The mystery of recent stratospheric temperature trends

The climate community relies on a single remotely-sensed set of observations for understanding temperature trends in the middle and upper stratosphere prior to ~2000: infrared radiance data from the Stratospheric Sounding Unit (SSU). Over the past decade, the community has become increasingly aware of the limitations of the primary SSU dataset for climate change detection. For this reason, investigators have recently developed a new SSU temperature dataset based on an independent processing of the original satellite-measured radiances.

However, rather than resolve key issues related to stratospheric climate change, the new SSU data raise new questions. The new data provide a strikingly different view of the time history of stratospheric temperatures than that provided by the original SSU data. They call into question our understanding of observed stratospheric temperature trends and our ability to test simulations of the stratospheric response to emissions of greenhouse gases and ozone depleting substances. We highlight the important issues raised by the new SSU data and offer suggestions for how the climate community can resolve the mysteries that they present.