Extreme Climate Risks: What are the worst-case scenarios?

so welcome um everyone to this panel on extreme climate risks what are the worst case scenarios the panel is part of cambridge zero's climate change festival 2021 and we'd like to thank cambridge zero and the organizers for their work in setting up this festival and the lead up to cop26 i'm catherine arnold um the chair of the panel today and the master of st edmonds college the topic for today is simple just how bad could climate change get what are the worst cases not just in the rate and magnitude of global warming but also in the overall consequences could climate change result in a global catastrophe or even more speculatively human extinction groups such as extinction rebellion have framed the climate crisis as a risk to billions of lives but what does the science say do we have compelling reasons to think this could be the case such questions may seem confronting but the kovit 19 pandemic has reminded us of the importance of considering high impact low probability risks as a former diplomat i'm used to discussions around 1.5 degrees or 2 degrees the science there is stuck the diplomacy remains often a challenge but could it be worse and why don't we talk about that more regularly today we have a panel of experts across climate science and policy to help answer these questions i'm going to give each panelist approximately 10 minutes to present followed by roughly an hour for questions and answers please do submit questions throughout the event our speakers today are professor tim london tim is a professor at exeter university and director of the global systems institute he's the author of multiple books and highlights cited articles on the future and history of the earth system tim is particularly known for his work identifying tipping elements in the climate system which won the times higher education award for research project of the year 2008. he's a fellow of the linnan society geological society and the royal society of biology welcome tim i also welcome today dr goodwin gibbons goodwin is a research associate at the future of humanity institute at oxford university where she studies catastrophic climate change scenarios she holds a doctorate in climatology from imperial college london in which she focused on stability properties and thermodynamic behavior of the climate system in 2017 she won the faculty of natural sciences prize for excellence for teaching and learning welcome goodwin and then dr luke kemp uh who has organized today's panel and to which i express a particular gratitude for that luke is a research associate at the center of the study for existential risk at cambridge university as well as a david mckay research affiliate with darwin college and cambridge zero he has advised the australian parliament on ratifying the 2015 paris agreement and holds a phd from the universe the australian national university where he lectured in climate science and policy luke is currently writing a book for penguin viking books on societal collapse and transformation welcome to all our panel and without further ado i'm going to hand over to professor tim lanton thank you catherine okay let's share screen and get this what could be a rather bleak year and a half underway um i have to say that usually i give talks on positive tipping points these days because this is going to be um tough listening uh to warn you anyway i'm going to start with the this little toy model of a complex system being pushed to and past the tipping point and just so we can get our eye in but you know many complex systems have alternative stable states like societies could be at peace or in conflict and as we'll see bits of the earth system can be in very different states and perhaps under um forcing like global temperature rise we might as well see past a range of tipping points both in bits of the natural climate system and in our complex human systems and those are surely one source of concern around worst case scenarios so before we get to the climate tipping points um it's kind of worth internalizing the knowledge that uh if we carry on where we're going and current policy would take us globally to about 2.9 degrees c of warming so three degrees c of warming give or take then we're going to see an extraordinary expansion of climates that hardly anybody experiences today so i'm just showing this in terms of temperature i'm showing you in the black spots places which have a mean annual temperature of 29 degrees c or above today a few spots in the sahara basically mecca one city is in that black area but in a three degree sea water world these hot regions expand considerably to some of the most densely populated parts of the planet parts of the planet like the indian subcontinent where already we're seeing combined hot and humid extremes that reach wet old temperatures as they're called equivalent to body temperature that become potentially fatal to all viral life let alone human life so in simple terms um if we do a calculation of in this three degrees c warmer world with a un central population projection how many people are going to be experiencing these pretty unprecedented hot climates we come up with a number um around or greater than three billion people i cannot avoid concluding from that that we are going to be looking at huge um huge movements of people across the planet because i don't honestly believe everybody is going to be rich enough or perhaps foolish enough to try and stay in in situ and cope with what can become intolerable climate extremes so that in my view is probably sadly um a path to cascading social breakdown but we come back to that in the discussion now let's move to the fact that we could destabilize fundamentally the climate system itself so yeah i mean over 10 years ago we identified a bunch of parts of the climate system that could be pushed past the tipping point by human activities global warming this century here's one version of my map with i think you know systems involving ice melting in blue circulation change in the ocean or the atmosphere or the two of them coupled together in red or a lot of major biomes in green um as we see these are not uncoupled things each has their own tipping points but but in tipping one can influence another first we need to ask ourselves something about how likely they are and then something about their magnitudes on the likelihood of these different tipping points well the risk assessment looks bleak basically 20 years ago we thought it would take four or five degrees of global warming to be a significant probability of passing some damaging climate tipping points now um the recent ipcc special reports converge on the view that i would share that we're already in the danger zone basically we're at about 1.1 degrees c of global warming and we're already in a situation where we can't rule out we've passed a couple of ice sheet tipping points and made long-term commitments to multimeter sea level rise and you're already in the paris agreement range of warming one and a half to two degrees c we're at the point where you'd almost say it as likely we'll pass some climate tipping points and yes there's plenty of empirical evidence to suggest i'm not um you know i'm not being a gratuitous alarmist here we see accelerating change in the wrong direction in several of the previously identified tipping elements and some of those changes are highlighted in the black boxes there but we also see the empirical evidence that just just like the organs of the human body the elements of the earth system causally coupled together and if you if you tip one you're going to have consequences for others most notably we know the arctic's warming up two or three times as fast as the global average because of the retreat of the sea ice exposing a dark ocean that absorbs far more sunlight we know that arctic warming is accelerating the amounts of the green and ice sheet it's also causing much more rainfall in the arctic that freshens up the surface of the north atlantic ocean and contributes to an observed weakening of the great overturning circulation of the atlantic ocean which kind of drags heat at the surface from the southern hemisphere to the northern hemisphere gives us a nice equitable climate in western europe but also sets the position of a great band of rainfall all the way around the tropics so as it weakens that band of rainfall heads south and that is effectively translates into disrupting the monsoons in the amazon west africa and india and it leaves heat behind in the southern ocean which can go to work threatening the ice sheets there which which in west antarctica is the place we already see the most compelling evidence that we're potentially past the tipping point that might have committed to more than a meter of sea level rise just from white stone clark to caroline so if those things interact and they interrupt interact like the proverbial dominoes arrayed upright we could get in the worst case scenario the domino dynamics you just tip one thing and then it triggers feedbacks that tip another and you we just lose control of the situation which is what the that's the the biggest risk in terms of fundamentally shifting the whole nature and state of the climate system potentially into what we called hot house earth a linguistic reference to some past climates that haven't been seen for about 40 or 50 million years and that look completely different well we don't want to go there we want to go to stabilized earth but we're here to talk about the biggest risks so there's one of them uh we don't need things to get that bad though i think for for for this to be an existential threat and i'm just going to finish by showing you what happens if you have a global warming of say two and a half degrees see a bit less than what we should expect on current policies but we're unlucky and we tip a collapse of that atlantic ocean circulation well it does some extraordinary things like it it cools uh it manages to override the warming and cool the north atlantic region giving us sort of little ice age conditions but the really epic thing is it does profound amount of drying over europe and a profound drying in this in the tropics where it shifts that band of rainfall south so it would effectively collapse the monsoons in west africa and india and you see it getting a lot wetter down here over the ocean and no one there to benefit from it really you can do simple things you can then put that through a model of suitability of the three major staple crops wheat maize and rice and you can look at the combined effects of global warming on its own or this particular climate tipping point and purple means loss in suitable area for growing crop green means gain the situation is kind of neutral for rice but i'm afraid for wheat and what maize it's a double whammy you get a significant decline in suitable growing area just from the global warming signal and the tipping point uh amplifies that if you like and takes out yet more area so that we would see this this double whammy scenario you more than half the suitable area for growing wheat or for growing maize um the simple conclusion would be there's a climate security and food security crisis right there and just to finish up if you think this is a little you know too global wonder what's going in you going to happen to the uk if you want to be parochial about it we've also studied this same roughly the same climate change same climate tipping point in scenario for the uk we've got a detailed model in exeter of econometric model of land use so we can do a detailed job of showing that the