The 20th century was a modern moment for people around the globe, with giant breakthroughs in steel, electricity, and the automobile. Yet industrial development has also led to climate change. According to a study by an international team of experts at the University of South Florida (USF), sea levels have risen by 18 centimeters since the beginning of the 20th century.
The study, which appears on the cover of Science Advances, seeks to determine pre-industrial sea levels and investigate the current contribution of the greenhouse effect to sea level rise. The team, including graduate students from USC, traveled to the Spanish island of Mallorca, which is home to more than 1,000 cave systems, some of which contain sedimentary rock dating back millions of years. Their survey focused on deposits from 4,000 years ago to the present.
The team found evidence of sea level rise of 20cm, which occurred nearly 3,200 years ago when the ice sheet was melting naturally at a rate of 0.5mm per year. Despite historical events such as the Medieval Warm Period and the Little Ice Age, sea levels remained remarkably stable until 1900.
The study’s findings are startling, with sea level rise since the 1900s unprecedented compared to natural changes in ice mass over the past 4,000 years. This means that if global temperatures continue to rise, sea levels might eventually reach higher levels than scientists had previously estimated.
To create the timeline, the team collected 13 samples from eight caves along the Mediterranean coastline. These deposits are very rare and only form in cave passages near shorelines that have been repeatedly flooded by seawater, making them an accurate marker of changes in sea level over time.
Each deposit holds valuable insight into the past and future, helping researchers determine how quickly sea levels will rise over the coming decades and centuries.