Tech & Innovation Climate Impact
© ESA–P. Carril, 2013 – EarthCARE
Can we cool the Earth with an artificial veil of aerosols high in the atmosphere? The European, Japanese satellite mission EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) should shed light on this.
Text: Tomas van Dijk
For a long time, climate engineering sounded like science fiction. But, in recent years, it has increasingly been the subject of serious research. So, what is TU Delft doing in this field and how ethical is it to adjust the Earth’s thermostat using technical tricks?
If we fail to sufficiently reduce greenhouse gas emissions, we could possibly cool the Earth artificially as a last resort. There are plenty of ideas for using technology to control the climate, each one crazier than the last.
How about screens that open up in space, reflecting back solar radiation? Artificial clouds containing sulphur particles that cool down the earth are also being considered. Then there is the idea of applying electric current to seawater, causing bubbles of CO₂ that can be captured, after which the oceans
draw more CO₂ from the atmosphere because of diffusion (through the recovery of concentrations of gas particles).
There are broadly two categories of climate engineering. Techniques that focus on removing CO₂ from the atmosphere and technologies that hold back some of the radiation from the sun. Research is being conducted into both at TU Delft. (See boxes). These are currently relatively small projects, with limited budgets and deployment of staff. But climate engineering research is set to gain momentum in Delft in the years ahead.
The earth absorbs a part of the incoming solar energy and let a part flow again. Clouds play a double role: they reflect incoming sunlight, but function at the same time as blanket that retains heat. (Image: via Prof. Herman Russchenberg)
© Pixabay Natalia Kollegova
The effect of ice crystals in the atmosphere can sometimes also be seen with the naked eye. When sunlight through a thin mist of ice crystals shines, leads that to spectacular light phenomena: so-called halos.
First fulltime researcher
In the Faculty of Civil Engineering and Geosciences, there will soon be an assistant professor in Radiation Management for Climate Engineering. This will be the first senior researcher at TU Delft to focus completely on the issue of whether global warming can be halted by using technical interventions to curb solar radiation. These could include aerosol injection in the stratosphere, using ice-forming dust particles to thin out cirrus clouds, placing mirrors in space and strengthening clouds by spraying sea salt into them.
Controversial
The new Delft colleague certainly has their work cut out. All of this research is controversial. Dozens of climate scientists and public administration experts recently organised a petition calling for a ban on solar climate engineering.
The risks of it are poorly understood and can never be fully known, according to researchers from the Copernicus Institute of Sustainable Development at Utrecht University, who initiated the petition. The group called on academics, civil organisations and concerned individuals to sign an open letter to governments, the United Nations and other organisations to halt the development and potential use of solar climate engineering on a global scale. The initiative was prompted by an academic article published earlier this year in WIREs Climate Change.
According to the initiators, international institutions are incapable of properly regulating the worldwide use of this technology. If just a select group of countries turn to these methods, it could have a negative impact on other countries, they claim, since one country’s climate has an effect on the climate in neighbouring countries. The research would also slow down the current global climate strategy focusing on emission reduction.
Reversible
“These are all justified concerns that I completely share”, says Behnam Taebi, professor of Energy and Climate Ethics. “We need to focus totally on mitigation (emission reduction). And I hope that we will never use solar climate engineering.”
But Taebi vehemently opposes a ban. “We need to research these techniques precisely because of the risks. Climate change is affecting some parts of the Earth more than others. Parts of India were recently so hot that the tarmac began to melt.
If we find ourselves needing to reduce the temperature in certain places in the future, we will benefit by having studied the underlying physics, ethics and political Waspects in advance”, he argues.
“We need to investigate whether the techniques can be used in a way that’s reversible. If the risks are unacceptable after application, it needs to be possible to reverse the effects. That’s an important ethical criterion. We also need to keep emphasising that mitigation is what matters most.”
© Vliegtuig: Springer Nature Ruimte: Elen11
For the aerosols to have an effect, you have to
apply them at 20 kilometers altitude
with special aircraft.
