A study recently published in the journal Proceedings of the National Academy of Sciences reveals that the planet’s sea levels are currently at their highest in the past 6,000 years, due to the warming of the Earth’s temperature and the melting of glacial ice and ice sheets.

According to USA Today, researchers of the study, led by Kurt Lambeck of the Australian National University, examined samples of past sediments in Australia and Asia dating back 35,000 years. The team found that the planet’s sea levels were fairly stable most of the past 6,000 years, but that began to change approximately 150 years ago, the same time greenhouse gases began being pumped into the atmosphere by the burning of fossil fuels.

“What we see in the tide gauges, we don’t see in the past record, so there’s something going on today that’s wasn’t going on before,” said Lambeck, according to Food World News. “I think that is clearly the impact of rising temperatures.”

The Washington Post reports that two main forces are driving the rise of sea levels: thermal expansion, which involves an increase in ocean water as it warms, and an influx of additional water, produced from the melting of ice sheets and glaciers.

“It’s like if you leave a big block of ice on the table, it doesn’t melt instantaneously, there’s always a delay in the system,” said Lambeck, according to The Guardian. “We know from the last interglacial period that when temperatures were several degrees warmer than today there was a lot more water in the oceans, with levels around 4 to 5m higher than today. The question is how fast that change occurs when you increase temperatures.”

Researchers warn that this rise in sea level will not go away quickly. “What we’ve seen is unusual, certainly unprecedented for these interglacial periods,” said Lambeck. “All the studies show that you can’t just switch off this process. Sea levels will continue to rise for some centuries to come even if we keep carbon emissions at present day levels. What level that will get to, we are less sure about. But it’s clear we can’t just reverse the process overnight.”