 Thank you all very much for your attendance and you're very welcome this afternoon to this presentation by our very distinguished speaker who has come to us just this morning across the Atlantic, and we're looking forward to hearing what he has to say. Ond yna, mae'n gwybod ei wneud, o'r angen i'r cyfnod, os ydych chi'n gwybodaeth ffono mewn gwirio, na chwy'n rhoi'r gwn yw'r ysgol, dwi'n meddwl y lle ar y cyfnod, ac os ydych chi'n cwmpio ar gyfer gwlad, dwi'n meddwl, oherwydd mae'n gwybod ei wneud i'r cwmpio. Ond oherwydd mae'n gwybod eich cyfnod o'r cwmpio sydd yn cyfnod. Os ydych chi'n gwybod i'n meddwl, mae'n ei ddweud, a dwi'n meddwl ym mwy o'r cyfnod. yn fwy o fewn fwy o bwysigol Cysylltion o'i gaelwyr yn dod yn 12-15 penodol, a nad ydy yn fwy o bwysigol o'r sessu i'r ddim yn cydnodio i'r wy improb. Gallwn i gaelwyr ar ychydig i ddweud yr adres yma yn urddangos, yr adres yma, ond mynd i gaelwyr i gynoes Ymgyrydiau Cwyrd andr swydd sy'n gwneud i Ymgyrch cyfelfigol cyfwyrraethau. Erbyn yn rhywbeth i'r practisiwn, dd wedi'u gyd wedi ei ddim yn gwneud yma cydym yn yr adrwyddo. Ac mae'n gwybod i gael gyda'r cwestiwn. Ac mae'n gwybod i gael cwestiwn, mae'n gwybod i'n ddim yn gwybod i ni ac mae'r oedd ond oedd yn ymgyrchu'r gwahodd. Yn gyfle y gallwn y gweithio'n gwybod. Cymru David Keith yn y casun o'r ysgrifennu a'r ysgrifennu o'r ysgrifennu o'r ysgrifennu o harvard o'n ysgrifennu o'r ysgrifennu o'r ysgrifennu Ac mae'n ysgrifennu o'r ysgrifennu of Engineering at Applied Sciences and at the Harvard Kennedy School and he's also interestingly founder of Carbon Engineering which is a Canadian company developing technology to capture CO2 from ambient air and he's going to talk to us as I said for 20 25 minutes on solar geoengineering, public policy and geopolitical consideration so please welcome David Keith. This is great I'm really happy to have I mean even even during my talk I'm happy to get interruptions and I look forward to a good back and forth afterwards. Maybe I'll start with just like five minutes of sort of my take on where we are in climate policy now so I actually did go to the climate march this morning in Dublin or in noon which was exciting really exciting and I mean truly exciting. I've been involved in climate for about 30 years basically it's been my full-time work for probably since 1990 or so and and I think we won't get real political action without the sort of politics of people marching on the street I think and it's exciting to see it. It's not the only exciting thing I think you know over the last decade the biggest surprise to me and the biggest real excitement has been the extraordinary drop and the cost of solar power. Wind power too but less important from my perspective in the long run and I just can't get over how amazing it is. It's always refreshing when you're just clearly wrong like wakes you up and makes you think why. For another talk I looked this up I among other things I published in 208 a paper that was a careful expert judgment survey of a bunch of people in the PV industry industry leaders in the photovoltaic industry and the conclusion of that paper was there was at best a 50-50 chance of getting module prices to 30 cents a watt by 2030 and we concluded generally that it was just not really you know that solar was over-height and it would be really hard to see getting cheap solar you know before 2040. So you know you just we could not have been more wrong in reality module prices will likely be the module price indexes will be 30 cents next year so it's just stunning and you know you go look around I was just looking in preparing for another talk I found a particular solar site in north India that's a 2.25 gigawatt solar site that was constructed at an all-out cost of less than $600 per kW it's just stunning that's a world that we really didn't expect and it truly is a different world with different possibilities very exciting yet as you know emissions are still up that is emissions are still going up and it's presumably you all know but it's easy to forget to solve the climate problem to stop the climate problem getting worse you have to bring emissions to zero but even when we do bring emissions to zero even when we have this day of global celebrations and whatever it's going to be 2050 or 2070 when man emissions are zero that doesn't solve the problem in a meaningful way it just means the problem isn't getting worse in that sense it's deeply different from air pollution you know air pollution is still by many measures the largest sort of large-scale environmental problem killing a few million people a year globally but the lifetime of air pollutants in the atmosphere is a week so when you when you restrict the pollution the problem goes away basically instantly yet the lifetime measured in terms of the climate impact of of carbon to climate you can think of as infinite in terms of human politics so more or less as you is presumably you all know temperature change or climate risk is proportionately cumulative emissions period and that means when you bring emissions to zero you haven't made the problem better you haven't solved the problem you've just stopped making it worse as presumably you all know well there's a lot of talk about the idea that there's a thresholds at 1.5 degrees or something like that these are political targets which i think are in many ways well-intentioned and thoughtful but i think it's fair to say that there's no deep scientific evidence that there are sharp thresholds it's clear that the warmer it gets the more risky it gets it's clear that's true on a non-linear way so it's much worse to make it two degrees warmer than this to make it one degree warmer but there's no sharp threshold and the idea there's some safe level is pure political fiction nobody in the elite climate science world believes