More than 20 years ago, NASA scientist Ralph Kahn authored a column for the Los Angeles Times anticipating the launch of a new satellite — and ultimately a whole fleet of satellites — that would study Earth.
“We want a picture of Earth that is more specific about what is happening to the climate, which after all is what makes the planet habitable,” he wrote. And that picture needed to be rich with detail. “Precisely where are deserts encroaching on grasslands? In what regions is it raining more than usual? Exactly how much are glaciers shrinking, and at what rate is the sea level rising?” he asked.
The first satellite, Terra (originally named EOS-AM), roared into space on December 18, 1999, began collecting data in February and March 2000, and collected its first complete day of MODIS data on April 19, 2000.
“About every seven weeks, the satellite archives will receive as much data from EOS-AM as are held in all the volumes of the Library of Congress. And the EOS-AM satellite alone is supposed to keep pouring numbers down from the sky, relentlessly, for at least six years,” Kahn wrote.
Amazingly, all those numbers from Terra continue to pour down 20 years later. Over time, the flood of data from Terra and several other satellites has turned into scientific discoveries. Bit by bit, the questions Kahn initially posed in his column have been answered.
We can say now that sea level is rising at 3.3 millimeters (.13 inches) per year. We can show you a map of where exactly green vegetation has become more common and where it has faded. We can point you to a long-term dataset that will show you precisely where rain has fallen over the past two decades. And we can give you a tour of the world’s glaciers that shows you where they are and many examples of where they are shrinking.
The question to grapple with now: what do we with all this information?