12th Conference on Middle Atmosphere

Wednesday, 6 November 2002: 10:15 AM
What is our understanding of the observed temperature variations and changes in the stratosphere?
V. Ramaswamy, NOAA/GFDL, Princeton, NJ
There now exists a well-documented observational record of the variations and changes in the stratospheric temperatures over the past forty years or so, with reasonably good and continuous global coverage over the past two decades. The time-series record includes measurements made by different instrument types as well as those resulting from various kinds of analyses. There is good coherency amongst the different observational datasets with regards to the estimates of temperature changes. The long-term change in the stratospheric temperatures reveals several interesting features. Analyses of the spatial (global-mean to zonal-mean) and temporal (annual to seasonal) changes will be presented.

The causal factors for the observed long-term changes have been and are being intensely pursued using models that have improved substantially in recent years. Model simulations have inquired into whether the observed changes can be attributed to "unforced" or internal dynamical variations within the climate system, or are the result of "natural" (e.g., solar, volcanic events) and/ or "anthropogenic" (e.g., trace gases including ozone) changes. Comparisons of model simulations with the observed variations have provided the basis for causality arguments. The evaluations from such exercises will be discussed, along with issues that are as yet unresolved.

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