it it's simply cumulative risk and risk goes up with cumulative emissions in some non-linear way that's the reality of the problem we're dealing with and emissions are still going up we need to bring emissions down and bring them down to zero but even when we've done that all we've done is stop making the problem worse that's really deeply different from many other environmental problems we deal with just the last couple words about the the policies situation i think there's this very interesting moment now i think it really is exciting i think there's a sense of more attention to climate and to this topic i'll tell you about solar geoengineering and there was over the last decades again at the same time or maybe because of it there is much less prospect for strong formal international needs so so we do have the un framework on climate change but given the reality of the world today with the rise of populism with more authoritarian government in some of the biggest countries there doesn't seem to be an immediate prospect for strong global agreements but that in fact may be linked to the rise of this kind of bottom-up activism that may actually drive action because the fact is the global agreements we have weren't really driving emissions down in countries anyway they were they were framework agreements but they weren't being translated that really were driving emissions down and i think to do that you need some level of political force country by country which forces governments to do it and i think there feels to me like there's more prospect for that now than i think there was a decade ago so what is solar geoengineering or solar radiation modification which now seems to be the ipcc standard name for it or srm we often call it um it is put simply the idea that humans might deliberately order the reflectivity of the earth to offset some of the risks of accumulated carbon dioxide the most important disclaimer i can give you is that nothing i will tell you about this technology gets us out of the need to cut emissions at the best it is a supplement to cutting emissions not a substitute for it so i think that complicated statement you can make is that a combination of emissions cuts and solar geoengineering might produce a safer world than emissions cuts alone or maybe not we don't know that for sure but that's the strongest version of statement you can make so let me say a little bit more about what it is how we could do this um if you want to offset some of what climate science calls the radiative forcing the amount that humans are pushing the climate we measure the radiative forcing in watts per square meter so we're now the long live greenhouse gases like co2 and methane and sf6 and whatnot are now warming the climate with a warming force of several watts per square meter so if we wanted to offset some of that by making the earth more reflective one way that could be done is to put aerosols in the stratosphere aerosols in this context just means tiny particles a micron or so in size which will stay in the stratosphere for a year or so the stratosphere naturally has aerosols in it including sulfuric acid aerosols so the idea would be to basically increase the concentration the most obvious idea is to increase the concentration of those sulfuric acid aerosols reflect away a little more sunlight to give you a sense of how this would actually work if you um wanted to say cut the rate of warming in half starting in 2025 or something one could start adding with a literally a small number a handful of a special class altitude aircraft new sulfur to the stratosphere and you'd start adding a little bit more each year so that maybe after a decade you were adding 100,000 tons of years something like that so that would be a kind of growth rate it would roughly cut the rate of warming in half so what what does it mean when you put sulfur in the stratosphere you're you're adding to the amount of scattering aerosols which are scattering a little more sunlight back to space which is offsetting some of the radiative imbalance that's causing climate change just by scattering some sunlight back so the big questions that you there's a whole bunch of governance questions you have about this but the technical questions i think really divided two one is if one could produce a pretty uniform that is spatially uniform that is the north pole versus the south pole or whatever if you could produce a pretty spatially uniform uh reduction in reindeer forcing that is increasing the reflectivity back to the back to space if you could do that how effective would it be in reducing climate risk we actually care about and reducing sea level rise or peak temperatures or tropical cyclones or what have you the other question is could one produce a uniform radial forcing like that without having some awful big side effects like what would be the side effects of producing so those are two of the sort of technical questions and there's a whole bunch of um um questions about how on earth we will govern it how we monitor et cetera um i i do want to emphasize it's both kind of i think an ugly fact but it's an important ugly fact that just the pure matter of doing it appears to be technically easy it appears to be in the realm of lots of states including small states which brings up the potential for unilateral action so uh lots of the ability to build aircraft that can fly to 20 kilometers is no longer a particularly hard thing hindustani aerospace could do it embraer could do it lots of of contractors around the world could do it it's not so hard um and and uh the number of aircraft you need even by the 2060s would be like 50 aircraft from one or two bases in the tropics so it's just not hard to do total expense for the direct expense of doing it would be of order billions a year that's the kind of ugly