How do scientists know that smoke from burning coal causes global warming?

Can global warming be demonstrated or proved, or is it just a another gloom and doom publicity stunt?

“What we think, or what we know, or what we believe is, in the end, of little consequence. The only consequence is WHAT WE DO.” John Ruskin (1819 - 1900)

“When we remember we are all mad, the mysteries disappear and life stands explained.” Mark Twain