SPACE.com Columnist Leonard David

These scientists want to put a massive 'sunshade' in orbit to help fight climate change

an illustration showing a giant reflector in space above Earth, partially blocking the light from the sun
Illustration of a planetary sunshade partially blocking light from the sun. (Image credit: Planetary Sunshade Foundation)

A group has been formed to study and promote a space-based sunshade to help fend off global climate change. 

The idea has been discussed for years, but the Planetary Sunshade Foundation is cranking out papers that support the concept and spotlight the practicality of the approach. 

A planetary sunshade, the Foundation advises, could be the best solution for solar radiation management and should be viewed as a key part of global efforts to counter ongoing climate change on Earth.

Related: Experts are certain 2023 will be 'the warmest year in recorded history'

A matter of degrees

Undoing the worst effects of climate change may well rest on three pillars: Emissions reduction, carbon dioxide removal and solar radiation management. 

There is an international agreement to strive to keep the world's average temperature from rising above 1.5 degrees Celsius (2.7 degrees Fahrenheit) over current averages. But the cold fact is that the lower the average temperature increase, the lower the climate impacts.

That said, climate change researchers have reported that our planet may well cross 1.5°C in the next decade. In the meantime there are now increased incidents of extreme weather, trends in sea level rise, widespread fires, along with melting ice caps. 

Coupled to these warning signs is political pressure to counter climate-change calamity.

Livable planet

Morgan Goodwin is the Executive Director of the Planetary Sunshade Foundation.

As for why the group is pursuing the initiative, Goodwin is clear that current decarbonization strategies are necessary, but they are insufficient for a livable planet. 

Decarbonisation is the lessening of carbon dioxide emissions by way of utilizing low carbon power sources to attain a lower output of greenhouse gasses permeating Earth's atmosphere.

"To avoid the worst impacts of climate change, the world should rapidly phase out the use of fossil fuels, remove gigatons of carbon from the atmosphere, and limit the incoming solar radiation," Goodwin told Space.com. Of all the methods broached to reduce solar radiation, he said, the sunshade has many advantages deserving of investment in the concept.

 A sunshade would be installed at the Sun-Earth Lagrange-1 point to reduce radiative forcing — the trapping of heat in the atmosphere due to greenhouse gas emissions — by reflecting sunlight back into space.  (Image credit: Planetary Sunshade Foundation)

Construction strategies

Touted as a "megastructure" in space, a sunshade would be installed at the Sun-Earth Lagrange-1 point. Once in place, it could reduce radiative forcing — the trapping of heat in the atmosphere due to greenhouse gas emissions — by reflecting sunlight back into space.

The foundation says that construction of a Planetary Sunshade is possible, drawing upon initial solar sail technology already flown. "The rapid technological progress of space launch systems has resulted in the cost of sending materials and people into space dropping fast, changing the scope of what is possible."

According to the foundation, there are two possible sunshade construction strategies. 

"We are pursuing both options, and think that if a planetary sunshade is built, the initial phases of construction will be an Earth-launched architecture while the later phases will use space resources and in-space construction," the group's website explains.

Large solar sail systems have been explored over the years, such as this NASA Solar Cruiser Technology Demonstration Mission of Opportunity.  (Image credit: NASA/Marshall Space Flight Center)

Hands-off Mother Nature?

But there are those that hold tight onto the belief: "You shouldn't fool with Mother Nature!"

Goodwin responds by pointing out that humans are messing with Mother Nature at a grand scale through state-sanctioned and often state-subsidized industrial practices. 

"Our survival as a civilization depends on our ability to wisely and intentionally change how we interact with our planet," said Goodwin.

Indeed, in the past year, the White House published a congressionally mandated report on geoengineering governance pathways, Goodwin said, a document that takes "a small but solid step forward," he added, into creating a framework for further investment in geoengineering research.

Techniques for solar climate intervention have been widely discussed to increase the quantity of solar radiation reflected back into space.  (Image credit: Chelsea Thompson, University of Colorado/CIRES and NOAA Chemical Sciences Laboratory)

Report takeaways

In June of this year, the White House Office of Science and Technology Policy released the Congressionally-mandated report on solar radiation modification.

As for report takeaways it cautions that any potential comprehensive research program must encompass the societal as well as the scientific dimensions of solar radiation modification. 

