Climate change is a problem in desperate need of a solution. According to the authoritative Carbon Action Tracker, even if all nations honour their pledges to cut their greenhouse gas emissions, the globe will still warm by around 3.2°C by 2100 – with catastrophic consequences for humanity and the animal kingdom.
If cutting greenhouse gas emissions isn’t enough, is it time for a plan B? Recent times have seen a surge of interest in geoengineering: China has recently embarked on a substantial research plan, while in the US, Prof David Keith of Harvard University is planning to launch a high-altitude balloon this year to test the feasibility of spraying reflective particles into the stratosphere. Meanwhile, other researchers are looking at the possibility of increasing the brightness of marine clouds to reflect more sunlight back into space.
But there are a number of risks, and not just because we’re unsure about how effective these interventions would be. There are fears that one country’s efforts to solve its climate problem could inadvertently mess up the weather elsewhere, creating a new source of political tension. And ultimately, this leads to a worrying question: could we be looking at the dawn of a new kind of war – one fuelled by a battle for dominance over our planet’s climate system?
The problem with geoengineering
Geoengineering is defined as a deliberate, large-scale intervention in the climate system, and schemes come in two varieties. The first type aims to remove carbon dioxide from the atmosphere. This can be done by capturing it from the air using natural or artificial means; making biochar (a type of charcoal) from vegetation waste; or adding lime to the oceans to reduce their acidity and therefore maintain their ability to absorb carbon dioxide from the atmosphere. The greatest hurdle for these schemes lies in finding somewhere to permanently store the huge quantities of carbon. The deep ocean offers one possible solution, but we’re still a long way from a feasible method of doing this.
The second kind of geoengineering scheme is known as solar radiation management or albedo modification. These techniques look to reflect a small amount of sunlight away from the planet to reduce warming. Some of these proposals are relatively benign, but also pretty ineffective. The technology receiving most attention – and the one most likely to be deployed because it’s cheap and feasible – is known as sulphate aerosol spraying.
The idea is to spray sulphur dioxide or sulphuric acid into the stratosphere or upper atmosphere to form tiny particles that reflect an extra 1 to 3 per cent of incoming solar radiation back into space, thereby cooling the planet in the way that large volcanic eruptions are known to do.
In effect, humans would be installing a radiative shield between the Earth and the Sun: one that could be adjusted by those who control it to regulate the temperature of the planet. The models indicate that if we reduced the amount of sunlight reaching the planet, the Earth would cool fairly…
This is an extract from issue 320 of BBC Focus magazine.
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