Geoengineering is the subject of conspiracy theories, but can it help save the planet?
- author, Simon King
- role Leading weather anchor
If we can’t control rising global temperatures by drastically reducing carbon emissions, could something called geoengineering be a way to cool the planet?
In what is already a £103 billion ($135 billion) industry, scientists around the world, including in the UK, are exploring geoengineering – ways to manipulate the climate to tackle global warming.
Some experts are concerned that there are too many risks associated with it, fearing that it could mess with global climate patterns or actually warm some regions rather than cool them.
As the industry grew, so did the conspiracy theories. BBC Weather has seen a large increase in social media comments around geoengineering since January, accusing us of covering up secret projects and incorrectly blaming geoengineering for the cool and wet weather we’ve had recently. Globally, there have been twice as many mentions of geoengineering this year on X, formerly known as Twitter, as there were in the last six months of 2023.
Some geoengineering ideas include reflecting sunlight back into space to cool the Earth. The most advanced area of geoengineering is the direct capture of carbon dioxide from the air, with small facilities in operation in Europe, the US and Canada. They currently remove around 10,000 tonnes of carbon dioxide a year (a third of London’s annual emissions), meaning a massive increase would be needed to make any difference to the estimated 35 billion tonnes we emit globally.
“We need to start thinking about other things we can do to limit further warming,” said Professor Liz Bentley, chief executive of the Royal Meteorological Society. “This is where geoengineering starts to become an interesting discussion.”
Beyond fears of exacerbating the effects of climate change, some experts worry that it’s tempting to see geoengineering as a quick fix that could also distract us from efforts to reduce carbon emissions.
Less strange than it seems
It sounds like science fiction, but the idea of reflected solar radiation, the technical term for sunlight, isn’t as crazy as it might sound and sometimes happens in the natural world. During volcanic eruptions, huge amounts of ash and aerosols – tiny particles – can be transported into the upper atmosphere, which can then reflect solar radiation back into space.
image source, Getty Images
The eruption of Mount Pinatubo in the Philippines in 1991 caused the average global temperature to cool by 0.5C over the next few years.
So can we really copy a volcano to cool our planet?
Professor Jim Heywood, an atmospheric scientist at the University of Exeter, is urging caution. “I really want to know about the detrimental impacts of climate change, but also the potential side effects and detrimental impacts of any deployments to manage solar radiation,” he said.
The researchers studied two types of solar radiation management: marine cloud brightening and stratospheric aerosol injection.
Marine cloud brightening involves spraying very fine salt water from a boat onto low-level clouds over the ocean to improve their brightness and reflectivity.
Modeling showed that if you spray a large area – about 4% of the ocean – near the equator and light up the clouds, the combination of more clouds and therefore lower sea surface temperature underneath could have a global impact.
Our atmosphere is complex, has no boundaries, and behaves like a liquid. You may have come across the ‘butterfly effect’, where if a butterfly flaps its wings in Mexico, it can bring rain to the UK. While that’s a big leap in reality, it highlights how time is connected around the world.
“Cloud brightening off the coast of Namibia could cause drought over South America and especially Brazil.” What’s in Brazil? Well, the rainforest,” Prof Heywood said.
In this case, due to the complex atmospheric and oceanic circulations, the increase in cloud brightness would cool the sea surface in the eastern South Atlantic, meaning that the precipitation pattern would be negatively perturbed across the South Atlantic to South America. Drought in the Amazon rainforest – often called the “lungs of the planet” because they absorb carbon dioxide – can cause significant damage.
While there is a focus on using marine cloud brightening to offset global temperature rise, some see an opportunity to use it on a much smaller scale.
Following the 2016 mass coral bleaching in the Great Barrier Reef, scientists at Southern Cross University in Australia are conducting cloud-lightening trials to protect and cool very coral-rich areas of the reef to prevent bleaching during sea heat waves.
image source, Southern Cross University
“Although we are in the early stages of understanding how marine cloud brightening can be applied over the Great Barrier Reef, we have made great scientific progress.
“We have greatly increased our confidence that the clouds over the reef can be illuminated,” said Professor Daniel Harrison, project leader from Southern Cross University.
Development of stratospheric technologies
The technology to perform small-scale marine cloud brightening with fans and sprinklers already exists, but the other method of solar radiation management — stratospheric aerosol injection — will need more progress to have the desired impact.
