Ocean heat drives ancient climate shifts, not CO2

In Short:
– Recent studies show ocean temperatures were key drivers of ancient climate shifts, not greenhouse gases.
– Ice core research highlights the ocean’s significant influence on climate and Antarctic ice dynamics over millennia.

New studies published in *Nature* reveal that ocean temperatures, rather than greenhouse gas levels, were the primary drivers of ancient climate shifts over the past three million years.Research conducted on Antarctic ice cores indicates global ocean temperatures fluctuated significantly, even as carbon dioxide (CO2) and methane levels remained relatively stable.

Ancient climate insights

One study reconstructed global ocean heat content using noble gas ratios trapped in ancient ice.

Results showed CO2 only decreased by about 25 parts per million between 2.9 and 1.2 million years ago, indicating greenhouse gases alone cannot explain temperature variability during this period.

Shifts in ocean circulation and heat distribution are highlighted as influential factors in climate change.

Researchers affiliated with the National Science Foundation-funded Center for Oldest Ice Exploration collected the ice cores used in these studies.

Dr. Sarah Shackleton from the Woods Hole Oceanographic Institution emphasised the value of ice cores in understanding past climate conditions.

The findings coincide with another study from the British Antarctic Survey, which demonstrates the ocean’s role in influencing Antarctic ice dynamics.

Researchers investigated 18,000 years of bottom-water temperatures on the Amundsen Sea continental shelf.

Warm ocean water was identified as a key factor in the retreat of the West Antarctic Ice Sheet after the last ice age.

Future climate research

The studies stress the need for deeper ice core records to enhance comprehension of Earth’s climatic history.

Projects like the European-led Beyond EPICA and Australia’s Million Year Ice Core aim to extend climate archives significantly.

Scientific efforts will focus on understanding Earth’s glacial cycle changes over the last million years.

These recent insights challenge previous notions that greenhouse gases alone dictated climate shifts.

They underscore the complex interactions between ocean temperatures and atmospheric conditions in shaping Earth’s climate history.