extraordinary drying that would happen with this climate tipping point would eliminate animal farming from the uk but i have to tell you that would be the least of our worries because we calculated how much of a water crisis it would cause in the popular southeast of the country um and it would be epic so that's more than enough misery for me but that hopefully gives you a favor of some of the worst case scenarios thanks for listening thank you very much tim and if i pass now to um dr goodwin gibbons thank you catherine um well thank you very much tim that was quite the place to start i liked how many pieces of examples we had from that it's going to be quite helpful because what i wanted to do in my 10 minutes is step us back a bit and think a little bit about how we're framing this discussion of what is the worst case so i'm relatively new to studying this head-on i've been a climate scientist until recently and moving into the philosophy department now um i'm thinking about what we're doing as scientists to get to the bottom of questions like these which is not easy because as scientists we have to answer scientific questions questions that we can get solid answers to so let's suppose we wanted to use the expertise we have to think about what are the worst case scenarios um before i launch into it i wanted to reference this issue of positivity and negativity and hope so normally we try and talk about climate change in a hopeful way um i think talking about it like we're going to talk about it today in terms of the worst case scenarios is really powerful for helping us understand our moral duty and opportunity um for future generations basically you know if we pass off something bad without realizing it it's it's not something to be proud of even if it feels like a hopeful situation so um as we're talking about this let's sort of realize that thinking about it give us opportunities to do something about it um and then the other thing i want to emphasize is that we don't need this worst case scenario i think we made this point very well tim we don't need the worst case scenario to act you know even what's currently happening is basically bad enough and so we'll talk about it but um you know if we're not sure about some things here in the worst case scenario we don't need to pause everything we're doing with climate change of course of course um and then the last thing i want to say before i launch in to some splitting up the question is um as a scientist i think a lot about what questions are answerable and what questions are important and those are not always the same ones so you know it might be easy some studies are easier to run than others and in this space we don't really have the science we need and it's going to be very hard to get the science we need you know we don't have complete models of the climate that can run out to the possible end of time you know it'd be really nice to have that um and so what we're going to do is we're kind of it's a bit of a sleeping mission i think gathering as many lines of evidence as we can um which again tim's given us a really good sample of those to begin with um and so yeah here we go into the puzzle so um i thought it was quite useful when i was thinking about this to split out what the worst case scenario is until like four sources of worse of worst cases four sources of extreme um extremes so the four i'm going to talk about is how bad it could be in terms of how much co2 we emit and then how bad what's the worst case in terms of how the climate responds to a certain amount of co2 emission because there's a worst case there as well there's a third worst case which is what's the worst case scenario of how badly humans respond to a certain amount of badness in the temperature response and then i think there's even a fourth worst case that's interesting which is what is the worst that can happen if humans try and fix something that's bad which is can be surprisingly bad as well so i'll just go through them again with a bit more detail so what's the worst case scenario of how much cumulative co2 we could admit so we have these targets in the paris agreement that would say we don't emit that much um but at the moment we're really in no sense on track to meeting those targets so the the ungap report just came out this morning i think um you guys might have seen it on the news it basically shows that um the plan that we have emits twice as much co2 as we should um to hit the targets that we had in mind um and if you look at if you when you look at projections of fossil fuel emissions it would even even the scenarios that we draw up for worst case emission scenarios have us leveling off our emissions reducing them to zero in 200 years which may or may not be something we're capable of doing as a species so i think the worst case scenario for how much of co2 we emit we have to realize plausibly unless we get to net zero soon it can be worse than we're really ready to discuss one possible upper threshold might be the total amount of fossil fuels that we know to exist unfortunately that number keeps increasing every year and so even that isn't a firm upper bound um and another point here to make is leaning into this pessimism can we expect the net zero if we did reach it to hold for 10 000 years what if there's a rogue state what if there's a war um because co2 stays in the atmosphere for so long um a net zero it matters if this the fossil fuels are ever emitted not just if they're emitted before 2100. so i think worst case scenario of how much cumulative co2 emitted very bad um one study that looked recently at um five thousand gigatons of co2 being emitted um estimated a temperature change of like between six and ten degrees celsius but that's already huge and that unfortunately wasn't taking into account the worst scenario of how the climate might respond to a certain greenhouse gas emission so what do we know about the climate response so the basic thing we know is that more co2 makes it hotter and there's a proportion constant proportionality that we work with the climate sensitivity and there's been a spread in our understanding of the climate sensitivity between about 1.5 and 4.5 degrees per doubling of co2 the thing is that the climate sensitivities distribution is probably fat-tailed we call it which means that there is there's more chance of it being high but surprisingly high than there is of it being surprisingly low and that's because it's an amplifying kind of system so if you imagine um because you if it gets warmer it makes things happen that makes it get even warmer the chance of it running away to a high climate sensitivity that distribution is skewed in that direction um then the other issue that comes on with the climate's potential responses is tipping points which i don't need to talk about in this panel um but uh one of them that i will mention that tim didn't mention yet is this recent two years ago we discovered a new tipping point um the stratocumulus cloud breakup and what this is is the idea that as co2 sits in the atmosphere which you know acts as a blanket in the atmosphere it changes the radiative properties and for clouds that rely on radiation um to exist which is the stratocumulus marine clouds that cover like six and a half percent of the earth's surface if the radiation patterns change those clouds might disappear and that might change the amount of sunlight that's absorbed by the planet and that alone in this study they thought maybe that could cause an extra eight degrees of warming and that might occur with um three times as much co2 as we have in the atmosphere now which could in a worst case worst case emission scenario a kind of plausible bad case emission scenario happen within a century um so the climate is kind of um it's an unruly beast and there is no there's no limit to the worst case scenario well that's not true the worst case scenario of what the climate can do is a scary thing and anticipating it is kind of like trying to anticipate an animal we can't run experiments our best models are made of something entirely different it's not like we even have like a mouse model so to speak um we have our climate models which are good at what they're good at but not good at everything and the hints that we have from the paleoclimate record show ice age is happening when the solar radiation changes like minutely so we have this example of in the climate in the record we have mass extinctions happening without really a sense of what the source could have been for a lot of them we know that the climate like tim was saying is very possible of finding dramatically different stable states than what it's in right now so the worst case scenario of the climate response to not the worst case scenario of the cumulative co2 is extreme and that's not even mentioning a runaway greenhouse effect which may or may not be possible on earth but it could involve a feedback feedbacks even beyond the ones that i've discussed okay so just in case we're still feeling positive let's discuss the worst case scenario of how badly human system might react to climate change so one thing that's striking about climate change as a stressor um that makes it particularly scary is that it's a simultaneous disruption of everyone across the world in different ways so covid was like this um covert had the advantage of disrupting different people in similar ways i would say um to have droughts in some areas floods in summer areas extreme weather events happening is quite a complicated issue um tim mentioned migration coming off the back of that that seems like a really reasonable concern or you know water shortages in some areas causing political unrest within the countries we are really not peaceful creatures at the best of times and as i think luke might touch on later a lot of the times when we have been our most unpeaceful has been when there's been quite a slight change in our climate like a small failing of a harvest or something um and we are incredibly capable of pretty scary things i mean it's only within the past generation that we had the nuclear crisis is reaching really significant proportions and um yeah i mean a question i think maybe we should ask ourselves in in addressing this aspect is what's the most mild change that you can imagine destabilizing society the most mild climate change and that that to me kind of flips the question and i realized i could imagine society being destabilized by quite a small um hiccup okay so let's imagine society is getting destabilized and let's imagine we try and fix it could we even have a worst case scenario from the fixing um and this is one that comes in when we talk about some people talk about geoengineering which is a loaded word because it includes both removing carbon dioxide from the atmosphere which is direct air capture which i want to separate that's pretty simple because that just undoes what we've done um but solar radiation management would be changing this sunshine um in order to try and cool the planet down to undo what we're doing with climate change the problem is that's probably not a direct undo and it's a really political thing so some countries will benefit from celebrating initial management more than others and someone could do it as a rogue actor and then also we have this system which maybe in other ways we might try and change but without fully understanding and i'm actually surprisingly worried about what happens if we feel empowered to then start influencing our climate um i think the general sense here i have is that the climate is the substrate on which we rely as a species and it's a very um