Is it possible to design our way out of the climate change crisis we have created? As we enter the anthropocene era, in which human activity is shaping the earth more than natural forces, the opportunity to redesign the planet to fix the problems we have created, becomes more tempting.
The field of applying engineering to alter ecosystems is termed, Geoengineering. It is ‘the deliberate large-scale intervention in the Earth’s natural systems to counteract climate change’. Also known as climate engineering, geoengineering could offer a more viable solution to climate change than modifying human behaviour, especially as many reports believe we are almost at the deadline to do this.
Instead, geoengineering provides a ‘plan B’. Indeed, the United Nations' Intergovernmental Panel on Climate Change (IPCC) report highlighted geoengineering as a crucial strategy if temperature rises can't be held at a manageable level.
Although there are many activities within this field, geoengineering can be generally split between two areas; carbon-dioxide removal (CDR) and solar radiation management (SRM). CDR goes to the root of global warming by removing greenhouse gases from the atmosphere through carbon capture and storage. Whereas SRM focuses on offsetting the impact of greenhouse gases by reflecting sunlight away from the earth. Whilst it is not a method of preventing emissions, it potentially holds a place alongside the reduction in emissions as a way of supporting the overall climate change initiative.
"If mitigation efforts do not keep global mean temperature below 1.5 degrees Celsius, SRM (solar radiation modification) can potentially reduce the climate impacts of a temporary temperature overshoot," says the IPCC report.
The IPCC has explored a number of proposed geoengineering solutions and here’s what they think:
- Carbon dioxide removal (CDR)
CDR include various techniques for removing carbon dioxide (CO2) from the atmosphere in order to reduce global warming. The most established of these processes is bioenergy with carbon capture and storage (BECCS), which involves burning biomass for energy, and capturing and storing the emissions underground. Other forms of CDR include direct air carbon dioxide capture and storage (DACCS). This method was used in a project by ClimeWorks to build a groundbreaking plant in Switzerland where carbon dioxide is sucked from the air before being resold. The plant is capable of removing 900 tonnes of carbon dioxide (CO2) from the air annually, which is then supplied as a raw material to customers in different markets, including to a nearby vegetable farm, where it is used as fertiliser. The CO2 can also be used to make carbonated drinks and carbon-neutral fuels. Other types of CDR include afforestation and ocean fertilisation, where added nutrients cause CO2 to be trapped in the deep ocean.
- Stratospheric aerosol injection (SAI)
SAI is a type of solar radiation management (SRM). Although it does not address the cause of global warming, or reduce greenhouse gases, SAI masks it or offsets the effects by pumping gases into the stratosphere to reflect some of the sun's heat, mimicking a natural effect that happens during a strong volcanic eruption. Whilst the IPCC agree that SAI could work to limit warming to below 1.5 degrees celsius, and the technology exists to carry out the task, the scale of SAI required to have this impact makes its governance difficult. For instance, whilst the gas is released in one country to block the sun’s ray, it can trigger rain and extreme weather across borders. The problem with this solution hinges on the safety aspects. It is untested and therefore there is no confirmation of what would happen when the SAI is discontinued. Critics argue that the atmosphere would suffer a "termination shock" which in turn would cause a spike in temperatures that could exacerbate the effects of climate change on the Earth’s surface. In essence, it is a short-term fix.
- Marine cloud brightening (MCB)
Marine Cloud Brightening (MCB) uses deign to reflect sunlight away from the earth. For instance, it could use sea salt or other particles sprayed into marine clouds to make them thicker and more reflective. Whilst the IPCC says MCB has potential to lower temperatures on a regional level, this too is an untested solution that could have longer term consequences for the atmosphere and ground below.
- Cirrus cloud thinning (CCT)
CCT is the opposite of marine cloud brightening. Cirrus clouds float at high-altitude and as they are thin and whispy, they do not reflect much solar radiation back into space. Instead, they trap long-wave radiation on Earth. CCT proposes thinning them further through cloud seeding, letting more long-wave radiation escape to cool the temperature below. This is such a new concept that very little is known about its potential benefits or risks.
- Ground-based albedo modification (GBAM)
The word ‘albedo’ refers to how much solar radiation Earth reflects from the surface. It may be possible to modifying Earth's albedo from the ground using architectural measures such as whitening roofs and differing approaches to land-use management such as covering glaciers or deserts with reflective sheeting.
Whilst the IPCC concludes that GBAM has real potential to lower temperatures — it is a regional as opposed to a global solution. But as it does not interfere with the biological composition of the Earth’s surface, it is deemed safer than other forms of CDR.