That’s a very new direction for the IPCC. Do you agree with that idea?

JY: I have a lot of respect for what Dr Pachauri did for the IPCC and as IPCC chair. But I’d like to disagree strongly with that suggestion, because I think it’s really out of the mandate of the IPCC and it would really transform the IPCC into an institution giving good points and bad point to countries and this is really something we need to stay away from. Now, that being said, we can help those who would make the assessment, possibly, by highlighting what’s in the past reports or what’s in the methodological report, which can be useful to their assessment. But the assessment itself certainly needs to be done by others than the IPCC.

CB: Why do you think there are no female candidates for the top job?

JY: Yes, that’s a question I had myself. As far as my programme [goes], I have to improve the gender balance in IPCC and I would most welcome having more women in the IPCC leadership. I would hope, even if the chair is a man, that there will be women in the higher position, among the vice-chairs, among the co-chairs, and I’m very hopeful that we will have that in the next round. And then, that means that probably, in the future, in the next cycle, AR7, the possibility of having women candidate for the chairmanship will be there. Now, maybe, it’s not only a question of having more women in the leadership, it’s also a question of having a leadership of IPCC that is sensitive to those issues and that would, also for women, make sure that there is a fully respectful atmosphere in the IPCC work so that nobody would feel any uneasiness, at any point, in their work for the IPCC. Whether it’s because they are a woman, because they are from a developing country, because they are a younger researcher than an IPCC author who has been there in three assessments already. I mean, when I speak about a respectful atmosphere, it is on all counts and it includes what is related to women, of course. But indeed there are no women among the candidates now.

CB: So, when you talk about inclusiveness and team spirit, it’s very important to you that it’s not just seen as tokenism, almost? You’re really determined….

JY: That’s really something that I have in my heart. I mean, I have been approached too many times during the past two cycles by authors from developing countries, for example, who’ve told me how they didn’t feel respected by some authors, in the author teams, and that’s really something I will not accept in the IPCC chair, if I am elected.

CB: You mentioned social media earlier. Do you use Twitter yourself and if so how do you use it, and how have you noticed it used to communicate the IPCC’s work?

JY: Yes, I started to use Twitter two or three years ago, or three or four years ago, I don’t remember exactly when [@JPvanYpersele]. I just crossed the 4,500 followers yesterday and I don’t buy any followers [laughs]. I mean, these are real followers that are adding every day. I use it to communicate about the products of IPCC, about progress in climate science, about particular events in the climate system, about new articles. Sometimes I interact with people with questions about the IPCC. Sometimes I live tweet some events I participate to, because I think they are interesting. And I use it in a variety of ways, I think I’ve tweeted more than 7,000 times since I started so I’ve tweeted on a number of subjects. I tweet sometimes about the relationship between climate change and development issues as well. But I really think that’s an important thing.

CB: Do you, on Twitter particularly, do you feel like you can ever comment from a personal perspective? Or are you at all time representing the IPCC?

JY: Yeah, I am very cautious. Being a vice-chair and being in the leadership of the IPCC for the past seven years I think I engage the IPCC if I speak. So I think I am trying to refrain from expressing my personal opinions when they relate to something that’s part of the IPCC mandate. And I am trying not to go beyond that mandate, so I am cautious not to express my personal opinion on so many issues.

CB: The IPCC is, I think it’s probably fair to say, a much-hated institution among climate sceptics. You may have come across that as a Twitter user yourself. How, if at all, would you address this as chair? Do you see this as an issue to address?

JY: It’s not an issue to address. I mean everybody has the right to have their opinions. I receive a lot of tweets from those people, which sometimes I find interesting. I mean, I don’t block any of them, contrary to some of my colleagues, because I am interested to see what they are saying and the kind of arguments they are using. I mean, 99% of the time it’s an argument that has absolutely no value and I actually never react to them because that would only give credibility to what they are doing. But I find it interesting too – it helps me to understand better where some people are coming from. And it helps me to communicate better, positively, not in reaction, but positively about, around climate change issues. So, sometimes they have arguments, and they use something that is totally wrong, totally false. I don’t react, but a little later I relay some correct information, often coming from IPCC reports about the same issue. But it’s never a direct reaction.

