> the earth emits about 12 trillion watts per hour Delete "per hour". The watt is already a unit of energy per unit time (1 joule per second, specifically).

> the earth emits about 12 trillion watts per hour Delete "per hour". The watt is already a unit of energy per unit time (1 joule per second, specifically). So 12 trillion watts is the same as 12 trillion joules per second.