Neptune’s Atmosphere Cooled Then Warmed for Unknown Reasons

Observations show that Neptune’s atmosphere has been changing in puzzling ways. Between 2003 and 2009, its stratosphere cooled by at least 7°C, even though it was summer in the southern hemisphere. Then, starting around 2018, the south pole suddenly warmed by about 11°C in just two years. The cause? Nobody knows. It could be linked to solar activity, changes in clouds and hazes, or even unknown processes deep inside the planet.