When in historical time the climate of Earth was warmer modern

That the climate of Earth continuously changes and that scientists, politicians and ordinary people of the whole world express alarm concerning occurring now "global warming", it is known also to the school student. Alarm the fact of warming, and its unnaturally rough character caused as proves the majority of scientists, industrial activity causes not civilizations. In this regard it is interesting to look what in historical time when already there was a civilization, but yet there were no industrial emissions, there were periods of warm climate, comparable with modern or are even warmer. What then happened to Earth? .