What would happen if the value of G was twice as large?

Explanation

(a) the value of acceleration due to gravity (g) would become double.
(b) Weight of all the objects on the earth will become double making simple tasks like picking an object difficult.
(c ) The atmospheric air pressure would increase leading to various climatic changes . To counter this change in air pressure, the blood pressure of human body will increase making it hard to survive on earth .
(d) The earth's orbit around the sun will be affected which will result in catastrophic climatic changes.