Tim Lenton is Professor of Climate Change and Earth System Science at the University of Exeter, where he researchers the coupled evolution of life and planet Earth, develops and uses Earth system models, and studies the prospects for early warning of climate tipping points.
His work won the Times Higher Education Award for Research Project of the Year 2008. He has also received a Philip Leverhulme Prize 2004, a European Geosciences Union Outstanding Young Scientist Award 2006, the British Association Charles Lyell Award Lecture 2006, and the Geological Society of London William Smith Fund 2008.
He is a Fellow of the Linnean Society, the Geological Society and the Society of Biology, and holds a Royal Society Wolfson Research Merit Award.
© The Open University
Interview Edit Transcript
Tim Lenton interview
RH: = Roger Harrabin, interviewer
TL: = Tim Lenton, Professor of Climate Change and Earth System Science, participant.
RH: So this is Tim Lenton. Tim let’s start with the science. Where do you think, just thinking of macro terms, not just your stuff, but including your stuff, what have we learned of where our science wasn’t good enough? I’m thinking of, you know, we’ve realised the oceans are much significant than we thought, we’ve been caught out by the tipping point, give me an honest appraisal, do you think, of where science has been found wanting and then we’ll move on to where it’s been successful.
TL: I think we always knew that we didn’t have really good observational data on the ocean and the deeper ocean, and it’s only in the last five or so years that we’ve begun to get a good look at the changes in the heat stored in the ocean and the carbon stored and that was simply we wanted to look but it’s only recently we’ve had the funding and had the initiatives to really begin to get good coverage of this incredibly important part of the climate system.
RH: And how much did that lack of knowledge contribute to us being caught out. I think you’d agree we were caught out by the pause.
TL: I would say that we knew as climate scientists there was the potential for periods of slowing down and in warming and periods where it would speed up, but we weren’t able to say when the slow down or when the speed up would happen, but now we have the kind of data from the real ocean that we can put in our models and give a better prediction of when those times will be.
RH: When do you think we will see the sort of dynamic warming that scientists were projecting 15 years ago, when will that assert itself or reassert itself?
TL: I think we might already be entering into the beginnings of a reassertion of the sharper warming trend. We should certainly expect there’ll be an interval of more accelerated warming in the near future, and then sometime later there’ll be another apparent slowing down and then another speeding up, I suspect, and that’s the way the climate behaves.
RH: What have been the successes in climate science over the past five years, do you think?
TL: I think we’ve come to a clearer understanding of a simple relationship between how much fossil fuel we burn and how much carbon we add to the atmosphere and what temperature change we expect to result from that on the long term and on the relatively short-term average. I think we’ve got a better understanding of potential tipping points and abrupt changes in the climate, and that’s partly because we’ve begun to see some surprisingly abrupt changes unfold, especially in the Arctic.
RH: So what have we seen in the Arctic that’s been noticeable?
TL: We’ve seen a marked jump up in the loss of sea ice in the summer especially, and since that happened in 2007 it’s been a kind of persistent feature and we’re seeing melts of big ice sheets at both poles, Greenland and in West Antarctica, evidence to suggest there’s already a potentially irreversible loss of part of the West Antarctic ice sheet that’s a bit like tipping the dominoes down there, once you unplug a bit of it, the rest of it has the potential to go, and the question becomes how slowly or quickly can that happen?
RH: Did scientists realise how fast the Arctic and the Antarctic would change, was that predicted?
TL: We didn’t fully predict the speed of change either in sea ice or in the much larger and slower ice sheets, because our models at the time weren’t good enough. As soon as we see some of these abrupt changes unfolding and we make a big effort to make better models using the most powerful computers, we suddenly get a much better grip on the problem and an understanding of the sort of speed and nature of the changes that can occur.
RH: I’m just thinking, it’s interesting, there’s been a lot of publicity about the pause and criticism of climate scientists for not predicting the pause, but on the other hand nor did you predict accurately the speed of change in the Arctic and the Antarctic, so the picture actually looks both ways, although it’s not really been reported like that.
