Garcia, RR, López-Puertas, M, Funke, B et al. (3 more authors) (2016) On the secular trend of COₓ and CO₂ in the lower thermosphere. Journal of Geophysical Research: Atmospheres, 121 (7). pp. 3634-3644. ISSN 2169-897X
Abstract
An analysis of recent observations (2004–2013) made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS) instrument indicate that total carbon (COx = CO + CO₂) has been increasing rapidly in the lower thermosphere, above 10˜³ hPa (90 km). The estimated trend (~9% per decade) is about a factor of 2 larger than the rate of increase that can be ascribed to anthropogenic emissions of CO₂ (~5% per decade). Here we investigate whether the observed trends of CO₂ and COx can be reproduced using the Whole Atmosphere Community Climate Model (WACCM), a comprehensive global model with interactive chemistry, wherein vertical eddy diffusion is estimated from a parameterization of gravity wave breaking that can respond to changes in the model climate. We find that the modeled trends of CO² and COx do not differ significantly at any altitude from the value expected from anthropogenic increases of CO₂ and that WACCM does not produce significant changes in eddy diffusivity. We show that the discrepancy between model and observations cannot be attributed to uncertainties associated with geophysical noise and instrumental effects, to difficulties separating a linear trend from the 11 year solar signal, or to sparse sampling by ACE‐FTS. Estimates of the impact of vertical diffusion on CO₂ in the model indicate that a large increase in Kzz (~30% per decade) would be necessary to reconcile WACCM results with observations. It might be possible to ascertain whether such a large change in vertical mixing has in fact taken place by examining the trend of water vapor in the upper mesosphere.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | ©2016. American Geophysical Union. This is an author produced version of a paper published in Journal of Geophysical Research: Atmospheres. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | COx trends; CO₂ trends |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 26 Jun 2018 14:26 |
Last Modified: | 26 Jun 2018 15:00 |
Status: | Published |
Publisher: | American Geophysical Union |
Identification Number: | 10.1002/2015JD024553 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:131572 |