Sofia Palazzo Corner and colleagues | What’s next after net zero?

In this Frontiers Forum Deep Dive session on 18 January 2024, Sofia Palazzo Corner, Prof Martin Siegert and Prof Joeri Rogelj discussed the amount of temperature change we can expect after CO₂ emissions from human activities reach net zero, and how this can be built into climate models. They were joined for a panel and question and answer session by Ben Sanderson, Charlie Koven and Tessa Khan.

The session brought together the authors of the Frontiers in Science lead article ‘The Zero Emissions Commitment (ZEC) and climate stabilization’ in which they present the first comprehensive analysis of Earth processes controlling global temperatures and our knowledge gaps for each – plus a pioneering framework for building climate models that are better equipped to predict ZEC.

Links:
• View the Frontiers in Science lead article at: https://www.frontiersin.org/journals/science/articles/10.3389/fsci.2023.1170744/full
• View the Frontiers in Science article hub at: https://www.frontiersin.org/journals/science/article-hubs/global-warming-after-net-zero

Speakers:
• Sofia Palazzo Corner | Imperial College London, UK
• Prof Martin Siegert | University of Exeter, UK
• Joeri Rogelj | Imperial College London, UK
• Ben Sanderson | Center for International Climate Research (CICERO), Norway
• Charlie Koven | Lawrence Berkeley National Laboratory, USA
• Tessa Khan | Uplift UK

INTRODUCTION
00:00:00 Opening
00:00:30 Welcome & introduction | Gilbert De Gregorio | Head of Partnerships, Frontiers Planet Prize
00:04:39 Setting the scene | Prof Martin Siegert | University of Exeter
00:06:53 The Zero Emissions Commitment and climate stabilization | Sofia Palazzo Corner | Imperial College London

PANEL DISCUSSION
00:21:53 Introduction of panel session | Gilbert De Gregorio | Head of Partnerships, Frontiers Planet Prize
00:24:26 Panel discussion on what’s next after net zero? | Facilitated by Prof Martin Siegert | University of Exeter

Q&A SESSION
00:55:20 Audience Q&A session

CONCLUSION
01:23:08 Closing remarks from Joeri Rogelj | Imperial College London

Frontiers Forum Deep Dive sessions bring researchers, policy experts, and innovators together from around the world, to discuss a specific area of transformational science published in Frontiers’ flagship multidisciplinary journal, Frontiers in Science, and explore next steps for the field. Watch previous sessions at https://forum.frontiersin.org.

We see this paper as being  part of a four-step process   to improving our assessment of ZEC. The first is to identify the Earth   system processes that drive this uncertainty and  that’s what we’ve tried to do in our 26 levers.  The second is to estimate their  impact in different timescales and  

The third is then to try and reduce this  uncertainty through targeted research.  And of course, the ultimate aim is  to build models that can better give   us an assessment of the Zero Emissions Commitment. Good morning, good afternoon  and good evening, everyone,  

And a very warm welcome to everyone joining us  today for this Frontiers Forum Deep Dive session.  Allow me to introduce myself. My name  is Gilbert De Gregorio and I’m Head of   Partnerships at the Frontiers Planet Prize  and I’m absolutely delighted to be your host  

And moderating today’s session that explores  global warming after achieving net zero CO2. So, today’s Deep Dive session will be focusing  on this lead article entitled “The Zero Emissions   Commitment and climate stabilization” which was  published last year on November the 14th and  

It’s already been featured in both Bloomberg and  the New Scientist right off the bat from COP28.  I guess we can all agree that this is  a very timely and topical theme that   we’re very interested in learning more about. So, in their Frontiers in Science lead article  

And its hub of complimentary content,  which I invite everyone here to read,   to explore, the authors, Palazzo Corner  et al. present the first comprehensive   analysis of Earth processes that control global  temperatures and our knowledge gaps for each.  Plus, and very interestingly, they introduce a  pioneering new framework for building climate  

Models that are better equipped to predict the  expected additional change in global temperature   once we reach and achieve net zero CO2  emissions. This approach is absolutely   crucial for effective climate policies,  as also discussed in the complementary   publications that you can find in this hub. So, the article itself acts as a centerpiece  

For a lot of great material including this  editorial by Professor Michael Mann from the   University of Pennsylvania; a scientific  viewpoint article by Professor Damon   Matthews of Concordia University; and a policy  outlook by Brook Dambacher and Tessa Khan of   Uplift UK, who we’ll hear from later today. There’s also a lay explainer, infographics,  

A video, and also an article that’s been published  in Frontiers for Young Minds which is our journal   for kids, and during this Deep Dive session, you  will hear from many of the different contributors   to this article hub and you’ll also have the  chance to connect and ask your questions to them. 

So, what have we got to look forward to  together today? So, this is today’s agenda,   we’ll kick off with Professor Martin Siegert,  who will set the scene for today’s discussions.  Sofia Palazzo Corner, lead author of the article,  will be presenting on whether global warming will  

Stop when we reach net zero CO2 emissions, and  will examine what determines the temperature   changes once we reach this threshold. The speakers will then come together in   a panel discussion who will also be joined by  Professor Joeri Rogelj from Imperial College,  

Ben Sanderson from the Center for International  Climate Research, Dr Charlie Koven from Lawrence   Berkeley National Lab and Tessa Khan,  founder and Executive Director of Uplift.  We’ll then open the floor to questions  from all of you, and finally we’ll then   close off with Professor Joeri Rogelj who  will be delivering some closing remarks. 

So, our first speaker is one of the co-leaders of  the Frontiers in Science lead article, Professor   Martin Siegert from the University of Exeter. A few words about Martin. He is also the Field   Chief Editor for Frontiers in Environmental  Science; a renowned, a globally renowned  

Glaciologist who leads the UK’s participation  in ground based airborne geophysical programs,   which have so far explored and charted the sub  glacial environment across 40% of Antarctica.  He’s also published more than 250  scientific articles in leading   international journals, is previous co-director  of the Grantham Institute of Climate at Imperial  

College, and Martin is now the deputy  Vice Chancellor of the University of   Exeter where he’s also responsible  for supporting the 2030 target for   net zero greenhouse gas emissions at both the  university and the county in which he resides.  So, Martin, with that, a  warm welcome and over to you. 

Well, thank you very much Gilbert for  that kind introduction. Just like with   all scientific papers, each of the authors  involved will have their own story about its   origin and I’m about to tell you about mine. Mine involves an early morning cup of coffee  

With Joanna Haigh, and Joanna and I were  co-directors of the Grantham Institute   at Imperial some time ago, and without going  into too much detail about that conversation,   it’s quite clear we had very different ideas  about what happens to the climate and the  

Environment of our planet after net zero emissions  is established, or the Zero Emissions Commitment.  And that conversation was interesting,  we suspected many other people would   have similar misconceptions about it from a  variety of different perspectives as well.  So, sometime later, with the help of  Joeri Rogelj, who we’ll hear from later,  

We configured a group of specialists from  all around the world to discuss and debate   the Zero Emissions Commitment, brilliantly  led, I should say, by Sofia who we will hear   from shortly to take us through the paper. We set ourselves about two or three months  

To reach a consensus on this. Actually, it was  probably more like two years I think of many   discussions and drafts and working things through.  But I think we’ve put together a comprehensive   guide to the Zero Emissions Commitment  and we hope it’s going to be informative,  

Useful, and interesting. So, to tell us more about it,   I’m going to hand over to Sofia who’s  going to explain everything that we did. A huge warm welcome Sofia. Sofia is a climate  science and climate policy PhD student at the  

Center for Environmental Policy at Imperial. Her  research focuses on Earth system extremes with the   aim of fully representing the spectrum of possible  temperature changes that occur, that could occur   by 2100, and a very interesting background,  if I may, an accolade of achievements. So,  

Sofia has a professional background in management  consulting at the Boston Consulting Group, energy   and environmental research at Chatham House and  quantitative risk analysis at Funding Circle. So,   Sofia, a warm welcome to you, the floor is yours. Thank you, thank you Gilbert, thank you Martin,  

