New research shows that Earth can experience climate shocks, even with little or no polar ice, at surprisingly high rates.
What's happening?
As ScienceDaily reports, Professor Chengshan Wang of the China University of Geosciences led an international research team studying sedimentary rock cores from the Songliao Basin in China, dating back to about 83 million years ago, during the Late Cretaceous period.
At that time, the planet had very high levels of carbon dioxide and there was virtually no polar ice.
Many researchers attributed the sharp climate fluctuations primarily to the growth and melting of large ice sheets. This view was consistent with the last ice age. Greenland's temperature increased by 16 degrees Celsius over several decades, and repeated waves of icebergs disrupted circulation in the North Atlantic.
However, new research points to another mechanism for the slow changes in Earth's orbit and wobble in its rotation axis.
A group of researchers linked solar radiation changes associated with precession, particularly in the tropics, to recurring alternations between wet and dry seasons with intervals of approximately 4,000–5,000 years. Longer orbital rhythms, with periods of 100,000 years, influence their intensity.
As ScienceDaily reports, the researchers combined geochemical data and other information to compare patterns in the cores with projections of how solar radiation in the tropics will change over time.
Why do these climate shock findings matter?
They challenge the idea that ice sheets are necessary for sudden climate changes, suggesting that even an ice-free planet may not be as stable as scientists once thought.
The Late Cretaceous period may serve as one of the best examples for comparison with a much warmer world in natural conditions.
«"In the Late Cretaceous, atmospheric CO2 levels reached approximately 1,000 parts per million – comparable to projections for the end of this century," said University of Vienna paleoclimatologist Michael Wagreich, as reported by ScienceDaily.
If global temperatures continue to rise, understanding how climate systems have behaved under similar conditions in the past could help scientists better predict risks.
Such understanding could help people adapt to changing rainfall and longer droughts, which can affect factors such as crop yields and wildfire risk.
The study also suggests that some high-frequency climate variations may be more predictable than previously thought, as Earth's orbital motions are stable and well understood.
What is being done?
The researchers used cores obtained by the Cretaceous Continental Scientific Drilling Project, a global drilling initiative that began in 2006. They compared these cores with more modern analytical and modeling tools to reveal subtle climatic rhythms hidden in the geologic record.
Such paleoclimate research can improve current forecasting by revealing how a hotter Earth responds to climate change over the long term. More accurate forecasts can help governments and farmers prepare for changes in precipitation and temperature before they become more devastating.
«"High-frequency climate oscillations similar to those observed in the Cretaceous may also occur in a warmer future—potentially in a more predictable manner than previously thought," said study lead author Zhifeng Zhang in a press release.
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