Now, an international team of climate researchers says it has fully explained the causes behind global sea level rise over the past six decades, solving a long standing problem that had complicated scientists' understanding of one of climate change's most serious threats.

Sea Level Rise Is Accelerating

According to the new study, published in Science Advances, global sea levels have risen at an average rate of 2.06 millimeters per year since 1960. But the pace has increased dramatically in recent decades, reaching 3.94 millimeters per year between 2005 and 2023.

Researchers found that warming oceans are the largest contributor, responsible for 43% of the increase. As seawater heats up, it expands and occupies more space, pushing sea levels higher around the world.

Melting ice has also become an increasingly important factor. Mountain glaciers account for 27% of sea level rise since 1960, while the Greenland Ice Sheet contributes 15% and the Antarctic Ice Sheet adds another 12%. Changes in land water storage make up the remaining 3%.

The study also sheds light on why sea level rise has sped up over time. Since 1960, ocean warming and reduced land water storage played major roles. Since 1993, however, the rapid melting of glaciers and ice sheets in Greenland and Antarctica has become a much larger driver of the accelerating trend.

Scientists warn these patterns are likely to continue for decades.

Scientists Solve a Long Standing Measurement Mystery

For years, researchers struggled with a frustrating mismatch between observed sea level rise and the combined estimates from its known causes. Measurements from satellites and coastal tide gauges did not fully align with calculations from ocean warming and melting ice.

The new research appears to close that gap.

"For years, there has been a frustrating gap between how much the oceans were observed to be rising and how much we could explain from the individual causes. This work shows that, with better instruments, processes, and smarter analysis, this knowledge gap can be closed. We can explain sea level rise with greater confidence," said Prof. John Abraham, School of Engineering, University of St. Thomas; co-author.

The research team was led by scientists from the Institute of Atmospheric Physics at the Chinese Academy of Sciences. The collaboration also included researchers from Tulane University, the NSF National Center for Atmospheric Research, the University of St. Thomas, and scientific partners in France.

The scientists credited several technological and analytical improvements for resolving the discrepancy. These included updated corrections to satellite measurements that had gradually shifted after 2015, improved methods for measuring land movement at coastal tide gauges, and more accurate estimates of ice loss from Greenland and Antarctica.

Rising Seas Expected To Continue for Centuries

Researchers say the findings reinforce a troubling reality about climate change. Even if greenhouse gas emissions are eventually stabilized, sea level rise will not stop anytime soon.

The oceans absorb heat slowly and continue warming deep below the surface over long periods of time. At the same time, massive ice sheets and glaciers continue melting long after temperatures rise. Because of this enormous planetary inertia, scientists expect sea levels to keep rising for many centuries.