it's a very delicate one and it's a it's a very complicated one and some the safest thing to do is to not mess with it for sure and when we mess with it we're really reliant on it we're not very stable ourselves it can change an awful lot it's a really terrifying situation um i think i've probably gone on for slightly more than 10 minutes i have a few more things to say um should i luke's giving me a hat keep going for now okay i'll say a few more things because i've got them lined up um so those are four ways that we could get a worst case scenario i didn't even suggest combining the worst case from those four categories right what if we had worst case emissions with worst case tipping points and feedbacks with work case human responses um we were not very adaptive we were not very peaceful as a species climate change could be an arbor like an art the source of arbitrarily large damage um another way to think about this is work backwards from what you value let's say we're thinking about the extinction of the human race um or maybe we want to think about not the extinction but just a long-term suffering a kind of a scrooge that just stays around our society or maybe you don't want to just focus on humans but you want to focus on um like all life the biodiversity loss when we break it down that way some of the things are definitely already an issue the biodiversity loss even with our current level of warming which is definitely not what's going to happen in the long run um is is definitely tragic things are happening there um and so what i mean to say here is though the extinction of humanity for example might be something that we think that we could get away with avoiding maybe we're settling exit planets or something there are things that are very tragic according to a lot of people's values that will happen before then um and if we're thinking about something like the extinction we also have to realize that the um the other forces that make society potentially humans that might cause humans to be struggling um those are going to be we're going to be more vulnerable off the back of climate change so i think i'll i'll leave that point for luke because i know that we've chatted about it offline i think you'll manage that well so um right i think that kind of concludes the main thoughts i wanted to say i think one more one more point is i've talked about about worst case scenarios with um climate change is a problem but there are also worst case scenarios for solutions so like if we cut off our usage of fossil fuels tomorrow and went cold turkey that would be that would also be very hard so we're really between a rock and a hard place i would say um if we're thinking about worst-case scenarios and um it's a bit like a war i mean one has to band together and do what it takes which brings me back to the hope that thinking about this head-on maybe gives us a bit more of a um a call to action so um thank you sorry to go a bit over and pass back thank you very much um goodwin and now handing to dr luke kemp excellent thank you catherine i'll just go ahead and share my screen so how bad can climate change get it feels like my two eminent colleagues have been exceedingly and impressively depressing but i'll see what i can do to up them so this and the remarks i have here are based loosely upon some work i'm doing with tim johan roxanne and several others which is trying to kind of address this question head on i really love the way that goody frame this in terms of those four questions and similarly i've actually always thought about this in four ways as well but with just slightly different questions attached for me a lot of this is about both the magnitude of warming we can expect in the worst case scenario which combines both the kind of epigenetic emissions we can expect the actual concentrations attributable to human emissions the climate sensitivity so what we expect the earth system to react and what that leads to in terms of end concentrations but also secondly the rate of change because obviously there's a huge difference between getting two degrees in the space of say a hundred years versus two degrees in space for a couple of decades thirdly is as could mention as well how societies react both through potentially things like geoengineering but also in the short term things like political change conflict etc and i think the fourth one i tend to have which is slightly different is how does the overall earth system respond because often we have this tendency to think about climate change and its risk assessment as just climate change and in reality we know it interacts the whole kind of load and system of other planetary boundaries and how things like ocean acidification biodiversity loss and collapse play out will obviously have huge ramifications using societies as well i'll now get into it so we've already actually covered some of this i think both tim and goody have mentioned some of the results be talking about here but there's good reasons to expect that we are going to potentially go above 1.5 or 2 degrees celsius by the end of the century and it could potentially be far far higher so one study a few years ago put forward the kind of likely range of two to four point nine degrees by two thousand one hundred the couple's model in the comparison project theme ip6 which underpins the most recent assessment report produced higher results than we usually have from models this could be for a number of reasons including kind of more refined treatment of cloud dynamics a number of the higher results were eventually excluded because they weren't fitting to observation results but nonetheless we did end up with a kind of a pretty high level of chlorine sensitivity ar6 so the sixth assassin report ends up both constraining the climate sensitivities or the amount of warming we can expect we double co2 in the atmosphere so it got constrained to roughly two to five degrees celsius that's the very likely range the interesting thing was that essentially 1.5 degrees or anything below that was ruled out but anything above 5 degrees and plus could not be ruled out as good as already mentioned there has have been some new mechanisms that have been discovered in recent years such as the potential for a stratocumulus cloud breakup with temperatures of roughly six to eight degrees being added on top of the warming we already have and overall we do know that the risk of climate change is roughly fat tail so work by i think was uh wagner and vitamin a number of years ago did some basic calculations and came up with the idea that if you have 700 parts per million which is a middle-of-the-road estimate for concentrations you have roughly 10 chance of exceeding 6 degrees celsius by the end of the century what do we know stefan the answer is somewhat very little so this is based upon a piece of research i did it with a number of colleagues led by florian oregen university eason we're essentially the text mining of ipcc reports to look at the mention of different degrees and of course this is a kind of imperfect proxy for whether they're kind of covering those degrees but we also combined that with some literature sampling to verify results and what we found was that we were essentially betting on the best case that the vast majority of research that the rpcc covers and the rpcc is supposed to be indicative of the state of research is focused on 1.5 to 2 degrees when you look at say for example a scenario of 700 per million which again is this kind of middle rate middle revert scenario you end up with two-thirds the probability mass the likelihood being above three degrees celsius but just around ten percent of the mentions of temperature rise in the ipcc reports is for three degrees or above the rpcc itself in ai five it's notes that there have been very few estimates of the aggregate impacts at three degrees or above so overall the topic seems to be neglected and understudied and that's just looking at the question of the kind of biophysical side of things so the rate of change and the amount of performing we can expect why should we worry about this i think both goodie and tim have already given you ample reasons for that i'm just going to add a few more on top of it so first of all i think as good mentioned climate change has been implicated in mass extinction in history there's been five big ones about the phenozoic history of planet earth and the most recent evidence just that warming has been implicated in every single one of them the worst of which was the great permian dying which is roughly 252 million years ago and estimates vary but it could have liked that roughly 89 to 90 percent of the biosphere at the time there was some work by a geologist by the name of rothman daniel rothman and he's done a lot of work trying to calculate what's the carbon threshold for a mass extinction and how much carbon do you need to have what's the rate of change necessary before you lock in place processes and feedbacks are likely to lead to a mass extinction at this graph or to the side figure four shows the outcome of those were published i think 2017 or 2018. and as you can see that the kind of essential red line here is his best estimate for the kind of the threshold effect for mass extinction and the lines above and below the dotted lines are the kind of 50 um certain intervals and basically pretty much every single one of the rcps represent concentration pathways end up crossing that line and end up creating a potential for a mass extinction event there's also just simply the fact that historically humans whether we like it or not have been very influenced by our climate if not actually adapted towards a very particular climate niche so tim mentioned the work of zucchini and others which looked at the idea of a human climate dish that when you look at things historically roughly 80 of population has been adapted to a lot of narrow climatic envelope of roughly 13 degrees degrees mean in your approach temperature and when we stray from that even a little bit it often has very large consequences so there's a very large body of literature looking at how the rise and fall of empires and different policies and their transformation throughout history has often been tied to climate change and this has notably been usually due to very very small regional changes so we're talking one to two degrees variation at a regional level so this is based upon a lot of different work including people like harveyvice who looks at as well as people like eric klein who's looked at how the bronze age claps in which a large other interconnected societies in the mediterranean collapse at the same time we experienced cooling and drying in that region what are the pathways that we can expect for climate change to have in order to reach a catastrophe one is just the sum total impacts the compound hazards we expect from climate change eventually overwhelm capacity the much more likely much more interesting one is systemic risk that we have what we call risk cascades where the a single hazard or risk has knock-on effects which amplify or trigger other risks and we still stick over 19 for instance and this is something that's already happened when it comes to climate change in 2010 there was a a heatwave in russia which actually reduced stereo crop yields leading to rush to do an export ban on their cereals and in turn that actually led to a price shock on the global food market which led in turns to a surge of food bank usage in the uk as well as actually contributed to the turmoil that was seen in egypt that yeah there's also potential for it to trigger other extreme risks