Paul F. Dietz wrote:

L1 is unstable, so keep shades there would require active stabilization,
probably involving light pressure.

You don't need a full shadow to reduce insolation at the Earth;
a shade that appears smaller than the sun's disk, as seen from
Earth, would still reduce insolation at Earth. What you'd want
is the shade placed so that for every illuminated spot on Earth,
the shade was fully in front of the sun as seen from that spot.

I still like the billion mylar balloons at high altitude concept; it's
very simple, they can be turned out at almost nothing per balloon, and
sunrises and sunsets are going to look very wild indeed with the whole
sky full of glittering points of light.
Could you bounce microwaves off of these things for telecommunications
or OTH radar?

Pat