TL: I couldn’t agree more Roger, we’ve been in the middle ground exactly, we may not have captured a slowdown in the global warming trend, but we also missed really rapid changes unfolding at the poles which are governed by, we would say, non-linear processes, and now the great leveller is real observations. And if we put the investment into getting better observations of the climate system and we bring that information into our model worlds, unsurprisingly we get better predictive power.
RH: A group of scientists who call themselves the Lukewarmers say that actually when you base your predictions on observations rather than on the very complicated global circulation computer models, that actually it looks like warming will be less than we thought when we double CO2, we might get away with perhaps 1.25, 1.5o warming, which would actually be quite tolerable?
TL: Well, if that were true, we should all celebrate that as a good news story, but the problem is at the moment we’re in, we call it a transient response of the climate to our activities, and that means the climate system is out of equilibrium and we can’t make a direct inference from say observed changes in heat uptake by the surface ocean or atmospheric temperatures, about the long-term warming, because in this transient situation the ocean is actually being very good at shedding heat, but in the long term there’s an adjustment where the whole, giant mass of the deep ocean eventually has to warm up and we’re not sure how much and that isn’t captured and isn’t constrained by what we observe now. And we know that there’s still the possibility that we can’t rule out of a very significant long-term warming.
RH: When you say we can’t rule out the possibility of a long-term major warming, where do you think the figures will end up according to your best science?
TL: <Laughs> I think it all depends on the timescale because we’ve traditionally looked at only a subset of the climate system, a subset of what we call feedbacks that we think are governing the temperature that are in the more physical ocean atmosphere parts of the climate, where our best guess might still be they could give you 3 degrees warming if you doubled the carbon level in the atmosphere, but if we think about longer-term parts of the system, the melt of ice sheets, the response of the earth’s carbon cycle, the great carbon stores, especially in the land soils and in the ocean, then we could see that number doubled on the timescale of say millennia, which may seem a long timescale for many listeners, but for a climate scientist that’s a tiny timescale compared to earth’s history. So in the long run we could be talking about 6 degrees warming for a doubling of the atmospheric carbon dioxide level.
RH: That would be extremely alarming. How can we come to terms with all these different numbers over these different timescales and so many uncertainties? How can we deal with this as a species?
TL: Well actually as a species I think we’re quite good at handling making big decisions under profound uncertainty and the recent financial crisis has plenty of illustrations of that. I think what we’re not used to dealing with is the kind of timescales combined with uncertainty that we’re talking about in the climate system. So we have to bring future generations and long-term future consequences into our present thinking, however difficult that is for our elected representatives on short electoral cycles, and we’ve got to reconcile that with the risks that we’re having to manage in our social and economic systems on the short term, but I think there’s real opportunities there. I think many of us begin to see that a cleaner, greener future could also be one with a very strong economy. The trick is to navigate those climate risks in a way that’s ultimately going to give us a different energy system and many different ways of doing things, but that doesn’t have to not mean the creation of jobs and happy people working in a healthy economy.
RH: Well at the moment the projections for over this century, almost all of them project that we will overshoot the level of CO2 that’s associated with a rise of 2 Celsius, and then by the back end of the century we’ll undo the problem we’ve created by burning biomass, trees, grass, whatever it might be, and then sucking the CO2 out and then putting CO2 cycle into reverse. Do you think that is a realistic prospect that we would do that?
TL: I’ve had a careful look at the numbers on that and it is conceivable that we could be in a position to do that but only if we were incredibly efficient in our development of agriculture and essentially feeding ourselves globally; only then we would have the window of opportunity actually do this really large-scale carbon removal from the atmosphere.
RH: You mean because we need lots more land to grow stuff which we can burn and then pull in the CO2 from.
TL: Precisely. If we’re going down the route of using plants to capture the carbon for us, we need land on which to do that but we’re going to use land to feed ourselves first before we start removing carbon, and because of trends towards an increasing amount of meat eating in the average diet of a citizen of this planet, that makes very inefficient use of land and that’s putting a large pressure on the land, so if we were to reverse the trend toward more meat eating and increase the efficiency of agriculture on all fronts, then we could start to have the necessary land to grow the bioenergy plants that we wouldn’t eat but instead would be feeding to power stations with carbon capture devices.
