Analysis of Earth's past climate changes suggest the onset of the next ice age could be expected in 10,000 years' time, researchers claim.
Their study tracks the natural cycles of the planet's climate over a period of a million years.
The international team, led by Cardiff University, 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.
Their findings, published in Science, 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 on which its axis is tilted.
Lead author Professor Stephen Barker from Cardiff University's School of Earth and Environmental Sciences, said: "We were amazed to find such a clear imprint of the different orbital parameters on the climate record."
It is quite hard to believe that the pattern has not been seen before.
Predictions of a link between Earth's orbit of the Sun and fluctuations between glacial and interglacial conditions have been around for over a century but were not confirmed by real-word data until the mid-1970s.
Since then, scientists have struggled to identify precisely which orbital parameter is most important for the beginning and ending of glacial cycles because of the difficulty in dating climatic changes so far back in time.
The team, which includes researchers from University College London (UCL), University of California, Santa Barbara, and the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, was able to overcome this problem by looking at the shape of the climate record through time.
This allowed them to identify how the different parameters fit together to produce the climate changes observed.
Professor Barker remarked: "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."
Coauthor of the study, Professor Lorraine Lisiecki of the University of California, Santa Barbara, added: "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.
"And because we are now living in an interglacial period – called the Holocene – we are also able to provide an initial prediction of when our climate might return to a glacial state."
"But such a transition to a glacial state in 10,000 years' time is very unlikely to happen because human emissions of carbon dioxide into the atmosphere have already diverted the climate from its natural course, with longer-term impacts into the future," added Dr. Gregor Knorr from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research and another of the study's coauthors.
The team plans to build on their findings to create a baseline of the Earth's natural climate for the next 10,000-20,000 years by calibrating past changes.
Used in combination with climate model simulations, researchers hope to quantify the absolute effects of human-made climate change into the far future.
Professor Barker added: "Now we know that climate is largely predictable over these long timescales, we can actually use past changes to inform us about what could have happened in a future without the influence of mankind."
This is something we couldn't do before with the level of confidence that our new analysis provides and is vital for better informing decisions we make now about greenhouse gas emissions, which will determine future climate changes.
Professor Chronis Tzedakis from UCL, and one of the study's co-authors, said: "This new study builds on our earlier work, and represents a major contribution towards a unified theory of glacial cycles."
Their paper, 'Distinct roles for precession, obliquity, and eccentricity in Pleistocene 100-kyr glacial cycles', is published in Science.