such as nuclear warfare warfare or as goody suggested potentially a geoengineering experiment gone wrong and i think a really interesting one we don't think that enough is latent risk that if we have warming which we can somehow adapt to or handle given high levels of gdp and technology but what happens if we have some kind of clap systems say for instance the wake of a nuclear war and suddenly six degrees of warming comes rushing back in after a nuclear winter that's what i call laser risk essentially an underlying risk built into the system would potentially re-emerge as eventually and this could be triggered by nothing but it's nuclear war or you know even a zombie apocalypse queue from laughter and we'll move on so what do we need to know i think i already partially covered this in the four questions but if you're really trying to put it down to really kind of streamline a gender of sorts i'd say extremes both in terms of magnitude and rate of warming the long-term impacts so thinking beyond 2100 and really thinking about these really big potential mechanisms that you see play in mass extinction events so things like ocean anoxia third is a more complex risk assessment looking at this cascades as well as risk responses which is something the ipc is slowly moving towards the most recent assessment report was the first time the ipcc actually started talking about risk responses which is a good sign and then moving on to kind of early warning signals which is really about making things more useful in terms of responding to climate change i should note that when it comes to early warning signals and complex risk assessment we really need to think about under what scenarios the climate change occurring because there's a huge difference between climate change occur in a world full of kind of competition and relative equality versus one that's occurring under fragmentation and inequality i've been doing quite a lot of work with a historian by the name of john houston his kind of big pet theory is that climate change is only leading to class when it usually coincides with a polity that has high levels of inequality that is something that seems to breed fragility and vulnerability and he has a number of case studies including devising empire to kind of buttress this scenario and then finally we have to kind of find a way to model all this together i think as good you mentioned the kind of worst worst case is when you actually have the worst case across all those for both the system respond to the human response as well as both the magnitude and the rate of warming cool there's some references and i'm very much looking forward to this exceedingly depressing discussion luke thank you very much indeed um if those of you who are participating please do put your questions forward um we would love to be able to ask the panel to answer the questions that you've had at the end of this very thought-provoking and sobering set of discussions but if i can actually take us away um from the detail of the science for a moment we will come back to that um and look at some you you've each separately and slightly differently touched on the human dimension of this and i'm going to start off by taking us completely away from the science and into mythology almost all of us i'm sure have come across the um the mythology of pandora's box and that the last thing that humanity needed to be in the box to survive was hope so i want to throw back to you at the end of what you have set out today which is as you say extremely sobering where does this leave us in terms of hope you've separately touched on how complex a system human psychology is let alone human psychology at the level of a society a country or the globe but what do we do as humans with what you have just presented and i'd love to hear a little bit more from each of you about where you see your responsibilities lying as both scientists but also those who are contributing to something that matters to all of us perhaps if i could start with luke i was hoping wouldn't start with since that's a huge question and kind of worthy of some reflection so what we think of tipping points as tim kind of mentioned it's not just simply about negative tipping points which we often tend to focus on but also positive tipping points so i have a number of colleagues like um otto at the potsdam institute who focuses more upon positive tipping points the fact that you can often have non-linear responses from society and you see this all the way from things like dietary change through to social mobilization social movements and it's worthwhile remembering that most of the kind of biggest improvements we've had when it comes to things like civil rights have happened often in very short periods of time and often have happened for this kind of non-linear effect and for me that's where i often hold the greatest degree of hope is that a lot of this is think about the worst cases predicated on as mentioned thinking about us not getting our act together when it comes to decarbonization and emissions and also us not responding appropriately responding through things like conflict level cooperation and i think when we realize that we have this vast capacity for changing our social arrangements often quite dramatically and quite quickly particularly in response to a crisis that gives me a fair bit of hope that we can potentially both decarbonize much more quickly than we're expecting and also respond in a much more pro-social way than the worst case would suggest thank you luke tim yep luke's taking the words out of my mouth a little bit because this is why i approached today's panel with some trepidation catherine and all because every talk i give now is at least 50 on the positive tipping points we need to avoid the climate tipping points if not more weighted two-thirds to the positive tipping points and one-thirds to the blue message because i i you know i've learned a little bit about about uh human psychology and how we respond to different messages and i think like like you suggest with your question it is absolutely essential to convey that this complex systems view of the world is the thing that leaves us at least with the door ajar with some light coming through and the chance of escaping the worst um and it that can actually be an empowering message because if if we can explain it uh at least to our audience um we know that that even humble phytoplankton cells once completely transformed the world and made an incredible atmosphere for us so this whole conception of the possibility of positive tipping points should give us back a sense of autonomy and agency that we can do something uh that really could trigger reinforcing feedbacks that have a real measurable difference in the face of what is otherwise a frankly terrifyingly enormous problem where we often get in a mental log jam where we think well i could do something but if x where x is usually chinese people or some other imagined other don't do anything then it won't matter well that isn't necessarily true so yeah that's precisely the angle i take and if i can't convince myself that way which i can at the moment then the other path philosophically for me which might not be to the taste of much of the audience is through wider identification with nature i mean i'm a card carrying um researcher on the guy hypothesis i believe all living things have agency just as we do there every all living things are trying to create their own conditions for flourishing in this complex interconnected system and if we you know fail uh to live up to our name of homo sapiens sapiens you know intelligent people then so be it we we just have to take that on the chin but if you can identify with a wider life process it sounds very daoist or zen buddhist then there's still a light there for me i know it seems almost anti-humanist but yeah that's my take on it thank you tim and goodwin those are great tim it's nice to have more sources of hope um so i thought of a few when you asked the question i've had a little bit of time to think about it um one one is just we manage sometimes we do manage label crises like these like the ozone situation so that was an easier one because it was easier to deal with the hydrofluorocarbons but we do have pretty amazingly strong international negotiation powers um i guess catherine you probably have that context as well um and that even just the mechanisms we're doing at the moment they have they have surprising power um but more maybe more profoundly i think issues like climate change are the co2 emissions we didn't know this would be the case and we set out um with the industrial revolution and we had both the progress that happened from the industrial revolution and the inadvertent situation of climate change emerge so here we're left up dealing left dealing with a really impossible mess but it's from this kind of human desire to also improve things um and so i think there's something actually kind of hopeful if we take into account all the good we've gotten from this fossil fuel caper and we put that in proportion with the difficulty of the repairs that are needed um in society society contains people who are willing to die for things they believe in i mean that's not the thing we need to do here with climate change but we we do as a species have this kind of ability to enter a situation with moral moral strength when we need to and that also gives me a lot of hope i mean climate change has gone to strange places in terms of the debate and the believing and not believing but if if we could get beyond those um there's a lot of reason to believe that humans have strength to do difficult things for each other um and then the last one there isn't necessarily we don't know of a particular moment when it's too late and so every because co2 sticks around in the atmosphere for so long every unit that you a matter i emit or anyone doesn't emit is a unit that doesn't exist that isn't emitted then for the next 10 000 years and so um while we're while we're doing these buying time steps now while we're waiting for the system to bring itself together every little bit of fossil fuels that we can not admit is going to put us in a better position when we get to net zero in the future so those are some little angles that give me a little bit of hope thank you very much um goodwin there are a few um detailed questions that have come in uh focused on tim's presentation to start off with so tim i wondered if for the benefit of the wider audience one of them is um how soon could the amok tip into its shutdown phase and how long would it take for catastrophic impacts to be felt if it does and then another one is when is the oecd report tim referenced due to be published tim i'll do the easy second question which is i think we were finalizing a figure today under pressure because it must be going to the printers tomorrow so it'll be out before cop 26 that report um it's we're just one part of chapter whatever it is but at least at least this message is in there coming back to that atlantic overturning circulation collapse it happens in some of the ipcc models and it happens at different levels of global warming here i'm actually referring to the the previous generations of models so if anyone knows that lingo the acronym is c note 5. in those models the model in some of the models it can happen around 2 degrees of warming but i have to tell you the ipcc have said repeatedly that they think that it's unlikely that an amok collapse could be triggered and unfold within this century so i should be absolutely clear i differ my view differs from that partly based