And thank you to everyone joining us online  today. So, I’m going to introduce this paper   that we published with a question, which is  probably the same question that brought you   here today and was certainly the motivation for  our study. That question is: will global warming  

Stop when we reach net zero CO2 emissions? So, what do we mean by this question, what do   we mean when we say, will global warming stop? Well historically, and of course still today,   global surface temperatures are rising in  response to anthropogenic CO2 emissions. We’ve  

Burnt some carbon, we’ve got some warming and so  the question is: once we stop burning that carbon,   do we also stop our warming? Does no carbon  dioxide being added to the atmosphere, mean   no more warming? And another way to phrase that  is how much additional warming are we committed  

To after we achieve and maintain net zero  emissions? What is the Zero Emissions Commitment?  So, there are three things that can happen  after net zero, to global surface temperatures.  The first is that temperatures stabilize  and the global warming that we reached at  

The point that net zero was achieved is the same  that we have going forwards, there’s no change.  The second is that we could have some warming,  some additional temperature rise after net zero,   in which case, that global surface temperature  will go up a little, or alternatively some cooling  

And global surface temperatures would reduce. The Zero Emissions Commitment is then a number   and it’s a number that quantifies  that change in the global surface   temperature between the point when net zero  was achieved and some point in the future.  And Zero Emissions Commitment or ZEC,  as we will abbreviate it, can be zero,  

Meaning no change and temperatures  stabilize. It could be positive,   indicating that there’s some additional warming,  or it could be negative, indicating cooling.  And so, the next question is, what is it that  happens to the Earth system exactly after net  

Zero and how does this affect temperature? So, if we, if we sketch out what’s happening   to emissions at net zero. So, historically  and still today anthropogenic CO2 emissions   are increasing. If globally we stop  emitting CO2 into the atmosphere,   there are two things that we expect to happen. First, is the atmospheric CO2 concentrations,  

Which have been rising alongside  rising anthropogenic CO2 emissions,   are expected to start declining. And that’s  because CO2 in the atmosphere is expected to   be redistributed to carbon sinks in the land,  in the ocean, by the natural carbon cycle. 

Now this on its own would be a cooling effect  but it isn’t the only thing that’s happening.  At the same time, we’re expecting ocean  heat uptake, which has also been increasing   as emissions have been increasing,  to start reducing after net zero. 

And this would mean that more heat  remains in the atmosphere and on its   own this would be a warming effect. And so, the question then is what   happens overall to global warming? Is there a balance between this  

Cooling and this heating effect, or not? And  so, we can imagine it kind of on a scale.  On one side we have heating due to  this slowdown in ocean heat uptake,   and on the other side cooling due to our  continued strong land and ocean carbon sinks. 

Now, if our slowdown of ocean heat uptake is  perhaps a little more rapid than we anticipate,   or our land and ocean carbon sinks are  less strong than we expect, then this   might result in some more heating after net zero. On the other hand, if our land and ocean carbon  

Sinks remain strong or if our heat uptake  reduces less rapidly than we’re expecting,   then we might get some cooling after net zero. But it’s important to bear in mind that we care   both about the magnitude of these effects  and also the rate at which they change,  

Because they need to cancel each other out  not only at the beginning but going forward.  So, if we go back to this picture that  illustrates the question that brought us here,   that balance is represented in this  uncertainty range that we see on the  

Right-hand side after the point of net zero. If we had balanced it one way, we might expect   a little more cooling and if we see the balance  go the other way then perhaps some warming.  Now our best estimate at the moment is that  there is no further temperature change after  

Net zero – that remarkably this balance  is struck and continues to be over time.  However, these assessments do come with an  important and quite substantial uncertainty   range and so that’s the second thing  that we decided to look at in this paper. 

And what we’re trying to understand is what these  processes are that underly these two macro effects   at the top – the heating and the cooling? What  are these processes that determine temperature   change after net zero? And so, what we did is  we took our quite large group of co-authors,  

Who are experts in different parts of the climate  system, and we tasked them with trying to build a   catalog of all of the different processes that  could affect global temperature after net zero,   and this is what we came up with: 26 levers  of global temperature change after net zero. 

We kind of accidentally built our own A to Z,  and so these processes are organized into four   subcategories. We’ve got land carbon processes,  ocean carbon, ocean heat, and physical feedbacks.  Now, these two on the left – land  carbon and ocean carbon – they  

Are processes that affect and determine, and  are determined by, the natural carbon cycle.  We’ve then got the kind of physics of the  ocean and how heat is transferred between   the different ocean layers and also exchanged  with the atmosphere, and then we have feedback  

Processes which affect, and are affected by,  a number of those other three categories,   and also other parts of the climate system. So, this is already a great resource for   anyone hoping to study the Zero Emissions  Commitment and reduce our uncertainty in it,  

But of course ultimately what we’re trying  to do is quantify the effect of each of these   processes, and so that was the next step we took. The way that we did this is we gave a case study,  

Or you might call it a scenario, and we asked  our group of experts to consider a world where   global warming was at two degrees at  the point where we reached net zero.  So, at the point where we reached net zero  there’s been two degrees of global warming. 

And we asked how much would each of these 26  processes move that global surface temperature up   or down as a percentage of that initial warming?? And that’s what we’re looking at here. So,   this figure has a few things going on,  so let me just talk you through it. 

On our x-axis we’ve got those 26  different levers – the A to Z.  And on our Y axis we have the change as a  percentage of that initial two degrees of   warming and our two levels there are 1% and 10%. Then some of those are stretching beyond 10%. 

The colors are indicating the  groups – the subcategories.  So, if we look at our key on the left, we’ve  got land carbon, ocean carbon, ocean heating,   feedbacks, and then the tone or the opacity of  those bars is an indication of the confidence  

That our experts had in those assessments. And so, this first panel here is showing   the potential impact of each of these  processes for global temperature change 50   years after net zero was achieved, so ZEC 50. We then extended that same assessment but for  

100 years after net zero, then further  for a thousand years after net zero.  Now the first thing I should say, which  is tempting, is that we can’t just add   all of these bars up together and come  up with a number, unfortunately it’s  

Very much not as simple as that. But there are two things that we   can definitely take away from this figure. The first is the number of processes where we see   an impact of plus or minus 10% and sometimes even  more, and that is not an insignificant change. 

The second is the proportion of these  bars where the assessment we can make   is still only speculative and that’s  a real indication of the uncertainty   that we still have in a lot of the processes  that affect the Zero Emissions Commitment. 

So if we come back to that illustration of  the question that brought us here, our results   are certainly not disagreeing that our current  assessment contains some significant uncertainty,   but perhaps what we’re adding to this is that the  uncertainty reported in our models at the moment  

Is perhaps not telling the full story and there  might be processes that are not yet included that   could either stretch that uncertainty range  wider or move it to one side or the other.  And why is that important? Well of course if  we assess that there is a plausible chance of  

Significant additional global warming after net  zero, that very much changes the implication of   what it means to burn carbon today. So, of course our ultimate aim is to   reduce this uncertainty, but to give you a  bit of a flavor of how complex that can be,  

We can plot it on a kind of simplified  version of what the Earth system looks like.  Just taking a handful of  the processes that we have,   we can already see how many connections we get. So, just starting with the atmospheric processes  

Here and bearing in mind that the connections  that are dotted are indicating processes that   are uncertain in our current models. If we add on here the physics of the   ocean we’re already seeing even  in this very simplified version,   connections between atmospheric feedbacks,  and for example the pattern effect which  

Is the pattern of surface warming on the ocean. Biogeochemical processes link the ocean and the   land, and then we have land processes which are  affected by things like land use and wildfire.  So, we see this paper as being part of a four-step  process to improving our assessment of ZEC. 

