For millions of years, Earth's climate has been driven by natural cycles related to Earth's orbit, varying between glacial periods and warmer interglacial periods. A new study has discovered a clear, predictable pattern in these changes, revealing that the next ice age should begin naturally in about 10,000 years.
However, human activity - especially greenhouse gas emissions - has disrupted this cycle, making it unlikely that we will see another ice age anytime soon. These findings not only help us understand past climate change, but also provide important tools for predicting future long-term climate trends and assessing the actual impact of human intervention.
About 2.5 million years ago, the Earth entered a cycle of alternating glacial and interglacial periods. The last ice age ended about 11,700 years ago. Now, a new analysis suggests that the next ice age could begin naturally in about 10,000 years.
An international team of researchers, including scientists from the University of California, Santa Barbara, made the prediction based on a new interpretation of subtle changes in Earth's orbit around the sun. These small changes drive major changes in climate over thousands of years. The study examined a million years of climate data, revealing new insights into Earth's glacial cycles. The findings, published in Science, mark significant progress in understanding Earth's long-term climate patterns.
The team studied a million-year record of climate change, which documented changes in the size of land-based ice sheets in the Northern Hemisphere and changes in deep ocean temperatures. They were able to match these changes to tiny periodic changes in the shape of the Earth's orbit around the sun, its wobble and the tilt of its axis.
"We found that over the past million years there was a predictable pattern in the timing of changes in Earth's climate between glacial 'glacials' and periods of milder warmth like today, called interglacials," said co-author Lorraine Liskey, a professor in the Department of Earth Sciences at UC Berkeley. One change in Earth's orbit caused the end of an ice age, while another change is associated with its return.
Lead author Stephen Barker, professor at Cardiff University in the UK, added: "We were surprised to find that different orbital parameters left such a clear imprint on the climate record. It's hard to believe that this pattern has never been seen before."
Decoding the triggers of glacial cycles
Predictions about a link between Earth's solar orbit and fluctuations between glacial and interglacial periods have been around for more than a century, but were not confirmed by actual data until the mid-1970s. Since then, scientists have struggled to pinpoint exactly which orbital parameters were most important for the beginning and end of glacial cycles, because it is difficult to date climate changes so far back.
The team overcame this challenge by looking at the shape of the climate record over time. This allowed them to determine how different parameters work together to produce the observed climate changes.
The authors found that every glacial period in the past 900,000 years followed a predictable pattern. This natural pattern - in the absence of human greenhouse gas emissions - suggests that we should currently be in the midst of a stable interglacial period, with the next ice age beginning in a few thousand years, around 10,000 years from now.
"The patterns we found are highly repeatable, allowing us to accurately predict when each interglacial period occurred over the past million years or so, and how long each interglacial period would last," said Barker. "This is important because it confirms that the tens of thousands of years of natural climate change cycles we observe on Earth are largely predictable, rather than random or chaotic. These findings are a major contribution to a unified theory of glacial cycles."
Co-author Chronis Tzedakis, a professor at University College London, said: "Because we are now living in an interglacial period - called the Holocene - we are also able to make tentative predictions about when the climate might return to a glacial state."
How human activities disrupt natural climate cycles
Co-author Gregor Knorr from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, added: "However, this transition to a glacial state after 10,000 years is unlikely, because human emissions of carbon dioxide into the atmosphere have already shifted the climate away from its natural trajectory and have long-term consequences for the future."
The research team plans to build on their findings and create a baseline for Earth's natural climate for the next 10,000-20,000 years by calibrating past changes. Combined with climate model simulations, the researchers hope to quantify the absolute impact of anthropogenic climate change in the distant future.
Barker added: "Now that we know that climate is largely predictable over such long timescales, we can actually use past changes to tell us what is likely to happen in the future. This is something we have not been able to do before, and our new analysis provides this level of confidence. This is crucial for us to make better decisions now about the greenhouse gas emissions that will determine future climate change."
Compiled from /ScitechDaily