This method of geoengineering involves artificially adding aerosols such as sulfate to the stratosphere, which extends from 6-12 miles (10-20 km) to 31 miles (50 km) above the Earth. These aerosols would reflect some of the sun’s radiation, reducing the amount reaching our planet’s surface and theoretically causing global cooling.
image source, Getty Images
It is not certain how much aerosol can be injected into the stratosphere, but one proposal is planes capable of flying at an altitude of 11 miles (18 km) – about 1.5 times higher than commercial aircraft can.
Millions of tons of sulfur dioxide would have to be injected to have any impact. For example, during the eruption of Mount Pinatubo, the resulting half degree of global cooling resulted from about 15 million tons of sulfur dioxide injected into the stratosphere.
Because sulfate aerosols last only a few years in the atmosphere compared to the decades that carbon dioxide lasts, stratospheric aerosol injection is considered only a short-term method.
That hasn’t stopped one company in the US from starting to sell “cooling credits”. For a fee, they will send a balloon filled with sulfur dioxide into the stratosphere, where it will burst and release the gas.
image source, Getty Images
They estimate that one of their cooling credits – two grams of sulfur dioxide – will “offset one tonne of carbon dioxide warming in one year”. That’s the equivalent of a single-passenger return flight between Paris and New York, meaning a lot of balloons would have to be released to have any cooling effect.
As with marine cloud brightening, there are risks with stratospheric aerosol injection. In a study earlier this year, computer modeling found that stratospheric aerosol injection could cause strong warming 15 km above the tropics, which would alter large-scale weather patterns, warming the polar regions and altering rainfall patterns over land.
“The regional impacts are very unknown,” Prof Bentley said. “We may be able to moderate the average global temperature.” [rise]but we may actually make things worse in certain regions of the world.”
Hazard warnings
This brings us to fundamental questions about the reliability and risks associated with this type of intervention. In 2022, hundreds of scientists signed an open letter calling for a global agreement not to use solar radiation management.
They said the growing calls for development provided “cause for concern” with the dangers being “poorly understood” and something that would deter governments, businesses and societies from decarbonising.
The group worries that even doing theoretical research will lead to real-world experiments without fully knowing the drawbacks. But other scientists believe that the risk of further research into solar radiation management is less than the risk of relying solely on decarbonisation.
In addition, some say misinformation and conspiracies keep them from doing research.
Dr Ramit Debnath, an assistant professor at the University of Cambridge, says “many funders are very skeptical about funding research” because they fear being targeted by conspirators. He analyzed almost 2 million tweets with the hashtag #GeoEngineering and found that over 70% expressed negative sentiments about solar radiation management, with the majority touching on conspiracies.
image source, Getty Images
One of these has to do with “chemtrails,” a widely debunked conspiracy theory about an alleged secret plot to spray people with dangerous chemicals, suggesting that the white streaks in the sky that come out of the back of airplanes are evidence of it. These are actually trails of condensed water vapor—known as contrails—that come from airplane jet engines.
The opposite tracks at this height actually absorb solar radiation and warm the planet and therefore have nothing to do with the geoengineering techniques currently being explored.
Dr Debnath says that by talking about solar radiation management on social media, he has been accused of “trying to kill people and control people’s lives”.
Solar radiation management is treated with caution – the UK government has not implemented the techniques and “has no plans to do so”. However, they invest.
The Natural Environment Research Council has invited applications for a £10.5 million fund to “provide a ‘risk-risk analysis'” to assess whether the negative impacts of the technique outweigh the damage that would be caused from climate change.
“It’s not a silver bullet that will solve everything,” Prof Bentley said. “But it’s possible that it’s part of a set of solutions.”
InDepth is the new home for the best analysis from BBC News. Tell us what you think.
BBC InDepth is the new website and app home for the best analysis and expertise from our top journalists. Under a distinctive new brand, we’ll bring you fresh, thought-provoking perspectives and in-depth reporting on the biggest issues to help you make sense of a complex world. And we’ll be showcasing thought-provoking content from BBC Sounds and iPlayer too. We’re starting small, but we’re thinking big and we want to know what you think – you can send us your feedback by clicking the button below.
