An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models

Abstract

The climate feedbacks in coupled ocean–atmosphere models are compared using a coordinated set of twenty-first-century climate change experiments. Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response. Large intermodel differences in the lapse rate feedback are observed and shown to be associated with differing regional patterns of surface warming. Consistent with previous studies, it is found that the vertical changes in temperature and water vapor are tightly coupled in all models and, importantly, demonstrate that intermodel differences in the sum of lapse rate and water vapor feedbacks are small. In contrast, intermodel differences in cloud feedback are found to provide the largest source of uncertainty in current predictions of climate sensitivity.

A fully coupled atmosphere–ocean wave modeling system for the Mediterranean Sea: interactions and sensitivity to the resolved scales and mechanisms

“…The large-scale perturbations in the general circulation of atmosphere and ocean, the temporal variability of dynamical air-sea interaction, and its feedbacks have already been incorporated into climate coupling systems (Battisti, 1988;Philander et al, 1992;Soden and Held, 2006;Roberts and Battisti, 2011). During the last several years, the importance of coupling at regional scales has challenged the research community (Hodur et al, 2002;Lionello et al, 2003).…”

A multi-site intercomparison of integrated water vapour observations for climate change analysis

“…Unfortunately, clouds are the greatest source of uncertainty in climate models. In a more direct sense, water vapour also provides the largest known feedback mechanism for amplifying climate change (Soden and Held, 2006). The tropospheric water vapour…”

On the Longwave Climate Feedbacks

“…The magnitudes of these residuals (an ensemble mean of 1.23 W m 22 ) are apparently nonnegligible, compared to the overall OLR changes (0.70 W m 22 ). The magnitude of the residuals is so big that they cannot be simply attributed to the nonlinear effect, which should be very small as shown by many previous studies (e.g., Soden and Held 2006;Huang et al 2007;Shell et al 2008;Soden et al 2008;Huang et al 2010). Moreover, there is a substantial spread (a standard deviation of 0.47 W m 22 ) of the residuals across these models; also, a significant correlation (a correlation coefficient of 0.55) exists between these residuals and global mean surface temperature changes.…”

“…The noncloud feedbacks are computed by multiplying the kernels of Shell et al (2008) with the linear trends in monthly mean temperature and water vapor as simulated by each GCM. The tropopause is set to linearly increase from 100 hPa at the equator to 300 hPa at the poles following the previous analyses (e.g., Soden and Held 2006;Soden et al 2008;Shell et al 2008). The cloud feedback is then obtained by using the cloud forcing adjustment (CFA) method (Soden et al 2008;Shell et al 2008), which combines with Eq.…”

“…(3) for estimating cloud feedback (Soden et al 2008;Shell et al 2008). Note, however, that the latter was used in earlier studies (e.g., Soden and Held 2006) and sometimes has to be adopted in analyzing observational data when clear-sky data are not available due to sampling limitations.…”