23-Nov-2018: Scientists weigh up stratospheric sunlight barrier to curb warming

Spraying sun-dimming chemicals high above the Earth to slow global warming could be “remarkably inexpensive”, costing about $2.25 billion a year over a 15-year period. Some researchers say the geo-engineering technique known as stratospheric aerosol injection (SAI) could limit rising temperatures that are causing climate change.

As yet unproven and hypothetical, it would involve the use of huge hoses, cannons or specially designed aircraft to spray large quantities of sulphate particles into the upper layer of the atmosphere to act as a reflective barrier against sunlight.

Total costs to launch a hypothetical SAI effort 15 years from now would be $3.5 billion, scientists at Harvard University said in a report published in the journal Environmental Research Letters, adding that average annual operating costs would be about $2.25 billion a year over 15 years.

Discounting other methods of deployment because of cost and feasibility, the research assumes a special aircraft can be designed to fly at an altitude of about 20 km and carry a load of 25 tonnes.

After direct input from several aerospace and engine companies, the scientists said they have developed a design that could be suitable and could be ready to be deployed in 15 years, aiming to cut the rate of temperature change in half. The scientists emphasised that this is merely a hypothetical scenario.

There are risks to such unproven potential technologies. Scientists have said SAI could result in negative consequences such as causing droughts or extreme weather in other parts of the world, harm crop yields as well as potential public health and governance issues.

It also does not address the issue of rising carbon dioxide emissions, the main greenhouse gas blamed for global warming.