Five climate megaprojects that might just save the world

WHEN it comes to fighting climate change, many strategies require relatively small actions from large numbers of people. It is about millions of us installing heat pumps, switching to electric vehicles, eschewing meat in our diets and so on. But given the sheer scale of the challenge, there are those who insist we need to think bigger and bolder too.

They are talking about audacious infrastructure projects that would cost billions and carry high risks, but could, if they work out, have a truly transformative impact on our stuttering efforts to get carbon emissions down to zero – and even mitigate the worst effects of current warming. They include plans to build a huge solar power station in space, regreen vast swathes of desert and prop up melting glaciers to hold back city-threatening sea level rise.

Here, we examine five of the most promising green megaprojects, weighing up their prospects and exploring what would need to happen next to make good on them. Realistically, what kind of impact could they have? And can we really pull them off?

Launch a solar power station into space

Clouds may be a source of inspiration for poets and romantics, but for solar power engineers, they are nothing but a nuisance. No matter how efficient the solar panel, when the sky clouds over, power output drops to nearly nothing. Move that solar panel into space, however, and this problem disappears. In orbit, a satellite can bask in the perpetual glow of sunlight and generate electricity at maximum capacity nearly all the time.

Engineers have been talking up the idea of a solar power station in space for decades, and when you look at how much energy it could produce, you can see why. A 10-kilometre-wide solar panel in geostationary orbit could produce 570 terawatt-years of energy, according to Ian Cash at International Electric Company. That would be enough to supply 10 billion people at six times the current US levels of energy consumption per capita. (For comparison, the UK’s total electricity demand in 2022 was 320 terawatt-hours.)

So, why haven’t we done it? For a long time, the answer was cost. A spacecraft with solar panels extending for kilometres would be heavy, and launching all the required equipment into space would be horrendously expensive. But with the arrival of reusable rockets built by companies such as SpaceX, that price has tumbled. Estimates suggest that it could cost just $5000 per kilogram to send materials into geostationary orbit, where space solar power stations would need to sit, with SpaceX’s upcoming Starship launch system. That is about half of what it costs with our most economical rocket technology today. “The advent of reusable launch vehicles completely changed the economics,” says Martin Soltau, co-CEO of Space Solar, a UK company dedicated to the commercial delivery of space-based solar power.

Assuming that we can build a huge solar power station in space, we would then have to get the power back down to us. Fortunately, we know how to do this: microwaves beamed to a ground-based receiver called a rectenna. Researchers at the California Institute of Technology in Pasadena demonstrated this was feasible for the first time in February, as part of their Space Solar Power Project.

That was an important milestone. But if we had a truly huge solar plant in space (or lots of quite big ones), the rectennae would no doubt prove contentious. There would have to be roughly the same number of them as solar power satellites, and each would need a collecting area of around 20 square kilometres for each gigawatt that it was designed to receive. At that size, the best solution would be placing them offshore. Imagine a giant floating net of antennae, sitting above the highest waves. “In terms of offshore engineering, they’re going to be much more straightforward than making offshore wind turbines reliably work for 25 years,” says Soltau.

Perhaps the biggest uncertainty is whether the carbon emitted while making the solar panels and getting them into space would outweigh the benefits of space-based solar power. A study by Andrew Wilson at Metasat UK, a space sustainability start-up, looked at the effects of manufacturing and launching the infrastructure for 25 solar power satellites, each capable of generating 2 gigawatts of power on the ground (collectively, about as much as 620 wind turbines). He found that this would produce about 80 per cent as much carbon as the UK does in a year. However, that would be paid back in carbon savings within six years and the system could operate for as long as 60 years.

Whatever the impact, interest in space-based solar power is growing. As well as the Caltech project, Japan and China have plans to build and test prototype solar power satellites in the next few years. At the European Space Agency, the Solaris programme is also investigating the concept’s feasibility. If the UK puts its shoulder behind this, it might realistically aim to get about 30 per cent of its electricity from space by the early 2040s, says Soltau. Stuart Clark

Build a set of energy islands

If Denmark has its way, the cold and choppy waters of the North Sea will soon be home to a new island known as Vindø. Not a seabird and sand kind of island, but one of concrete, steel – and clean energy galore. The plans for Vindø are part of a broader scheme to solve the energy crisis by building artificial “energy islands” to support vast wind farms.

