READ FULL STORY: Engineering the climate
Director of the Centre for Climate Repair at the University of Cambridge, Dr Fitzgerald coordinates research efforts into solutions that could help repair the climate, including refreezing sea ice, injecting aerosols into the stratosphere, and brightening marine clouds.
We spoke to Dr Fitzgerald about the need for geoengineering discussion in mainstream engineering, the importance of community-led projects – and why he hopes his research is never needed.
What areas does the Centre for Climate Repair focus on?
The first is emissions reduction, which is blindingly obvious – stop the problem getting worse. The second one is greenhouse gas removal, coordinating projects and efforts in that particular area. Both of those together, when successfully deployed, get you to a position of net zero.
After Reduction and Removal, the third ‘R’ is Refreeze, which is basically climate engineering. The reason we're doing research into that is we've got grave concerns about the timescales involved in scaling up emissions reductions and greenhouse gas removal to an extent that keeps you on track for a 1.5ºC target by 2100. Unfortunately all the IPCC scenarios involve exceeding 1.5ºC now. It's like the best kept secret hiding in plain sight, because why aren't we talking about it?
What should we therefore do to stave off the worst effects of climate change, to buy us enough time to get to a carbon dioxide level of 350 parts per million, which is what James Hansen has gone on record saying we should be targeting? We're way ahead of that already, so we want to do research to see whether there is any band aid that we could possibly use, and that would be for wider society to choose to pursue or not.
At the moment we have a huge paucity of knowledge in this area, and therefore society can't make informed decisions – which, by the way, could be ‘They're all a terrible idea and therefore we shouldn't pursue deployment’ – but we just don't have that knowledge base, and there's nothing worse in our view than a knowledge void.
Geoengineering hasn’t received much mainstream attention in engineering. Does it need to be discussed more widely by engineers?
I completely agree. There has been a reasonable amount of work done on modelling by scientists, atmospheric chemists and atmospheric physicists. But there have been very few field experiments to generate observations that can corroborate, validate, or actually show where models are wrong. You can't just live in a modelling world, you've got to have real-world data to be able to test those models.
The second point is what would be required to make something happen? That's all about engineering. So how would you deliver material to a set place at an appropriate rate, that isn't going to use so much energy that it's going to be completely unreasonable? In the area of, let's say marine cloud brightening, how do you generate aerosols that are in a sufficiently narrow size range distribution, to be able to have a positive effect?
We need to do engineering research and engineering testing, engineering development at pace. Geoengineering has not had the attention it needs, to see whether some of these ideas might actually ever be plausible and viable.
Why is ‘refreezing’, or reversing sea ice loss, such an important aim?
Our interests are bigger than the Arctic. That said, the idea of refreezing the Arctic and preserving ice cover is really important, and the reason is that ice is a particularly wonderful and weird material.
Firstly, it can hold temperatures at a certain level as a result of the phase change. With your gin and tonic, or whatever you're drinking with ice in a beaker, when the ice melts, the temperature starts to go up considerably. As a result of the phase change, it has a huge temperature buffering effect.
Secondly, ice cover in the Arctic ends up having quite a significant effect on solar radiation itself, because you have quite a big change in reflectivity, the albedo (the fraction of light that a surface reflects). Sea ice with snow can have albedos as high as 0.9, certainly 0.8, whereas the dark ocean has probably got an albedo of about 0.1 or 0.2.
If you don't have the areal extent of sea ice being preserved over the Arctic summer, you then get this massive change in the radiation balance, the heat balance for the Earth. The length of the days in the Arctic is 24/7 in high summer. So what you find is that the Arctic is really important in terms of temperature regulation.
One area that we're looking at is growing more sea ice in the Arctic winter. If you can make it thicker over the Arctic winter, can it last longer over the Arctic summer?
There are two sorts of approaches there. The first is that you pump seawater on top of sea ice, to get that water to freeze from above. The big idea there is that when sea ice forms naturally, you get the accumulation of more ice on the underside of existing ice. But as the ice thickens it becomes more insulating, and the latent heat of solidification has got to go somewhere. It doesn't go into the ocean, it basically goes out to space.
