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The oceans are rising. Globally, the average sea level is more than eight inches higher now than it was in 1880, and the trend is accelerating. NPR's Rebecca Hersher has the story about a new satellite that could help scientists understand how climate change is changing our seas. Here's her story.
REBECCA HERSHER, BYLINE: If you live near the coast, you've probably seen buoys and other contraptions along the water's edge that measure what's going on in the ocean, including how high the water is. But when it comes to understanding global climate change, there is no substitute for satellite data.
JOSH WILLIS: From space, you can see the whole thing.
HERSHER: Josh Willis is a scientist at NASA. He's leading the U.S. team that's launching a new satellite called Sentinel-6 in collaboration with the European Space Agency. Sentinel-6 will zip around the globe 800 miles up and look at the surface of all the oceans.
WILLIS: It's really kind of an incredible feat of technology. We can actually measure the water level with an accuracy of about one inch from 800 miles up.
HERSHER: Sentinel-6 uses radar to make continuous measurements.
WILLIS: A radar beam comes down out of the satellite. It bounces off that surface, and then it measures the signal coming back. And by figuring out how long it takes to go down and come back, you can tell how far away the water is.
HERSHER: If you know how far away the water is, you can figure out how high it is relative to the land. Sentinel-6 is the latest in a string of satellites that do this kind of measurement going back to the '90s. But those missions were somewhat ad hoc, and scientists couldn't always be sure that there would be a next mission when the current one ended, which is a nightmare when you're trying to understand how the climate is changing over time, which is why they are really excited that this time, the satellite will be up there for five years and then another identical satellite will launch to do another five years - so a decade of reliable data. LuAnne Thompson studies oceans at the University of Washington.
LUANNE THOMPSON: I use that data every day in my research.
HERSHER: Thompson has been studying how the oceans have been changing for decades. She says obviously sea level rise is tangibly important to people who live on the coasts, but ocean changes affect everyone. What happens in the ocean doesn't stay there. For example, currents and ocean temperatures affect weather and fish populations.
THOMPSON: We can also use the sea level measurements to understand how currents are changing, how the ocean is storing heat.
HERSHER: And hotter oceans can drive more powerful hurricanes. And scientists use sea level data from satellites to figure out exactly how hot the oceans are getting, too, because water gets bigger as it gets hotter.
THOMPSON: So by knowing the sea level, we have an indication of how much the ocean has expanded because of warming.
HERSHER: Josh Willis of NASA says the Sentinel-6 satellite is crucial because climate change is happening fast. In the past, scientists had to make do with less data about the oceans. But now, with the Earth rapidly warming, climate scientists need as much information as possible about what's happening around the globe.
WILLIS: Sea level is continuing to rise, and we can't stop measuring it. Every year, every decade, we're remaking the climate and raising sea levels higher and higher.
HERSHER: Sentinel-6 is scheduled to launch on November 21 from California. Rebecca Hersher, NPR News.
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