Particle injection could abate climate change

The team involved with the SPICE (Stratospheric Particle Injection for Climate Engineering) project has received £1.6m from the EPSRC to test the feasibility of constructing what some in the research community have refered to as a ‘garden hose to the sky’.

Principal investigator, Bristol University’s Matt Watson explained that the idea is inspired by volcanoes and the way they can affect the climate after eruptions.

An extreme example took place in 1815 when a volcanic eruption on the Indonesian island of Sumbawa led to 1816 being known as the ‘year without summer’. The eruption from the volcano Tambora spewed out 400 million tons of sulphur-rich gas that spread worldwide, blocking sunlight and lowering temperatures.

Watson said the SPICE project isn’t looking to recreate a Tambora, but it will be relying on the same principle of using stratospheric particles to refract light and cool the Earth.

Their work will begin at the Rutherford Appleton Laboratory in Oxford, where the researchers will use lasers and molecular spectroscopy to choose the particles they want to use. According to Watson, the team is drawn to the use of sulphate because of its particular ‘shininess’ to visible light. However, the team will trial other particles including clays, salts and mineral oxides.

Whatever they choose, Watson said, won’t matter unless they can get it into the stratosphere.

The current proposal sees the construction of a 20km Kevlar pipe tethered by one or more balloons. Cambridge University’s Hugh Hunt, who is leading the delivery systems portion of the project, will address the engineering challenges inherent in such an ambitious idea.

Hunt and his team of PhD students will address material-science questions ranging from how the pipe will be manufactured to how it will withstand the extreme stresses and pressures when in use. 

Watson said the team will be especially concerned with how the pipe and tethered balloon or balloons will behave in different types of weather systems.

‘If you’re going to loft a helium balloon to 20km you’d need have to have a very good handle on what the wind is doing at these elevations.’

Watson said the base of the pipe will have to be especially reinforced because it will be subjected to pressures of about 6,000 bar as the stratospheric particles are pumped through. The tethered balloons will equally need to be capable of resisting pulling forces. 

The location for the deployment of the tethered pipes has yet to be considered. Former Microsoft chief technology officer Nathan Myhrvold, who is co-founder of Intellectual Ventures in the US and leading a similar project to SPICE dubbed ‘Garden Hose to the Sky’, has suggested that the enormous sulphur-pumping pipes should be placed near the North and South poles.

Watson said he is unsure whether the North and South poles are the right locations and is relying on his co-investigator Lesley Gray, a meteorologist at Reading University, to model where the best places in the world would be to inject their specific particles and the amount to introduce into the stratosphere.

Public opinion

The idea of pumping sulphur or other particulates into the Earth’s stratosphere is to be put to the public in a sister project organised by the EPSRC.

That project − Integrated Assessment of Geoengineering Proposals (IAGP) − has received £1.7m to increase public awareness of the benefits and potential drawbacks of geoengineering projects such as SPICE.

Principal investigator Piers Forster, a professor of physical climate change at Leeds University, said the public might be wary of what they perceive as ‘hardcore artificial interference’ with nature.

‘I think we’ve definitely learnt our lesson from the debate over genetically modified food − that it is really important to inform the public from the beginning and to be as transparent and open as possible about what we’re doing with this work,’ he said.

Watson said public opinion will influence the direction of the SPICE project. Initially, the project researchers will restrict their ideas to computer modelling, but their eventual goal of a 1km tethered pipe demonstrator may be impeded by the EPSRC if the IAGP team is confronted with significant public disapproval. 

‘The research councils are still considering the possibility of being exposed to some sort of reputational risk,’ he said. 

One thing is clear though, Watson said, and that is no one is endorsing the SPICE solution as a ‘get out of jail free card’ to carbon emitters.

‘It’s a Plan D,’ he said. ‘It’s essentially an insurance policy for the situation where we hit a tipping point in climate change quickly.’