Despite the fact that Neptune’s southern hemisphere has been in its summer season for the last 17 years, Earth temperatures have fallen. A perplexing discovery that leaves astronomers with more questions than answers, according to the team who made the discovery. Michael Roman, a postdoctoral research associate at the University of Leicester and the lead author of a study published Monday in the Planetary Science Journal, says that since they have been observing Neptune during its early southern summer, “we would expect temperatures to be slowly increasing, rather than decreasing.” According to Space.com, the findings are based on studies of the ice giant’s thermal-infrared brightness, which is a measure of heat in the atmosphere, for almost two decades—roughly half the duration of the 40-year summer, according to NASA.
According to a press release, the researchers discovered “a decrease in Neptune’s thermal brightness since reliable thermal imaging began in 2003, indicating that globally averaged temperatures in Neptune’s stratosphere—the layer of the atmosphere just above its active weather layer—have dropped by approximately 8 degrees Celsius (14 degrees Fahrenheit) between 2003 and 2018.” However, observations of Neptune’s south pole suggest that the polar stratosphere warmed by approximately 11 degrees Celsius, or 20 degrees Fahrenheit, in just two years between 2018 and 2020, “reversing the previous globally averaged cooling trend,” according to the release. This is the first time that this has been observed. “Such polar warming has never been recorded on Neptune before,” the paper continues.
Researchers know relatively little about Neptune’s seasons, which occur throughout the course of the planet’s 165-year cycle around the sun. According to the researchers, seasonal changes in Neptune’s atmospheric chemistry might be responsible for the temperature oscillations. According to ScienceAlert, “photochemically generated hydrocarbons—primarily ethane and acetylene—are potent infrared emitters that serve to cool the stratosphere,” as the research points out in its conclusion. However, the alterations detected between 2018 and 2020 “appear to be rather quick for a seasonal response,” according to the researchers. According to the press release, “random unpredictability in weather patterns or perhaps a reaction to the 11-year solar activity cycle” may have had a part in the event’s occurrence. Researchers aim to learn more about the solar system this year through observations made possible by the James Webb Space Telescope.