A stratospheric aerosol injection (SAI) program to cut global warming could be remarkably inexpensive, costing about $1.75 billion a year over a 15-year period, claims a new study by scientists from the Harvard University.
So far, SAI is an unverified, hypothetical technology; if implemented in the near future, it would involve use of big cannons, hoses or special types of aircraft to spray huge quantities of sulphate particles into stratosphere - the upper layer of the atmosphere.
These particles would serve as a reflective barrier against the sunlight to reduce the amount of heat trapped in the atmosphere. Scientists believe the technology could help solve the problem of global warming to some extent.
The new study by Harvard University scientists suggests that the total costs to start a SAI program 15 years from now would be £2.7 billion, although the average operating cost for running the program over a period of 15 years would be approximately £1.75 billion a year.
"While we don't make any judgement about the desirability of SAI, we do show that a hypothetical deployment program starting 15 years from now, while both highly uncertain and ambitious, would be technically possible strictly from an engineering perspective," said Dr. Gernot Wagner, from Harvard University's John A. Paulson School of Engineering and Applied Sciences.
"It would also be remarkably inexpensive, at an average of around £1.55 to 1.95 billion (US$2 to 2.5 billion) per year over the first 15 years."
According to researchers, no existing aircraft - even with wide-ranging upgrades in their design - would be able to fulfill the mission. It would require new, purpose-built aircrafts with capabilities to carry substantial payload to high altitudes.
The team has developed the specifications for a plane dubbed 'SAI Lofter' (SAIL). The plane would have the same weight as a large narrow body passenger aircraft but will require about double the wing area, four engines to sustain a level flight at altitudes of 20 kilometres, and a narrow fuselage to accommodate a dense mass of molten sulphur.
The total costs for developing the airframe for SAIL is estimated to be less than £1.55 billion. An extra £275 million would be required for the modification of existing low-bypass engines. About 100 such planes would be needed over a period of 15 years, completing about 4,000 flights in the first year and then increasing to nearly 60,000 by 15th year.
"Given the potential benefits of halving average projected increases in radiative forcing from a particular date onward, these numbers invoke the 'incredible economics' of solar geoengineering," said Dr. Wagner.
"Dozens of countries could fund such a program, and the required technology is not particularly exotic," he added.
The findings of the study are published in the journal Environmental Research Letters.
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