Decarbonising flying, cleaning up AI and the personal cost of climate change
Professor Brian Cox takes a deeper dive into the science of global warming and how society should adapt, with two experts returning to answer more of your questions.
Will new green technologies really help us reach net zero? What is solar forcing? Which regions of the planet will become uninhabitable and when?
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More Questions of Science gives you extra episodes that continue the conversations started in A Question of Science.
From his home studio, Professor Brian Cox catches up with expert panellists from earlier in the series. Together, they tackle your follow-up questions, explore new angles and go deeper into the topics that sparked your curiosity.
Brian: Welcome to this bonus episode of A Question of Science, the show where we tackle your questions about everything from Artificial Intelligence to the future of fertility, with the help of a panel of leading experts.
Now, the original debates were recorded in front of a studio audience at the Francis Crick Institute in London. But this show is a chance to hear some of your feedback and answer some extra questions that we didn't have time for.
Now, since recording an episode on the changing climate, we've had Cop 30 in Brazil and an announcement from the UN Environment Programme that we are likely to breach the 1.5 degrees celsius temperature rise, as set out in the Paris Agreement, within the next decade. The UK's Met office has confirmed that 2025 was one of the hottest years on record and back with me to discuss where this leaves us are Professor Myles Allen, head of Atmospheric, Oceanic and Planetary Physics at Oxford University and Kathryn Brown, director of Climate Change and Evidence at the Wildlife Trusts.
Let's start with Cop 30, though. So it took place in Brazil in November, and I was interested to ask both of you, maybe we'll start with Myles, of what you made of COP 30?
Myles: I think on the really important question of fossil fuels and how we stop them causing global warming, I think everybody acknowledges not much progress was made, but I'm not sure much progress was expected on that front.
The focus of Cop 30 taking place as it was in the Amazon was much more about land use change emissions, slowing deforestation, that sort of thing. And in many ways people saw it as a success simply because it kept the whole COP process alive because, there was a lot of doom and gloom beforehand that the whole thing was going to fall apart.
Kathryn: I think what, what we see in COPs is there a, what we call a consensus-based process, which means that what is decided at the end has to be agreed by every single party and there are nearly 200 countries in the room at any one COP. So we tend to think of them as showing us what the lowest common denominator is on climate action in any one year.
And as Myles says, you know, we didn't see a lot of progress on fossil fuels. We did see some pledges to further cut deforestation and protect the Amazon. And actually, interestingly, what the Brazilian presidency has been trying to do is then set up some follow on processes where we might actually see a bit more ambition, which is with smaller groups of countries.
And we've now also seen the United States actually saying it's going to leave not only the Paris Agreement, but also the UN Framework Convention on Climate Change and what that would mean is it won't be attending future COPs. And that obviously has downsides, but actually, if you think about it being a consensus-based process, it might make it easier to agree some of these things amongst other countries in the future, so that's going to be something we're going to be watching very closely going forward for the next COP.
Brian: We had quite a few questions actually, but one specific one from Nathan Shelly about air travel which currently accounts for around two and a half percent of global CO2 emissions.
So I want to come to you, Kathryn. The question was: Is there a credible solution to decarbonize aviation in the next 30 years or so? And I suppose the corollary I would add is, is do we need to at 2.5% ?
Kathryn: Yeah, it's a good question. The very quick answer is no, there isn't a credible solution to completely decarbonize aviation at the moment.
This is looked at a lot in the UK context because aviation emissions are actually a bigger percentage of the UK footprint of about 8% at the moment. But because aviation is so hard to decarbonize, it's likely to become the major contributor to the UK's emissions by about 2040. But that being said, there's a lot of action underway and new technologies coming through to try and reduce emissions from aviation as much as possible.
So there's something called SAF, which is sustainable aviation fuel. There's also action underway to try and electrify some aircraft, mainly smaller aircraft at the moment. And you can imagine if you're putting a big battery in an aircraft, obviously you don't want aircraft to be heavy. That's part of the problem with trying to decarbonize aviation.
So, there's lots of trials going on at the moment. I would say we haven't seen anything yet that's gonna be the silver bullet, although politicians like to suggest there will be one. And what we're seeing in the policy on this going forward, particularly in the UK, is that the suggestion is that the aviation industry should pay for the carbon removals to offset their industry footprint through engineered carbon removals.
