Welcome everyone and thank you for coming to 100 Climate Conversations. I’d like to acknowledge the Gadigal People of the Eora Nation on whose land we meet today and of course, pay my respects to their Elders past and present, and acknowledge, of course, their custodianship of the land we’re on. Today is number 37 of 100 conversations happening every Friday. And the series presents 100 visionary Australians that are taking positive action to respond to the most critical issue of our time, climate change. We are recording live today in the Boiler Hall of the Powerhouse museum. Before it was home to the museum this was a power station. It was a coal fired power station. It supplied coal powered electricity to Sydney’s tram system in the 1960s. And now in the context of this architectural artefact, we shift our focus towards the innovations of the net zero revolution.

I’m Craig Reucassel I’ll be your host today thanks for coming along. Dr Daniel Harrison began as a civil engineer before pursuing his passion to become an oceanographer. This dual expertise combines in his experimental cloud brightening machine, a tool aimed at cooling the Great Barrier Reef. Harrison is based at the National Marine Science Centre at Southern Cross University. His team hope to quickly scale up their experiments given the urgent threat of more coral bleaching amid warming oceans. We’re thrilled to have him join us today so please join me in welcoming Daniel. Thank you. So, Daniel, you grew up on Sydney’s Northern Beaches, one of 10 children and all who seem to have quite a connection to the ocean. You have found yourself working on the Great Barrier Reef. When did you first go to the reef? When were you introduced to it?

So, the first time I went up to the Great Barrier Reef was when my father decided to organise a big family trip to northeast Queensland for the whole family. So, I think we had two Land Rovers, one Land Cruiser towing a boat, a caravan and a tinny upside down –

And ten kids?

Ten kids spread amongst those cars. And so, yeah, we made it all the way up there. But then we had a few dramas. The axle on my dad’s large boat broke and we were stuck in Cardwell, which is quite up there in north Queensland, but it’s about 60 kilometers out to the reef from there. And we were stuck for about two weeks waiting for a new axle to make it up there. And so, we’d just take Dad’s boat out to the reef every single day and go snorkeling and spear fishing and have little picnics on isolated patches of sand out there. And it was just the most wonderful experience ever. And after a while, my dad got sick of going so, he was like, ‘You kids just take the boat and have fun’ sort of thing. That was when I really fell in love with the reef.

From a young age you were slated as a kind of engineer by your family, and you went into engineering. How did you end up in oceanography?

That’s an interesting story as well. So, growing up, all of my family always would say, I’d like to be an engineer because I’d take my brothers and sisters’ toys apart and not always be able to put them back together, which sometimes led to fights. Everyone always said I’d be an engineer. And I was like, ‘No I won’t, no I won’t, no I don’t want to be an engineer.’ And then by the time I got to the end of high school and looked through the little booklet that I used to have back then, to choose your uni degree, I was like, oh geez, engineering sounds pretty interesting. And so, I made it through the engineering degree and at the end I did an Honours project and I was lucky to choose a project – like I was very interested in marine things and there was a professor there who unfortunately died earlier this year. But he took me on for an Honours project developing an underwater sonar with the Australian Navy. And that sort of set me off on my career of combining engineering with oceanography.

Well, before we get onto the specific work that you are doing there, let’s just, I guess, go back to the reef and the problems that it’s facing. Why is the reef such a vulnerable ecosystem?

So, corals are very sensitive to temperature change and it’s very interesting I think of them a little bit as the canary in the coal mine of climate change. It’s probably the first major ecosystem that we’re going to lose, but it’s only the first. And I’m not sure that people realise that. They worry about the corals, and they hear, oh, yeah, we might lose the coral reefs. But I think about what’s going to be next after the coral reefs. If we can’t save the coral reefs, then how are we going to save the mangrove habitats? How are we going to save some of the forest ecosystems that are very sensitive to climate change? I think that corals are just especially sensitive. The symbiosis between the coral host and the algae that provides most of its food source is very delicately balanced. And that’s why they’re so sensitive to warming ocean temperatures.

I think you’re right about the canary in the coal mine, and I think we’ve seen all these mass bleaching events happening. How permanent are these mass bleaching events? How does coral kind of resuscitate itself and how much time does it need to do that?