on some of their models but they you know when they see it happen in one or two or three of 26 models they say well it's unlikely i say well it could happen and we need it on the radar so yes it could happen at 2 degrees c in the in if you if you were to trust those models and we can discuss the fact that those models have weaknesses and they might be biased stable um if it does happen that that corresponds to about the middle of this century on the current warming trajectory in about you know 2040 to 2050 to 2060 give or take how quickly could it unfold well the past climate record shows us abrupt shifts in climate associated with this overturning circulation that essentially unfold in a decade but the models they take longer to break the overturning so again the models might have some flaws they may be too stable it may be that what happened in the past climate record was a couple phenomena that we're not fully capturing changes in the ocean triggered changes in the faster systems the atmosphere and the sea ice um but the worst case would be yeah it gets triggered in the 2040s because we've got high warming high climate sensitivity and we looked at a scenario where it unfolded over sort of 20 30 years within this century because i felt that was reasonable given what we know from earth's recent history so it would be with in my in my scenario it's plausible it could happen this century i'm not i'm gonna hang my hat on how lightly i think that is or not um but you can press me on that in the q a if you want thank you tim do any other panel members want to come back on anything that tim has said before we move on to some other questions no in which case moving on to another question we've received which is there's a prediction that humanity will be devastated in 25 years due to phytoplankton loss they're predicting in this research a tipping point when ocean acidity reaches 7.95 in the early 2040s and then that all marine life and plankton based on carbonate dissolve dissolves along with the loss of all whales and fish that's a quote leading to runaway climate change does this sound like a realistic scenario and are they right in thinking that eliminating plastic and chemical pollution could restore health to phytoplankton quickly helping them mitigate co2 emissions and keep the oceans alkaline so i'll have another go sure yeah um no it's not not as described a realistic scenario it's it's it funny for me to be accusing other people in illinois we might think but it's just not scientifically sound as stated i mean it would be a catastrophe for marine life if we have an acidification to the point that it is killing off all calcifying organisms but that would not be killing off all marine life i can't remember the exact fraction of phytoplankton production that would be calcifiers it would include eukaryotic algae lithium walls if you have any inkling what they are but it wouldn't be hurting diatoms that make salacious cells that are also algae and it wouldn't be helping it wouldn't be hurting cyanobacteria which produce about 50 percent of marine primary production and don't calcify so it's wrong on those fronts um as for the plastics well we've got empirical evidence that microplastic particles in are being eaten by zooplankton which are little animals to you and i um and for sure that is not good news because they can't digest them and then everything else above them in the food chain is not going to like that problem for the zooplankton but it's wrong to say that the microplastics are an obvious risk to the phytoplankton the primary producers i'm not aware of a great body of empirical evidence to say that the plastics easily or directly harm the primary producers but suffice to say these are serious issues um and then in the question there was something about is that this group are saying that it will cause runaway climate change well no even if you could collapse the biological pump in the ocean you would release carbon from the deep ocean you'd it sort of there's a disequilibrium at the moment where all this pumping of carbon down is concentrating in the deep ocean but the amount you'd release would raise the atmospheric co2 level by about 200 parts per million that's bad news but it's not runaway uh not unless you kick in other feedbacks it's just a construct what we call a constrained positive feedback not a good one all bad things but but we must i think if we're scientists we've got to be scientific about this so that's what i try to do there thank you very much tim we've got two slightly different questions that have come in about actions that we could take so the first is dr gibbons seemed to want to rule out our solar radiation management which one could imagine being used to give humanity more time for a period of net carbon dioxide removal maybe my i misunderstood what do the panelists think i'm also going to come in with the second question because i think they both speak to the same area which is what are the actions that we could take and then i think perhaps speaking to what um dr gibbons was focusing on should we take them the second is i work with a group advocating what we call the climate triad accelerated emission reductions massive greenhouse gas removal of trillions of tons including methane undirected cooling perhaps iron salt aerosols or marine cloud brightening and re-freezing the arctic as ways to get temperatures increases to well below one degree c to ultimately restore a safe climate your thoughts goodwin do you want to start yes um i do want to make sure i'm giving a more balanced view on this um part of the issue is this concept of a safe climate and also like a safe long term after the usage of solar radiation management so um just to give a little bit of a background on the science that makes me concerned the fundamental thing is that um the sort of two knobs that change the energy balance of the climate there's the outgoing long wave radiation and the incoming solar radiation and when we change the greenhouse gases we're turning the long wave knob and the idea of celebration management is to twist the shortwave knob and the issue here is that they are not they are not opposite from each other so this point about the triad accelerated emissions reductions is a direct counter to the emissions that we're producing that's a simple win there's not a problem with reduce reducing our co2 emissions there isn't a possible negative consequence um well that's not that's not entirely true but the the chance of a negative consequence is much less um whereas uh solar radiation management just carries this innate riskiness um things that might happen is that the the like the precipitation pattern or the the ability for crops to grow the pattern of warming the cycling of warming throughout the day these are things that are climate changes but maybe not global warming that can happen when you do solar radiation management to combat climate change not to mention issues with um what happens when you stop doing solar radiation management does the climate respond very quickly um and uh you know how are other things happening like the ocean acidification that are not directly related to the warming so um there might i don't want to say that there isn't a scenario where certainly radiation management is better than the alternative um but it's a dangerous thing to put in place and i think um i think that goes to answering both questions maybe we can talk about um the removal of trillions of tonnes including methane depending on the mechanism maybe is is not such a scary thing because it's reversing the the i mean if you're removing co2 then that's just reversing the emission of co2 so that's my my sort of prior i would say on the solar radiation management issue um used carefully might not be might be part of a solution but it's dangerous i'm really curious to hear what the other panelists would say though um let's let's pass it off tim you've unmuted yourself and then we'll go to luke yeah thanks so yeah good he made a lot of important points there i mean my broad brushstroke take on this is um solar radiation management because it's globally called could be equivalent level of riskiness to the risk you're trying to avoid so it doesn't sound to me like a particularly sane risk management strategy to introduce a poorly understood potentially similarly risky intervention to fend off a known a sort of known partly known risk i think what we're learning you know by seeing those questions come up is that if we choose to shine a light on tipping points and extreme climate impact scenarios we are necessarily inviting ourselves to think about how on earth can we stop that and we are necessarily inviting this discourse about solar sunlight reflection methods as i rather we prefer to call them so let me try to add a little bit in terms of why why do i think we could get that badly wrong or it could be dangerous well first you know when we were emitting aerosols into the northern hemisphere troposphere in the 70s we now know that that was contributing to the profound drought in the sahel we can all remember the 84 famine and so on and so forth so if you don't you know there's a simple case where we know if you didn't evenly distribute aerosols at whatever altitude in the atmosphere you can really cause serious impacts for in parts of the world with many people on top of that you have the geopolitical points that uh many people will reflect on this would think that if pakistan or india thought that india had disrupted the monsoon because they'd done some stratospheric aerosol injection or vice versa both nuclear armed states might it might heighten tensions between them and who who's to say whether it wouldn't provoke conflict that's been we've all well many of well has been borderline for a long time so that's but though the broader point from an earth system point of view is we've heard from luke how we don't know what the climate sensitivity is now my biggest beef with the would-be solar radiation managers is they're still operating in this sort of modernist mentality of a mechanistic universe where they think we do know fully how the earth system works and we kind of do know the climate sensitivity and therefore we know how much aerosols to inject the point here is you have to inject quite a lot to get a signal above the noise to actually be able to demonstrate that you've had an effect if you're unlucky and you you stick quite a lot in but it does turn out we're in a high climate sensitivity world well then you're just running the risk of over cooling the system right um i probably made more than enough points there i i could go on a painful length on this topic as to why basically i think philosophically it's flawed to to introduce this this completely different kind of intervention in a into a complex system that we have to be totally honest we don't fully understand um in with thinking humoristically that is going to cancel out the greenhouse forcing thanks thank you tim luke this is a very juicy topic so luckily one of my phd students back at the australian national university aaron tang is doing some wonderful work on geoengineering both solar variation management and negative emissions so first of all negative emissions i agree with both goody and tim that this is the less dangerous and probably more benevolent option when we look at large scale interventions into the earth system the problem with negative emissions is first of all there are trade-offs still so if you're looking at really large scale bio energy carbon capture and storage decks or even really large scale deck capture it's likely going to