Geoengineering is a term that describes how humans could intervene in the functions of the Earth in order to slow or reverse climate change.
Currently, there are two main ideas for combating global warming: reducing the Earth's exposure to the sun, or reducing the amount of carbon dioxide in the air.
Reducing the Earth's exposure to the sun
The idea is to cool the planet by reducing the amount of solar energy it absorbs. To achieve this, an astronomical number of reflector panels would have to be deployed in orbit around our planet, thus limiting the amount of solar energy captured by the Earth.
Another proposed approach is to inject aerosols into the stratosphere and mimic the effect of explosive volcanic eruptions, such as that of Mount Pinatubo in 1991. This eruption released nearly 10 cubic kilometres of particles into the stratosphere, scattering sunlight into space. The effect was such that over the next 15 months there was a general cooling of the planet by approximately 1°C, not to mention the climatic disruption associated with the eruption.
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Capturing CO2 from the air
In order to limit global warming, a second idea is to capture carbon dioxide (CO2) from the air and thus reduce its accumulation in the Earth's atmosphere. Proposals for carbon geo-engineering suggest that CO2 can be removed from the atmosphere through a combination of biological and mechanical methods on a global scale. Massive tree planting is the best known example.
Another approach has also been proposed to reduce the CO2 in the air. This would require machines capable of capturing and storing the carbon dioxide in the atmosphere. This innovative idea was taken up and deployed by the Swiss start-up Climworks. In 2021, its project removed 4,000 tonnes of CO2 from the atmosphere after sucking it out and petrifying it in the earth's rock.
The consequences of geoengineering
Geoengineering involves significant risks and uncertainties, as intervening in a complex system can lead to sometimes unexpected results.
While the benefits can be measured on a global scale, the impacts could vary considerably on a local scale and not benefit certain regions. For example, changes in global precipitation levels could lead to local droughts.
The economic cost of these ideas can also be questioned: some of them seem to have a huge cost if they are to be made efficient.