You can think of a bleaching event just as a disturbance. And so, the coral reef does naturally recover, and different corals recover at different time scales. So, the very fast-growing corals can recover in 10 years or so or even less. But they’re also the easiest to bleach, the fast-growing ones. And then the older ones can take hundreds of years to recover. And so, what happens when you have a mass bleaching event is it depends a lot on the severity, the less severe ones, a lot of the fast-growing corals die, but they also recover quicker. The more severe bleaching events also kill the older corals, which take much longer to recover. And then you have this sort of increasing frequency of these mass bleaching events, which is not giving enough time for recovery.

And so, what we’re seeing and there’s been interesting news about this lately, that the coral covers back up again. And so, the reef’s recovering quite well if the only metric was coral cover, right? But what’s actually happening is the ecosystem is shifting from a more diverse ecosystem of lots of different types of corals to favor the more faster growing corals. And so, it’ll be interesting to see how that plays out over time. It’s something that we’re still learning about, I think.

So, cloud brightening, what is it?

I’ll describe it by how it works first. So, how scientists discovered this principle is essentially by when satellites started taking photos of the world. And you can see where shipping goes across under certain atmospheric conditions, these lines suddenly appear through the clouds that are much, much brighter. And the reason for this is that when a cloud forms every single droplet in the cloud, it needs a nucleus to condense around. We call those cloud condensation nuclei, and essentially it can be nearly anything, tiny little speck of nano sized material floating around in the atmosphere. Over the ocean they’re mostly the sea salt crystals that are formed by breaking waves and then the wind whipping off the surface of the waves. The sea water evaporates and leaves that little salt crystal. And then they’re also formed by biology in the ocean. So, phytoplankton that live in the ocean, they produce sulfur-based compounds that gas out from the surface of the ocean and then undergo some chemical processes to form little particles.

And what happens is when the air is very, very clean and the number of cloud condensation nuclei is low, the clouds form, but they’re forced to form large droplets around each nucleus because there’s a certain amount of water that’s there from larger physical processes forming the cloud. And then whatever condensation nuclei it has, it has to form on those. Large droplets are not very good at reflecting light, small droplets are. And so, when you have more cloud condensation nuclei added, more light is reflected, the cloud becomes brighter. So, it’s the same cloud, you’re not making clouds, but it’s brighter. And so, when they saw these ship tracks, what was happening was the sulfur compounds in the exhaust of the ship were adding cloud condensation nuclei in lines to the clouds above and you could see these bright streaks in the clouds.

So, the pollution of the ships was actually brightening the clouds. Now, presumably you are not wanting to do this with pollution from ships.

No.

So, how are you going to try and brighten the clouds?

So, the marine cloud brightening technology aims to replicate that natural process of creating the sea salt based cloud condensation nuclei, which are about 50 per cent or so of the natural nuclei over the ocean. And so, to do that, we pump seawater and then we atomised it. It’s similar to a big misting machine you might have at a concert or an outdoor pub that’s sort of supposed to cool you down, except that we produce much, much smaller droplets of seawater and they evaporate as we spray them out. And then the salt crystals are mixed up into the clouds. And so, you’d space these stations around the reef and then nature does the rest, basically.

And so, the point of this is that the brighter the cloud, the more it reflects the sun that’s coming in. So, that’s basically protecting the reef by reducing the warming of the oceans or reducing the sunlight that’s coming through?

It does both. Most of the benefit is from actually cooling down the ocean. And so, you couldn’t go and do this just anywhere. You need two things for the idea to work. One is that the clouds need to be susceptible, which means you need to have very low existing levels of cloud condensation nuclei at the time that you need them. And you also need low clouds because you’re not influencing higher clouds through this process. And we think we have those over the reef. It’s a lucky coincidence that we have those natural system over the reef during summer when the water is normally hot, and the corals normally bleach.