and frightening fact allowing all sorts of potential for unilateral action so that's the idea of stratospheric aerosols there's a bunch of other ways one could do this including potentially space-based technologies including ways of altering high cirrus clouds including uh altering a certain kind of marine stratus clouds there's a bunch of different ideas but for now i'm going to leave it at this idea of of um stratospheric aerosols um so let me give you well let me step back actually so why has this idea been such a taboo why has there been so little research why hasn't it gone like that seriously i think the answer has been a i think in many ways sensible political fear that the very idea of solar geoengineering would be exploited by forces that wanted to block um emissions cuts uh and that this is often called a moral hazard and though it's not quite clear it really fits as a moral hazard but that it would be politically exploited by forces that wanted to block emissions cuts and and for that reason the environmental forces that have been pushing for climate action have generally not wanted to support serious efforts to develop or understand this technology so that's kind of part of why we don't know very much um nevertheless over the last decade or so there has been while it's small a fair bit of research done so while this is still tiny compared to the global scale of climate science which is itself tiny compared to the cost of cutting emissions um the the research on solar geoengineering is not zero anymore there's small tiny research programs in india australia china weeden turnorway significant germany there was a uk one um us there's quite a few and there's as i said something like 500 papers written essentially every major climate model has sort of formally been tested with this thing including formal model in a comparison project and it's been sort of formally built into some of the big assessments so so we know something we know more than we did a decade ago and some of the obvious questions about side effects have at least been looked at it doesn't mean we know all the answers it doesn't mean that we can confidently say that certainly doesn't mean we could make informed decisions about deployment today in my opinion but it means we know something and i think part of the reason that this topic is more visible is actually simply the accumulation of knowledge and the fact that in many ways these ideas look better than they did before in the sense that as we've looked we found less risks than we thought and the technologies actually look more effective in climate models than we thought we know it's about reality than in climate models um that really is i think a surprise so i'll give you a little flavor of that because i think it really is new and important and then pretty quickly close and take questions um so maybe first on climate model response so it there was never any question that solar geo-eventuring could reduce global average temperatures so if truly all you cared about was keeping the world under 1.5 degree c if that was really all you cared about then the answer is solar geo-eventuring is perfect it works without fail and you don't need to bother to cut emissions anytime soon but of course 1.5 c is a proxy for all the stuff people really care about which are local impacts to ecosystems changes in water availability changes in storms changes in sea level ocean certification a whole big range of things so 1.5 is a proxy um and and the question is how well solar geo-eventuring works not at the global level but how well it works regionally to reduce changes that people actually would care about so on that i think we truly are learning more there's there's a big model in our comparisons i'll tell you about a study that we published in nature climate change about half a year ago but i think it's an important illustration so i'll give you some sense of the background this isn't a technical talk but but personalities and motivations matter so this study used one of the really best climate models from the geophysical fluid dynamics lab um which is one of the oldest climate modeling groups actually the one that suki minabi originally wrote the climate models in the mid 60s for and um they had previously never worked on this topic and we persuade them to try this super high resolution climate model for the first time ever on this topic and this turns out to be a model that is one of the very few models that does a really impressive job on tropical cyclones it's really quite exciting that can be a climate model geek for a second in the old days we had little 4 trans subroutines that kind of pretended to be tropical cyclones and now with these modern models that have like a quarter degree resolution the tropical cyclones emerge from the model physics and they look remarkably like real cyclones like they have the right distribution of of wind speeds and season of the year and so on and so it really you begin to believe these models have some skill and say something meaningful about tropical cyclones which you know for for the tropical world is a big fraction of all the the the variability and a bunch of the damage from climate change so we did that totally new set of investigators this guy Terry Emmanuel is one of the global experts on cyclones from MIT we did a careful analysis looking region by region using some standard regions that the IPCC uses to look for each region whether for different variables I'll tell you the variables whether solar geoengineering exacerbated that is made worse that is made farther from pre-industrial or moderated that is made closer pre-industrial or better so we looked at not just temperature which is obvious but we looked at water availability uh and and what we find like every other model is you see this thing you probably