The first is to identify the Earth system  processes that drive this uncertainty and   that’s what we’ve tried to do in our 26 levers. The second is to estimate their impact in   different timescales and that’s what  we’ve been doing with those bars that  

You saw across three different timeframes. The third is then to try and reduce this   uncertainty through targeted research and  there’s more details on that in the paper,   but we’ve listed out quite a long  and detailed table with suggested   research questions and modeling exercises. And of course, the ultimate aim is to build  

Models that can better, or with a lower,  with a narrower uncertainty range, give us   an assessment of the Zero Emissions Commitment. So why is it important? What do we gain from   knowing more about the Zero Emissions Commitment? Well perhaps one of the most important things to  

Take away is that if the Zero Emissions  Commitment is positive, if we can expect   additional warming after net zero, that changes  our assessment of how much warming we can expect   from burning one unit of carbon today. And if we want to stay below particular  

Temperature thresholds then the budget we have  left to do that may be smaller than we think.  On the other hand, if the Zero Emissions  Commitment is negative, then we may be   able to achieve more ambitious targets with  the same action which would be fantastic. 

And so, we’ve been talking a lot here about  temperature stabilization, but unfortunately   a world that has stable temperature or  global warming that stops at net zero is   not necessarily a world that has a stable climate. In fact, we know number of things that are that  

Are guaranteed to continue changing. For example,  sea level rise in response to the warming that   we’ve already caused, disruption to ecosystems  due to changes in weather, wildfires, droughts,   the melting of glaciers and ice sheets also in  response to the warming that we’ve already caused,  

Ocean warming which will be disrupt the  life that depends on the temperature there,   and the same again for ocean acidification. So, if we were going to conclude with a couple   of messages from this paper, they’d really  be that the risk of additional warming after  

Net zero is just another reason for us  to reduce our initial disturbance to   the Earth system as much as possible. And the second is that a world that   has a stable climate, a world where global  warming stops after net zero unfortunately is  

Not equivalent to a world with a stable climate. In climate targets both mitigation and adaptation   need to take these two things into  account, and with that I’m going to   hand over to the rest of our panel. Thank you. Thank you very much Sofia – it’s great having  

That, I can only imagine the level of  complexity it was to get all the data,   26 levers, and understanding the uncertainty  and interactions between them as well.  So, thank you for sharing that in a  way that we can all identify with. 

So, what I’d like to do now is to explore  some of the issues that you raised there   and also have some input from Martin and the  Frontiers in Science article in a panel session   that will be moderated by Martin himself. And a quick introduction to all of those  

Who are joining the panel, we have Professor  Joeri Rogelj, who is the current Director of   Research at the Grantham Institute, who leads  research training and innovation towards effective   action on climate change and the environment. So Joeri’s work connects Earth system sciences  

To the study of societal change and policy,  and his work on climate change scenarios has   informed international climate policy  over the past decade, and he is a long   serving lead author on the annual Emissions Gap  Reports by UNEP and also on the IPCC reports. 

He was also a participant on the  transformational science panel discussion   at COP28 which was hosted by Frontiers. Next up we have Ben Sanderson who is a   climate scientist and Research Director  of the Climate Mitigation Group in Oslo,   Norway and his work looks at how to better  characterize the uncertainties of mitigation  

Technology and negative emissions alongside the  development of statistical tools to highlight   the conditional risks of mitigation decisions. We have Dr Charlie Koven who is a staff scientist   at Lawrence Berkeley National Lab, whose research  focuses on the relationship between climate change  

And the Earth’s carbon cycle looking specifically  at high latitude feedbacks. And he was also a lead   author on the Sixth Assessment Report of the IPPC. And last but very much not least, I’d love to   welcome Tessa Khan who is an international  climate change and human rights lawyer who has  

Spent decades supporting grassroots regional  and international movements for justice,   serving as an expert adviser to UN human  rights groups and national governments.  She’s also the Co-founder and Executive  Director of Uplift UK, which resources,   connects, and elevates ideas for a just  transition away from fossil fuel production. 

And to end this introduction with an impressive  fact piece, in 2019 Tessa was named by TIME   magazine as one of the 15 leading women  in the fight against climate change.  A huge warm welcome everyone and I’d love to  now pass this over to our moderator Martin. 

Thank you, Gilbert and well done Sofia  for that really very well put together   presentation about the paper. We’ve got a whole  series of questions to ask. The first question   is going to go to Joeri, and it’s this: Considering the policy and technological  

Landscape, what are the most critical  interventions or actions that can be taken to   optimize our chances of achieving and maintaining  a stable climate after we reach next zero?  Yeah thanks, and also my thanks  to Sofia for a great introduction. 

If we look at the implications of what we have  learned from this exercise and what this exercise   has been further supporting and corroborated,  there are key milestones that we need to take into   account, and that also international climate  policy as such needs to take into account. 

And net zero or achieving net zero  emissions is one of those key milestones.  This research has not changed  that in the slightest.  What this research also shows is that there is  some uncertainty about what happens thereafter.  That uncertainty can fall in our favor and  that’s really good, then we would be very happy,  

But from a risk management perspective,  which policy basically needs to pursue,   it is rather the side where we see  additional warming that concerns us most.  Now the uncertainty there is not necessarily  something that we will be able to avoid or  

Reduce immediately, but that doesn’t mean that  we can’t take it into account and prepare for it.  And how can policy prepare for it? Well  policy can, or policy and decision makers,   can prepare for it and can take it into account  by seeing net zero only as one step on the way  

Towards a longer term stable or longer-term  response to the climate change challenge, and   really prepare for a world where we actively are  able to remove carbon dioxide from the atmosphere.  I think that is of course the long game. First things first. A key aspect in reducing  

The risks that are implied by global warming and  the Zero Emissions Commitment or the potential   Zero Emissions Commitment, is of course  to reach net zero or to stop adding CO2   to the atmosphere as soon as possible, and  keep those cumulative emissions until then,   to as low levels as possible. Thank you Joeri, wonderful,  

I’m going to bring in Tessa now. So, as I said in my little preamble   at the start, I thought I knew about the Zero  Emissions Commitment before I had that cup of   coffee with Jo, and it quickly turned out that  I didn’t, and also it turned out that it was  

A lot more complicated than I first imagined. Given that it’s complex but important, how are   we going to explain it best to policymakers who  might not necessarily have scientific expertise?  How do we do that? Well, actually I think Sofia’s,  

And hello everyone, I mean I’m really delighted  to be part of this discussion – thank you to   Frontiers for the invitation to join you, and  to Sofia for the really clear presentation.  I was just about to quote Sofia actually  and thinking about how best to encapsulate  

I think some of the findings of this research. And that was really I think Sofia you said that   reaching net zero emissions doesn’t mean a stable  climate, whether that’s still the possibility of   increased warming or increased cooling. And I think that that uncertainty,  

Because the risks are obviously much more  considerable, if there is up to 0.3 degrees of   additional warming even after we reach net zero. I think what that reinforces for policymakers   which to be completely honest given the  amount of uncertainty that’s built into  

So many of the risks associated with climate  change, I think what we have to insist on,   is that policymakers abide by the precautionary  principle, which is a principle that’s you   know existed under international law and in  international policy for decades, and basically  

Means that where there is uncertainty, if the  threat is great, then that shouldn’t be taken as   a reason not to take action, precautionary action. And I think that this research really underlines   the importance of that way of thinking, and  indeed that principle in informing policymaking  

So I think it’s not an entirely new dynamic,  I think, for policymakers to keep in mind.  Do you think many policymakers are even aware  of the concept of the Zero Emissions Commitment?  I don’t. I mean I think that my experience is  in short, no. There is always a remarkably,  

I think, superficial engagement, you know  from the perspective of people like us who   think about these issues day in, day out, with  the science underlying all of the policies   and of climate change that we discussed, so I  imagine this would be new to most people, yeah. 

Yeah, so good for us to discuss it here, of course  I mean given that the first step towards the Zero   Emissions Commitment is zero emissions, what are  the sort of regulatory frameworks and government   policies that are needed to overcome the  practical challenges just to get to that point? 

