Scientists are worried by a pattern of natural climate shifts that they unearthed from 125,000 years ago. The last time ocean temperatures were this warm, sea levels were up to 30 feet (up to 9 meters) higher than they currently are, their findings show.

The team took sediment samples for more than 80 different sites globally, and these samples acted as “natural thermometers” that allowed them to estimate sea surface temperature during that ancient period.

“The trend is worrisome,” the report stated, saying the results may assist scientists in better understanding how oceans will react to global warming today.

‘Rapid Impact’ Of Human Acts

In the analysis of 83 marine sediment core locations, each core site was compared to dataset from 1870 to 1889 and 1995 to 2014. The review showed that 129,000 years earlier, global ocean surface temperature was already quite like the 1870 to 1889 average.

Temperature climbed in the next 4,000 years, attaining a level “indistinguishable” from the 1995 to 2014 average.

This reflected a warming of around 0.5 degrees Celsius, a similar increase achieved mostly as an aftermath of human activity, such as burning fossil fuels and sending more carbon emissions into the air.

According to previous research, sea levels at that time were 20 to 30 feet higher, offering a grim picture of what sea levels might look like once the massive oceans and ice sheets melt in the next couple of centuries and millennia. In this scenario, sections of London and New York — as well as nearly all of the Netherlands and big parts of China — would be lost to the vast sea.

The bad news is the scientific models used to make the estimates failed to pick up temperature rises some 125,000 years ago, meaning these projected sea levels at different temperatures could have been underestimates.

Cause For Concern

While it remains unknown how fast the seas may surge in the coming decades, some experts already consider these findings a cause for alarm.

“[S]ustained and substantive cuts in greenhouse gas emissions from energy-intensive activities remain vital and beneficial to societies,” said climate science professor Richard Allan from the University of Reading, explaining that the cuts in fossil fuels are still helpful given that it likely takes thousands of years for modern sea levels to rise.

Another recent research suggested that climate sensitivity to greenhouse gas emissions could be much higher than believed, potentially putting Earth on track to over 7 degrees Celsius of warming by 2100 — a situation that’s good as “game over” for life on the planet.

The new study’s lead author and Oregon State University professor Dr. Jeremy Hoffman clarified, however, that while those ancient sea levels might be a good peak into our future, that last major warm period has many complicated factors on its own and may not be viewed in a simple way in order to predict our future.

“There are a lot of things that have happened over the last century that far outpace the natural world,” Hoffman said, pertaining to carbon release from fossil fuels that “took millions of years to form” and are being wiped out in decades.

He said the planet would need something like a Mount St. Helen’s eruption every two and a half hours to keep pace with current emissions.

The findings were detailed in the journal Science.

Recently, a separate study delving on global temperature rise asserted that a so-called climate change hiatus is not happening, and the oceans are actually warming at a relatively steady pace over the past 50 years.