We have atmospheric systems that predominantly move very, very clean air in over the reef with low natural condensation nuclei. And then the other part of the process is that you need a sort of a large, shallow captive body of water because it’s only a very little bit of brightening. And so, it works over a long period of time. You get a little bit of shading each day, you know, maybe something like 5 or 6 per cent. And what happens is over the period of about 4 to 6 weeks, the interaction of the clouds moving around over the reef and the water mixing around in the Great Barrier Reef lagoon, we call it the Great Barrier Reef Lagoon because that water is quite captive in there and it’s quite shallow.

It’s, most of it’s only about 30 or 40 meters deep. And so, that water is mixing around under that slightly brighter clouds. And over time in our modelling, you can see the water gradually cools down and then it levels off after about five weeks or six weeks. And that’s sort of the matching of the amount of time that the water spends within the reef and starts flowing out again with the clouds overhead. And so, that reduction in sea surface temperature that you get over that period of time is what relieves most of the stress. Now, the shading does also relieve some stress on the corals. And in fact, you can stop corals bleaching just by shading them, because the process that the corals bleach by, it’s actually an interaction of temperature and light. It’s driven by the warming temperature, but it’s actually light that causes it. And so, if you take away the light, then you can prevent the corals bleaching. Unless the temperatures are so hot that the corals are just essentially physiologically cooked like you or I if you if you put us in a room that was too hot –

This is this is where you kind of go, people have talked about shade cloth over it. We cannot have shade cloth the size of Italy to solve this problem. So, take me through, I just want to hear how this actually works. Like you get on a boat, what is the kind of machine and how are you pumping this out? And presumably if you’re saying you need clouds there already. If Daniel gets up in the morning, looks out and goes, ‘There’s no clouds over the reef at the moment,’ you can’t do anything at that point.

But you can, you could use other technologies. So, yes, you wouldn’t bother doing it on days when there was no cloud. And so, the modelling sort of takes that into account, right? We’ve looked at past bleaching events and what we do is we add up when there is cloud and is that enough? And it’s such an integrative process that it doesn’t matter, right if there’s no clouds for a few days because you’re cooling the water down over five or six weeks and it stays cool. If you suddenly stop that, it would take that amount of time to build back up to where it otherwise would have been.

The other sort of technologies that we’re also looking into, we’re calling it fogging, but it’s more akin to that misting process that you’d have at the pub producing where you’re directly spraying a lot more seawater in much larger droplets to directly try and create like a sea fog. So, you could do that when there’s no clouds. Typically, when there’s no clouds, you have doldrum conditions over the reef where there’s not much wind, there’s not much cloud. The ocean gets very still. And that’s actually when the coral is mostly bleached. You have this buildup of stress over the summer and then when the doldrums come along, which they inevitably do several times every year, that’s when the corals really get pushed over the edge. And it’s actually, again, because of the light and the temperature when the ocean gets still, you don’t have waves on the surface reflecting some of the sunlight. The sediment in the water settles out, so more of the sunlight penetrates all the way to the corals. You have less mixing of the water, which is a way that corals use to get rid of the toxins that are actually building up because of the light. And it’s actually that buildup of toxins that causes the coral to reject the symbiotic algae.

So, the most danger is actually when there’s no clouds. So, your work is to try and reduce temperature at other times when there are clouds there, is that how it works?

Well, the gradual reduction in temperature, it’s cumulative. So, you’ve cooled the ocean down half a degree or 0.75 of a degree. And then you’ve lowered that baseline. So, you’ve lowered the stress for the corals over the whole summer by doing this. This is why it makes a difference.

So, I’ve seen vision of this and you’re on a kind of a big boat. It’s got like a giant fan on the back, taking out seawater and pumping it into the air. And despite the fact that it’s a big boat, when you look at it in the context of the space you’re in, you look like this tiny little speck on the ocean. How much impact does this have? Like, what’s the space that you are actually able to affect with one boat out there doing this?

