Stratospheric Temperature Variability and Trends from Observations and Models

Abstract:

Temperatures in the stratosphere have decreased over the last several decades, in response to the combined effects of increases in CO₂ and changes in stratospheric ozone. Observed long-term changes in stratospheric temperatures can be evaluated based on merged satellite observations, and there has been significant recent progress in producing such data over recent years. New merged data sets show long-term stratospheric cooling which increases in magnitude from the lower to upper stratosphere (-0.5 to -0.7 K/decade), in addition to variations linked to the 11-year solar cycle, QBO, ENSO and volcanic effects. The time series provide evidence that upper stratosphere temperatures have responded to observed changes in ozone, in addition to cooling from increases in CO₂. Comparisons with a state-of-the-art chemistry-climate model (WACCM) show good overall agreement in the simulation of temperature variability and trends over the past 4 decades.