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This Pulsing Earth

John Nelson
IDV Solutions

It's breathing, he thought. "All of a sudden I see a thing with a heartbeat."

John Nelson is a designer, well known for tracing complex weather patterns or cultural information on maps, so considering what he usually does, this was easy. NASA's Visible Earth team publishes pictures of our planet every month of the year, so John thought, why not stitch them together, and see what the seasons look like from outer space?

So he stitched, and then looked.

"I was surprised," he writes on his UX.Blog. Talking later to Fast Company's Mark Wilson, he remembers:

These images are gripping. What they show are the comings and goings of ice and snow. It's mostly a white pulse, more white, then less, then more again. I look at that dance of white and think, how gentle it seems.

Snowball Earth

There have been times on Earth when the white didn't go. Around 600 million years ago, it got so cold some scientists believe the whole planet was covered in ice; the oceans froze, so it was white from pole to pole. They call this the "snowball-earth hypothesis." It was first proposed in the 1990s and so much evidence (see below) has turned up, it now appears the earth stayed frozen for up to 100,000 years, making our planet, says science writer Craig Childs, "a completely white Earth ... bald and smooth as an eggshell." In those years, the Earth almost stopped breathing.

And it's gone the other way too. There have been eras where it got so warm, the white spots on Earth dwindled to a point where there were almost no glaciers, no icebergs, no snow caps hanging on in high places. No winter wonderlands. More deserts.

Our era — and you can see it on John's map — is a beautiful in between, in a Goldilocks way, "not too hot, not too cold, just right." Every year when the Earth turns, snow in high places creeps down into our valleys covering us with white, and then, a few months later, it tiptoes back up again, giving us seasons of green and seasons of frost.

The Dance Of Whiteness

And it is exactly this dance, the dance of whiteness, that is now, in more and more places, at risk. The white pulse you see in John's maps may soon get smaller ... and smaller. That's what makes these GIFs so compelling. This is a picture of something precious.

That's my take. John has a different notion, more personal. As he told Mark Wilson:

Either way — every way — seasons are a gift.

Planetary climate change is a modern idea. It took a Swiss-born Harvard professor, Louis Agassiz, years to make the case that the world did not have only one great disaster — Noah's flood in the Bible — but many; that the Earth has a long history and our climate is constantly changing.

As Craig Childs writes in his book Apocalyptic Planet, Agassiz looked at glaciated rock and seashells on mountaintops and concluded "the epoch of intense cold which preceded the present creation has been only a temporary oscillation of the Earth's temperature." Says Childs: "We now call these oscillations "ice ages" and knowledge of their existence altered the way we thought of time passing on Earth."

Childs says evidence for several (still hypothetical) snowball-earth events keeps coming in ...

" ... mainly from the glacial debris found in rock formations dating to that time and positioned in what were then tropical landmasses. These episodes would have likely been caused by an extreme tilt in the Earth's axis, where the tropics may have actually been colder than the poles. Or the cause may have been runaway ice ages where positive feedback loops could have cooled the planet as more ice reflected solar radiation into space until the Earth's surface gave up far more heat than it stored."

[Ice core drilling helps:] "In Greenland, cores drilled out of the ice have hit bedrock thousands of feet below, and one drill site came up with spruce tree needles. There had been forests down there, a very different Greenland, actually green. Before the ice."

Copyright 2023 NPR. To see more, visit https://www.npr.org.

Robert Krulwich
Robert Krulwich works on radio, podcasts, video, the blogosphere. He has been called "the most inventive network reporter in television" by TV Guide.