Constraining Cloud Feedback Uncertainty over the Atlantic with
Bias-corrected Downscaling
Abstract
Clouds exert a significant impact on global temperatures and climate
change. Cloud-radiative feedback (CRF) is one of the major sources of
climate change uncertainty. Understanding CRF is therefore crucial for
accurate climate projections. Biases like the double-ITCZ problem in
Global Climate Models (GCMs) hampers precise climate projections. Here,
we employ a bias-corrected downscaling method to constrain the cloud
feedback uncertainties in the tropical and sub-tropical Atlantic region.
We use high-resolution regional climate model (RCM) simulations with
resolved deep convection, driven by debiased driving fields from three
different global climate models (GCMs). Our simulations project a
narrower range of the CRF over the tropical and sub-tropical Atlantic
(-0.7 to 0.6 $Wm^{-2}K^{-1}$) compared with the driving GCMs
(-0.9 to 1.0 $Wm^{-2}K^{-1}$). Furthermore, using linear
regression between equilibrium climate sensitivity (ECS) and the CRF
over the studied domain, a slightly narrower range of ECS (3.05 - 4.87
K) is inferred after the downscaling, compared to the GCMs’ result (2.98
- 5.15 K). The narrowed range is mainly due to a reduced range of
stratocumulus feedback.
Our study highlights the potential of bias-corrected downscaling in
constraining the uncertainty of simulations and estimates of cloud
feedback and equilibrium climate sensitivity. The results advocate for
further simulations with additional RCMs and domains for a more
comprehensive analysis.