The other big emitter is going to be the agriculture sector. So aviation and agriculture are going to be the two big sectors that are still emitting in 2050 from a technological point of view. And we'd want the agriculture sector to be investing in natural removals to offset their footprint. That's the technical proposal.
Myles: So I might just disagree with one thing Kathryn said, which is that I think you can decarbonize aviation and we could decarbonize aviation, actually relatively quickly by capturing the carbon dioxide it generates back out of the atmosphere and disposing of it permanently. This is the engineered carbon removal that Kathryn talked about, which I would see as a way of decarbonizing aviation.
We can nitpick over words, but this is where you are still using kerosene to fly planes. But instead of leaving the carbon dioxide they generate in the atmosphere, you capture it back out of the atmosphere and stick it back underground. Now we can do that today. The problem is it's expensive. It would roughly double the cost of jet fuel.
And jet fuel is a big fraction of the cost of your air ticket. Now, all of that said, making aviation climate neutral in the sense of disposing of the carbon dioxide it generates, could be done and would only make aviation about as expensive as it was back around 2000. So while people get, you know, anxious and, and sort of, I often get asked, well, what about the person who wants to take their family to the Canaries for, for, for a holiday and so on?
And that's fine. Low cost air travel has been a great benefit to us all, but it's a relatively new one. And the idea that we're all totally entitled to this level of extremely low cost air travel, which is a very new phenomenon - it's only been around for a couple of decades - I think needs to be challenged.
Brian: That that actually feeds into a question John Angel asked, which was: Might it be that by 2050 we'll see the end of choice to fly when and where we wish?
But I think what you're saying, Myles and I'd, I'd like to hear Kathryn's view on this, is that, no, you could choose to fly as long as you pay the full cost.
Myles: I mean, when you buy water, you also pay for waste disposal. It's more than half of your water bill is the cost of disposing of the waste, and exactly the same should apply to fossil fuels.
Brian: Because I think Kathryn, you see that the force of it.
Because essentially what you would be saying is that people who don't have high incomes are not able to travel to places they'd like to travel to, so it does, it does feel like that's a problem. I can see why that question would be asked.
Kathryn: It is a problem and I think fairness is a really, really important component of how we address climate change in the UK and globally.
We talked about this previously as well when, when we spoke about climate change before, and this is why I find concepts like having your own personal carbon footprint is quite useful cause actually it tends to be wealthier individuals who have a higher carbon footprint in general globally. And understanding what that actually looks like, so looking at the detail of it and seeing, well, if I'm, you know, I might not be spending a lot of money on other things that are high emitting, but I might want to choose to fly somewhere on my holiday. That's a perfectly reasonable personal choice to make. And also, as we see, hopefully, aviation emissions start to come down, we would hope that fairness aspect is easier to achieve because there'll be technological solutions that are helping as well.
Myles: And I think most people subscribe to the idea that to start with at least you should pay the cost of the things you use so that you get to choose how much of them you want to use, and it, you don't impose that cost on other people. So, you know, on that score, why should everybody not pay the full cost of flying?
And yes, that would make flying more expensive, but effectively future generations are subsidising our flying today by dealing with the climate consequences of it. Is that fair?
Kathryn: One other thing just to add is that actually a lot of the choices people make on how they travel is around cost. I've started getting the train to European countries a lot more recently.
I love doing it. It's part of the holiday. It costs quite a lot. You can get very good deals, but subsidising rail travel and subsidising lower carbon forms of travel would do a lot to help people make more informed choices from a carbon point of view.
Brian: Thank you. we have a question now on another industry, the carbon footprint of another industry, which is A.I. from Catherine Lad, and she asks: How will the UK's net zero targets be affected by the aim to be a global leader in A.I.?
Given the need for more data centres, the carbon cost of materials to build them, and the reported high energy use of A.I., how should we balance these competing aims, Kathryn?
