We’ve all seen the iconic Blue Marble photo of the earth from space, the image that launched a thousand nature essays, but Bill Nelson and Piers Sellers are among the few people who have enjoyed that perspective on the planet in the flesh. Nelson is now a U.S. Senator from Florida, Sellers is a top NASA science official, and this morning, at an Earth Day hearing in my Miami Beach neighborhood, I got to hear the two former astronauts reminisce about the view from 10 million feet.

Senator Nelson recalled the color contrasts in the Amazon that illuminated the growth of deforestation. “The earth looked so beautiful, so alive—and yet so fragile,” he said. “It made me want to be a better steward of what the good Lord gave us—and yet we continue to mess it up.” Dr. Sellers remembered catching a glimpse of the Florida peninsula between his boots during a spacewalk. When you go around the world in ninety minutes, he said, you realize it’s a very small world.

“My take-home impression was that we inhabit a very beautiful but delicate planet,” said Sellers, a meteorologist who is NASA’s deputy director for science and exploration. “And the dynamic engine of planet Earth is the climate system that allows all life here to prosper and grow, including us humans.”

Now that climate is changing, and as Nelson said at the start of the South Florida hearing: “This is Ground Zero.” Scientists have documented that the seas along the Florida coastline have risen five to eight inches over the last fifty years, and Biscayne Bay now floods the streets of my neighborhood just about every month at high tide. “It’s real. It’s happening here,” Nelson said. “Yet some of my colleagues in the Senate continue to deny it.”