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