Kathryn: Yeah, we don't know, and that is a big problem. One of the things we're doing at the Wildlife Trusts is trying to obviously reach our net zero target, but also to measure our emissions, and we do not know how much emissions are being caused by our use of A.I. and cloud-based IT services and actually nobody does. it's not currently possible to measure that in this country or elsewhere as far as I'm aware, but we know that yes, A.I. is a big, big user of energy. It's one of the most energy intensive industries that's likely to emerge in the next 10 years.
What we're seeing in terms of how that's being dealt with is that it's being included in models that are looking out to how to decarbonize the power sector in the UK. The target is for 2030 and how to drive what's needed in terms of that infrastructure through renewables so that it's not the, a big cause of emissions as well as energy use.
And actually there's a wider angle here as well, which is the, wider environmental impact of A.I. technologies and data centres in particular. So they're very big users of water and very big users of land. From a nature and climate point of view, that's a big issue that needs to be looked at, but we need to see a lot more investment in resilient solutions to allow these, these things to operate. That can be through things like closed loop water cooling systems, so you're effectively recycling water. It can also be through making sure that, any biodiversity loss through the development of these centres is being offset. And we have something called biodiversity net gain in England and English policy that allows that to happen.
But globally, we're, we're not necessarily seeing that and that's a big topic for debate. And actually it's in the interest of these businesses to make sure that they're resilient as well, so that, you know, they've got business continuity for these services.
Myles: And, and just to chip in on this, that, I think we should see it as an opportunity as well in the sense that because A.I. is so profitable fixing its environmental impact would have a relatively small impact on what we pay for A.I.. We pay so much for A.I. at the moment that it's, it's actually a real opportunity to differentiate, you know, our A.I. so to speak, compared to other peoples. If we can make sure that we're delivering the cleanest A.I. in the world, and that should be a real ambition for Britain.
Brian: We had a question on a specific term that was used, I think we may have used it very briefly in the initial discussion, which was, solar forcing of the Earth's climate. And I know that Myles as some of your, your first research was on, on this phenomenon. So could, could you explain solar forcing, what, what it is and what it isn't and why it causes a lot of debates and confusion?
Myles: There are theories out there about sort of indirect impacts of the sun, of solar activity on climate, such as, for example, through the modulation of cosmic rays. So particles coming in from, other parts of our galaxy and universe these could affect the climate on long time scales, and I remember back in the early 1990s, there was a flurry of excitement because a small number of researchers suggested that perhaps we could explain pretty much all of the warming we'd observed up until that point by an increase in not the power output of the sun, but the way the sun potentially was affecting, the cosmic ray flux onto the earth. You know, it was an interesting correlation they observed, but, you know, correlation does not prove causation and in fact, what happened afterwards was that the solar indices went in one direction and global temperature went in the other. So it's often joked that, the best way to break a correlation is to publish it. And, this was actually just one of those cases where, you know, people thought at one point that the sun might be playing a much bigger role in driving the observed warming than we thought.
But these days, yes, it plays a small role, particularly on the sort of 11 year timescale, but on the century timescale, it's not a big driver of the, warming we see.
Kathryn: It comes up a lot when we talk to people about what is causing climate change, often the sun is one of the things that we get quizzed about and questioned about, and you can see why, because the sun is very, it's a very significant driver is the driver of our climate, you know, from, from day to night and from season to season, obviously. But Myles is absolutely right when you look at particularly the warming we've seen since the 1970s, there is no way that the sun's activity explains that warming. The only plausible explanation we have for that warming is human release of greenhouse gases, and all of the climate models show that very, very clearly.
Myles: And by the way, it's not just a sort of after the event explanation. This warming was predicted back in the 1970s at a time when global temperatures weren't warming particularly. In fact, if anything, there was a slight cooling going on. But scientists already understood enough about the relationship between carbon dioxide and global temperature to predict that that slight cooling would soon reverse and start a steady warming trend, which is exactly what we've seen.
And it's always quite important in science if, if something's predicted before it happens, we find this a lot more impressive generally than if you explain it after it's happened because you know, we are, as a species quite good at explaining what we see and coming up with explanations. But predicting the future is always harder and this one was predicted with remarkable accuracy.
Brian: We have a question actually, which perhaps is, is linked, at least I suppose philosophically to the discussion we had about aviation emissions, which is about attribution research, this is from Robert Jack. It's a question about potentially compensating the people and communities most affected by climate change.