The document highlights several key priority areas for further solar radiation modification research, including determining climate and environmental impacts of solar radiation modification deployment; assessing potential societal outcomes and ecological consequences; and the need to examine how research might be done in cooperation among international partners.

That report also acknowledges that research on solar radiation modification impacts to date has been ad hoc and fragmented, rather than being the product of a comprehensive strategy. As a result, substantial knowledge gaps and uncertainties exist in many critical areas.

Uncertainties, risks, challenges

Earlier this year, the Global Commission on Governing Risks from Climate Overshoot (the "Climate Overshoot Commission") issued their report. 

This independent group of global leaders recommended a strategy to reduce risks should global warming goals be exceeded, that is a "climate overshoot" that crosses the 1.5 °C threshold.

In the commission report, they broached space-based reflectors; stratospheric aerosol injection, cirrus cloud thinning and marine cloud brightening — all solar Radiation Modification (SRM) techniques.

"But SRM would counter climate change imperfectly and poses serious uncertainties, risks, and governance challenges," the commission study reported.

"The governance gaps for SRM are the most acute," that reported said. "How can it be researched and evaluated without distracting from essential reductions of greenhouse gas emissions? Who decides whether to undertake SRM and under which conditions? How could countries' differences on this question be resolved?"

Goodwin of the Planetary Sunshade Foundation concludes that this year will close as the hottest year ever recorded, replacing 2022 which in turn took that title from 2021. "As the rate and impacts of warming increase, more and more tactics and perspectives will be brought to the table."

Whether or not a sun-deflecting, "made-in-the-shade" sail remains a bright prospect on that discussion table is yet to be determined. 

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

Leonard David
Space Insider Columnist

Leonard David is an award-winning space journalist who has been reporting on space activities for more than 50 years. Currently writing as Space.com's Space Insider Columnist among his other projects, Leonard has authored numerous books on space exploration, Mars missions and more, with his latest being "Moon Rush: The New Space Race" published in 2019 by National Geographic. He also wrote "Mars: Our Future on the Red Planet" released in 2016 by National Geographic. Leonard  has served as a correspondent for SpaceNews, Scientific American and Aerospace America for the AIAA. He was received many awards, including the first Ordway Award for Sustained Excellence in Spaceflight History in 2015 at the AAS Wernher von Braun Memorial Symposium. You can find out Leonard's latest project at his website and on Twitter.

  • George²
    Impossible to release today by many reasons. Maybe after 60+ years.
    Reply
  • Unclear Engineer
    So, given that the L1 orbit is dynamically unstable, and the solar pressure tends to move the shade toward Earth, what is the probability that this whole thing would someday depart from its L1 orbit and eventually cross Earth's orbit and Earth would crash into it? What would the effects of such a crash be on Earth?

    Yes, it is thin and a square meter weighs very little. But, it is also enormous in diameter. So, how much would the whole thing weigh? And, as it approached Earth, how would it collapse in Earth's gravitational field? What would it do to our other satellite infrastructures? What effects would it have on the Moon? What effects would reentry have on our atmosphere? How much heat will be radiated to the surface if this shield ends up "burning up" on reentry?

    Scientific daydreaming can be useful. But hard engineering questions need to be answered before anybody tries to turn such dreams into reality. And, those questions should not be limited to how to do it and how much it will cost for how much benefit. Engineering assessments need to be made about what can go wrong and what the consequences of those possibilities are. It is not just a cost vs benefit decision, it is a risk vs benefit decision.
    Reply
  • George²
    There would have to be frames to keep the shape and to fit engines to maintain position and orientation, fuel and oxidizer tanks, or some kind of propellant that could be electrically heated. For power supply, the canvas can also have a photovoltaic layer. In general, there would be a really huge table, given the dimensions. I can't even imagine just building all of the above and how it would be delivered, even with thousands of launches of the heaviest rockets we have today. For price suggest not less of whole GDP of the planet Earth for 2 years.
    Reply
  • Unclear Engineer
    I have seen proposed statite orbits that use the carefully directed reflections of the sunlight to control attitude and position, without using propellants. Energy for control systems would be solar. The reflectivity would need to be controlled by some sort of mechanism that might be electrical effects on materials used to make the shades/sails. By controlling reflection vs absorption, sail shape can be modified, and shape controls the forces from reflections at various parts of the sail/shade surface.

