Response to Steve Baker’s answer to Sunshade answer to Global climate change
This is true if you make the assumption it is launched from Earth.
If all you launch from earth is a package capable of soft landing a set of machines on the moon, and those machines are capable of manufacturing a copy of themselves (largely automated, with occasional remote help from human beings), and it takes 2 weeks for them to turn lunar regolith into a duplicate set of machines (including the solar panels to power the system), then within 4 years the moon can be covered with solar cells, and we have a lot of manufacturing capacity on the moon.
You then manufacture large long linear motors, capable of launching mass to escape velocity (no atmosphere to worry about, so no chemical rockets needed).
Then it takes about a day to manufacture the required cloud of objects, and about 10 minutes to launch them into an appropriate orbital trajectory (to reach Geostationary or L1). Ion thrusters could be used for finer navigational adjustments.
So it is technically quite doable, once you start thinking in terms of exponential technology and cooperative systems (rather than linear technology and competitive systems).
A slight variation on this theme that includes the use of mirrors (widely spaced, connected by thin cables) allows us to manage sunlight (up or down by up to 2%) and thus eliminate the climate variation of ice ages and sea level change that has dominated earth (and human) history on the larger scale.
Ted Howard NZ's Blog 