require in very large amounts of land as well so at least one study i think back in 2019 which suggested that in order to meet a fairly low level of carbon capture you're probably looking at something like the size of india in terms of apple land which obviously is going to have a large competition when it comes to food security etc and secondly this is for me the much larger one is feasibility but one of the articles that aaron did was looking at the rate of change for different large-scale industrial or energy system changes and these tend to take even once you have the technology coming to market and taking up roughly 20 pups in the market share they still take someone between half to it for this country to occur and right now when it comes to negative emissions none of these technologies are deployed at scale and the idea that we can have these deployed at a really large scale and potentially have something that is equivalent to the fossil fuel industry being created in the space of you know 70 years or less potentially possible but it seems like it's resting on pretty heroic assumptions so i think this very large question marks about how much naked emissions can actually contribute to the climate response soil radiation management is the kind of more dangerous and interesting one and what i want to focus on here is one particular form of solar radiation engine called stratospheric aerosol injection which is where you proper aerosols essentially cooling agents into the atmosphere this is one of the most attractive options because it's believed it can be done at a fairly low cost in terms of just billions of dollars and it could be also unilaterally employed by a single actor whether it's a billionaire or a potential state an article that aaron and i just finished which has been acceptable frontiers and should be published in the coming months is called worse than warming we're essentially try to actually look at what are the worst cases of stratospheric aerosol injection and we use this framework that i put up before the slides of looking at both the aggregate impacts systemic risk latent risk and also its ability to trigger other extreme risks in short we don't really know too much it's a very neglected area of study both tim and goody mentioned that we do know it's likely to change precipitation patterns it's also interestingly likely to change the range of different vector-borne diseases as well as invasive species so we can probably expect potentially news and of infections emerging if it is used we also do know it's going to transportation patterns which can have knock and effects in terms of the agricultural system we at this stage really don't know if it could have direct impacts in terms of causing some kind of large scale tipping point which tim mentioned but we can't rule that out either and it's worth remembering here that most of the models are done with the assumption that this is deployed in a fairly kind of perfect manner by a single global rational agent in reality of course is not going to happen and we could very easily see different countries trying to compete and micromanage their own regional climates and on top of that you could also potentially have something like a super volcanic eruption occur or even a nuclear war which would actually pump up more coolants and kind of heighten the risk that you push a tipping point away so that's that but basically our main conclusion was the biggest risk when it comes to geoengineering or stratospheric aerosol injection is latent risk that even if it works perfectly you still essentially just masking a certain level of warming and we're most likely to use geoengineering straight through aerosol injection when it comes to large levels of warming it's going to be used in a set escape course most likely and if you're hiding you know two degrees three degrees or even more of warming there's this problem of termination shock that warming that could occur over the space of decades up to even a century is likely to occur over the space of roughly nine to twelve months instead so that's obviously going to change the challenges associated warming of all of a sudden warming that we expect to occur is happening in like magnitude so what is magnitude faster and this is the real problem we foresee is that if geoengineering is used it's used to cover a large amount of warming and in some way that system is knocked out whether it be just due to something like a solar flare large-scale war nuclear war etc essentially have a much larger climatic response all the warming comes fresh back in so we kind of frame it's this planetary sword democracies hanging overhead and in a way it's just a kind of shifting of the risk distribution where the kind of median scenario if the system plays the status in place is quite good if it gets knocked out all of a sudden these kind of extinction level scenarios become much more plausible we can't hear you you're muted catherine absolutely right sorry there was some noise outside so i muted myself we've had another question come in um addressing climate change and avoiding negative tipping points appears to require major changes in human human behavior at scale yet human opinions seem to be very polarized is anyone factoring this into the probabilities of achieving even modest climate goals tim great great question there's there's a bit of work on it but probably not enough would be a good answer um this actually connects us back to the discussion about um positive tipping points or social tipping points because they are sort of framed around the often around the idea that you have critical mass effects where for a certain fraction of the population adopts the new norm or behavior or possibly product or technology then you the critical mass is where one more person adopting will tip all the others to follow um trying to interface that with a polarization might seem unintuitive but uh sometimes you're in a situation where you have clusters of population in the one camp or the other and it doesn't preclude that you can't have a shift to one extreme or the other that's more of a mass shift but yeah a very very interesting reflection and many of us i'm sure are troubled by the sort of uh the flight i was going to call it the flight from rationality without a flatter wanting to flatter rationality too much but let's split it this way i am troubled i am troubled by uh anti-vaxxers by um yeah apparent popular movements that just seem to turn away from fairly solid evidence and science on certain issues whatever those issues are if that's the trend that continues um then my the door that was showing a little bit of of light that we could get our stuff together on a problem as complex as climate change is frankly going to close close so yeah fantastic question really um there's a little bit of work that uses so-called agent-based models which would actually literally try to represent this polarization and a little bit of work that some of us do on on sort of network theory and analysis analysis of social media data to actually track this polarization and discourses and the like um it often is perceived bad we discussed it some more we might also find cases where it doesn't have to be a bad thing that we might even have it to our advantage in the great transformation but but yeah i think i probably share the question as uh worries about it and goodwin is you set out in your explanation of your own journey you're now in a faculty of philosophy what are your thoughts about this question actually i would say um i think my thoughts come from my experience of being a scientist as well um i was a scientist studying a kind of niche area kind of like tim i was studying a theory of self-organization of the climate which is not the normal way that climate scientists study and the climate which is normally through these big models um and i was privileged during that to also get to speak to some people who are very much on the polarized other end of the spectrum um so sometimes skepticism in one arena might be well placed but it gets mapped to skepticism and something that it doesn't quite apply to and so i have a bit of a um a sense of hope that there is more common ground in the center than we're taking advantage of right now so part of the reason that the debate on climate change has become polarized is because the people on um on the side of climate action also are pulling are pulling the situation maybe wider than um than is than as palatable to the people we need to work with across the aisle what i suppose i'm trying to say is it seems to me that the basic um the basic elements of the climate change problem are are solid and that we should be able to build more cohesiveness around it i see there's another question that come up came up i might invoke the next question that um someone's asked about for example suppose um we're looking at the maybe a more right or motivation to to not have migrants into a country that's something that i think most people who are um climate activists are not of that political persuasion at all um but that is a a value from which you might consider action on climate change how do we deal with um how do we deal with being a team on the issue of climate change whereas we might not be a team with some of our other social values um and that i think that there is simple science in the middle of this that doesn't need us to take on um too many things that are politically divisive might be a safe place to come back to to decrease the polarization on this issue um i hope that made sense i think i meant didn't manage to i haven't delivered that point often it's not a question i often get asked but it's definitely um the science that we do have at the center of this the co2 increases the temperature that the earth is a crazy place that we don't understand um and that this is scary it's just so um so far from all the pieces that have come into the polarizing debate that it feels promising to return to the basics tim looks concerned so i'm curious what he's thinking maybe he's not you know i'm i'm frowning because i'm trying to address also the question in the chat about is it legitimate to talk about the climate refugees triggered by climate change scenario um as a way of motivating the right wing who are fairly xenophobic to come on board with the climate issue which is a killer question from stephen i'm not friending it here sorry goody i might i don't know if i should carry on with my answer but i might quickly jump in before you head on to that question i think it's a it's a very important one um so first of all like i'm not aware of modeling which actually tries to integrate in kind of episodic belief patterns with mitigation efforts it may exist but it's something i'll come across i want to give both kind of reasons for optimisms and reasons about pessimism underneath so first of all reasons for optimism is that it may be a bit of a red herring that when you look at polling data across a larger different countries including countries that are usually considered to be quite recalcitrant and climate action countries like australia as well as the us most people are actually pretty supportive of climate action as well as surprisingly high levels of carbon pricing unfortunately it doesn't seem to impact the way they vote which is a different matter and when you actually let people even if they're quite polarized deliberate in a structured process whether it be in for an assembly or a jury everything we call diligent democracy they tend to come to surprisingly good conclusions we have a whole bunch of both theoretical and practical