Well I think that’s the discussion that we’ve  all been having for many years now given that   net zero, I mean obviously after the endorsement  of the Paris Agreement in 2015 that’s emerged   as the sort of collective North Star in  policymaking, and now a net zero policy  

Commitment covers I think most countries  in the world, I think there’s generally   an understanding as Joeri was saying that that  means that we’ve got to reduce carbon emissions.   Ultimately you know that’s the bottom line. And you know I will say that one of the  

Good things that came out of COP28 in  December is I think finally connecting   that understanding with the role of fossil fuels. You know we had for the first time the language of   fossil fuels appear in a COP decision text. An understanding that we need to transition  

Away from fossil fuels, and  ultimately it’s as simple as that.  I mean obviously in terms of actually  operationalizing that and transitioning   our economy and our industries away from fossil  fuels, that’s going to require a whole host of   different policies and practices but I think  you know it’s as simple as ensuring that we  

Eliminate fossil fuels as quickly as possible  from our energy systems and from our economies.  Thank you, Tessa. Charlie, to bring you in. You’ll be   aware of course that I mean 2023 was the hottest  year on our record by some margin compared to  

Others and the likelihood that this year will be  equally if not warmer than that last year, I think   it’s provoking some people, some scientists to  predict a sort of runaway warming of our planet.   Is that likely? And how is the notion of the Zero  Emissions Commitment countering that type of idea? 

Yeah, it’s a great question and yes again thanks  everybody for this really interesting discussion.   You know, I think it’s too soon to say, how out  of, whether this incredibly hot year we’ve all   just experienced, is going to be followed by an  additional, you know, whether it really represents  

A step change beyond just the proportionality  of warming to our cumulative carbon dioxide   emissions, versus if it’s just one extreme year. And whether we’ll see things back to the trend,   the longer-term trend that we’ve seen. But I think one of the things that you do  

See from this is the enormous disruptions to  ecosystems that are happening – particularly   things like the fires in Canada over the  summer, is exactly the kind of thing that   we don’t have a good ability to include in  our coupled climate and carbon cycle models. 

And these are the kinds of effects that  we identify in the article as being real   uncertainties about the size of the Zero Emissions  Commitment. If these kinds of large-scale fires   that that we saw last year and in Canada, if those  become regular features because of legacies and  

The lags of the ecosystems to the warming, can  continue long after the warming has stabilized.  Those are the kinds of things that could be  contributing to you know a more positive Zero   Emissions Commitment and prolonged warming. And so  I think these extreme years that we’re seeing and  

The legacy of responses to ecosystems and as well  to impacts around the world in response to these   extreme years like last year are what we need to  really focus on in order to reduce our uncertainty   and understand how these abrupt changes that we  start to see, whether or not those you lead to  

Longer term legacies. Thank you.  I mean I guess the way to quantify predicting  our future has to lie with models one way or   another to do that. How good are our models?  They’re needed for that issue, are they up to  

The challenge of doing what we need them to do? Yeah, I mean I think the difficulty of a metric   like the Zero Emissions Commitment is that it’s  not just the physical climate system, it’s the   coupling between the physical climate system and  the ecosystems both on land and the ocean. And so  

That’s an extremely difficult problem right, and  it’s in particular the representation of ecology   in these models is not as strong, say, as the  representation of the physical climate system.  For a long time the legacy of development of  physical climate models versus quantitative  

Ecosystem models is the ecology part of is  not as well developed and I think that’s one   of the key things that we need to better focus on  because particularly because these legacies in the   system – a lot of them are driven by ecology  which is not always been thought of as a as  

A predictive science, the way weather prediction,  which then gave rise to climate modeling has been.  And so, it requires a very deep assessment of  the uncertainties and understanding, and so we’re   building them, they’re getting better, and they  tell us this information that we have, and it’s  

Useful information but it could always be better. Thank you, Ben.  On this issue really, so surface warming  is going to stabilize quite quickly after   next zero emissions, but the sea level rise and  ocean acidification that continues potentially   for centuries due to committed deep sea warming  and ocean acidification etc., how is this sort  

Of disconnect between stabilized warming and  continued other effects going to be affecting   adaptation measures and climate resilience? Well, I think we have this idea of net zero   being a specific point in time but it’s really  just one mile marker along the trajectory of  

Decarbonization, and in the real world hopefully  we will reduce emissions and then as soon as we   do so we’ll see different effects emerge on  different time scales and we’ll learn a lot.  As soon as we start reducing emissions, we will  see how different elements of the Earth system  

Are responding to those emissions coming down and  this question of zero emissions, we’ll have a much   better idea as soon as we start reducing emissions  and we see what the Earth system does in response.  And it’s the same for sea level and ocean  acidification – there are different processes  

Which influence this, and they will emerge  on different time scales and the models   which tell us about sea level rise in  particular remain on the cutting edge   really of what we can do with our system models. Only a few of our system models have interactive  

Ice sheets which tell us about the potential  time scales and melting rates and their   sensitivity to both existing warming to date and  any additional warming which you would experience.  But the uncertainties are quite big and so we’re  going to have to live with those uncertainties in  

Sea level projections potentially for centuries  to come. And that part of the equation, so,   it’s going to be a long time before the  uncertainties get reduced – other parts   of the system, we might learn something quite  quickly, as soon as emissions start to come down. 

I’m interested in the other disconnects as well –  I mean we talk about global climate stabilization,   but does that mean stabilizing the weather  systems on our planet – will they remain the same?  I don’t think we should expect the weather  system to stay the same. I mean global  

Surface temperature, even if ZEC is zero, so the  discussion this paper focuses on this global mean   temperature response after zero emissions –  but a zero global mean temperature change can   hide evolving patterns of warming in the ocean,  as the deep ocean temperatures begin to warm,  

Equilibrate, and then you get transfer in  the ocean – and that could result in weather   systems which, and weather patterns,  which continue to evolve over time as   the system adjusts to a new equilibrium state. And in order to understand what that looks like,  

We need to build better models clearly but also  we have to acknowledge that different models   currently respond in quite different ways and with  post net zero emissions conditions in some models,   ocean overturning circulation slows down and  these can have effects which emerge even a century  

After net zero has been has been achieved. So, yeah, again there is some fundamental   uncertainty there that means that climate change  even in an optimistic scenario may be with us for   centuries to come and will continue to change. So, Joeri, climate scientists are really good  

At acronyms so the ZEC is the Zero  Emissions Commitment and the TCRE   is the Transient Climate Response to  cumulative Emissions of carbon dioxide.  In combination they provide a sort of  means by which we can estimate carbon   budgets consistent with temperature limits.  Do you believe the carbon budget framework  

Adequately captures the uncertainties relevant  to guiding our pathways, emissions pathways?  Yeah, it’s a good question I mean the common  budget framework in one sentence is the fact   that we have a total budget of CO2 that can’t  be exceeded if we want to limit warming below  

A certain temperature level. So, the total amount of   carbon that we can ever emit is limited. I think that is a very a very strong and powerful   first order framework and for all the challenges  that we are dealing with currently, it’s a very  

Good framework, I think. And to be sure the  challenge we are dealing with now is that our   emissions are still going up globally – they have  slowed down, the annual emissions, the increase   has slowed down, but they’re not going down yet,  and to reach net zero they need to go down quite  

Steeply from the more than 40 billion tons of  CO2 that we are emitting in the atmosphere.  Now, where the carbon budget concept and  the framework and the interaction between   the Zero Emissions Commitment and the  kind of linear relationship between the  

Total amount of CO2 and global warming  might not be the perfect tool anymore,   that is if we are in a world where we have to  start caring about the second order effects.  And those second order effects we will  see if we start to become close to zero,  

And so I think until then this  budget concept is still very valid.  It has actually been proven to be also quite  robust for projecting what needs to be done   if we might be missing a target and we try  to try to return. Also there, it’s a first  

Order approximation, but in order to communicate  between very complex scientific understanding and   systems and with policymakers, and to make that  translation, I think it’s a very powerful tool.  So, but that doesn’t mean that the scientific  community can’t start to think about how we  

Can more accurately use Earth system  information at the time when we would   have already reduced our global emissions by  90% or so ideally over the coming decades.  Okay, Tessa on policy work, so your policy  outlook paper highlighted the tension over the   language regarding fossil fuel phase-out  in the COP28 negotiations for example,  