Europe already has a lot of offshore wind turbines. But energy industry insiders reckon we need vastly more if we are to successfully transition to net zero. “In the next 25 years, many countries are looking at building 10 to 15 times as much as we built in the past 35 years,” says Samuel Magid at Copenhagen Infrastructure Partners, a green investment fund. “That’s a huge challenge, and in order to succeed, we have to do things differently.”

Wind power has two main drawbacks. One is that the power generation is intermittent, meaning it can be hard to match supply to demand. Another is that the power must be transported via cables to where it is needed on land – and the infrastructure required is wildly expensive, especially if each farm is connected through a dedicated cable, as at present.

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Energy islands could solve both problems. They would act as hubs in a continental supergrid, with connections from the islands splitting off to several different countries. This would make it easier to balance supply and demand and mean fewer cables are needed overall. “Building anything offshore is expensive,” says David Flood at Statkraft, Europe’s largest generator of green energy. So the idea is to just build a select few islands that have a lot of connections to various nations. “It’s like a mega junction box,” says Flood.

Denmark’s Vindø is one of at least four such islands intended for the North Sea. The Netherlands, Germany and Belgium all have plans to build similar structures. Each would be built of sand and concrete and would support a huge wind farm nearby. Put all the plans together and they would produce 56 gigawatts of power, roughly equivalent to that provided by 30 nuclear power plants.

The other big attraction of energy islands is that they could be used to produce clean fuel. Certain industries, such as air travel and steel and cement production, are hard to electrify, but could be powered by clean-burning hydrogen. Energy islands could act as hubs for its production, using the green electricity to power machines called electrolysers, which split water apart to make hydrogen. This could then be shipped or piped back to land.

For Magid, this is the real, long-term attraction of energy islands. “It costs five times as much to transport electrons through a cable as it does to transport the green hydrogen through a pipeline,” he says. Perhaps the hydrogen could be converted into ammonia – much touted as a future shipping fuel – and the energy islands could also act as maritime refuelling stations.

Green fuel production will probably be a feature of a second generation of energy islands, says Flood. “You could imagine that you don’t have cables at all, you are just producing huge volumes of green hydrogen,” he says.

In that case, other locations could come into play. The sea off the west coast of Ireland, for example, has huge potential for wind generation, but it is largely untapped because the demand for electricity nearby is relatively low. It would, however, be a fantastic place to make green hydrogen. Joshua Howgego

Stabilise the doomsday glacier

The Thwaites glacier in Antarctica – often dubbed the “doomsday glacier” – is in deep trouble. Since 2000, it has lost more than a trillion tonnes of ice. The speed of its flow has also doubled in 30 years, meaning twice as much ice is being spewed into the ocean. Some think it is on a runaway path to collapse.

Even more alarmingly, this glacier buttresses much of the ice sheet covering West Antarctica. If Thwaites fails, the worry is that it will precipitate a widespread melting of the ice – a huge concern because this vast ice sheet contains enough water to raise global sea levels by up to 5 metres. “That will seriously threaten cities like New York, Shanghai, Calcutta and Hamburg,” says Anders Levermann at the Potsdam Institute for Climate Impact Research in Germany.

John Moore at the University of Lapland in Finland has been exploring ways to shore up the Thwaites glacier for years now. He and his colleagues made several proposals in a 2018 commentary published in Nature. One idea was to bore through the glacier to extract the thin layer of water at the bottom that lubricates it and speeds up its flow. However, when Moore calculated the energy needed to bore multiple holes through the ice using a hot-water drilling technique – and keep them open in sub-zero temperatures – he baulked and largely abandoned the idea. “The amount of fuel you need is just insane,” he says.

