He was the first person to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes would cause global warming. Arrhenius clearly believed that a warmer world would be a positive change. Nevertheless, until about 1960, most scientists dismissed the greenhouse effect because they thought it was very unlikely to happen. Milutin Milankovitch had presented a mechanism for ice ages: it used cyclical changes in the orbit of the Earth (Milankovitch cycles). Nowadays, the accepted explanation is that orbital forcing sets the timing for ice ages with CO acting as amplifying feedback.