Massive sun 'umbrella' attached to asteroid could help fight global warming, scientist says

[Admin]

Hoping to combat our planet's rising temperatures, a scientist from the University of Hawaii explains a very futuristic way of shielding the Earth from sunlight.

Massive sun 'umbrella' attached to asteroid could help fight global warming, scientist says : Read more

 

[Homer10]

Bad idea ! The blocking mirror attached to the asteroid will cause the asteroid to be pushed more (a lot more), by the Sun. This will change the orbit of the asteroid a little bit by little bit until it finally gets dislodged from it's nice safe place at a La Graunge point. Then only God knows where this nearby asteroid goes. Chances are it will head towards Earth.

 

[Ken Fabian]

As a thought experiment these kinds of ideas a learning and teaching function I suppose but they aren't really global warming solutions. In-space resource utilization even at small demonstration scale is not yet a thing, let alone large scale manufacturing that uses asteroid resources. Launch capabilities of sufficient scale and low cost are not yet a thing either. They aren't even close to viability. Addressing global warming can't wait on that changing.

Homer10, I would expect the hypothetical positioning to account for light and solar wind pressure, ie a bit sunward of where "stationary" would be without the attached mirror, with the mass making it move less, but anything expected to stay in an orbiting position long term has to have the ability to move.

 

[Unclear Engineer]

To deal with the solar light and "wind" pressure, the reflective surface would need to be aimed to slow the orbital velocity in an orbit closer to the Sun than L1, so that the net effect is that it orbits at the same period as Earth and L1 to stay in line. It's distance from the Sun is controlled by being closer, which would make it feel greater gravitation from the Sun, being balanced by the outward pressure of the solar light and particle emissions. And, being closer would make it orbit faster (shorter period), so the sail orientation needs to be at an angle that slows the forward speed enough to stay in line with Earth and L1. See https://en.wikipedia.org/wiki/Statite .

 

[RikF]

How much would the temperature sink, and where on earth?

 

[Unclear Engineer]

The "where on Earth" is the important question. A solar-blocking satellite would not make a dark shadow on Earth even if it blocks 1.7% of the solar radiation hitting Earth. It would be something like the transit of Venus, the last one occurring June 5-6, 2012. Didn't notice that, right? With this "umbrella", you would still be able to see 98.3% of the Sun's surface when standing in its "shadow" on Earth.

My question whether that shadow reaches the polar regions if it is centered on the equator. I could spend the time doing the geometry, but I am lazy enough to ask here before spending the effort.

 

[Helio]

Only a small change may be needed to offset warming. The IPCC studies and models show a range of warming based on a several scenarios. These range from about 2 watts to 4.5 watts (per sq. meter).

The suffix in the RCP (Representation Concentration Pathways) models are the wattage increases. Thus RCP2.6 is 2.6 watts/sq. meter; RCP4.5 is 4.5 w/sq. meter; etc.

Their earlier extreme model used 8.5 watts/sq. meter, but this has been deemed unlikely. [These are estimates for 2100.]

Retrograde rotation of objects reflecting sunlight will slightly offset movement as well (Yarkovsky Effect), though it may be too little for these larger objects, perhaps.