The question is that there have been significant advances in attribution research linking emissions from fossil fuel companies to damage from specific extreme weather events. This potentially paves the way for a legal framework that maps cause and effect evidence in support of lawsuits against those companies.
How effective a weapon is this in the fight against climate change?
Kathryn: I mean, it's a fascinating one, isn't it? We're seeing a big increase in lawsuits and litigation action on climate change. I think today there's been around 3,000 individual lawsuits globally that are about assigning responsibility to climate change and then trying to get those who are contributing most to the problem to pick up the bill.
The attribution research has come on. I mean, I've been working in climate change for about 20 years and since I started it's come on in leaps and bounds and we're now able to see through the research of many people, Myles included, there's a fantastic initiative called World Weather Attribution that does very, very fast responsive attribution studies as events are unfolding and it's able to, to give data to the media, you know, a couple of days afterwards on, on what the attribution from climate may have been. Those are really powerful for communicating, I think, to to everybody what the role of climate change is in a lot of these, these events, and as you say, it's now feeding through into litigation space as well.
One thing that's really interesting is the International Court of Justice last year put out a statement saying that governments of countries do have responsibility to protect the public from the impacts of climate change. That certainly was something that a lot of people were very pleased to see happen, and we're waiting to see the effects of that.
But is it really a deterrent? Because how much is the cost at the end of it to, to the fossil fuel companies? And in some cases, governments who are not taking enough action? Are we seeing it really have an impact yet? And I think it's still a little bit too early in the process to see that happening.
Brian: Yeah, and of course Myles, I suppose there, there's a very common, debate or argument about linking specific events to climate change, isn't there? It's one of the things that we hear about a lot is that storm, that bad storm, is that to do with climate change or is it just a bad storm? I suppose when you put this into a legal framework, then does that cause a problem in litigation?
Myles: Yes, well I mean, back in 2003, I published an article actually basically asking the question, will it ever be possible to sue anyone for damaging the climate? My wife refers to it as the only interesting article I've ever written, to be honest. But, one of the points the article raised was precisely this point you just made is that, you know, for most of the damaging impacts of climate change, it won't be a case that but for climate change, this impact would not have occurred. It's about how much has climate change loaded the dice in favour of that kind of event happening as against other events? We argued then that, you know, maybe there are other analogous things like lung cancers caused by smoking, for example, where the same kind of logic would apply. And the courts have accepted that kind of probabilistic evidence, and it does indeed seem that the courts are pretty comfortable with accepting, changing probability as a reason for attributing harm. But of course, it, it depends, and this is where the lawyers come in. It depends on exactly the kind of harm that's being argued and the, the nature of the responsibility and so on.
What I argued then, and I would stand by it now, is the only thing I think that would really encourage the fossil fuel industry itself to become active supporters of climate action, which may sound a rather implausible scenario, but I think it's one that we will eventually need, is if the alternative is impact liability.
And so I think even if impact liability at scale is never established by the courts, I think the fact that it's being talked about, the fact that these court cases are happening does focus minds. And it may be bringing forward the day in which it becomes unacceptable simply to sell stuff that causes global warming and those that want to sell stuff that would otherwise cause global warming, except they have a responsibility to fix it.
Kathryn: I'll just add another thing as well on attribution research and that it's very, very powerful if you put litigation to one side. It's actually very powerful in addressing climate scepticism when events occur. We've actually seen an increase in climate scepticism after some of the really horrendous severe impacts we saw, for example, the floods in Valencia in Spain there was actually an upsurge in, in climate scepticism in the media and in public polling after that event. It's the exact opposite of what you'd expect to see and the attribution research that happens very quickly after these events. So the UK Centre for Ecology and Hydrology has shown that the Palisades, Los Angeles Fire, the area that was burnt through that fire was 25 times what it would've been without climate change and that's really, really solid research. And having that to hand as these events are unfolding and soon afterwards is really helpful to try and counter some of this misinformation that we're seeing.
Myles: But by the way, one thing which is not yet happening, but I hope will happen relatively soon, is for this kind of research to get taken over by National Met Services and just made part of the standard suite of climate services that our Met offices provide, because you mentioned the World Weather Attribution, initiative, which is great, but in in many ways we almost rather we didn't need it, in the sense that it would be better for this to be just part of what the Met offices do, because that would make it much easier for both the media and in particular the courts to use the information 'cause they could see that it was coming from a dispassionate source.
