Scientists match Earth’s ice age cycles with orbital shifts – suggest next one in 10,000 years

Earth’s Axial Tilt, or Obliquity [Credit: Wikipedia]

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We’re told ‘One type of change in Earth’s orbit was responsible for the end of ice ages, while another was associated with their return.’ The study is billed as ‘a step-change in understanding the planet’s glacial cycles’. Annoyingly they suggest interference from recent CO2 emissions could affect the future timetable. In the abstract the authors say: ‘We find that the set of precession peaks (minima) responsible for terminations since 0.9 million years ago is a subset of those peaks that begin (i.e., the precession parameter starts decreasing) while obliquity is increasing. Specifically, termination occurs with the first of these candidate peaks to occur after each eccentricity minimum.’
— Journal Editor’s summary and a brief version of the paper here.
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Beginning around 2.5 million years ago, Earth entered an era marked by successive ice ages and interglacial periods, emerging from the last glaciation around 11,700 years ago, says Phys.org.

A new analysis suggests the onset of the next ice age could be expected in 10,000 years’ time. The findings are published in the journal Science.

An international team, including researchers from UC Santa Barbara, made their prediction 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.

The study tracks the natural cycles of the planet’s climate over a period of a million years. Their findings offer new insights into Earth’s dynamic climate system and represent a step-change in understanding the planet’s glacial cycles.

The team examined a million-year record of climate change, which documents changes in the size of land-based ice sheets across the Northern hemisphere together with the temperature of the deep ocean. They were able to match these changes with small cyclical variations in the shape of Earth’s orbit of the sun, its wobble, and the angle at which its axis is tilted.

“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.

“We were amazed to find such a clear imprint of the different orbital parameters on the climate record,” added lead author Stephen Barker, a professor at Cardiff University, in the UK. “It is quite hard to believe that the pattern has not been seen before.”
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The authors found that each glaciation of the past 900,000 years follows a predictable pattern. This natural pattern—in the absence of human greenhouse gas emissions—suggests that we should currently be in the middle of a stable interglacial, and that the next ice age would begin many millennia in the future, approximately 10,000 years from now.

“The pattern we found is so reproducible that we were able to make an accurate prediction of when each interglacial period of the past million years or so would occur and how long each would last,” Barker said. “This is important because it confirms the natural climate change cycles we observe on Earth over tens of thousands of years are largely predictable and not random or chaotic.”

These findings represent a major contribution towards a unified theory of glacial cycles.

Full article here.
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Image: Earth’s Axial Tilt, or Obliquity [credit: Wikipedia]