atmosphere

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400 ppm: A Milestone that Means Everything, and Nothing

For the first time in history, the atmosphere’s concentration of CO2 has topped 400 ppm

Commentary by Michael D. Lemonick

SAUL LOEB/AFP/Getty Images

CO2 levels have been climbing since the Industrial Revolution.

I’m not big on taking note of milestones. They’re artificial, and usually meaningless, but people get all worked up about them anyway. I don’t like to stay up late on New Year’s Eve, for example, because Dec. 31 is a purely arbitrary date. Nothing real actually begins the next day, but we all pretend otherwise. I have similar feelings about the first day of spring, the temperature reaching 100° as opposed to 99° and all sorts of other magic-sounding dates and numbers that don’t have any real significance.

But since no law says I have to be consistent, I’m going to take note of a milestone that happened some time in the past couple of months, and which was reported last week by NOAA. For the first time in recorded history, and almost certainly for much longer than that, the atmosphere’s concentration of carbon dioxide, or CO2, has nipped above 400 parts per million in at least one part of the world. Monitoring stations in Alaska, northern Europe, and Asia have all noted readings above that level during this past spring.

In one sense, this isn’t all that important. There’s no meaningful difference between 399 ppm and 400, and the current world average is more like 393. Even in the Arctic, scientists know the CO2 level will drop back below 400 this summer, as trees in the Northern Hemisphere suck carbon dioxide back out of the atmosphere (you can see the annual ups and downs as trees start growing in the spring and go into hibernation in the fall). We won’t get to a world average of 400 for several years yet.
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A Year-Long Sky Journal as Video Mosaic

A motion mosaic of our ever-changing, endlessly fascinating atmosphere

Ken Murphy / Murphlab

Detail from Ken Murphy's video sky mosaic

About two years ago, Ken Murphy set up a tripod on the roof of San Francisco’s Exploratorium science museum and aimed his video camera at a particular patch of sky. He’s spent the two years since shooting time-lapse sequences from his makeshift observatory and has stitched them together into this wonderful visual tableau.

Murphy, who is a web developer at KQED and a former artist-in-residence at the Exploratorium, says the project grew out of — well — boredom. He became restless with his experimentation with art works using LED lights. He says he was looking for more natural movement. So Murphy went dumpster-diving for parts and cobbled together a computer-controlled camera that would record the same sky segment every ten seconds, around the clock. He says it took two years of shooting to stitch together one full year of images. Eventually he found himself sorting through three million video frames for the mosaic. Continue reading