It is not possible to answer this question with any precise degree of accuracy. The atmosphere’s behaviour is determined predominantly by the intensity of solar radiation energy that reaches the Earth’s surface (insolation). However, fluctuations in insolation and the distribution of the Sun’s radiation across the Earth also affect our planet’s energy budget and climate. The intensity of insolation changes with the long-term variations of the Earth’s orbital elements (variations in the spatial relationship between the Sun and Earth). Climate cycles occur as a result of the axial precession of the Earth, variations in the Earth’s axial tilt as it orbits the Sun, and changes to the Earth’s elliptical orbit. These cycles were described by Serbian astrophysicist and mathematician Milutin Milankovič. Such cyclical changes in the Earth-Sun constellation take place across long periods of time and, nowadays, are seen as one of the many natural factors that are responsible for climate change – particularly for the transition between glacial and interglacial periods.
The transition between periods of cold climate with expanding ice sheets (glacial periods) and periods of warm climate with retreating ice sheets (interglacial periods) has so far been the characteristic feature of the geologic Quaternary Period (technically an ice age itself due to the presence of at least one permanent ice sheet) that we are currently living in. Over the last 800,000 years the Earth has experienced eight glacial periods and nine interglacial periods. The length of one such glacial-interglacial cycle averages between 80,000 and 120,000 years. The periods of cooling and formation of ice last much longer than the periods of warming and melting of ice.
Interglacial periods have an average residence time of around 10,000 to 15,000 years; glacial periods remain from 75,000 to 85,000 years. The transition from an interglacial period to the next glacial period is characterised by a slow cooling phase, whereas the transition from a glacial period to the subsequent interglacial period involves a rapid rise in temperature. The last glacial period (commonly known as the Ice Age) peaked around 21,000 years ago. Considering this time scale, the Earth could find itself heading towards another glacial period, or “ice age” in roughly 10,000 years’ time. However, human activity is currently having a heavy impact on the Earth’s climate cycle.
This question was answered by the team of Climate Office the at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI).