A proposed solution to Global Warming?

http://www.bbc.com/future/story/20160425-how-a-giant-space-umbrella-could-stop-global-warming

BBC - Future - How a giant space umbrella could stop ...
www.bbc.com
Our rapidly warming world could cause serious problems for civilization in the decades to come. But could a giant space umbrella help cool down our planet? Zaria ...

My OWN idea:
Rocketing A cloud of aluminum particles, every month for decades, at the L1 Orbit point, might do it.
Or, alternatively, using a rail-gun to fire small mirror-polished steel ball-bearings into the L1 Balance point between the Earth and the Sun might do it. A constant stream, several decades worth!
Build a mile-long rail-gun on an Andes hillside?
That would set up an actual umbrella, shielding us from the Sun, which is the SOURCE of Global Warming!
An ACTUAL, EFFECTIVE, Solution! Cost? A bit less than 2 TRILLION!!!

Not just a gesture like the "Paris Accord", which does basically NOTHING!
NASA says the "Paris Accord" would make a -0.05 degree drop in the rate(estimated +3 to +7 degrees) of Global Warming by 2100, that costs about 2 TRILLION dollars? We would STILL get a +2.95 to +6.95 degree rise!
Let me repeat: -0.05 degree drop = 2 TRILLION dollars!!!
Is that LOGICAL???

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