If you think ice is a good insulator – and it is – the snow that falls on top of sea ice is an even better insulator. One idea is that in the early part of winter, when you've got ice forming and you've had snowfall, what if you pump some seawater on top of the sea ice to fill the voids of the snow? If you allow that to solidify and turn into solid ice, you've now turned what was an ice-snow matrix into an ice matrix, which is rather more conductive, and therefore you're going to increase the rate at which natural sea ice forms on the underside. That could involve rather less pumping.
The second thing is can you reduce the rate of melting in the Arctic summer? We're beginning to look at the way that sea ice melts – it doesn't just melt from the bottom, it melts from the top. But when it melts from the top, you get melt ponds forming, which is darker than the ice. So should you drill small holes in the middle of where melt ponds are forming, to allow them to drain and therefore maintain their reflective surface?
What stage is the refreezing work at?
We are part of a small but very collaborative research community worldwide. So we are collaborating with a not-for-profit company called Real Ice. And there is another for-profit company that we're collaborating with called Arctic Reflections.
Cambridge are doing more on the laboratory experiments side, looking at what actually happens when water flows over ice. Shockingly, precious little research has been done on what happens when water flows over ice and then freezes. Does it freeze, does it melt then freeze?
We're fortunate that in the university here we have a cold room that goes down to -40ºC. We're doing flow experiments as well as non-flow experiments, watching what happens in a static environment during the freezing process. We're also doing simulations or mathematical modelling of these processes and comparing those with the laboratory measurements. We’re also planning to do regional-scale modelling over the Arctic and different regions.
In terms of field experimentation, there have been two winters now. In the 23-24 winter, Real Ice went to Cambridge Bay in Northern Canada with Arctic Reflections, to do some snow flooding experiments.
They went back in May to go and look at the ice thickness and see how it compared with a control region. They showed that you got about 50cm of accumulation of ice, half of which was as a result of the flooding, and half of which was as a result of a higher rate of ice accumulation following the flooding. We have got plans in place to go back this winter and the following winter, to do more experiments over a slightly larger area in deeper water.
Real Ice have put a lot of time and effort into engaging with the local community, and anything they do outdoors is governed by, overseen by, led by the local community. It's their land, it's their environment, and therefore we're their guests.
When people ask me, ‘Shaun, if you go and do outdoor experimentation, do you engage with the local community?’ I often say ‘No’, which provokes a shock reaction. And I do this on purpose, because if you're just thinking about ‘engaging’, you are shooting way too low. We shoot way higher than that – we don't want to just engage, we want to involve the local community and ideally be led by the local community.
If you were ever to do deployment, that's the kind of model you need to have. I think it applies across the board.
Looking at the other methods you are researching, could marine cloud brightening have an easier route to deployment than stratospheric aerosol injection?
Possibly. What I would say is they have different characteristics.
If you do marine cloud brightening, let’s say over the Great Barrier Reef, it's actually a relatively small scale, areally. The modelling work that's been done thus far suggests that it doesn't have major impacts elsewhere in the world, and that's kind of interesting. You're doing local effort for a local impact.
The challenges come where you might be operating over a slightly larger length scale, and depending on the climate system you operate in, it is possible that an effect in one area might have an effect in another.
That's something you need to be mindful of, that you might have some unintended consequences somewhere else on the planet. But that's what modelling efforts are there for, to give you prior warning. And then if you did some experiments, you'd go and monitor for those effects.
Another argument I've heard is that stratospheric aerosol injection is more of a uniform blanket. Even if you’re reflecting everywhere, if it’s more uniform it might well be a case that you don’t get the same regional discrepancies.
So I'm just saying they've got different qualities and different characteristics, rather than saying one is better than the other. That's for others to judge.
How do you feel about the future? When will there be serious questions about deployment?
I think there will be serious questions in about 20 years’ time about deploying some of these, if they're shown to be viable widely. But don't get me wrong, I'll be the happiest man alive if those discussions aren't had, for the right reasons – in other words, we've made progress on emissions reduction and greenhouse gas removal, way beyond any of the scenarios that are considered now by the IPCC. In other words, we've done something that the world never thought we were going to be able to do – we've reduced our reliance on fossil fuels, we've decarbonised, we've got greenhouse gas removal scaled up.
I will be so happy if all the research that we're doing never sees the light of day in terms of deployment. But I think that's unlikely. That's why I think we should be doing this work to provide ourselves with a knowledge base, so that these discussions – if they're going to be had in 20 years’ time – are more informed discussions than they otherwise would be.
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