Scientists have become very good at taking air samples from the ground and plugging them into global carbon dioxide models. What is missing from this picture is a comprehensive view of what is happening higher up.

Enter HIPPO—a three-part pole-to-pole mission designed to fill in those gaps. Led by Harvard University researchers and the University Corporation for Atmospheric Research, the plan was to fly a specially outfitted former corporate jet from one pole of the planet to the other and back again, collecting samples all along the way. The first of the three flights finished in January and returned some surprising results. It found that carbon dioxide seems to migrate north, accumulating above the Arctic. Meanwhile, the Antarctic seems to collect more than its share of oxygen. Scientists say this may be a new kink in the global CO2 picture, or it may just be a seasonal shift. To find out which it is, the jet will fly two more identical flights at different times of the year.

The Arctic, as seen from HIPPO's converted corporate jet, called HIAPER.