So, at the moment, our sort of prototype that we’re using for research, it’s only about 1/10 scale of what we think we need to scale up to. But that prototype, that’s about 1/10 scale, it’s actually affecting an area about 20 kilometers by one to five kilometers wide. So up to about 100 square kilometers. It’s actually very interesting and it can be quite misleading because when you look at the videos of our work, you see this mist coming out of the huge cannon. But those particles that you can actually see are less than one per cent of the particles that we’re producing. So, we produce the particles it’s sort of a bell curve of different sizes coming out. And it’s that tiny little, little tail that’s large enough that you can visibly see it that you see in the spray. 99 per cent of those salt crystals we’re producing are too small to see. And so, it can be a little misleading when you look and you see the mist coming out, you think that that’s all that’s happening. Actually, what’s happening is invisible, the mist is sort of a byproduct.

Well, it’s the effect that it has on the clouds anyway. But even if you talk about 20 kilometers by a couple of kilometers wide, when you’re talking about something, the reef, the scale of Italy, that’s quite small. So, is your purpose to only go where the worse bleaching is? Like, how does this work in terms of solving the problem of mass bleaching on the reef?

Well, there’s a few things at play. So, one is that’s the direct area over which you produce the sea salt cloud condensation nuclei. Then what happens is they’re taken up into the clouds, but the clouds continue to move over the reef. So, you end up impacting a much larger area. That’s part of it. The other part of it is like considering, well, A, they’re scaled up ten times from what we’re doing now. And then B, you space them out and they each cover that much area. But it’s largely the wind taking what you’re doing. And then as well the clouds form using these cloud condensation nuclei, then they dissipate, but the nuclei are still there. So, then when the next cloud forms again down wind, it also still has those extra nuclei as long as the air mass remains over the reef.

But to answer your question, I think certainly you could increase the efficiency and reduce the overall cost and the energy cost, of course, by targeting the areas of the reef that were going to bleach. But of course, you also need to have good prediction then of where it’s going to bleach because you really want to get out and start cooling the water down before it gets too hot. It’s sort of a preemptive action. You want to do it when the forecast of bleaching that summer is particularly hot.

You’re playing here with a naturally occurring process. Are there risks that come from this? Like, are you changing the weather? What’s the effect here?

Yes. I mean, there’s certainly risks. And that’s one of the things that we’re also looking into very heavily. I think the thing that people naturally worry about is could we be changing rainfall patterns? So, we’re doing a fair bit of modelling on that now. It’s extremely preliminary, but it doesn’t look like by much it looks like a very minor potential change.

And have you had, I mean, there’s obviously not just the Great Barrier Reef that is threatened around the world. Have you got other people who are looking at other reefs around the world who are fascinated by this, who are talking to you and hoping to use this technology around the world?

Yeah, it’s certainly come up. But again, it’s that same problem, right? It’s just a very unique and fortuitous set of circumstances that apply to the Great Barrier Reef that mean this could work there, right.

So, this wouldn’t even necessarily work on other reefs?

No. So, say you’ve got a reef, I don’t know near Hawaii or something. The water is just coming in, flying over that reef and going off again. The two reasons that this works over the Great Barrier Reef are, one, we think that the clouds and the atmospheric concentrations of CCN are suitable – sorry, cloud condensation nuclei are suitable. And two, we’ve got that water captive in that big shallow lagoon, and that means we can actually cool it down. If it wasn’t trapped in that big Great Barrier Reef Lagoon, we wouldn’t be able to cool it down enough to make any difference. Remember, it takes 4 to 6 weeks to sort of equalise and cool that water down. So, that’s not to say it wouldn’t work on any other coral reefs. We’re just so flat out we haven’t had the time to look carefully.

So, do you think there’s probably other reefs that do have this kind of lagoon situation around the world?

Yes, but not many. And then if you combine that with also needing to have the air mass coming, I mean, the air mass over the Great Barrier Reef during summer when it’s bleaching is coming from some of the cleanest and lowest cloud condensation nuclei air in the world. It’s coming out from the very, very remote South Pacific and sort of cycles in and then blows up over the reef. And it’s just pure luck that that’s what’s happening during the summer when the reefs bleaching. If the reef bleached in winter instead, cloud brightening wouldn’t work because the air’s mostly sort of coming the other way and it already has high concentrations of CCN already.

It’s quite amazing to realise how specific and how many different inputs there are in to make this idea work. At what point are you at right now? So, you’ve got – you’re focusing obviously on the reef there. At what stage is your experiment at, like where are you in terms of, you know, how close are we to solving the problem or having 800 boats out there doing this? Where are we on this journey?

