The 2019 floods in Venice rose to over six feet in some areas and put 70 percent of the city underwater at one point. The floods caused $1.1 billion in damage, including priceless cultural heritage sites. Extreme flooding used to occur in Venice once every 100 years. By 2050, it’s expected to happen every six years. To combat this, Venice has spent decades building a multi-billion euro flood barrier system. In an initial test this October, it successfully held back floodwaters though it’s not clear that this will be a long-term solution.
While Venice is investing billions in flood defense infrastructure, many low-lying regions throughout the world are ill-prepared for global sea rise caused by climate change. More than 150 million people worldwide are now living on land that will be underwater by 2050.
In the United States, nearly 40 percent of the population lives in coastal areas. In many locations along the U.S. coastline, high-tide flooding is 300%-900% more frequent than it was 50 years ago. By 2045, sea level rise will threaten more than 300,000 of today’s U.S. homes with chronic flooding, impacting more than a half-million people, according to a 2018 study. Another consequence of global sea rise is the threat to our drinking water from the incursion of saltwater. Saltwater is both impacting tidal rivers and contaminating aquifers.
And the rate of sea level rise is accelerating. In 2019, the global sea level was 3.4 inches above the 1993 average—the highest annual average in the satellite record. Average sea levels have risen more than eight inches since 1880, with three of those inches in just that past 25 years.
Climate change is influencing the three factors that contribute to the global sea rise. As greenhouse gases warm the planet, the world’s oceans are absorbing more than 90 percent of the heat. When the water heats up, it expands. About 50% of the sea rise in the past 25 years can be attributed to warmer water taking up more space.
A second cause of sea level rise is melting glaciers. Mountain glaciers are disappearing at an alarming rate. There used to be a balance between summer melts and winter snows to maintain glaciers. Now warmer weather has led to more melting and less snowfall. The rate of glacier melt has increased from 9 inches/year in the 1980s to 3 feet/year from 2010-2018. This increase not only causes sea level rise, but loss of these frozen reservoirs threatens our supply of fresh drinking water.
The third factor contributing to sea rise is the loss of ice sheets across Greenland and Antarctica. A recent NASA-led study says with the current rate of greenhouse gas emissions, these ice sheets alone could add 15 inches of sea level rise by 2100. And climate experts fear ice melt projections for Antarctica have drastically underestimated the impact that weather fluctuations will have on rising sea levels.
The impact of global sea rise is affecting regions throughout the world, including major Asian cities like Tokyo, Jakarta, Ho Chi Minh City, Guangzhou, and Shanghai. Other cities such as Dubai, New York, and Alexandria, Virginia, are also at high risk from rising sea levels. These regions are exploring different ways to adapt, either investing in sea walls for flood defenses or trying to relocate people. In fact, Indonesia will be moving its capital from Jakarta to the island of Borneo.
Ocean currents have also been the focus of numerous recent studies, which indicate that key current systems are weakening due to climate change impacts and will continue to do so if emissions remain unchecked. (Learn more about the importance of ocean currents here.)
Looking forward, if we take aggressive action to fight climate change and succeed in slowing the acceleration of sea level rise, many coastal communities in the U.S. and around the world could be saved.