    So, continuous use of chemical or nuclear power plus expendable propellants would be avoided, as would the cost of launching those weighty components.

    However, what would be the effects on such a shade from collisions with things like orbiting asteroids and clouds of "comet tail material" such as we frequently see here on Earth as meteor showers? Can we really control such a huge surface? Does the answer take into account the known collision intensity for various sizes of solid particles that cross the orbit of the shield? What would the effects of a solar mass ejection be on the shade system - damage to sail material, damage to control electronics, perturbation of shade shape, perturbation of sail orbit?
    Reply
  • George²
    There is no way to allow drift, as with terrestrial sailboats. In a drift, the ships shift their position, although less than in the downwind movement. In space, however, the motion is not two-dimensional on a relatively flat surface...I don't think it is at all possible to do without actively and constantly adjusting the parameters by using engines. We do not yet handle other possibilities for the target, such as those described in the works of fiction, "trajectory beam", "anti-gravity", "manipulated force fields" and so on. Not even having nanorobots to take care of construction, meteorite damage repairs, and anything else needed to build and maintain it in working order.
    Reply
  • Unclear Engineer
    Regarding your post about sailboats and "drift", see https://en.wikipedia.org/wiki/Solar_sail , particularly where it says:

    "Robert L. Forward has commented that a solar sail could be used to modify the orbit of a satellite about the Earth. In the limit, a sail could be used to "hover" a satellite above one pole of the Earth. Spacecraft fitted with solar sails could also be placed in close orbits such that they are stationary with respect to either the Sun or the Earth, a type of satellite named by Forward a "statite". This is possible because the propulsion provided by the sail offsets the gravitational attraction of the Sun. Such an orbit could be useful for studying the properties of the Sun for long durations. Likewise a solar sail-equipped spacecraft could also remain on station nearly above the polar solar terminator of a planet such as the Earth by tilting the sail at the appropriate angle needed to counteract the planet's gravity."

    Diverting to sailboats for a moment, my actual experience sailing boats upwind, plus my background in aeronautics and physics, allows me to understand the interplay of forces involved. In that case, it is not the "reflection" of the wind, but rather "lift" created by the changes in pressure of the air flowing at different speeds in different places around the sail, which keep the sail in its designed shape and impart a net force on the sail that is somewhat "upwind" of the straight "downwind" direction. This is played against a similar force created by the boat's keel moving forward in the water at a slight angle under the boat, which imparts a "lift" force on the hull that is "upwind" of the straight downwind direction, and to the opposite side of the net forces from the wind on the sail. The boat responds to the combination of those forces it go upwind at an angle to the wind. (And, of course, the boat leans to one side because the air and water are causing opposing forces at different elevations, so gravity is also being used to keep the boat from simply laying over flat on the surface of the water.)

    So, sailboats gong upwind are far more complicated to understand than the forces on a statitie, where reflected photon momentum is being used directly to counteract gravitational attraction in a vacuum with no aerodynamic or hydrodynamic forces, and no interface between fluids.
    Reply
  • George²
    Unclear Engineer said:
    Regarding your post about sailboats and "drift", see https://en.wikipedia.org/wiki/Solar_sail , particularly where it says:

    "Robert L. Forward has commented that a solar sail could be used to modify the orbit of a satellite about the Earth. In the limit, a sail could be used to "hover" a satellite above one pole of the Earth. Spacecraft fitted with solar sails could also be placed in close orbits such that they are stationary with respect to either the Sun or the Earth, a type of satellite named by Forward a "statite". This is possible because the propulsion provided by the sail offsets the gravitational attraction of the Sun. Such an orbit could be useful for studying the properties of the Sun for long durations. Likewise a solar sail-equipped spacecraft could also remain on station nearly above the polar solar terminator of a planet such as the Earth by tilting the sail at the appropriate angle needed to counteract the planet's gravity."

