How do scientists know about the climate cycles?
Geologists found that every 100,000 years the climate cycles are affected by the Earth’s orbit around the Sun. Earth’s orbit is not circular. The orbit is elliptical. According to the article in www.geocraft.com called "Global Warming: A Chilling Perspective", scientists predict that the Earth’s orbit changes from circular to elliptical every 100,000 years. This matches up with the sequence of the ice age periods and the interglacial periods. Interglacial periods happen between ice ages when the climate is slightly warmer.
One way scientists can observe this evidence is by studying coral reefs. Coral reefs provide support for this theory because they grow faster in warmer climates and when the sea level is high. Therefore, studying in which periods these corals grew more, can tell scientists when the temperature was warmer.