Simplify the following text for a Grade 11 native English-speaking person.
Original: Nevertheless , until about 1960 , most scientists dismissed the hot-house \/ greenhouse effect as implausible for the cause of ice ages as Milutin Milankovitch had presented a mechanism using orbital changes of the earth ( Milankovitch cycles ) .
Simplified: Nevertheless , until about 1960 , most scientists dismissed the hot-house \/ greenhouse effect as implausible . Milutin Milankovitch had presented a mechanism for ice ages : it used cyclical changes in the orbit of the Earth ( Milankovitch cycles ) .