How can clearer, more universally accepted terms  and commitments be established to facilitate   the rapid transition from fossil fuels? That’s a great question and I think that the   hugely contentious nature of the language around  fossil fuel phase-out at COP28, which ultimately  

Resulted in fairly weak language around transition  that was heavily caveated at the national level,   I think reinforces the importance of these  conversations actually taking place at the   national level, because reaching international  consensus on these concepts and exactly how to   express them is just so fraught. And I think the closer we get to  

Addressing the root cause of the problem,  the more entrenched I think those countries   and constituencies that benefit from the  current system are likely to fight back,   and I think we saw some of that emerging at COP28,  with a sort of contingent of countries who are  

Heavily invested in fossil fuel production  for example, really refusing to compromise.  And given it’s a consensus process at the UN  Climate Summits, it just makes it very difficult.   So, I actually, I mean I agree with Joeri that  the concept of a carbon budget is one, and not  

To make discussion too UK-centric, I appreciate  a number of us are in the UK but you know that’s   been translated, in to national policymaking  in the UK I think to great effect, in the way   that there is real accountability for five or six  yearly carbon budgets for the UK government at the  

National level, and that’s obviously a translation  of the global carbon budget into what policymakers   consider to be appropriate at the national level. So, I think if yeah if there’s a way of   reinforcing some level of certainty around what  the global carbon budget is and then enabling  

National policymakers to translate that into  a national carbon budget which you know in my   view should then be adapted to reflect principles  of equity so countries like the UK moving faster   and ultimately having less of that access to  that carbon budget than other countries for  

Various reasons, then I think that that’s a really  strong basis on which to continue policymaking.  I guess there are initiatives like Beyond Oil  and Gas Alliance and the call for The Fossil Fuel   Non-Proliferation Treaty, those organizations  in vital important for this this transition. 

Yeah, they are right and I think, I mean,  the Beyond Oil and Gas Alliance, I think is   a particularly powerful initiative because it is a  multilateral initiative, it’s the diplomatic club,   basically of countries that have decided to end  oil and gas production or set an end date for oil  

And gas production have decided to end new oil  and gas licensing. You know that’s very useful   in so far as I mentioned earlier, it spotlights  fossil fuels as needing phasing out. Whereas I   think just discussing emissions reductions can  sometimes avoid the root of the problem which  

Is that need to transition away from oil gas  and coal, and I think you know, it’s exactly   those kinds of initiatives that are helping to  build momentum towards the transition away from   fossil fuels that are desperately needed and it’s  great to see them starting to get off the ground. 

Thank you, okay Charlie in the article  as Sofia explained really nicely,   26 levers of global temperature change after net  zero, that’s a lot of complexity, going back to   what we sort of talked about before, how confident  are we that we’re able to predict the trajectory  

Of global temperatures post net zero and what are  the major sources of uncertainty in all of this?  Yeah, so the part that I focused on  in the article was the land ecosystem,   the land carbon cycle response and the various  processes which include things like permafrost  

Thaw and the legacies of permafrost thaw in  terms of carbon emissions, and as well as   wildfire and dieback of forest in the in tropical  ecosystems and boreal ecosystems around the world.  What all those things have in common is the  legacy of the ecosystems to prior climate change,  

Prior disturbance, prior land use change and these  are the things that, because we are focused on,   you know what are the remaining uncertainties,  these are the things that are still the most   highly uncertain, these slow legacy responses to  things that had happened you know decades before,  

Because you know the essence of the idea that  ZEC is small is, you know, as Sofia explained,   is this this trade-off between the sort of  declining CO2 uptake on land, in the ocean,   and the declining heat uptake, and so it’s  really about the rate of that decline,  

The relative rate of those declines, and because  you know the relative rate of those declines is,   you know a function of these  time scales and legacy responses,   those are the key things that we need to focus on. And again because we’re focused on the article,  

On the biggest remaining uncertainties, you know  those aspects of the system are quite uncertain   and that’s why if you look at the current set  of climate models they give us this uncertainty   of you know about plus or minus, a third of a  degree Celsius, you know that uncertainty that’s  

Represented in the models is then reflected  in the widespread ensembles of these coupled   carbon climate models, and so again you know  these models are useful in that they tell us   something that we can use to influence our  policy, but again, in order to improve them,  

In order to narrow that uncertainty that’s what  we need to focus on or better understand these   legacies of the carbon cycle to the response. Thank you. Ben, on this issue on uncertainty,   okay so money no object, geographical location  no object, where should we best target research  

That will most reduce uncertainty on this  issue would you say, you know you, might talk   about your own research or anyone else’s? That’s a big question, so I think well   let’s say firstly one thing which was  good about this article and is rare,  

Is it didn’t just talk about what’s in the  models, it also talked about what’s not.  And attempted, you know, even though it’s  difficult, attempted to sort of like order   magnitude assess what the magnitude of those  processes which are not in the models is, and  

So that that’s a useful exercise in informing the  question that you’re asking, is okay, well, that’s   how do we triage? How to include processes in the  models which are not currently represented? And   so that exercise is a direct useful takeaway from  this article and aside from that we need to think  

About how to deploy the resources that we have. I know you said that money was no object but as   we move into another big round of IPCC Assessments  it’s useful to think about what resources we have  

On the table and what experiments to do to better  get our handle on these questions moving forward.  So involved in that is how we use the  different types of models we have on the table.  We have some complex models like several of us  work on here, like Charlie, and we have lots  

Of different sort of simple models which allow us  to sort of more look in a more formal statistical   sense at all of the uncertainties in the problem. And so what we’re trying to do now is how to   use those two different types of model in  parallel, noting that neither one is perfect. 

The complex models we can never run them enough  times to get a full grasp on the uncertainty   and the simple models we know there’s a  bunch of stuff missing and so you know,   we need to sort of mash these things  together in a way that gives us a better  

Understanding of what’s happening moving forward. And then together with that, you’ve already raised   the issue of like 2023 and how that’s taken some  climate scientists by surprise. That’s the other   element of this, how can we get more efficient  at more rapidly incorporating observations which  

We have of the climate system back into the  models to influence how they’re calibrated   and what processes are missing and so  with that in mind this question of ZEC,   the Zero Emissions Commitment, is one of the few  which really matter in terms of framing policy. 

Another one is what’s going to happen  as the aerosol emissions come down,   I think that’s really been highlighted as a big  uncertainty which we need to do better really   rapidly. And then how do we incorporate  observations for example from satellite  

Time series’ which are now becoming mature  enough to actually be used as ways to either   to determine between good models and bad models  so there’s a lot of things which are happening   simultaneously which we need to incorporate. Thank you, I was rather hoping you’d say  

Deep field Antarctic glaciology  research is really needed but   let’s have another conversation about that! Final question to Sofia, and thanks again   Sofia for organizing us and for putting  all this paper together, is net zero   enough or should we be aiming for negative  emissions, and in that case how do we do it? 

Good question and I’m glad that you  phased it like that and not, ‘is net   zero worth it?’ because it absolutely is. Well, I think this paper has highlighted   that perhaps zero won’t be enough  although it is absolutely required,  

And I guess that in order to answer that  question we need to be able to look into   the future a bit and know what level of warming  we’ve reached at the point that we’re at net zero.  And if it’s quite high then absolutely we’re  going to want to bring that temperature down  

And the way to do that is through net negative  emissions, so yeah, I think the it’s a bit of   a case of the more that we know the more that  we notice our uncertainties and the more that  

That tells us that we need to keep global  temperatures as low as we possibly can in   the first place. And if we can’t do that then to  bring them down as much as possible afterwards.  Thank you, Sofia. It’s good to know we’ve got  an awful lot of questions coming from the Q&A  

And so with that I’m going to hand back to  Gilbert. Thank you, Sofia, thank you Tessa,   Joeri, Charlie and Ben. We’re going to hand back  to Gilbert he’s going to take us through the   audience Q&A from here. Thank you ever so much. Thank you, Martin. It was a really great  

Discussion for charting a real path forward.  Yeah, we’ve had loads of questions coming in   thick and fast and a lot of them are elaborating  on the points that all of you mentioned, so I just   picked a couple out and hopefully this will add a  little bit more depth to this discussion. So let  

Me just get started and I think the first question  I’d like to discuss is actually perhaps one of the   most challenging ones and it’s on the practical  challenges of reaching and sustaining net zero   emissions and as moderator Martin, I would  love to kind direct this one to you if I may. 

