Bill Gates Is Thinking About Dimming the Sun The billionaire is backing a study of the controversial technology called solar geoengineering.

Let us suppose that the research shows that cooling the Earth by seeding the atmosphere with Calcium Carbonate is feasible. Could an evil overlord (not necessarily Gates) realistically threaten the Earth with extinction by bringing on a new ice age?

Note: I'm not asking about other methods. This is specifically about the feasibility of releasing calcium carbonate into the atmosphere in such quantities as to be catastrophic. Please do not suggest that this is a duplicate of one about large satellites.

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    $\begingroup$ I feel like, since this is a technology being investigated by real-life scientists, you'd probably get a much better/more authoritative answer to this question simply by searching for articles about it. Googling "solar geoengineering possible problems" is giving me lots of news/academic articles covering the topic... that said, it would of course be fun to see what the WB community here comes up with :) $\endgroup$
    – Qami
    Apr 9, 2021 at 13:09
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    $\begingroup$ Isn't this the prestory for Snowpiercer? $\endgroup$ Apr 9, 2021 at 13:23
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    $\begingroup$ Does this answer your question? How big would a satellite need to be to block out the sun? $\endgroup$
    – rek
    Apr 9, 2021 at 14:22
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    $\begingroup$ Insert joke about Windows flaws here. $\endgroup$
    – hszmv
    Apr 9, 2021 at 14:37
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    $\begingroup$ @Dragongeek - Who knows why evil overlords do things a certain way? Most of them are insane. $\endgroup$ Apr 9, 2021 at 21:25

2 Answers 2


Using Geoengineering to cool the climate to the point of collapse is going to be significantly more difficult than heating the planet to accomplish the same means.

The basic idea involves spraying Calcium Carbonate dust into the upper atmosphere to reflect a fraction of incoming sunlight before it has a chance to get trapped and absorbed.

How effective this is depends on how much dust you can disperse, how much light it actually reflects away, and how long it persists in the upper atmosphere.

The point of this study is to test to see if they can determine any of those values (and of course to see if they can assess the biological safety).

Some assumptions we can make are: The dust won't be SUPER effective at blocking light, the dust won't stay there for a very long time, and it will therefore take a LOT of dust to be even partially effective.

We're talking about dedicating a sizeable fraction of our global industrial capabilities to harvest the raw materials, process it into super-fine dust, and then fly it many miles into the sky.

The effort will undoubtedly take many years and will RELEASE a ton of additional CO2 into the atmosphere.

It would not be possible to accomplish this in the sneaky "evil overlord quietly gets a dooms-day device in place".

You'd be much better off trying to heat the planet up, since that's the trajectory we're currently on.

If you are insisting on accomplishing Global Cooling on a catastrophic level, consider attempting to jump start a super volcano such as Yellowstone.

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    $\begingroup$ Bearing in mind that "jumpstarting" anything geologic is also extraordinarily hard and requiring an enormous amount of energy. $\endgroup$
    – jdunlop
    Apr 9, 2021 at 22:10
  • $\begingroup$ @jdunlop Indeed. I tried to convey that with the comment about requiring a sizeable fraction of our industry, as well as hinting about all the CO2 the process would release. $\endgroup$
    – abestrange
    Apr 9, 2021 at 22:13
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    $\begingroup$ Oh, sure. I meant the final paragraph, suggesting trying to make Yellowstone erupt before it wants to erupt. Generally, the kind of energies required to make supercalderae erupt early involve asteroid impacts. $\endgroup$
    – jdunlop
    Apr 9, 2021 at 22:17

Ozone layer

In the very thin upper atmosphere, calcium can be found as neutral Ca, Ca+, or Ca++, because it is struck by ionizing ultraviolet radiation. There are quite a few different ways that these can interact with ozone to break it down into ordinary O2.

Microbial balance

Microbes in the atmosphere could spread disease or change climates, according to the above Smithsonian article at least. Putting large amounts of calcium ions into the air will change the available nutrients - hence the range of bacteria. The results could take time to manifest, since populations would need to increase and decrease until an effect was noticed.

Moral hazard

It would take some doing to try to apply Revelations texts about blotting out a third of the sun, but some people will find a way. Others will simply look to the sky and note the discoloration. As known from treatment of seasonal affective disorder, light balance has a powerful psychological effect on people. Think of how some people rejoiced to see the contrail-free clarity of the sky during the September 2001 flight ban. The Highlander movie about people living "under the shield" might give a subjective sense of the mood produced.

Hard air

Constant spraying of massive amounts of calcium carbonate implies that often rain water will be hard water. How does this affect plants, mountains, glaciers, or your rain gutter?


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