"For the past 4.5 billion years that our #planet has existed, the #climate has changed countless times. However, we need not concern ourselves with changes to climate that occurred billions or hundreds of millions of years ago. After all, determining the concentration of #greenhouse#gases in the #atmosphere that early on is virtually impossible. However, scientists are able to determine the composition of Earth's atmosphere up to about one million years into the past using ice cores from #Greenland and #Antarctica. Ice cores and #geological evidence strongly indicate that the #Earth has gone through multiple periods of #climatechange, wherein the temperature either increases or decreases, as does the CO2 concentration. The cooling periods are referred to as #IceAges while the warmer periods are called interglacial periods. For hundreds of thousands of years, the Earth has gone in and out of these phases.
Why the #Earth goes these periods has to do with the position of the planets. #Venus, small but close, pulls on the Earth ever so slightly. #Jupiter, massive but far, has a similar effect. The Earth is pulled on by these two planets, and the result is that every now and again the Earth's orbit and/or axis tilt change. The Earth may move farther from the #sun, and temperatures decrease as a result. At other times, it may move closer, and temperatures begin to increase.
Earth has gone through multiple #iceage through its long history. The first occurred about 2.4 billion years ago, called the Huronian glaciation, in which the entire Earth was covered in massive #glaciers. The latest of which is actually still occurring. Called the Quaternary glaciation, it began about 2.7 million years ago and it continues on to the present. During these ice ages are relatively short periods of warming, called interglacial periods. Although they occur in an ice age, they are relatively short and may only last a few tens of thousands of years. )