Sea level rise has been happening on a steady basis since humans started measuring the ocean, but it’s rising much faster now than at any other time in recorded history. This is mainly because Earth’s climate is warming due to human activity such as burning fossil fuels. This warming is causing the polar ice sheets to melt, and that’s a big factor in raising global sea levels.

The world’s sea levels fluctuate a lot, and those fluctuations are caused by a bunch of factors, including daily tides, natural year-to-year variations like the El Nino effect, and passing storms that push ocean water higher up or down. Scientists who study the ocean and its changing sea levels use a network of tide stations, satellite laser altimeters, and other tools to try and understand long-term trends.

These sensors provide important insights about what’s happening to the ocean’s surface and help scientists make accurate predictions. For example, a new 2021 study found that if greenhouse gas emissions continue on their current trajectory, by the end of this century global sea levels could be about a foot (0.3 meters) higher than they are now, which is a huge increase over just a few decades.

The good news is that if we significantly cut greenhouse gas emissions, it would slow the rate of sea level rise. But that still leaves many people living in low-lying coastal areas at risk of flooding. So it’s important for policymakers to have the best information about sea level rise, so they can prepare their communities.