    Diverting to sailboats for a moment, my actual experience sailing boats upwind, plus my background in aeronautics and physics, allows me to understand the interplay of forces involved. In that case, it is not the "reflection" of the wind, but rather "lift" created by the changes in pressure of the air flowing at different speeds in different places around the sail, which keep the sail in its designed shape and impart a net force on the sail that is somewhat "upwind" of the straight "downwind" direction. This is played against a similar force created by the boat's keel moving forward in the water at a slight angle under the boat, which imparts a "lift" force on the hull that is "upwind" of the straight downwind direction, and to the opposite side of the net forces from the wind on the sail. The boat responds to the combination of those forces it go upwind at an angle to the wind. (And, of course, the boat leans to one side because the air and water are causing opposing forces at different elevations, so gravity is also being used to keep the boat from simply laying over flat on the surface of the water.)

    So, sailboats gong upwind are far more complicated to understand than the forces on a statitie, where reflected photon momentum is being used directly to counteract gravitational attraction in a vacuum with no aerodynamic or hydrodynamic forces, and no interface between fluids.
    If you follow link to "statite" will read this:
    No statites have been deployed to date, as solar sail technology remains in its infancy. NASA's cancelled Sunjammer solar sail mission had the stated objective of flying to an artificial Lagrange point near the Earth/Sun L1 point, to demonstrate the feasibility of the Geostorm geomagnetic storm warning mission concept proposed by NOAA's Patricia Mulligan.
    So, we don't have any practical experience if it would actually work. Only theoretical productions. From that point to eventual full-scale implementation, if it turns out to be a working concept, is again at least 60+ years away, as I've written. No matter how much we tend to brag, and even that we are capable of self-destruction, such a project is far beyond the present capabilities of our entire civilization.
    Reply
  • Unclear Engineer
    I agreed from the beginning that it isn't something we can just do with available technology.

    And, I also pointed out that it may have risks that are unacceptable, even if we can develop the technology to do it.

    I don't have a problem with some people studying the concept, so long as it gets some realism before the study gets into substantial expense.

    I think statites will probably be developed, but I am not convinced that they will be robust enough and useful enough to warrant significant deployments.

    I think it would be ridiculously stupid to bet on the success of any sort of orbiting sunshield as an excuse to not deal with the climate problem sufficiently in some other ways. And, if we fail to do so in some other way on a much more rapid time-line than I expect an L1 sunshield to require, I think we will have so much damage to on-Earth infrastructure that we will probably no longer have the wherewithal to implement an L1 sun shield, anyway.

    All of that aside, I don't see how an L1 sun shield could be cheaper or faster than on-the-ground CO2 removal technologies. And, what is the CO2 emissions cost of building and launching all of that stuff to L1? We are still having trouble getting a net CO2 emission reduction from building electric cars.
    Reply
  • billslugg
    If the goal is to reflect solar energy it is done much cheaper on the ground. We could simply dictate that everyone paint their roofs white.
    Reply
  • Unclear Engineer
    Bill, there are lots of things like that we could do, but aren't even talking about.

    For one thing, we have a lot of parking areas that are paved with black asphalt, on which we park our cars in summer and then come out and turn on their air conditioners to cool them down, at the expense of burning gas or, at best, using EV range. Meanwhile, we are taking open fields that used to be crop lands and turning them into "solar farms".

    How about we put "solar roofs" over shopping area parking lots instead? Use the solar power to top off the parked vehicle batteries and the excess to light the stores, at least, not to mention run just about everything else in the daytime? Plant some trees instead of planting solar cells on ag lands, if we don't want to use that for crops.

    Cities would benefit most from white roofs. And, maybe cisterns to catch some of that rainwater that is producing dangerous flooding? More suburban and rural buildings could use black roofs in the winter, shaded by deciduous trees in the summer. That is what my family has done for generations.

    Where I live, we have plenty of empty commercial buildings, some not even very old. But instead of "repurposing" those, we are still permitting crop and forest lands to be turned into more buildings with sprawling parking lots.

    All of the planning seems to be about short term profits, especially for folks who already have a lot of money to invest, with minimal initial outlays. Long-term effects aren't in their picture, especially if somebody else needs to pay for them.

    But, the people who are focused on zoning rules seem to be only interested in prohibiting new gas furnaces and stoves - very prematurely in my evaluation - because those things are more energy efficient and CO2 emission reducing than electric versions - until we get nearly all of our electricity from sources that do not emit CO2.
    Reply