Humans are responsible for rising sea levels 

Humans are responsible for rising sea levels  Experts at Rutgers University have found evidence to confirm that modern sea-level rise is linked to human activities. While historical sea-level fluctuations were primarily influenced by changes in Earth’s orbit, this is not the case today.

The researchers were surprised to find that, over the last 66 million years, there were times when ice-free conditions coincided with carbon dioxide levels that were not much higher than what they have reached today. The experts also pinpointed time periods that were expected to be ice-free, but glacial ice was present.  

Study lead author Kenneth G. Miller is a professor in the Department of Earth and Planetary Sciences at Rutgers University-New Brunswick.

“Our team showed that the Earth’s history of glaciation was more complex than previously thought,” said Professor Miller.

“Although carbon dioxide levels had an important influence on ice-free periods, minor variations in the Earth’s orbit were the dominant factor in terms of ice volume and sea-level changes – until modern times.”

Sea-level rise has accelerated in recent decades, threatening to permanently submerge many coastal cities and communities. 

For the investigation, the scientists reconstructed the history of sea levels and glaciation over the last 66 million years. Using deep-sea geochemistry data, they compared estimates of the global average sea level with continental margin records. 

The study revealed that periods of nearly ice-free conditions, such as 17 million to 13 million years ago, occurred when the concentration of atmospheric carbon dioxide was not much higher than it is today. 

On the other hand, glacial periods occurred when the Earth was assumed to have been ice-free, such as from 48 million to 34 million years ago.

“We demonstrate that although atmospheric carbon dioxide had an important influence on ice-free periods on Earth, ice volume and sea-level changes prior to human influences were linked primarily to minor variations in the Earth’s orbit and distance from the sun,” said Professor Miller.

The largest decline in sea levels took place during the last glacial period about 20,000 years ago. The average water level dropped by around 400 feet. 

After this, the sea levels rose about one foot per decade until the pace slowed down 10,000 years ago. 

By 2,000 years ago, the sea level was stable until human activities began influencing the climate around 1900.

Future research is needed to investigate the times when the Earth was entirely ice-free, as well as the role of atmospheric carbon dioxide in glaciation. 

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer