Shading the Earth could combat global warming: study

Transporting materials into the stratosphere that can reduce the amount of sunlight hitting the Earth could lower the effects of global climate change, a new study has found.

Researchers from the US found that the basic technology to transport solar geoengineering materials in the atmosphere currently exists and could be assembled and implemented in a number of different forms for less than USD 5 billion a year.
Put into context, the cost of reducing carbon dioxide emissions is currently estimated as roughly USD 200 to 2000 billion.

Currently, a technique of geoengineering called Solar radiation management seeks to reflect sunlight and thus reduce global warming.

It creates stratospheric sulfur aerosols but the study found that it was not a preferred strategy as reducing incident sunlight does nothing at all to reduce greenhouse gas concentrations in the atmosphere.

It also did not address the issue of oceans acidification.
The researchers noted that other research has shown that the effects of solar radiation management are not uniform, and would cause different temperature and precipitation changes in different countries.

"As economists are beginning to explore the role of several types of geoengineering, it is important that a cost analysis of SRM is carried out. The basic feasibility of SRM with current technology is still being disputed and some political scientists and policy makers are concerned about unilateral action," co-author of the study, Professor Jay Apt, said in a statement.

In the study, the researchers, from Aurora Flight Sciences, Harvard University and Carnegie Mellon University, performed an engineering cost analysis on six systems capable of delivering 1-5 million metric tonnes of material to altitudes of 18-30 km.
It included an 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.

Based on existing research into solar radiation management, the researchers performed their cost analyses for systems that could deliver around one million tonnes of aerosols each year at an altitude between 18 and 25 km and between a latitude range of 30°N and 30°S.

The study concluded that using aircraft is easily within the current capabilities of aerospace engineering, manufacturing and operations.

The development of new, specialised aircraft appeared to be the cheapest option, with costs of around USD 1 to USD 2 billion a year; existing aircraft would be more expensive as they are not optimised for high altitudes and would need considerable and expensive modifications to do so.

The study was published in journal Environmental Research Letters.