The record of formal sea level observations includes tide gauge measurements dating back to the 19th century and precise satellite altimetry measurements that began in the latter part of the 20th century. (Images credits: NOAA, NASA)

The science writer Jeff Goodell began his latest book, The Water Will Come, with a frank assessment of our current situation: “Sea-level rise is one of the central facts of our time, as real as gravity. It will reshape our world in ways most of us can only dimly imagine.” A peak into the past shows us that Goodell is right: average global sea level has increased by about 9 inches since the 1880s; moreover, projections show that the rate at which waters are rising is accelerating, exacerbating what is already a daunting problem. Still, many climate skeptics have taken the position that the world is saturated with alarmists, and that, like so much of climate change science, sea level projections rely on computer models and lack hard data. But now we have an answer for these deniers: researchers have used satellite data stretching over the past 25 years to map out sea level rise, confirming what many in the scientific community have been saying for quite a while - the rate of sea level rise is accelerating.

“A concern that I’ve heard a number of times from skeptics is that projections of accelerated sea level rise are based on computer models, and it hasn’t been detected in the data yet…and data is king, so I can sort of understand that,” said Gary Mitchum, Associate Dean at the University of South Florida and co-author of the new report. “But now we can tell them that the data is detecting this acceleration as well.”

The study, which was published in the Proceedings of the National Academy of Sciences, used satellite data to find that sea level rise is accelerating by about 0.08 mm/year every year. This means that we’ll gain an additional millimeter per year in each coming decade, and by 2100, the world’s oceans are expected to be on average at least 60cm (2ft) higher.

Sea level has been rising over the past century, and the rate has increased in recent decades. In 2016, global sea level was 3.2 inches (82 mm) above the 1993 average—the highest annual average in the satellite record (1993-present). The light blue line shows seasonal (3-month) sea level estimates from Church and White (2011). The darker line is based on University of Hawaii Fast Delivery sea level data. Graphic credit: NOAA

“This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate—to more than 60 cm instead of about 30,” said Steve Nerem, the Associate Director of Colorado Universities Center for Astrodynamics Research, in a press release. Nerem went on to say that even this projection, of 60 cm (about 2 feet), was a conservative estimate, as it’s likely that the rate of change will continue increasing in the coming years.


This image illustrates water level differences for storm surge, storm tide, and a normal (predicted) high tide as compared to sea level. Storm surge is the rise in seawater level caused solely by a storm. Storm tide is the total observed seawater level during a storm, which is the combination of storm surge and normal high tide.

Across the world, including in the U.S., about 40 percent of people live in high-density coastal areas, and by 2100, up to 650 million people worldwide are projected to live in regions that are at risk from rising water levels. “We’re talking about major impacts on coastal infrastructure…so we really need to start a discussion what that means for coastal communities,” said Mitchum.

The largest threat presented by sea level rise is the increased risk of storm surges, which are caused by a storm’s winds pushing water onshore. Storms that might have resulted in little flooding a few decades ago will be much more dangerous as seas rise; already the probability of a Hurricane Sandy-level storm surge has doubled since 1950.


This topic is quite heavy on doom and gloom, but there are ways that we can keep ourselves safe and dry. One of the best places to look for solutions is the Netherlands. Since the Middle Ages, a series of dams and dikes have protected Dutch cities from flooding, and in recent years, the Netherlands has invested billions of dollars in innovative water management systems. A combination of massive sea walls, canals and floodplains, and even floating neighborhoods have allowed the country to stay dry even though a quarter of it sits below sea level.

Of course, the first step needs to be accepting that climate change and sea level rise are problems, and Trump doesn’t seem like the President that will best prepare the U.S. for the rising tide. Even though 2017 was one of the worst flood seasons in U.S. in history, Trump is still ignoring the role that climate change is playing in these natural disasters; in August, Trump rolled back Obama-era regulations requiring government agencies to take into account sea-level rise when building federal infrastructure; and even after Irma devastated Florida and Harvey flooded Houston, Scott Pruitt didn’t think it was the right “time” to discuss how climate change is affecting these storms.


“What we really need is to have a complete discussion of these sea level rise projections,” said Mitchum. “And if we can now say the computer models have been confirmed from data, then my real hope is that we can stop questioning them and start having a discussion about what we need to start doing to plan for [rising sea level].”