It might be better to protect Thwaites in a different way. One key threat is that increasingly warm seawater is seeping under the glacier’s protruding ice shelf, melting it from beneath. Moore and his colleagues think that there might be a way to mitigate this by deploying a buoyant, 80-kilometre-long undersea curtain tethered to the seabed close to the glacier. The aim is to reduce the flow of warmer water reaching the ice. Early tests of a small prototype curtain by researchers at the University of Cambridge have just begun. “We’ve got to figure out a way to at least keep the ice where it is whilst we get greenhouse gas levels down,” says Shaun Fitzgerald, who is co-leading this trial.

Needless to say, carrying out a massive engineering project in possibly the most inhospitable place on Earth won’t be cheap. Moore estimates that the sea curtain could cost a whopping $50 billion to $100 billion. However, when you compare that with the tens of billions of dollars that individual cities like New York are spending on flood defences, he argues it is good value for money since it offers global protection.

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Twila Moon at the National Snow and Ice Data Center in Boulder, Colorado, says that these geoengineering ideas give the “sense of assisting with the climate crisis, while failing to actually do that”. But Moore doesn’t see it that way. “No one is saying this is a substitute [for tackling emissions],” he says. “It’s an extra tool. The best we can hope for is to avoid this collapse process, so the ice sheets gracefully retreat without very rapid sea level rise.”

Ultimately, Moore thinks the stakes are high enough that these ambitious ideas are worth entertaining. “I don’t think civilisation could manage without the West Antarctic ice sheet,” he says. “It’s an existential threat.” Alison George

Regreen the Sinai peninsula

Once upon a time, the Sinai peninsula was a subtropical paradise. This area, in modern day Egypt, boasted rivers weaving through forests and grasses sparkling with dew. Then, around 10,000 years ago, the hills turned brown, rivers dried up and dusty sands drove away the remnants of life. Changes in Earth’s orbit may have been partly to blame, but human intervention – felling trees and grazing animals – is probably what tipped the balance.

What if we could return the Sinai to its former Eden? In principle, the reintroduced vegetation would not only suck a huge chunk of carbon from the atmosphere, but also reinvigorate local water cycles, ushering in desperately needed rainfall and allowing flora and fauna to thrive.

The Sinai has the benefit of being well-studied for regreening by a Dutch firm called The Weather Makers. At the heart of the company’s plan is Lake Bardawil, a shallow, saline lagoon on Egypt’s Mediterranean coast. This was once 40 metres deep; today, you could find the bottom with a long stick and it is largely stagnant with little seawater exchange. Researchers at the firm would like to deepen the inlets to the sea and dig out the sediment that has built up in the lake itself over millennia.

According to The Weather Makers, this would improve the water quality and restore fish stocks. Both would be a welcome boost to the fishing industry in North Sinai, a region affected by poverty, terrorism and the war in neighbouring Gaza. Together with the planting of salt-tolerant species, the excavation would also help enlarge the surrounding wetlands, creating a better habitat for migratory birds. The sediment itself, being full of organic matter, could be worked into the land, improving its fertility.

There is only one thing missing: fresh water. Those at The Weather Makers have several ideas of how to capture it. One is to use fog collectors, taut nets erected at high altitude, on which atmospheric water vapour can condense and trickle down into reservoirs. Another idea is to store the excavated wet sediment in huge, lowland polytunnels, where its water content can evaporate before condensing on the structures and dribbling down to irrigate plants. Once the plants become sufficiently mature, the polytunnels can be moved elsewhere. Eventually, once a critical mass of land is regreened, the region’s biosphere will naturally tip back to its former state and a self-sustaining water cycle will continue all the hard work – or so the idea goes.

Francesco Pausata, a climatologist at the University of Quebec in Montreal, cautiously welcomes the proposal, but thinks that the knock-on effects for the climate elsewhere need to be studied. “This sort of geoengineering can be good for the local population,” he says. “But it’s worth investigating in more detail to avoid unintended consequences.”

