I recently wrote an article talking about noctilucent clouds—relatively rare high-altitude clouds usually seen just after sunset and before sunrise. They have a milky, silvery appearance, and are usually pretty hard to capture on photos.
It can be even harder from space, where lighting conditions are harsher and getting the right exposure balance is difficult. But astronaut Reid Wiseman got it just right recently, snagging a photo of the odd clouds from the International Space Station:
Conditions to create noctilucent (literally, “night shining”) clouds are touchy, which is why they’re rare. But there have been a lot seen recently—check out this astonishing photo taken over an alpine lake in Germany—and that has many folks wondering what’s going on. There could very well be a link with them and global warming, which is intriguing but doesn’t have a lot of evidence to support it yet.
But if we keep seeing more of these clouds, we may yet get a better understanding of them, and whether or not they are a canary in a coal mine of global warming.