examples one recent one was actually in paris where in response to the yellow best uh riots macron organized a climate change assembly the french climate change assembly and this had i think roughly 150 people come together of this space for around about a year to discuss and deliberate what would be inadequate and appropriate climate response and they ended up coming up with over 100 different recommendations which together formed a very comprehensive and very ambitious policy package and the problem was that macron only accepted three of those despite having agreed prior to um accepting all of them and i think this is just to me the biggest problems about polarization right now the fossil fuel will be in the political economy of climate change so that's one reason for optimism reason for pessimism very very briefly is that there's some emerging evidence that one of the problems and drivers of polarization is wealth inequality so there's some really good examples of this in the u.s where you some people actually mapped out the number of bipartisan bills being put forward as well as voting across the floor in the u.s and you see it slowly splitting apart between the democrats and republicans and that maps almost perfectly onto the intro and sorry increase in wealth inequality within the us and the downside to this of course is that we can expect wealth and equality to probably increase going into the future a very influential book in this area is called the great leveler by walter scheidel which is a deep history of oil for inequality and his fairly depressing conclusion is that it always increases inextricably until you have a great level of mass mobilization warfare estate collapse a pandemic or a bloody revolution and so at least for the simple future we can probably expect wealth and equality to increase both within countries particularly countries and for that to drive for polarization so that's both kind of good points it's potentially about hearing and bad points it's probably going to worsen into the future so we're coming towards the end and we've got a whole constellation of questions that are all nibbling at the same point which tim and goodwin you've begun to touch on so there's the question that we've already raised the excellent question about um given that this needs to be an entire global movement and a whole of society movement what are the ethics around how we engage different constituencies in this debate with different messages there's also a question that's come in around national differences even in societies which we might consider to be fairly similar at another level so looking at the response to climate um in the uk for example versus the response to the us and then there's a question which actually looks back into history um and brings together the fact that around the second world war there was a very high degree of mob global mobilization around an issue so i'm going to because we haven't we've only got 10 minutes left and i do want to give the panelists an opportunity to have a final word maybe in um the next five minutes if each of you could look at that constellation of issues from whichever you think is most pertinent and powerful to your research but i think the fundamental point is this is a global problem how do we mobilize most effectively a global answer goodwin perhaps if i could start with you first in part because you were talking very interestingly i thought about the power of this framing questions of what we value thank you yes um and it's also particularly interesting this u.s uk division as a dual national myself and having spent time in both of these countries so um i've noticed in the us that when people need to make up their mind about climate change often they check in with their religious values and make up their mind about abortion first and based on their feelings about abortion as a as a right versus a crime um they find that they have to take a certain stance on climate change and to me like i was trying to say before that um that wrapping up of something so simple and universal um that really should appeal to people with different constituencies people with different values as our common substrate our common landscape that isn't an issue that belongs only to the left the fact that that's wrapped up with these other political debates which are maybe more open for political debate than climate changes seems um seems really concerning and i think thinking about world wars there was something very um unifying about having your whole country a threat i mean whether or not you valued this church or that church within your country if your country was not going to exist you could get on board with that and so um i i feel like a releasing of the issue to more common ground allowing it to belong to people from different values and different backgrounds and being able to say well you know i didn't get there from the same values but i'm glad we got to the same conclusion on this issue um feels to me like the only way um to do this collectively um and that feels really really important because this isn't something that we need one side can do for the other side um that will result in too much resentment and upheaval i think um so that's that's sort of my feeling separate it from these maybe more um legitimate political differences thank you goodwin luke or tim do you have any thoughts on this wider ethical and you know how do we concert as countries or indeed the world i could i was read a brilliant piece yesterday about this i don't need to remember the author to credit them properly but it was what we're looking at with climate change classic kind of potential tragedy of the commons common poor resource situation where we all sort of reap the benefits if we limit climate change and the altar varying degrees carry the costs if we don't but then tackling climate change is also the the costs of doing so and the benefits are also unequally distributed so one has to get oneself in a sort of strategic mindset of okay if we embrace the transformation if we accept the argument that we just can't afford to go to a two degree that lone three degrees c warmer world if we could come to together on that then we've still got to answer the question of okay how to make the transformation happen in a just way so on the one hand you have the gelation as as luke mentioned so essentially one side of the problem is if your you know some initial costs to trying to trigger the transition are hitting the pockets of the poorest people or poorer people in society they will rebel so we have to have a re-sensible thought out redistribution strategy to not to nullify that to not penalize the poorer in society that's sort of transparently obvious perhaps but not so transparently obvious that the french got it right the first time let's put it that way now on the other side of the coin you'd think well why worry about the rich people but the problem is some of the rich people are standing to lose here they're the ceos of the fossil fuel companies or whatever and there's a different dynamic to work out how to win um against them now part of this is about a coalition of those of us in the middle ground who are on a partly mo you would could argue a moral quest here to to to make the transformation happen um we certainly have to come together um to to tip the dynamic away from rich vested interests in the current status quo that's perhaps another statement of the blindingly obvious um but we might even unfortunately in some cases even have to think about heaven forbid that we shouldn't really morally be thinking about having to compensate in any sense the rich that stand in the way so i i'd rather not go there but it is clear that it needs subtle thinking to work out how to to win over the very strong rich vested interests that have been standing against progress on this existential matter for for most of my lifetime so i don't know if those reflections help i'll try and um find and put in the chat the piece i was enjoying that articulated this better than i could tim thank you very much we've got four minutes left and so to wrap up what i'd really like to do is thank you to all our questioners um and thank you also for taking us through some detailed signs and into these broader ethical and societal questions but i want to turn us back into the science in the last four minutes and perhaps if i could ask each of our panelists to say um from the scientific start of this conversation what is the one fact message or piece of research that you would like all of us to go away remembering tim maybe if i could start with you messages we are in a climate emergency and if you're in an emergency you should be acting urgently to do something about uh lowering the risk and the existential risk you're running um so i suppose the taking and then the other the other side of taking messages we all have some agency in that in this to be part of that urgent action it's not good enough to sort of point the finger at the government poor though they often are um let's take matters into our own hands sorry that's not a reference to one study but that's my honest view thank you tim goodwin that is not an easy question but it's a nice one i think agreeing with everything tim said and to add another one um of those list of four ways that we could hit a worst case the two that we have most control over is the amount of co2 that we emit and the way that we are prepared to adapt to this the changing of the climate in terms of the human impact and so keeping a focus on those two priorities um mitigation adaptation as being the two things that we know we need to be working on whether or not we're waiting for further updates to the details of the science that will come in the future ipcc reports thank you goodwin and luke yeah both tim and goodwin we are in a crisis and we don't know how bad it could get that should not be brown's complacency but precaution and understanding and thinking through the worst cases can lead us both to a better risk management but also to hopefully responding in a much more coherent cooperative and better fashion and just one very very brief quick answer to the previous question we're discussing uh plugging some work i did with a rebecca coleman back at the nu we do know that if you have picked the right messenger and if you avoid ideological bundling and you choose the right frame you can find ways to actually appeal to a vast place of audiences and evolve polarization this is all kind of common lessons from social psychology and communication and i think that when it comes to getting broad cooperation a lot of this is also about talking about positive in particular co-benefits the big really positive story designs over the last couple of decades has been an emerging picture that we should be trying to decarbonize even if it was for climate change purely due to things like reducing the health costs of greenhouse gases there's a really really compelling reason that the carbonizing is building a better world even if we are concerned about climate change thank you very much indeed luke so thank you again to our panelists to um professor tim lenton dr goodwin gibbons and dr luke kemp particularly luke for bringing together um this panel and a final thank you to cambridge zero's climate change festival 2021 and to all of you for joining us um luke i think you ended with three bullet points and as a former diplomat one should always end with three but the reason this matters is because we need better risk management better coherence and better cooperation so thank you very much indeed thank you thanks everyone

