How big would a satellite need to be to block out the sun?

I have a story idea that involves a human attempt to halt and reverse global climate change. The idea is a simple one - a satellite that partially blocks out the sun. The satellite is located at the L1 lagrange point and is stabilised to always cast the most efficient shadow on earth.

The satellite would be similar to a solar sail with a surface area many square kilometers.

Ideally, I would aim to block 1% (or less) of solar energy. It would only need to cool the earth by a fraction (say 0.1) of a degree per year.

This is where I need clarity.

• Would 1% be too much cooling?
• What would the size of the satellite need to be to block that much sunlight? 100 km square?
• Is there anything else I haven't thought of?

Edit: This question isn't about being visible from Earth. In the world I'm working on, it's not even noticeable from earth without high tech equipment.

posted over 6 years ago

Coomie‭

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