RH: The other problem is, of course, that there are many parts of the world where there aren’t suitable rocks to capture the carbon once you’ve burned it, that’s the other trouble, isn’t it?
TL: Exactly. So it’s conceivable that we could do this a giant recycling operation for our excess carbon pollution in the atmosphere, and I suspect that we may at least explore the capability to do that and work out, trial by doing if you like, how much is possible and we’ll hopefully start working that out soon, ‘cause if we’re going to need the technology in anger we’ve got to do some research and development now. At the same time, the climate problem is going to need a kind of diversity of responses, so efforts to increase our resilience to some of the climate change that’s now unavoidable, and to have constructive ways of adapting to it and buffering ourselves from it is certainly a smart investment as well.
RH: You’re an earth systems scientist, you don’t just worry about carbon dioxide; you worry about the whole earth system, and if we need to turn across so much of our land to say forestry to grow trees that we can suck the CO2 out of, we will be losing the biodiversity of the existing slow-growing forests which in themselves capture huge amounts of CO2 in their soil and provide tourism and pleasure and all sorts of different species and biodiversity. Wouldn’t that worry you?
TL: I’m 100% with you on that, Roger. In fact I think the smart thing to do if our task is to get carbon back out of the atmosphere and into stable stores, is actually to stop degrading forests across the planet, especially the tropics, and let those biodiverse forests that support local populations recover their natural level of carbon storage, both in the trees and in the soil. Now that might be a century-long view but it would benefit both the climate through the carbon storage, and biodiversity, which is under assault on all fronts, especially because of these demands for land use. So I would say very efficient agriculture will help preserve those natural ecosystems and biodiversity and if we really want to get carbon back where it belongs, we want to stop degrading our forests and their biodiversity and let them recover.
RH: OK, can we talk a little bit about the economics of doing this? I know you’ve been looking into that as well.
TL: So there’s a mixture of good news and bad news stories I think. <Chuckles> I think even with a relatively low price on carbon emissions, which could take the form of a tax but doesn’t have to, I mean something around maybe the $30 per ton of carbon emitted, could have the potential to essentially shut down the global coal burning industry, at least at the moment. Whether it would stay shut down in a changed future economy is open to question, but we know that we can’t really afford to burn the carbon in coal that we know is available in the ground and fairly economically accessible, for the climate consequences it would have. There’s been 10, 15, 20 years of talk about supposed clean coal burning with carbon capture and storage, but nothing really substantive has happened even in terms of large-scale demonstration plants for that. So a modest price on carbon pollution and a corresponding incentive, if you have a credible way, a verifiable way of getting carbon out of the atmosphere, will already start doing some good, but if we wanted to really avoid the climate tipping points that I look at, or minimise their likelihood, when we put them into a standard kind of economists’ cost-benefit analysis of the climate problem, that model comes back with the answer that really we should set the carbon price much higher now, more like the order of $500 per tonne of carbon, and that the optimal thing to do would be to set the price that high, it would essentially ramp up efforts to shut down carbon emissions and mitigate on all fronts it would max them out within a few decades and essentially stop fossil fuel burning without carbon capture and storage by the middle of the century, and ultimately lead to a warming of around 1.5 degrees above preindustrial and that would be an incredibly difficult thing to achieve, and there are many reasons we can discuss why it might be hard for that to happen, but if standard economics can come back with that result …
RH: Standard economics can come back with that result, but standard politics can’t, can it?
TL: <Laughs> I think that’s right, because the kind of economic model we’re talking about is, like all models, a tool that we use to try and get some understanding but it makes some heroic assumptions. It imagines a kind of omniscient single social planner, who’s making an optimal decision under a kind of perfect foresight although here they’re having to deal with some fundamentally uncertain dangers that they can’t eliminate the uncertainty around. We know the real world’s not like that. We don’t have one, single, global governance body, we have a much more messy and complex process through which we try to negotiate towards these kind of initiatives.
That said, I think I feel some kind of strange tide of change even in big business, to take this problem seriously and to perhaps start to force the hand of governments and policy makers to set a price on carbon and encourage the kind of entrepreneurial efforts that are going to be required to transform our energy system and our whole socio-economy.
