The first action of October 24 took place at sunrise in New Zealand. The last was probably this tiny gathering for the end of the sunset in Hawaii, almost all the way back around the world.

And this one is especially significant. This hardy crew trekked up Mauna Kea so they could send back a picture of Mauna Loa, the largest landmass on earth. It’s also the place where, 50 years ago, the first instrument to measure co2 in the atmosphere was set up by a team from Scripps Oceanographic Institute as part of the World Geophysical Year. It’s that machine that’s been steadily recording the rise of co2 in the atmosphere–and it’s that machine that we dearly hope someday soon will start to record its fall, back towardes 350.

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