global warming is when worldwide temperature increases & gases released during the use of fossil fuels causes global warming ->  gases released during the use of fossil fuels cause an increase in worldwide temperature  gases released during the use of fossil fuels cause an increase in worldwide temperature & worldwide means global ->  gases released during the use of fossil fuels cause an increase in global temperature  gases released during the use of fossil fuels cause an increase in global temperature & if something causes something else then that something contributes to that something else -> gases released during the use of fossil fuels contributes to an increase in global temeperatures