Brian: Do you believe that really the key to this is information disseminated by trusted sources, or, is it rather, and I suppose the answer's gonna be yes, is it rather more complicated than that?
Kathryn: It's rather more complicated, but you have to have the information first before you do anything else.
So it's absolutely fundamental to countering misinformation we need really high quality, really clear science, excellent science that shows as well as we can, as scientists across the world, what we really think is happening and what's driving it. You then also need to combine that with really good public communication that's been missing in lots and lots of countries, including in the UK. And one thing we've seen, we've, we've held, you know various organisations have held, what we call public dialogues or citizens panels with, representative panels of members of the public to look at climate change and what should happen either nationally or, or regionally, on both mitagation, which is reducing emissions, and adaptation, which is dealing with the effects of climate change.
And it's really interesting. I see the same process unfold whenever we do one of these panels. It's when you give people information and you do the communication with them, you talk them through what it's showing and why and where it comes from. You often see a really big shift from initial scepticism to absolutely understanding what's being said and then you get anger that they haven't been told this before, and then actually you move, the whole panel moves into a solution space pretty quickly. They want to know what they should do and they want to know why governments haven't been telling them what's just been told to them. So I think that that those panels are a really good indicator of maybe some of the work we should be doing much, much more nationally with trusted partners as well. Sometimes governments are not the most trusted partners, but, but other organisations are very well trusted, whether it's NGOs or the Met Service or others, and being able to understand who is the trusted voice for any particular community, any particular group of people, I think is really important.
Myles: And I think maintaining that trust and making sure that you are trusted by every sector of society, not just the ones you normally talk to, is a real challenge for universities because almost by definition we mostly talk to graduates or talk to people who are about to become graduates. That's our job as universities, but we have to perhaps work harder at reaching out to people who have never been to university and never want to go to university and have no interest in going to university and making sure that they understand the work we do and that we don't have a political agenda behind it, we're just trying to understand what's going on. I think that's really important.
Brian: Let's end with a question about adaptation and how we'll cope with the health impacts of global warming from Benjamin Burns.
So he asked: With climate change increasingly recognised as a public health emergency, how should healthcare and or its professionals evolve to address its growing impact on disease patterns, health equity, and how should we build resilient systems? Kathryn?
Kathryn: In the UK Climate Change Risk Assessment, there's a whole set of emerging diseases that's been looked at over the years, and there was a new one, which I find hard to pronounce it's called chikungunya virus, which we only really started to highlight in the most recent Climate Change Risk Assessment, the one that was done about five years ago. it's a mosquito-borne virus that can lead to death and certainly leads to severe illness. And it's popping up all over the world, even in southern Europe.
So France is getting cases at the moment and from an emerging disease that we talked about five years ago. If you go to London now and you're on the tube, you can see posters that's talking about this virus and, being able to be vaccinated for it if you're travelling, you know, that's a huge change in a very short space of time and there's other viruses, dengue is likely to increase.
Obviously malaria is one that's been looked at for, for quite a long time, but there's other issues as well for public health. Extreme heat is a really big one that's been quite, I would say, a hidden risk in the UK in recent years, but it's by far the biggest climate-related killer in the UK. So we get about 2,000 heat related deaths in an average year.
Myles: And if I might just add to that, there is one very important risk that's perhaps indirectly related to health impacts with climate change, which is that it, it's very clear that many parts of the world, the summers are going to reach temperatures where it's simply unsafe for humans to work outdoors.
That's not predicted to happen anytime soon in Britain, but you know, much of the tropics are predicted to see climate changes that will make them literally uninhabitable for certain times of the year, and that's almost certainly going to drive a very significant increase in pressure for people to migrate to cooler climates.
And we are seeing migration pressures as a huge driver of social instability at the moment and it's something I think we should be all be very concerned about.
Brian: That's unfortunately all we've got time for, but thank you to both Professor Myles Allen and Kathryn Brown for coming back to answer more questions of science and we will have more questions of science next week. Goodbye.
