Scientists who have studied the Earth’s climate over the last million years believe they see a concrete link between the Earth’s orbital path around the Sun to an always-evolving climate on earth. Based on that link, they believe the Earth is headed for another significant Ice Age –but don’t pack your winter clothes yet. Project scientists believe the next Ice Age is about 10,000 years away but when it arrives it may linger around for about 100,000 years. With scientists unlocking secrets on climate change, the hope is a better understanding on the Earth-Sun relationship could lead to accurately forecasting how conditions will change over time.
The Last Glacial Period lasted for roughly 103,000 years. It started at the end of the Last Interglacial Period and ended with the beginning og the Holocene Interglacial Period. The Last Glacial Period saw multiple glacial advances, with the Last Glacial Maximum occurring about 26,500 years ago. At that time, vast ice sheets covered North America and northern Europe.
Scientists have assumed we were simply somewhere in between two ice ages, but now researchers at UC Santa Barbara, as well as other international scientists, are now able to make predictions based on a new interpretation of the small changes in Earth’s orbit of the Sun, which lead to massive shifts in the planet’s climate over periods of thousands of years. Their work and findings appear in the journal “Science.”
“We found a predictable pattern over the past million years for the timing of when Earth’s climate changes between glacial ‘ice ages’ and mild warm periods like today, called interglacials,” said co-author Lorraine Lisiecki, a professor in UCSB’s Earth Science Department. One type of change in Earth’s orbit was responsible for the end of ice ages, while another was associated with their return.
“Despite decades of research, precisely how the various parts of the solar insolation cycles affect glacial cycles is not known. Barker et al took a new approach to answering this question by looking at the morphology of glacial inception and deglaciation. They found that those steps depend strongly on the relative phasing of precession versus obliquity, with precession having more influence on deglacial onset and obliquity being more important for reaching peak interglacial conditions and glacial inception. Thus, glacial-interglacial variability in the relevant period, called the 100,000-year world, is largely deterministic,” wrote Science editor Jesse Smith.
The Earth’s rotation around its axis, and revolution around the Sun, evolve over time due to gravitational interactions with other bodies in the Solar System. The variations are complex, but a few of the cycles appear to be more dominant than others. The Earth’s orbit varies between nearly circular and mildly elliptical. When the orbit is more elongated, there is more variation in the distance between the Earth and the Sun, and in the amount of solar radiation, at different times in the year. In addition, the rotational tilt of the Earth changes slightly over time too. A greater tilt makes the seasons more extreme. Finally, the direction in the fixed stars pointed to by the Earth’s axis changes while the Earth’s elliptical orbit around the Sun rotates.
One scientist that studied these changes in the movements of Earth was Serbian geophysicist and astronomer Milutin Milanković (known in English as Milankovitch.). In the 1920s, Milankovitch studied changes in these movements of the Earth, which alter the amount and location of solar radiation reaching the Earth. Now known as solar forcing, Milankovitch emphasized the changes experienced at 65° north due to the great amount of land at that latitude. Land masses change surface temperature more quickly than oceans, mainly because convective mixing between shallow and deeper waters keeps the ocean surface relatively cooler. Similarly, the very large thermal inertia of the global ocean delays changes to Earth’s average surface temperature when gradually driven by other forcing factors.
Milankovitch was able to build upon theories proposed by James Croll who had earlier hypothesis that variations in eccentricity, axial tilt, and precession combined to result in cyclical variations in the intra-annual and latitudinal distribution of solar radiation at the Earth’s surface, and that this orbital forcing strongly influenced the Earth’s climate patterns.
The Earth orbits the Sun in an elliptical path, completing one revolution in approximately 365.25 days. This journey around the Sun is also known as Earth’s revolution. The Earth travels about 584 million miles during this orbit. But because this orbit isn’t perfectly elliptical and because the Earth wobbles as it orbits the Sun, those slight variations appear to have significant impacts to climate and weather on Earth.
With research like that recently published in Science getting examined, scientists are improving their ability to understand how the Earth’s orbit and slight wobbles and shifts here and there can have huge implications to conditions on the planet. At some point in the near future, scientists may be able to make accurate climate predictions and models based on these factors.