So, you know Tessa mentioned that we know  the outcome of COP28 about the importance   of vocabulary when we talk about the  fossil fuel industry, phasing out,   phasing down, transition away. So, the fossil fuel industry and   its enablers remain a major obstacle to  achieving that zero and this we all know. 

What can academics do to minimize the  fossil fuel industry’s influence on   international policy and politics? Well, that is a terrific question,   thank you and not an easy one, but then again  you know, maybe it is an easy one. There are,  

When we talk about the fossil fuel industry, it’s  a wide variety of different types of companies,   different types of behavior, different  appreciations of the climate problem,   so it’s easy to sort of put them all, lump  them all together, as the fossil fuel industry,  

But actually, it’s actually quite diverse. There are some people who think we should   simply not have anything to do with the fossil  fuel industry and put them all into one place.   I don’t know what other members of the panel are  like but I’m not in that position for two reasons. 

Firstly, actually there are some companies that  are more enlightened than others and it is,   I think, appropriate to work with companies  that are serious about the transition to net   zero and not work with the companies that  clearly, through their records and through  

What they say actually, they’re not at all. The second reason I’m interested in continuing   dialogue with this industry is that they’ve  got tremendous expertise built in, in terms   of putting very large bits of kit in difficult  places, raising amounts large amounts of income,  

Investing in that, making it work  financially, turning into a profit,   providing energy to our global system, that’s  exactly what we need to advance renewable   energy at pace and at scale. And so just to say  we’re not going to work at all with the fossil  

Fuel industry stops us working with the very  companies that are good at doing what we need.  Now there will be some fossil fuel companies  that you just know won’t do it because they   obfuscate and they, you know, they lobby against  climate actions and so don’t work with those,  

But there will be some and hopefully more into the  future that maybe do get it better and it’s for   those companies and it’s for each of us to work  this out, it would be for those companies that we   should maintain our focus I think. Thank you very much Martin. 

Tessa, I don’t know whether you have  anything you’d like to add to that.  No, I actually I appreciate Martin’s perspective  on this, I think. I mean I think it’s right that   there is diversity in the fossil fuel industry. I do think though, that you know, it’s important  

To bear in mind the sort of the gulf at the moment  between the sort of rhetoric that we’re often   hearing from the industry in terms of the role  that they’ll play in the transition and where   their capital expenditure is going and their  investments are going, and I think the real,  

So you know the International Energy Agency,  one of their recent reports made it clear that   fossil fuel companies are responsible for only  1% of investments globally in renewable energy   generation, so overwhelmingly it’s not the  fossil fuel industry that’s currently driving  

The transition, and I think that for a lot of  us, the last year or so when the industry’s   been making record profits, you know, has been  a real test of the intention of that industry   to play a part in the transition. And what we’ve  seen overwhelmingly is that they are paying out  

Their shareholders and paying off debt and they’re  not investing in diversifying their portfolios.  In fact, we’ve seen rolling back of some  of the commitments to expand renewable   energy production from some of the carbon majors. So, I mean, I certainly appreciate, and you know,  

We work with the oil and gas workforce in the  UK because they absolutely do have the skills   that could be repurposed for, certainly if  you’re looking at offshore oil and gas into   offshore wind for example, and I think it’s  very important to think about how to harness  

The expertise within the workforce, but I do  think that you know it’s really important to   be quite discerning about which companies are  acting in good faith and which ones are trying   to take advantage of the reputational boost  they get from talking about being part of the  

Transition when their investments and you know  where they’re putting their money belie that.  Thank you very much Tessa. I guess that’s a contentious topic   that we can talk about for a very long time,  but I would like to now pivot the discussion,  

And maybe let’s look at the modeling  and the work that Sofia was presenting,   and we actually have a question from one of  the co-authors that came in, Gabriele Hegerl.  I guess this will be for all takers,  but I’ll read it out and it’s about,  

It’s about the evolution of the earth system  processes after reaching net zero emission.  So the question is: as you said, land vegetation  responses are highly uncertain and most earth   system models don’t couple it fully (of the five  with fire in the recent IPCC carbon cycle chapter,  

Only one or two also have interactive vegetation).  To understand what happens in response to   extremes, for example, like some of the ones we  see, we need to know about these interactions.  How can we entice modelers to fully couple it  even though it is difficult and may go wrong?  

Is there a way we simulate the future  models that can be still appropriate?  The community is definitely doing this, right,  we’re building models that do a better job,   each successive generation of earth system models  includes more processes than the prior ones. 

If the table that Gabriele is describing if  we, you know, if that equivalent table was   there in the prior IPCC report, now I can’t  remember whether or not it was, you know,   it would have a lot more sort of missing processes  than the one for the sixth assessment report. 

I think we expect the seventh assessment report  to, when it comes, to have more models with more   processes, but it’s slow and I think that, so  much of the focus right now, and historically,   has been on increasing the resolution of the  atmospheric models and in these physical processes  

And I think a somewhat smaller focus has been on  representing the fidelity of ecosystem models in   the land and the ocean in these coupled earth  system models, and so it takes you know to sort   of, the point that Ben was making before, it takes  some prioritization and it takes resources and  

It takes better data and observations. We can only build these very complex   models if we have very good observations from  satellites and from field observations etc. I   mean we need all these things together right,  there’s no single solution to every, you know,  

That’s going to make our models great. It’s a whole large set of interacting   processes and a whole large set of interacting  institutions and observational resources and   modeling resources, so all these things are  needed together, and it just takes time and   effort and people and resources. Thank you very much Charlie,  

That was a quite a challenging question  that your co-author also shared.  I’d like to maybe kind of pivot this back now  thinking about monitoring and measurements, so we   have a question here from someone called Cheng-Zhi  Zou and it’s on the research priorities for  

Reducing Zero Emissions Commitment uncertainties. So, the question is: I appreciate the talk on   the uncertainties in the projection of future  climate change. To narrow down the uncertainty,   we need to have better climate models. There  are multiple studies showing that the current   climate model simulations of climate trends  are much warmer than independent satellite  

Observations which have global coverage. How can  the climate model community take steps to improve   the climate model simulations to have better  agreement with these recorded observations?  Would anyone like to take that, I don’t  know Ben if you would like to tackle it? 

Yeah sure, I mean, this question of whether the  current models are too warm or not is constantly   moving, it’s constantly changing, we  get more observations all the time.  Last year was very hot, we still haven’t,  you know, the papers, which disentangle how  

To interpret the models we have given last  year’s observations, haven’t come out yet,   so that would be, my first point is that, this is  the conclusion which the next assessment will have   on current models will be different to this one. And also, there are lots of different lines of  

Evidence here. It’s not, there’s no  single axis through which a model can   be better or worse because a climate model  simulates thousands of different processes   in different parts of the Earth’s system. One way to assess it is through global   mean temperature but also you can look  at any aspects of local climatology or  

The land surface or the carbon cycling  or anything else, so we need to then   process that information to say what they mean. How can we build better? So, the question was   framed as we need to build better climate models  to have a better, to reduce our uncertainty. 

I would say it’s not quite as simple as that.  We need to identify our uncertainty, there’s no,   firstly, there’s no single way to assess  when a model is getting better or worse.  You know, you have to come at this from lots  of different directions at the same time,  

But also you have to be satisfied that you’re  sampling the degrees of freedom which you have   in that model to sample processes. So we need to  be confident that our samples and our sampling   strategy are exploring the degrees of freedom  which we have in order to be confident that we’re  

Not missing a potential worst case scenario. Thank you very much. Would anyone else   like to speak to that or I can  move on to our next question?  Yeah, oh okay, Joeri, would  you like to kick us off.  Maybe I also want to actually link this  back to what Ben mentioned earlier. 

The most complex models that we have are extremely  expensive to run. We will have one calibration   of them and we don’t expect that calibration to  be perfectly in the center of the distribution.  That means that we can’t just rely on these most  complex models to give us the best estimate,  

Central estimate of our projections. Instead  we can use this kind of ecosystem of modeling,   models with the most complex, the most  advanced ones and then simpler ones,   that can be run thousands if not millions of  time and that can capture all the uncertainties  

Included, then have a median response that is  really also consistent with the kind of median   estimate of what happens, happened in the  observations, and it’s really this interplay   between these different levels of complexity  of modeling that needs to be further developed. 

We saw a first really good indication of this  actually in the last IPCC assessment report   where the most complex models, the temperature  projections of those were not taken as the   standard by which future warming will be judged. They were taken as information, as insights that  

Are then integrated in our assessment of  what future warming will be and it is this   kind of integration of these different lines  of evidence that is really very important and   will become ever more important in the future. Thank you very much, and Martin you wanted to… 

Yeah, thanks Gilbert. Briefly and just to sort  of exemplify this issue in Antarctica last year.  The sea ice in Antarctica was reduced over  winter by an area about 10 times the size   of the United Kingdom, that should have been  covered by ice on the ocean and it wasn’t. 

And it was remarkable how little it was and  how far away from previous years that ever was.  It’s been happening in the Arctic for some time  since really, since the 1970s that we’ve been   revealing that Arctic sea ice has been lost. Up until 2017 that really wasn’t happening  

In the Antarctic but most climate  models kind of had that, you know,   the Antarctic sea ice behaving kind of like  the Arctic and I always wondered why that was.  Maybe the Arctic the models are just overheating,  maybe they’re doing this. Actually since 2017, the  

Sea ice in Antarctica has been getting less and  less, and this year remarkably, so it just might   be the models are right after all and there’s  a lot of sort of variability and uncertainty   in the Southern Ocean but actually over the  long term, they’ve probably got that right. 

Well, that actually leads to a great follow-up  question about the predictability of these models,   and it’s good to see, you know, empirically,  you managed to get them pretty accurate.  So, I actually have a question that comes in  from one of the Frontiers’ chief editors so  

That’s Professor Michael Heinrich, so a warm  welcome to you, and thank you for joining us.  So, this question is to Sofia, and you have partly  answered this, but I think it’s just nice to see   the research direction you’re going to go into.  So environmental systems are always fluctuating  

And there is a high level of uncertainty, a  point that you highlighted very eloquently.  So, Sofia, what do you think is needed  to increase the predictability of these   models or the next stages, I would say? Yeah, thank you for the question. I guess  

This is the part of the paper that I didn’t  really go through in the talk because there’s   quite a lot of information that comes with it. But one of the main things that that we tried   to do was really articulate what it meant for  research taking each of these processes and  

Trying to improve the predictability we have about  them. So, I would perhaps inconveniently refer you   to our paper where we have that that full list  of the 26 processes and suggestions for research   questions and then beyond that, suggestions  for actual modeling exercises that either are  

Waiting to be done in the sort of near future or  that we need to make some effort to make happen.  And we’ve really tried to prioritize  those via like a few different dimensions,   so whether we already have, we may  already have like the correct materials  

To be running some of these experiments  separately from our most complex models,   so it might be that we have a model that  just runs something about land carbon or   just runs something about CO2 exchange between  the ocean and the atmosphere or whatever it is. 

And that trying to reduce our uncertainty in a  certain measure that can then be fed into the   more like coupled comprehensive systems. And so we’ve made an assessment based on   that what’s available at the moment but also  what the kind of big modeling exercises are  

That are coming up in the future that we know  about, and also the big reporting exercises,   so the future IPCC reports and also the coupled  model intercomparison projects and thinking about   how this question can be integrated into those  exercises that we know are going to happen anyway. 

And then the Zero Emissions Commitment model  intercomparison project, which has been run   separately and underlies a lot of the kind of  question that came that led to this paper coming   about in the first place, there’s going  to be a second iteration of that as well. 

So certainly, there are things that are  going to be put into practice going forward   and if you’re interested in what those specific  questions are, if for example you’re interested   in forming some of those pieces of research  then that would be a great resource for you. 

Wonderful Sofia, thank you  very much for sharing that.  I’d like to follow this up with a question, we’re  all familiar with the nine planetary boundaries,   so this will obviously have an impact on how we  understand our interaction with our natural world,   and I just want to paraphrase  this question somewhat because  

I think it’s kind of missing a point. So, this is a question from someone   called Leonard Neamtu on the implications of Zero  Emissions Commitment uncertainties for climate   policy. Should the planetary boundary thresholds  be adjusted if we’re considering the possibilities   of what would follow a net zero world? That’s an open question if anyone  

Would like to take it. Joeri, I see your hand up.  Yeah, short answer, no, because the planetary  boundary, well as currently defined, there are   nine of them, looking at different parts of our  planetary system and one of those boundaries   is on climate change and for example on  CO2 concentrations and climate forcing. 

They are kind of on the interface and they  strike a balance between scientific evidence,   scientific understanding, and ultimately  value judgment of what we consider safe,   what we considered acceptable, and  what threshold should not be exceeded.  A similar question or has been answered  by countries under the Paris Agreement  

And they were asked what is a safe level  of warming, or what is an acceptable,   I don’t think they would call it safe level of  warming, and well they translated this in that   the aim should be to keep warming well below  2 degrees, while pursuing to limit it to 1.5. 

So, that’s a similar kind of boundary, well that  boundary should not change with this information.   The implications of what we need to do to stay  within that boundary, or to stay within the Paris   Agreement temperature goal, yes that should take  into account the information of this research. 

And well I already highlighted some of those  implications before. There are implications   for how large the remaining carbon budget  would be, there are implications for what   we do after net zero, there are implications for  how we prepare today for that later eventuality.  Great, thank you very much Joeri,  that’s super clear. Anyone else  

Would like to share on that? We’re all good? Okay, we are running out of time, but I’d like   to just bring in Tessa in again to perhaps  speak a little bit more about climate policy   and elaborate what you were saying before. So, this question is from someone called  

Amelia Delgado and it’s the  implications of Zero Emissions   Commitment uncertainties for climate policy. So, Tessa, thank you for reminding us of the   precautionary principle. It should be widely  known however from experience that environmental   related risks seem to be categorized in  some special category and they’re not  

Regarded in the same way, and they’re discarded. So, any advice on how we can make it more visible,   make these more visible to decision makers? Yeah it’s a great question and I think it’s,   you know, it’s a frustration that lots  of us who work on climate change policy,  

And who also understand how long the precautionary  principle has been around in sort of international   law and policymaking, it’s frustrating that it’s  yet to translate I think in any persuasive way   into domestic policymaking, although there are  some exceptions to that where environmental  

Impact assessments, for example have incorporated  the precautionary principle when thinking about   the approval of big new infrastructure projects. But I mean honestly, I think that just the fact   that, you know, as we’ve been discussing, the  last year was warmer than people had predicted,  

That we are sort of starting to see how  the uncertainties that we’re grappling   with can often mean that risks manifest  sooner than we expected and not later.  I actually think that the evidence that people  are experiencing, directly physically seeing  

Around us, you know, policymakers aren’t immune  from that, and we know just in the last year,   every continent more or less has experienced  I think some manner of extreme weather event   or the implications of our changing climate in  a way that’s affected their local communities. 

So basically what I’m saying is, I think, the  case is easier and easier to make with every   passing day and I think it, intuitively  is more and more appealing as we see more   evidence of our failure to take account of  those risks and act in a precautionary way. 

So hopefully the external context in some  ways is going to make that task easier.  Thank you, Tessa. It sounds like a complete  double-edged sword, but yeah I think the fact   and the reality that we’re all facing, it should  usher in more climate action on policy fronts. 