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At present, the Sinai plan is just an idea. The team at The Weather Makers is still in talks with the Egyptian government. But many large-scale greening projects are well under way – for example, the African Union’s Great Green Wall initiative, a 15-kilometre-thick strip of planted trees that is intended to stretch from Djibouti to Senegal. Another modern example is the Loess plateau in China, an area roughly the size of France that was reforested in 20 years, starting in the late 1990s.

The merit of these particular projects is debatable. The Loess plateau was transformed so quickly because it relied on unsustainable monocultures. “We need to realise that regreening projects are easy to market, but they are a distraction in most cases from [what ought to be] the real priorities and solutions of protecting the habitats we will otherwise lose,” says Alice Hughes, a conservation biologist at the University of Hong Kong.

On the other hand, a 2020 study suggested that, in a little over 30 years, human activity and climate change has helped desertify 6 per cent of the world’s drylands – that’s some 270 million hectares. Plausibly, all of this desert could be regreened in a nuanced, sustainable manner that is sympathetic to the former habitats. Jon Cartwright

Suck 80 megatonnes of CO₂ from the air each year

Over the next few decades, it won’t be enough to merely avoid putting more greenhouse gases into the air. We also need to actively remove carbon dioxide to avoid the worst effects of global warming. There are plenty of ways to do that, including planting trees or restoring seagrass beds. But if you want to mop up CO₂ in an easy-to-quantify way with few uncertainties, then direct air capture is a solid – if expensive – option.

The idea is to absorb CO₂ from the air and then release a stream of the concentrated gas that can either be buried in the ground or sold as a useful product, such as synthetic jet fuel. In that sense, you can think of it as recycling CO₂.

According to the International Energy Agency (IEA), we will need to suck 80 megatonnes of CO₂ out of the atmosphere each year by 2030 in order to hit net-zero emissions by 2050. That amount of the gas is equivalent to what is produced by 185 million barrels of oil; it weighs nearly 15 times as much as the Great Pyramid of Giza.

This is a huge step up from where we are now. Today, there are 18 direct air capture pilot plants in operation globally, collectively sucking up just 0.01 Mt of CO₂ per year. The biggest of these is run by Swiss company Climeworks in Iceland: its Orca facility can soak up 4000 tonnes per year. A much larger effort is under way in Texas. The company 1PointFive broke ground in April 2023 for an industrial plant called Stratos, which aims to extract 500,000 tonnes of CO₂ from the air per year starting in 2025.

A handful of megatonne-scale plants are on the drawing board, but the pace needs to be dramatically accelerated. To reach our goal of 80 Mt per year by 2030, we would need to build about 10 such plants a year, starting now. That is epic, but viable. “It’s technologically feasible,” says Katie Lebling, an environmental analyst at the World Resources Institute in Washington DC.

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How do we get there? Firstly, by improving the technology. For now, most direct air capture uses one of two main strategies. One soaks up CO₂ into a solid sorbent material and uses low pressure to pull the concentrated CO₂ out. That requires a lot of energy, says the IEA. (This is what the Orca facility does, using geothermal energy.) The other strategy, as followed by Stratos, for example, soaks up CO₂ into a liquid and then pulls it into limestone pellets that are heated at very high temperatures to release the CO₂. This process uses more water and typically burns fossil fuels to get the necessary heat.

Water and energy are big issues. In 2022, the IEA estimated that building and operating enough direct air capture plants to hit the 2050 target could require 50 gigatonnes of water per year – about 1 per cent of current global water use – and 6 exajoules (or 6 billion billion joules) of energy per year, which is also 1 per cent of current global use. Powering that with solar panels would require 23,000 square kilometres of land, which is perhaps another argument for putting the panels off-world (see “Launch a solar power station into space”, page 37).

All this means that cost is a problem too, so we will need the right mix of policy incentives to get direct air capture going at scale. The good news, though, is that the plants can be built pretty much anywhere and relatively quickly. By 2050, with an investment boost, we could have dozens of 1-Mt-scale plants whirring away around the world. Nicola Jones