all know that the wet get wetter and the dry get dry that's the general fact we see from climate models so it's interesting that solar geoengineering almost perfectly reduces that so there was no region that was made that where there was significant exacerbation uh of of dryness for extreme precip solar geoengineering is extraordinarily effective reducing extreme precip and there's some basic physics why that should be true but again we see strong reductions in extreme precip this was the max five day precip over a year basically everywhere temperature is easy so temperature is reduced everywhere so extreme precip extreme temperature water availability which is precipitation minus evaporation those are the big ones we looked at tropical cyclones for sure and and that really is extraordinary result that's getting to be many of the key what the IPCC calls climate hazards the thing that drives human risks and that means for many of these things uh on a region by region basis solar geoengineering could at least in principle has simulated theoretically in a model reduce these risks and there was no region none of the IPCC's so-called srex regions that was made worse off that's really kind of a stunning result the question I think at this point is is it true and I don't think we know so I wouldn't make policy decisions on this basis yet right now the group of us working on this is still quite small maybe we're inbred maybe we're group thinking so so I think we need at this point I'm not advocating for doing solar geoengineering I'm advocating for having a much larger international serious open access research program that's the decision we face is do we bring this thing out of the shadows and really look at it really research it do experiments make it sort of central to our understanding of climate science that's the debate we're having but I would say there's evidence from not just that particular model I told you about which happens to be something I was involved in but really every one of the major climate models and I think the following is true it's now 19 years since the first serious climate model was run for solar geoengineering and a lot of communities had a bias to look for problems the bias this is a crazy idea there's still senior colleagues I respect a lot like say Susan Solomon MIT who just thinks we shouldn't be working on this and she hates it and and given that bias and given that it's been 19 years the fact that there are no papers that show that uniform solar geoengineering produces particularly bad results anywhere if it's done at a moderate level but if it is done as a supplement to cutting emissions on a substitute for it if it's done in combination with emissions cuts given that I think there's reason to take it more seriously than once we have begun to look at some of the risks so there's a risk of it damaging the ozone hole there's risk of adding the air pollution there's risk of more scattered light there's a series of risks I'm happy to answer questions about those but I'd say on each of them we at least have the beginnings of some real investigation um so me in the last couple of minutes I want to say I've talked mostly about solar geoengineering I mean I want to step back and say geoengineering is often used for two I think completely different things solar geoengineering and carbon removal my view is they basically have nothing to do with each other they are both things that we might do in response to climate change along with emissions cuts and adaptation so to me the the high level of climate responses can be divided into mitigation or emissions cuts carbon removal solar geoengineering and adaptation and they're all things we might do about climate change but carbon removal excuse me in many ways there's much more resemblance to emissions cuts both technically and politically than it does to solar geoengineering so I think it's actually kind of unhelpful to what that is geoengineering there are some carbon removal technologies and the one that in fact was first prominent which was ocean iron fertilization which basically doesn't work and has been forgotten um that make it look more like solar geoengineering but in general it really looks more like mitigation happy to answer questions about it but it's a different animal um I guess in closing I'd say I'm happy to answer a number of questions but many of the big questions are how we would develop a search program that was stable and it didn't weaken the case to cut emissions and how we would ever move towards actually giving the institution we can make stable international decisions about deployment if that if we get to that and I don't know the answers what I can say is at least there is more international dialogue about this in a way there wasn't before so for example a gentleman called Yanos Pasteur who was previously the chief advisor to Ban Ki-moon for climate so the person in some sense most in the middle of the UN climate process when Ban Ki-moon stepped down Yanos is now running an effort called C2G which is the Carnegie climate governance climate geoengineering governance has changed its name but it was a a NGO devoted to getting dialogue about geoengineering governance globally and and that they've got access at near ahead of state level and kind of been traveling around the world talking to people and that at least has got more conversations to happen and it's moving on to the agenda some of you may have seen that there was a formal agenda item in fight at the UNEA the United Nations Environment Assembly about a motion to have a um um working group focused on geoengineering that that motion failed but it was an example of this topic beginning to get kind of traction in the formal international community i'll stop there i'm really looking forward to questions thank you very much