Channel: Cambridge Zero

Views: 58,267

Keywords:

Id: dkDbCpn0_9I

Length: 87min 34sec (5254 seconds)

Published: Wed Dec 15 2021

Reddit Comments

[u/CollapseBot]

The following submission statement was provided by /u/corn_cob_monocle:

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This is an extremely detailed talk from Cambridge about the “worst case scenarios” on climate change which, as you’ll see from their data, is increasingly the likely scenario.

Preaching to the choir on this sub but I personally find it refreshing to give scientists a forum where they abandon all pretense of hope and just give us the straight dirt.

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Please reply to OP's comment here: https://old.reddit.com/r/collapse/comments/wcp322/extreme_climate_risks_what_are_the_worst_case/iidqwju/

[u/[deleted]]

Thank you OP for this. It was really informative.

The essence of catastrophic climate change is in the initial talk of Ms. Gibbons. The underlying distribution is fat tailed and that is very, I mean very unfortunate for us (fat tails are my scientific and professional field).

For anyone interested to learn more, there is an excellent paper from Martin Weitzman titled: Some basic economics of Extreme climate change.

[u/OldEstimate]

Just started. This owns.

Our human geography is built atop a physical geography which will be ripped out from under us.

Sample 'Worst Case' daisy-chain:

• Worst Case #1: +2C by 2034 (via current trajectory)
  
• Worst Case #2: +2C locks-in +4C (via cascading feedbacks)
• Worst Case #3: +4.5C gaps up to +12.5C (via stratocumulus cloud deck failure)
  
• Overall Scenario: +2C by 2034 locks-in +12.5C by ~2150
  

Please note that #1 is just business-as-usual until 2034 lol.

fake edit: lmao

[u/corn_cob_monocle]

This is an extremely detailed talk from Cambridge about the “worst case scenarios” on climate change which, as you’ll see from their data, is increasingly the likely scenario.

Preaching to the choir on this sub but I personally find it refreshing to give scientists a forum where they abandon all pretense of hope and just give us the straight dirt.

[u/uk_one]

Sadly, no matter how accurate, scholarly and urgent this is almost no one will get past the first five minutes.

Drone, drone, drone. Stare a 4 unengaged faces, yawn and switch off.

Eventually the movement will remember Ali G and re-learn that it's imperative that people listen to the message.

[u/Termin8tor]

These academic institutions do a great job of breaking things down. My only criticism is labelling the business as usual scenarios as "worst case". Business as usual is the most probable case and should therefore be the baseline. When communicating with the general public the assumption people will make is "Oh that's the worst case! It won't be that bad..."

The reality is it'll be that bad or worse as it's the bloody baseline.

[u/wawakaka]

Noah's ark

[u/Classic-Today-4367]

Thanks for this. Turned it on and realise I saw it last year already, but its good to revisit this stuff in light of this year's droughts and heatwaves.