So, I’d like to now end this with  something a little bit more positive,   and after reading Michael Mann’s editorial about  how technology and the ‘know how’ actually we’re   there but the actual obstacle is policy  really, but then we also are thinking about  

Capacity building for the next generation, right? Like we know that we’re going to be passing this   on and this is an open question for anyone who’d  like to share. What do you hope schoolteachers   are doing to help the next generation to  understand the latest climate change research  

And the roles they can play in mitigation  and adaption? Is your research relevant to   climate change education in schools? I’m happy for the first person who’d   like to put their hand up to take it. I imagine that all of us care about the  

Next generation and the leaders of tomorrow – that  they’re at school today right, and the better we   can equip young people with the determination and  with the knowledge and the skills that they’re   going to need for the next 40 years, which is  the net zero transition period, the better it  

Will be, and so we have an obligation to talk  to school kids about this and to be open to it.  Now, something like the Zero Emissions  Commitment, and it is quite challenging,   you don’t have to start at that position,  that’s kind of quite advanced level stuff,  

But the great thing about climate research  is that it’s easy to engage a broad audience   with it because it’s our planet, right. We need to fall back in love with nature   and with the planet and in my experience,  and I go to many schools and secondary  

Schools in the UK all around the country,  the level of engagement is spectacular.  Kids really do want to understand and know about  this, and as I say, it’s our obligation especially   those of us who work in research institutions and  in universities to reach out to those, because  

In 10 years’ time, and then afterwards, many of  those will be working as we do now in this area.  We must advance things, we must pass on  knowledge and for the next generation to   build on it as rapidly as possible, thank you. Thank you, Joeri would you like to share? 

Just adding to this, I also wanted to highlight  the resources that are already available,   and actually Sofia led an additional paper  in Frontiers for Young Minds on this topic,   for example, as an explainer to school children  which might already be a starting point. 

There are also lots of initiatives including  research projects to translate earth system signs   for mostly primary and secondary school children. So there are really targeted resources available   and I cannot agree more with Martin that we need  to equip the next generation, at the same time  

We should not abdicate responsibility because  the decisions that need to be taken need to be   taken today, and the actions that are actually  required for a safe planet or the actions that   happen in the next 5 to 10 years, and  that’s when they are still in school. 

Thank you very much Joeri, that’s really useful. Any other final thoughts from anyone,   maybe Sofia how did you find the…  oh Ben sorry, I just missed you.  Yeah, just very briefly, so questions like this  tend to make us focus on uncertainties because  

That’s the way the question’s framed,  and they tend to underplay how much we   are kind of confident about, and in this  particular question we are confident that,   as Joeri said before, the first order effect. Like every ton of carbon you put into the  

Atmosphere you get a certain amount of warming,  broadly that remains true, and we’re talking about   like the second order details on top of that. And so, I think the first thing to do is   communicate that a lot of climate science  can be explained very simply, very clearly,  

And then also be very clear about where scientists  do disagree, like on mitigation strategy and what   we should do about it and how we should structure  technology and society and everything else.  We have a clear open discussion about why  different people have different opinions,  

And so yeah, that’s I think there’s a job for  climate scientists to sort of know, say what they   know and why they disagree on what they don’t. Brilliant thank you, thank you very much Ben.  I’m just cautious now that we’ve just reached  the end. It’s 20 past so we can, you know,  

Charlie if you have anything to share, you  can also share in your closing remarks,   but I’d like to say thank you to our audience and  I’m really sorry we just scratched the surface   with the plethora of questions that came in. It’s been an absolute pleasure to see how engaged  

Everyone’s been, but I’d like to now close this  and now just follow up with some closing remarks,   and I’d love to offer the opportunity to  Joeri, perhaps looking at the critical next   steps for this research as you see it. Listening to, knowing the material,  

Listening to the conversation that we had  today, I think there, the critical next   steps are really first and foremost to translate  it to policy and to translate the insights and   make sure that the consequences are understood. I mean, this evidence should incite action,  

Not necessary surrender, but it is  also clear that additional warming   does not mean unstoppable warming, not at all. Net zero still becomes even more important as   a milestone, but it’s not the end point of how  society responds to the climate change challenge.  

And there is uncertainty about how much warming  we would get, which additional impacts there   could be, the damages and the challenges, but  this uncertainty doesn’t mean we cannot act.  And from a precautionary principle, actually a  precautionary approach allows us to take this  

Uncertainty into account and hedge against these  risks, and so the consequences there are clear.  Emission cuts over the next years and  decades become ever more important in   order to limit the peak warming as low as  possible, and besides those reductions,  

Also investing in long-term removal of CO2  from the atmosphere as a key protective measure   against additional warming becomes important. What that means for research, what I heard from   today’s conversation is an important focus on  better understanding the different factors that  

Influence the Zero Emissions Commitment, that have  now been identified by this study, and this better   understanding can be built through modeling and  observations. And we should particularly look at   those factors that are currently only identified  as speculative, that are not in the models,  

And we heard for example, legacy effects  of warming on ecosystems and ecology,   but we equally heard not just the challenges  of building a model but also the challenging   challenges with the observational coverage  and the observational evidence of the systems  

That we try to model. If we have not observed  them it’s really hard to build a strong model.  Together these steps will really ensure that  society is better equipped to respond to the   climate change challenges and that we  are, of the climate change challenges,  

Which we are and will be facing over the  course of the coming decades, if not centuries.  Thank you, thank you very much Joeri. We are very, very close to running out of time   so I’m going to give the panelists a challenge. If there is one word or phrase that you would  

Like to share with our online audience  as a take-home message, what would it be?  Ladies first, Sofia, may I ask, do you  have, how would you impart your knowledge?  Well I think, yeah, the most important thing  really is to echo what we’ve heard a lot today,  

Which is that this uncertainty in the earth  system does not translate into any ambiguity   about the action we need to take. The message  is still the same and it has been for decades,   we need to reach net zero and we need  to reach it as quickly as we can. 

Crystal clear, thank you. Over to you Tessa. Yeah honestly, I don’t have much to add to that.   I think just the urgency of the imperative to get  to net zero given potentially the importance of   getting to sort of net negative emissions, if  it turns out that we fall on that side of the  

Uncertainty spectrum, so I really just think that  it underlines the importance of that really rapid   and deep cutting emissions in the short term. Thank you very much. Over to you Ben.  I think in addition to everything which has been  said today, a great challenge is now to assess  

Policies which claim to get us to net zero and  really dig into the details of what’s implied,   especially on the negative emissions side,  so it’s a different discussion but I think   that’s really important. Fantastic. Charlie.  Yeah just that the zero missions agreement is,  you know, it’s very closely related to this idea  

That warming is proportional to cumulative  emissions, and that’s the important model,   the most important model is the one we have in  our minds. All you really need to understand   is warming’s proportionally accumulative to  emissions, and if we just want to stabilize  

Warming, we need just to get to net zero. Absolutely, thank you very much, and Martin.  The co- benefits of decarbonizing  are really important, right.  The things that we care about on our planet will  be protected with rapid deep decarbonization. If  

We don’t do that, those things that we  care about – the polar regions, oceans,   and things, our climate will be devastated. So,   the sooner we do this, the better. Those are very compelling closing words, thank   you very much Martin. Thank you everyone,  

To all our speakers and our expert contributors. Thank you, Sofia, Martin, Joeri, Ben, Charlie,   and Tessa, and also thank you  to everyone who joined today.  I really hope you enjoyed the  session as much as I did hosting it.  So quick note, please do visit  the Frontiers in Science website. 

Do read the article that we’ve discussed  today and explore the hub of content.  There’s really, really, great material that  you can get your teeth into. As I mentioned,   the conversation is still going on social  media so use the hashtag #FrontiersForum,  

And also I invite you to subscribe to the  Frontiers in Science newsletter via the website.  So, for now a big thank you. Thank you to  our panelists and have a lovely morning,   afternoon, evening, and catch you at  our next Forum. Thank you very much.