Are they possible? I once bought lead foil advertised at "ten thousanths of an inch thick" thinking it might provide the envelope for a lead balloon. Sadly it was 10/1000 inches thick not 1/10000 inches thick. I think a balloon made from gold foil is possible but getting lead to the same thickness may not be.

The climatic situation is desperate. Feedbacks such as Siberian Methane, the loss of Artic Sea Ice and the Amazon Forests disintegrating will interact. Siberia's already 5 degC hotter; Artic Sea Ice at an all time low; and the Amazon has had summers that are dangerously dry.

Don't argue about the cost. Just get on with doing something. Tax carbon so until energy sources are carbon zero or carbon negative.