A VEIL OF AEROSOLS
‘A specialised delivery system for stratospheric sulphate aerosols’. That is the title of the article by Martin Janssens from the Geoscience & Remote Sensing department and TU Delft alumna Iris de Vries (now based at ETH Zurich) published in the journal Climatic Change in 2020. “Our idea was to investigate how you could spray small droplets (aerosols) containing sulphur compounds into the stratosphere”, explains De Vries. “A volcanic eruption releases similar particles into the upper layers of the atmosphere, cooling the planet. One thing we looked at was how you get the aerosols out there. You need aircraft that can fly at a height of 20 km. That’s a challenge – at that altitude, the air is very thin. You need aircraft with huge wing surfaces.” Further research will aim to show how the aerosols behave. What chemical reactions could they have with other particles high in the atmosphere? Equally important, will the climate benefit be completely nullified by the emissions from the aircraft flying to and fro to create the veil?
© 3DSculptor
SOLAR SHIELD
IN SPACE
A membrane the size of the European continent. Jeannette Heiligers, assistant professor of Astrodyamics & Space Missions, is working with colleagues from about ten other universities to study whether it is possible to combat global warming by positioning a huge solar shield (ten million km² in size) in space. The idea involves sending a fleet of small satellites into space which all then open up a sail and together they form a blanket that reduces sunshine on earth by two per cent.
Heiligers is calculating the optimum position in space. “To reduce sunlight by two percent, the solar shield only needs to cast a shadow on part of the globe”, she recently told TU Delft Stories. “We have a location in space in mind that seems perfect for this purpose – the L1 Lagrangian Point. This point is located between the Earth and the Sun at approximately 1.5 million kilometres from the Earth. At that point the forces acting on a satellite or other object are such that it remains stationary in relation to the Earth.”
Giant shade cloth are a suggested option to cool the Earth.
© NASA
Colour in the debate
During his inaugural address on 29 April, entitled ‘Battling Climate Dystopia with Engineering? A view from Ethics’, the professor advocated more nuance in the debate. Taebi notices a tendency to reduce discussions about ethics and technology to for or against. “It’s often so black and white. I’d like to see more colour in the debate about the ethics of this technology. The same happens with debates about nuclear energy.
The fact that there are different types of nuclear energy often gets forgotten.” The effects of climate engineering are uncertain, agrees Herman Russchenberg, professor of Atmospheric Remote Sensing, in whose group the new Assistant Professor in Radiation Management for Climate Engineering will be working. “I’m certainly not calling for people to start combating warming with aerosols immediately.
We need to explore the technologies in order to make a carefully-considered decision as to whether we wish to apply such measures. There are significant margins of uncertainty around the climate models. If we end up facing higher temperatures in 2050 than we expect, it would be nice if there is still something we can do. That said, it would of course be a major error not to focus primarily on reducing CO₂ emissions.”
You can also store carbon dioxide in rock formations, deep in the sea, or in biomass by growing extra crops in deserts or algae in the sea. (Image via Herman Russchenberg)
LIMESTONE FROM THE OCEANS
It works quite nicely in the lab. Adjust the acidity of a solution and you can use the CO2 in it to make calcium and magnesium carbonate, in other words: limestone. This method could be used to remove carbon dioxide from the atmosphere. But we are already able to remove CO2 from flue gases, so why not pursue that method? “That could tackle barely half of all CO2 emissions”, says David Vermaas, associate professor in Electrochemical Systems. “The challenge for the future involves developing technology to compensate for the other half, and capturing CO2 from seawater is one solution for that. There is 150 times as much CO2 in a litre of water than in a litre of air.” The oceans form a great buffer, absorbing large quantities of CO2 from the air. If you reduce the concentration in the oceans, they will absorb even more carbon dioxide from the air. The idea is to adapt existing desalination plants, so that in the future they can also remove CO2 from seawater. An additional benefit is that this technique prevents lime scale deposits in the desalination plants.
You need electrochemical cells that make acids and bases. But there are numerous variations on the theme. Vermaas and his research group worked with engineering firms Wetsus and Caltech on an analysis and comparison of the methods. The findings were recently published in Energy & Environmental Science: ‘Electrochemical carbon dioxide capture to close the carbon cycle’. Vermaas and his team are even working on a technique in which a current is applied to a membrane underwater. Water molecules break down into acidic H+– and basic (alkaline) OH–-particles. “Placing a membrane between the acidic and basic parts initiates two chemical reactions. Carbon dioxide is formed in the acidic part – the bubbles in a fizzy drink. This gradually bubbles out of the water and can be captured. In the basic part, chemicals such as calcium and magnesium carbonate form. You use that to draw CO2 from the water and indirectly from the air, in order to combat climate change.”
© ESA/Planetary Visions