We’re probably still a fair way from 800 hundred boats. It would be 800 hundred stations, by the way, maybe not 800 boats. Again, part of trying to do it with renewable energies, you wouldn’t want to just have 800 boats, but –

So, you’d actually just kind of build a fan in the ocean that’s fed by renewable energy, had solar panels or something.

There’s a whole bunch of different scenarios. So, one that I sort of most favor is – essentially, it’d be a bit of a mix. You’d use islands or other shallow areas where they’re available to put something permanently. You might have a system where you had sort of one work boat looking after 20 or so barges with the equipment on them, moving them into position at the start of the summer, servicing them during the summer, and then bringing them back at the end. And then there’d also be the opportunity to use Ships of Opportunity. So, there’s actually quite a lot of vessel traffic already up and down the reef and in and out with tourism boats. And so, you could potentially outfit a lot of those boats with the cloud cannons as well. But then you might need dedicated ships to do more remote regions. I think the most likely implementation scenario is that kind of technology mix making use of what’s there as much as possible.

Where are we? It’s interesting, right. People have been studying cloud brightening for 30 years, all of it theoretical until now, people have run models, people have done calculations, people have designed these renewable energy wind powered ships to ply the world’s oceans to do cloud brightening. Because the idea actually came from trying to cool the whole planet down. So, people started looking at cloud brightening as a potential geoengineering technique to actually cool the entire planet. And we’re sort of borrowing the technology and applying it in a very different way, because if you did it to cool the whole planet, you’d need to do it 24/7 all year round. And there’s a whole suite of risks that apply to that, that don’t apply to what we’re doing, because we’re doing it sort of intermittently as an emergency response, if you like, to a marine heatwave.

You wouldn’t even do it every summer, although in the future as climate change gets worse, you might end up having to do it every summer, it depends on the trajectory. So, no one had done it before. And so, one of the first challenges we had was sort of convincing people that you could even generate these sea salt crystals at suitable sizes in sufficient quantities out there in the real world on the ocean. So, we sort of did that a couple of years ago. Then our most recent work last year, we upscaled somewhat because that was looking positive and that was enough to sort of secure us the research funding to go forward.

The next major hurdle, if you like, was to prove that we could actually get sufficient numbers of these to influence the clouds. There was a lot of concern in the scientific community about that. One of my PhD students has been working on this because people said, ‘Well, when all the water evaporates, that’s going to create a cool air mass. And the plume of these cloud condensation nuclei might just sink and flow along the ocean and not reach the clouds at all.’ So, last year, we proved that that’s not the case. We measured with an aircraft and with laser equipment, all the particles going up and getting into the clouds. So, early next year, our next fieldwork, we’re going to, for the first time hopefully measure the actual brightening in the clouds. So, now that we understand how to get the salt crystals into the clouds, we’ll be flying through the clouds with an airplane and measuring how much they brighten.

We’re going to have two large research vessels. We’re going to have teams on two different islands out on the reef. And the part of the purpose for that is some drone operations. We want them to be away from where we’re measuring all of the background. And so, one of the islands is basically a background station. So, it’s going to measure how the atmosphere, everything in the atmosphere is without us perturbing everything. And then downwind one ship is going to have the cannons and making the cloud condensation nuclei. And the second ship is going to measure downwind from that to see what we’ve changed. Then the aircraft and drones are obviously also doing that same sort of tasks up in the sky by flying in unperturbed areas and then in the perturbed areas. And so, we’ve got one airplane, two research boats, two islands and about six drones or something that will be operating. And just the aircraft alone, we’re fitting out with about 20 different instruments. That’s just the aircraft, the ships and the islands have more. So, it’s a lot of parts.

This is where the engineer comes into the kind of scientist here. How many years have you been doing this now?

So, we sort of formed our first working group to look at this problem after that sort of first of the more recent mass bleaching events in 2015, 2016. So, since then, the first few years, we’re just in the lab trying to develop a nozzle technology that might do the job. And then only the last couple of years we’ve been out doing things in the field, about three years now. This isn’t a technology that we’re going to be able to roll out tomorrow. We’re sort of looking at another 5 to 10 years of research before we’d be sort of ready to try and actually do it, I think.

