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Robust Acceleration of Stratospheric Moistening and Its Radiative Feedback Under Greenhouse Warming
Author(s) -
Xia Yan,
Huang Yi,
Hu Yongyun
Publication year - 2020
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033090
Subject(s) - radiative forcing , atmospheric sciences , environmental science , global warming , radiative transfer , tropopause , stratosphere , climatology , climate sensitivity , greenhouse gas , climate change , climate model , forcing (mathematics) , meteorology , aerosol , physics , ecology , quantum mechanics , geology , biology
Stratospheric water vapor (SWV) changes, in response to increasing CO 2 , as a feedback component may play an important role in the Earth's energy budget. It has drawn extensive studies in the past decade. Here, we calculate the SWV climate feedback using the 150‐year CO 2 forcing (1pctCO2) simulations in the CMIP6 ensemble of models. All models robustly show a moistening of the stratosphere, causing a positive radiative feedback to surface warming. We find that the stratospheric moistening rate and the SWV feedback both increase with surface warming. The moistening occurs at a rate of 0.9 ± 0.1 ppmv K −1 and its radiative feedback measured by the fixed dynamical heating method is 0.11 ± 0.02 W m −2 K −1 in the first 50 model years; the moistening rate increases to 1.2 ± 0.2 ppmv K −1 and the feedback increases to 0.16 ± 0.03 W m −2 K −1 in the last 50 model years when the global‐mean surface temperature is 3.3 K warmer. These increases are found to be caused by an amplified rate of tropical tropopause warming with respect to surface warming, which is 0.6 and 1.1 K K −1 for the two 50‐year periods, respectively. We conclude that the SWV feedback is strengthening with surface warming, which can contribute to increasing climate sensitivity in the future under global warming.