CB: Will that continue if you get the job as IPCC chair? Will you dedicate that time to Twitter?

JY: I think it’s important. I am inspired by Helen Clarke from the UNDP, she is also managing a Twitter account herself. I mean, she may have some help, which I don’t have – I manage my Twitter accounts myself. But she is quite successful in projecting the image of UNDP across Twitter. I would like to, if elected, to continue using Twitter, in a cautious way, as I am doing now. But still, it’s a nice way to interact directly with the audience. Now, I know Twitter doesn’t cover all countries either, so I know I cannot rely only this communication, but it’s an important medium.

CB: How about other social media? Do you use Facebook or is Twitter the only one?

JY: Only in a very limited way. If I become the chair, my public account on Facebook is only actually a relay of my twitter, of my own tweets. So when I tweet it automatically goes on my Facebook, but I do not do anything more to my Facebook page, it’s quite dormant – apart from the tweets.

CB: Which of the other candidates, or potential candidates, would get your vote?

JY: Yeah, that’s a hard question. There are some good people who have in their capacity as co-chairs, for example, done a good job. But the position of chair at the IPCC is different. I mean it’s not a scientific job, it’s not the same as leading a team of authors to produce a scientific product, which an IPCC report is. This is very much a cross-working group, a cross-boundary, and also cross-disciplinary boundary job. It’s also a job at the interface of the scientific community and the international community, and – let me see – I don’t think any other candidate has the same skills I have in terms of science background. Of course, many of the other candidates, several of the other candidates have very strong science backgrounds. I have no problem to recognise that some have a stronger science background than I have, I have no problem with that. But what I have, and that no other candidate has, is that capacity to be at the interface between science and policy, understand the needs of policymakers, and also manage groups with different opinions in a way that makes consensus appear, even if the opinions are very different. So at this stage I don’t have another candidate that I would vote for directly, even if I would have cordial relations with all of them.

CB: You’re not able to put forward a name of, perhaps, someone you’d like to see as your vice-chair?

JY: [Pause] Well, vice chair is a wider question than just filling the vice-chair position with chairs who have not succeeded to become chair, because there will be candidates for the vice-chair position, I hope there will be women for those candidates, by the way, for those positions. So it’s a broader issue. I cannot become a vice-chair again because it is one mandate only. My only option is to become the chair of the IPCC. I think I was ready already in 2008, to put my candidacy for the chair position. But only if Dr Pachauri wouldn’t run again, because I knew that there was no hope I would have more than a few votes if he was running a again. He ran again, so I didn’t put my candidacy then. I’ve been ready for a long time, and been preparing myself for a long time to become the chair so I think, I hope I’ll become the chair, and I’ll be happy to work with any vice-chairs and co-chairs that the governments decide to appoint.

CB: One final question, which is: what advice would you give young people starting out in their career in climate science? What opportunities and challenges do you think that they might face that you didn’t?

JY: [Pause]. You know, I think that the key thing to do a scientific career is the passion that you put in it. If you are really interested by the scientific challenges and possibly – not always – by the societal aspects that are related to the science you are studying, then you will succeed, whatever the difficulties are. The passion is really a key element of having an interesting scientific career, and also a key element of being a good IPCC author, I should say. Given it’s a voluntary position, you have to have a passion to do it. Otherwise, I would say learn, read and talk to scientists from other disciplines. It’s very important to know one’s discipline fully, and to know one’s subject fully. That’s what’s done during a PhD, all the aspects on the small subject as well as possible. But it’s also important after having done that, having this very solid background on a small subject maybe, it’s very important to broaden the perspectives and to talk to scientists from other disciplines. Maybe working on the same subject, maybe not. Maybe working a bit at the side of the given subject, and that will be an asset for a new scientific career, if I was talking to a young scientist, that you will use for the rest of your career.

CB: That’s great, thank you very much.

Main image: Prof Jean-Pascal van Ypersele , Vice Chair of the Intergovernmental Panel on Climate Change.

(The interview was conducted by Roz Pidcock on 27 March 2015 at 38 Belgrave Square, London.)

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