What’s the next step for you? Where is this going now?

Well, we’re very focused on this next field campaign. It’s a little bit, I guess there’s a lot riding on that. If we show that the clouds actually do brighten as we expect, that won’t be enough in and of itself. So, there’s still a lot of work to be done on those nozzles, right, back from the lab days. We’ve got them good enough that we think they’ll work, but they’re very far from optimised. And one of the real side benefits of this research is that in all the global climate models looking out at how the earth’s going to look in the future, the greatest uncertainty in those models is that we still don’t very well understand this process of cloud brightening.

So, this is going on all the time, right? There is different concentrations of cloud condensation nuclei in the world which have been hugely influenced by human activities. In fact, we’re already geoengineering, the clouds globally, inadvertently. All of that pollution from the ships and everything else we do is adding cloud condensation nuclei to the atmosphere. And by some estimates we’re offsetting about 40 per cent of global warming by inadvertently brightening the clouds globally.

And so, the uncertainty about those interactions between the particles and clouds are one of the greatest uncertainties in climate models going forward. And so, there’s getting it to work and then there’s really understanding how does it work in different types of clouds, in different types of conditions, with different velocities of updraft is a fairly important factor into the cloud. And so, there’ll be a few more years of research in A, refining our understanding and B, optimising that nozzle technology because we know at the moment that it’s not ideal. We think it’ll brighten the clouds, but that tail, those 1 per cent of larger particles that you can see in the videos of the spraying machine, they actually have the opposite effect. They dim the cloud a bit and we don’t quite understand yet how much of an offset that is. I mean, in a worst case, maybe the large particles are offsetting all of the good effects of the correctly sized particles. And so, we’ll probably move on to trying to work on optimising the technologies after that.

Well, when people say why isn’t science quicker at responding to things, I guess the reason you’re doing this is to ensure that there isn’t some hidden negative effect from what you’re doing. I mean, if you find this is creating this problem here, does that mean the project’s over like are you kind of like, let’s pack up, this is not the solution.

So, potentially, I mean, this is what my whole career has been about, right. People look into these ideas in this case for 30 years and theorise about it. I’m interested very much in two things like can it actually work? Because we waste a lot of time and energy and money just theorising about these things without actually testing them. And I mean, often what we learn is that they don’t work as well as people first think. You know, people tend to get very excited about these new ideas and like, ‘Oh, it can solve all of our problems.’ And then often the trajectory is as we learn more and more and more about it, we go, oh, well, actually this offset some of their benefit and there could be these negative impacts and it starts to look less rosy. So, it’s certainly a possible outcome and it’s probably as important, I think, to rule some of these ideas out as it is to rule them in.

But to more directly answer your question, it depends. We expect, that there’s likely to be some tradeoffs or some risks, probably not so much tradeoffs. One thing that I worry about a bit is if it worked too well. So, if you tried to cool down the whole planet, not necessarily with cloud brightening or any of these ideas, as there’s a lot of other ones, people worry about the termination effect. What happens if it’s all going well, we’re cooling down the planet and then a world war breaks out and we suddenly stop doing it, or it becomes too big a drain on the economy, and we suddenly stop doing it. And they call this the termination effect. And then the global temperature could very quickly jump back, because really, you’re masking the problem, right. In the case of the reef, I sort of think of it a little bit like life support, right. It’s not solving the underlying problem, we absolutely have to reduce emissions and otherwise the reef doesn’t have a chance I don’t think.

That’s exactly what I wanted to come to, because I think there’s a certain response whenever you talk about any of these adaptation methods on the reef, whether it’s shading or whatever it is, there’s a certain response from climate scientists saying, ‘No, no, no, we’ve just got to reduce emissions. That is the only thing that can save the reef.’ So, you’re not proposing this as an alternative to that?

