What are some ways by which humanity could quickly work to cool down the planet to minimize the effects of global warming?

One idea humanity to implement to rapidly cool the planet to help minimize the effects of global warming would be to block some or all of the sunlight (UV radiation) hitting the planet from the sun. Sometimes referred to as GeoEngineering, these are projects on a truly planet-size scale. A project like this could, for example, consist of large reflective lightweight solar sails or other loft-able reflective material which could be seeded into the upper atmosphere to reflect some or all of the sunlight back into space. Another Idea would be to create massive and plentiful Co2 scrubbers to remove a noticeable quantity of the greenhouse gas, Co2, which works to reflect and prevent heat from the planet from leaving back out into space. Greatly reducing the quantity of Co2 in our atmosphere would allow more heat to escape the planet and consequently cool it down. Yet another thought might be to artificially and greatly increase the size of our ice caps which would lead to more sunlight being reflected back out into space. Yet another approach could be to mimic nature in prior heavily volcanic periods and inject massive quantities of sulfur dioxide into the atmosphere in the hopes of producing conditions that in the past led to mini ice-ages.