To have an effect you need to launch multiple orders of magnitude more mass than we have, and that mass would need to be optimized towards having as large as an effect as possible by being very very thin film positioned so that it is consistently between earth and the sun (or you could add on a few more orders of magnitude).

You can look at proposal for doing this intentionally to get a sense for the scale: https://en.wikipedia.org/wiki/Space_sunshade

Bus = 0.0002 km²

Earth = 510.1 million km²

(Earth / Bus) / 100 = 25,000,000,000 bus sized satellites needed to cover 1% of the sky.