A number of things would change on the planet if it were to have another ice age. First, it would be colder than usual; snow would cover everything, and as a result the amount of sunlight that would be able to be absorbed would be low (becaues it's reflected back). This is a dominoe effect because this causes the temperatures to drop even further. Additionally, the atmosphere would change temperature which would affect the gases present there. The cold temperatures would trap any particulates in the air and hold them there, shielding the planet from the sun's warmth even further.