Geoengineering refers to a set of emerging technologies that could manipulate the environment and partially offset some of the impacts of climate change. Solar geoengineering in particular could not be a replacement for reducing emissions (mitigation) or coping with a changing climate (adaptation); yet, it could supplement these efforts.
29 philanthropists pledged $4 billion over the next five years to combat climate change—the largest-ever philanthropic investment focused on climate change mitigation. 29 organizations from the United States and around the globe have committed this funding to advance affordable, low- and zero-carbon solutions to reduce the harmful emissions that cause climate change.
Carbon geoengineering seeks to remove carbon dioxide from the atmosphere, which would address the root cause of climate change — the accumulation of carbon dioxide in the atmosphere. In the chain from emissions to concentrations to temperatures to impacts, it breaks the link from emissions to concentrations.
Solar geoengineering seeks to reflect a small fraction of sunlight back into space or increase the amount of solar radiation that escapes back into space to cool the planet. In contrast to carbon geoengineering, solar geoengineering does not address the root cause of climate change. It instead aims to break the link from concentrations to temperatures, thereby reducing some climate damages.
There are several proposed solar geoengineering technologies. These include marine cloud brightening, cirrus cloud thinning, space-based techniques, and stratospheric aerosol scattering, amongst others. Marine cloud brightening would attempt to brighten marine clouds to reflect more sunlight back into space. Cirrus cloud thinning would attempt to reduce the thin, high-altitude cirrus clouds to emit more long-wave radiation from the earth to space. Space-based technologies would attempt to reflect a small fraction of sunlight away from the earth by positioning sun shields in space. And stratospheric aerosol scattering would introduce tiny reflective particles, such as sulfate aerosols or perhaps calcium carbonate, into the upper atmosphere, where they could scatter a small fraction of sunlight back into space.
Stratospheric controlled perturbation experiments (SCoPEX) are seen as “critical” to this process and the first is planned to spray water molecules into the stratosphere to create a 1km long and 100m wide icy plume, which can be studied by a maneuverable flight balloons.
IF lab tests are positive, the experiment would then be replicated with a limestone compound which the researchers believe will neither absorb solar or terrestrial radiation, nor deplete the ozone layer.
Bill Gates and other foundations are substantially funding the project, and aerospace companies are thought to be taking a business interest in the technology’s potential.
The “StratoCruiser” long-duration observing system is being developed:
(1) the use of long-duration super-pressure balloon technology for flight durations of six weeks in the stratosphere at altitudes of 20 km capable of sustaining a payload mass of 1500 – 2000 kg on a modest 1 million (1M) ft3 balloon, or larger payloads with increased balloon volume,
(2) a stratospheric solar-electric propulsion system for horizontal navigation and station keeping in the stratosphere that provides drive velocities up to 8 m/s for a 1M ft3 balloon volume,
(3) a “reeldown” system providing in situ observations over an altitude range of 10 km below the balloon float altitude of 20 km, and finally
(4) recognition and engagement of the unique anti-cyclonic flow in the lower stratosphere over the US in summer that provides to-this-point unrecognized opportunities for long duration flights of balloon platforms over the US.
The Bill & Melinda Gates Foundation is not currently counted among the world’s leading climate change funders. When 29 philanthropists came together to commit $4 billion to climate change mitigation over the next five years during the Global Climate Action Summit in San Francisco last week, the Gates Foundation was not among them. But Bill Gates, the billionaire co-chair of the largest foundation in the world, is in the midst of doubling his own investments in renewable energy projects.
The Gates Foundation’s agricultural development strategy focuses on improving crops, protecting crops, and providing farmers with more advanced ways to manage crops in a changing climate.