Geoengineering 'feasible and affordable'
Injecting material into the stratosphere to reduce global warming may or may not be a good idea - but it is both possible and cost-effective, according to a thorough cost analysis.
The basic technology currently exists, says the team, and could be put into practice in several different ways for less than $5 billion a year - a fraction of the $200 billion to $2,000 billion that reducing carbon dioxide emissions is estimated to cost.
"As economists are beginning to explore the role of several types of geoengineering, it is important that a cost analysis of [solar radiation management] SRM is carried out," says professor Jay Apt of Carnegie Mellon University.
"The basic feasibility of SRM with current technology is still being disputed, and some political scientists and policy makers are concerned about unilateral action."
The researchers carried out an engineering cost analysis on six systems capable of delivering between one and five million metric tonnes of material to altitudes of 18 to 30km.
These were existing aircraft, a new airplane designed to perform at altitudes up to 30 km, a new hybrid airship, rockets, guns and suspended pipes carrying gas or slurry to inject the particles into the atmosphere.
And they concluded that using aircraft is perfectly possible, with the development of new, specialized aircraft looking like the cheapest option, at around $1 to $2 billion a year.
Existing aircraft would be more expensive as they're not optimized for high altitudes, and using guns and rockets would cost even more.
The cheapest option - although it's completely theoretical right now - is a large gas pipe, rising to 20 km in the sky and suspended by helium-filled floating platforms. But this system carries a lot of uncertainty, says the team.
"We hope our study will help other scientists looking at more novel methods for dispersing particles and help them to explore methods with increased efficiency and reduced environmental risk," says Apt.