RH: I’m not sure whether this is realistic or not because people who’ve been following climate change for a long time have got pretty desperate with the usual gloomy narrative of governments not doing enough, but I do sense that we’re at a moment, so new technologies are coming through extremely fast, big business (at least parts of big business) seem to be signed on to the agenda to do something, countries are cooperating in a way they never have before, cities are cooperating in a way they never have before. There seems to be a lot of citizen interest about this in parts of the world and it does seem like if we got lucky, if climate sensitivity wasn’t too high, if climate action was strong, if cooperation was widespread, we might just get away with it.
TL: Yeah, wouldn’t that be a fantastic result? And there are reasons to be excited. Many of us are hoping that 2015 might go down in future history as a kind of social tipping point where many tides, if you like, of change, came into alignment. There’s reasons to be excited. The price of solar photovoltaic electricity installation has been plummeting and its market share in new energy installation rocketing up. We are seeing these new alliances and allegiances between cities, countries, localities, we’re seeing a tide of I think willingness to act, based on a sort of collective moral conscience that this is the right thing to do now for our generation as well as for future generations, and let’s keep working for that.
RH: There have been moments of hope before. I remember all the excitement among climate scientists and activists, and indeed some governments, before the Copenhagen Climate Summit. There was a great sense of expectation and it ended in enormous failure.
TL: Yes. So having lived through that one as well, I think there’s always the possibility of failure and there’s the possibility of failure again this year, but I see a very different social context where different actors have stepped up to the plate and started to show some leadership on this profound issue for all of our kind of collective futures. Being an eternal optimist, I hope that that difference in the social dynamics is going to make a real difference, and in some ways the Paris negotiations are going to have to be presented as a success. The really hard question is whether the agreements that come out, that’ll be presented as a success, will really be a success for the earth system and the climate. I think what they’ll be is hopefully a very useful step in the right direction and then we have to rely on the creativity, innovation and dynamics in our social systems to start amplifying a step in the right direction to the necessary walking up the ladder of change to a very different future if you like. <Chuckles>
RH: I mean there are many problems of course, but one enormous problem is coal; what to do about countries that have coal, vast reserves of coal and want to be able to sell it; what to do about other countries that are in the very early stage of the development curve and who want to burn coal to power their economies? What are we going to do about that?
TL: We have to strike some kind of economic deal where there’s effectively subsidies to sidestep the coal burning stage and go straight to a more renewable electricity, a new kind of electricity grid, way of doing things, and I think actually in large parts of Africa, for example, that’s a huge development opportunity to go to clean, green electricity and side-step the mucky stuff, and in China I think there’s, despite an understandable spate of installing coal-fired power stations, I know that there’s also appetite to go cleaner, go renewable, and I think with the right deal struck in this always difficult international negotiation, a compromise could be made. But it will mean rich nations that have had the luxury of burning dirty, polluting fuels are going to have to in a sense help subsidise other, sometimes poorer nations that we want to avoid going down that path.
RH: We can power villages with solar or wind. At the moment we don’t know how to power industrial economies, big cities, with renewables, do we? That’s the problem.
TL: We have progress though. So people will often talk about the storage problem for renewable energy, but there’s incredible progress being made on that. Ultimately of course energy ends up being a kind of portfolio of options, depending your country’s context, of course there are some countries that can do base low power from hydroelectricity, but <chuckles> obviously not everywhere. So I think there’ll always be some subtleties and complexities and depending on the geographical context of how you navigate this space, but we’re trying to imagine and talk about very different kinds of energy systems, very electrified perhaps, with a lot of the energy stored in the batteries of an electric vehicle etc.
Agreed that some high-demand industrial uses want concentrated energy sources, but even there when we look at say refining metals, we’re moving into a future where it’s less about mining increasingly low-grade ores and the very large energy demand it takes to get those as far as say iron ore to steel, and it’s much more about recycling what we already have in circulation, and the energy demands of remaking steel if you like out of existing iron and steel is a lot lower than refining it from low-grade rock ores
RH: Tim, thank you.
<End of Interview>