Linear trends and closures of 10-yr observations of AIRS stratospheric channels

This paper investigates the linear trends of 10 years (2003–12) of AIRS global-mean radiances in the CO₂ v₂ band that are sensitive to emissions from the stratosphere (stratospheric channels). AIRS lower-stratospheric channels have a cooling trend of no more than 0.23 K decade⁻¹ whereas the midstratospheric channels consistently show a statistically significant cooling trend as large as 0.58 K decade⁻¹.

The 95% confidence interval for the trend is ~±0.20 K decade⁻¹. Two sets of synthetic AIRS radiances are computed using the principal component–based radiative transfer model (PCRTM), one based on a free-running GFDL Atmospheric Model, version 3 (AM3), over the same period and one based on ERA-Interim. The GFDL AM3 simulations overestimate the cooling trends in the mid- to upper-stratospheric channels but slightly underestimate them in the lower-stratospheric channels.