No, I couldn’t agree with your statement more. The only thing that’ll save the reef is reducing emissions. Unfortunately, we’ve left it too late which is why we need to look at these other things. At the moment, we’re still increasing emissions every year, right? So, there’s lots of rosy talk about moving to renewable energy and Paris climate targets and all the rest of it. But we’ve got to take stock that our emissions – not just how much is in the atmosphere, but how much we’re adding to the atmosphere – is still increasing every single year, right. So, we haven’t even turned that corner yet.

Now, the only way to meet the Paris climate targets is for us to eventually start to get so good at reducing emissions that we have none anymore and that we’re actually got technologies taking it back out of the atmosphere. That’s what the IPCC has now in their future reports. So, these ideas, they come out of necessity, not anywhere else, I think. The idea is that if we can help the reef for a while through this period, because we’ve been too slow to reduce our emissions, which is the most important thing, then maybe we can still get there to a future where we have a functioning reef ecosystem that’s – look, it’s almost certain to be degraded from what we have today. That’s just the reality of it. But that we will still have something.

So, you’re saying that if emissions keep going up as they are, or even if we don’t turn them around fast enough, there’s a limited lifespan of even cloud brightening, you know, how many years can this be effective?

Our modelling shows about, if you’ve got business as usual climate change and the cloud brightening works as well as we hope, which is still a big if because we’re still in fairly early stages of trying to understand the technology itself and how the clouds do respond. But if it works as sort of somewhat optimistic, but reasonable assumptions that we’ve put into the models, it’s about 2050 or so, I think, because the modelling runs out to 2070. And if cloud brightening works and you do it over the whole reef, the ecosystem is kind of preserved out to about 2050 and then sort of drops off, whereas if you don’t do it at all, it’s dropping off really dramatically within the next 10 years or so.

I guess there’s an argument from some people in the climate space that say, you know, by coming up with these ways that we can prolong the life of the reef, that it means people go, ‘Well, we can run gas plants slightly longer or keep going with coal’ or that kind of thing. Do you think there’s a risk of these kind of adaptation plans being used to justify, continuing with that behavior as they are?

I don’t think so, to be honest. So, this is the so-called moral hazard argument. It’s been around for a long time, particularly in that sort of global geo-engineering space. You know, the idea being exactly that, if even researching these ideas might give people a false hope that we don’t need to reduce emissions. I don’t think so, because that that idea has been around for a very, very long time, right. And I don’t think it’s made any difference. I don’t think anybody believes that we can afford to keep coal fired power stations around because we might be able to somehow dim the sun in the future. To me, the argument doesn’t really make sense.

We’re better off understanding, and this is the foundation of science, right? We’re better off understanding everything. All of the options that we have, all of the options we don’t have. I actually think some of those ideas are potentially more problematic if we don’t research them, because we might keep believing that they’re going to work and they’re going to save us when we don’t really know. So, I think that the research is incredibly important. And then the time to make decisions about whether you should implement something or not is once you understand it, once you understand the potential benefits and the potential risks. And I mean, an interesting thing in the world now is that it’s no longer really benefit versus risk. It’s risk risk, right. Not doing anything has immense risks. Not doing stuff fast enough in terms of reducing emissions also has immense risks. And some of these ideas have risks, too. And you can’t make a sensible decision between different options if you don’t understand them.

Well, it’s fascinating work, and it sounds like there’s a lot of things that have to be sorted out. The rest of us will continue to hassle politicians, businesses, change your own behavior and try to get emissions down. You try and buy us an extra at least 20 years on the reef because at the moment it really doesn’t look like it’s going to survive unless we find some kind of, you know, life support to keep it going. Please thank Daniel, please join me in a round of applause. Thank you, Daniel. You can follow the program online, you can subscribe wherever you get your podcasts. You can also visit the 100 Climate Conversations exhibition or join us for a live recording like this one. You can go to 100climateconversations.com and just search for 100 Climate Conversations in your pod catcher of choice.

This is a significant new project for the museum and the records of these conversations will form a new climate change archive preserved for future generations in the Powerhouse collection of over 500,000 objects that tell the stories of our time. It is particularly important to First Nations peoples to preserve conversations like this, building on the oral histories and traditions of passing down our knowledges, sciences and innovations which we know allowed our Countries to thrive for tens of thousands of years.