Churning of Earth's molten interior behind sea level changes.
Geophysicist Dietmar Muller from University of Sydney said that the levels vary because of natural processes on Earth on timescales from thousands to hundreds of millions of years.
In the past they have been more than 120 metres higher than present day levels.
"The reality is we live on a dynamic planet - even in the absence of human-induced warming, sea levels would still change dramatically because it's been doing it for a very long time," ABC Science quoted Muller as saying.
"This paper points this out, controlling and taming the planet is to some extent a futile exercise.
"If you want to develop intelligent responses [to climate change] we need to identify our own contributions to sea level change from natural fluctuations," he said.
While the causes of long and very short term (less than 2 million years) changes in sea level are well understood, Muller suggested there are also cycles of change on intermediate timescales of between 2 and 20 million years.
Another research led by Kenni Petersen from Aarhus University has also shown sea levels may change at a regional scale due to heat from below the Earth's crust forcing sea floors to rise.
Professor Kurt Lambeck of Australian National University said Petersen's research is "likely to be an important part of our understanding of long-term sea level change".
But he said these sorts of changes are of "no consequence on the human timescale."
"What's important is the rate of change, which is now several millimetres per year, several orders of magnitude more than in has been in the past," he said.
The findings were published in the journal Science. (ANI)
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