A promising but highly controversial technique called "stratospheric aerosol injection (SAI)" has a better than even chance of slashing the rate of global warming by up to 50 percent and cooling down the climate.
This solution was proposed in a study authored by researchers from Yale and Harvard published recently in Environmental Research Letters, a peer-reviewed, open access international scientific journal covering research in all aspects of environmental science.
Re-engineering or cooling down Earth's atmosphere to reverse the trend of rising global temperatures has long been seen as a potential solution to catastrophic global climate change. SAI might take up to 15 years to complete, however.
In SAI, reflective sulfites that reflect sunlight back into the cosmos will be scattered in the stratosphere, which is located 20 kilometers above the surface of the Earth. If successful, this massive seeding will prevent solar energy from adding to our steadily warming planet. The end result will be an eventual reduction in climate change
Dr. Gernot Wagner from Harvard University's School of Engineering and Applied Sciences and co-author of the study wrote that these numbers invoke the incredible economics of solar geoengineering given the potential benefits of halving average projected increases in radiative forcing from a particular date.
He said dozens of countries could fund such a program, and the required technology is not particularly exotic or expensive. The study proposes using a high-altitude aircraft, balloons or large caliber cannons to scatter the sulfites in the stratosphere.
It focuses on the hypothetical practicalities of this large-scale project beginning 15 years from now. The project's aim will be to halve the projected increase in man-made temperature rises, a process is also known as anthropogenic radiative forcing.
Dr. Wagner said solar geoengineering is often described as fast, cheap, and imperfect. He said that while the study doesn't make any judgment about the desirability of SAI, it does show that a hypothetical deployment program starting 15 years from now could be technically possible strictly from an engineering perspective.
He said the project will also be remarkably inexpensive. It might only cost $2 million to $2.5 billion per year over the first 15 years.
Co-author Wake Smith believes new aircraft will be needed for this project. He said it will indeed take an entirely new plane design to do SAI under reasonable, albeit entirely hypothetical parameters. No existing aircraft possesses the required combination of altitude and payload capabilities.
A new aircraft called the "SAI Lofter (SAIL)" will be the means of delivering sulfite payloads to the stratosphere. SAIL, however, will be a massive aircraft. To sustain level flight at 20 km, it needs double the wing area of an equivalently sized airliner, and double the thrust. It will also have four engines instead of two.
The SAIL fuselage would be stubby and narrow. It will be designed to accommodate a heavy but dense mass of molten sulfur rather than the large volume of space and air required for passengers.
A fleet of eight SAILs will be needed in the first year. The fleet size will increase to 100 SAILs within 15 years. The fleet needs to fly more than 4,000 missions a year in year one. This number will increase to more than over 60,000 per year by year 15.
