Observations of Local Positive Low Cloud Feedback Patterns and Their Role in Internal Variability and Climate Sensitivity

Abstract

Modeling studies have shown that cloud feedbacks are sensitive to the spatial pattern of sea surface temperature (SST) anomalies, while cloud feedbacks themselves strongly influence the magnitude of SST anomalies. Observational counterparts to such patterned interactions are still needed. Here we show that distinct large‐scale patterns of SST and low‐cloud cover (LCC) emerge naturally from objective analyses of observations and demonstrate their close coupling in a positive local SST‐LCC feedback loop that may be important for both internal variability and climate change. The two patterns that explain the maximum amount of covariance between SST and LCC correspond to the Interdecadal Pacific Oscillation and the Atlantic Multidecadal Oscillation, leading modes of multidecadal internal variability. Spatial patterns and time series of SST and LCC anomalies associated with both modes point to a strong positive local SST‐LCC feedback. In many current climate models, our analyses suggest that SST‐LCC feedback strength is too weak compared to observations. Modeled local SST‐LCC feedback strength affects simulated internal variability so that stronger feedback produces more intense and more realistic patterns of internal variability. To the extent that the physics of the local positive SST‐LCC feedback inferred from observed climate variability applies to future greenhouse warming, we anticipate significant amount of delayed warming because of SST‐LCC feedback when anthropogenic SST warming eventually overwhelm the effects of internal variability that may mute anthropogenic warming over parts of the ocean. We postulate that many climate models may be underestimating both future warming and the magnitude of modeled internal variability because of their weak SST‐LCC feedback.

New Generation of Climate Models Track Recent Unprecedented Changes in Earth's Radiation Budget Observed by CERES

“…Large decreases also occur for IPSL-CM6A and CESM2, but the locations differ from CERES. The SW flux decrease with SST off the west coast of North America is qualitatively consistent with other satellite studies that found a negative correlation between low-cloud cover and SST from passive (McCoy et al, 2017;Myers & Norris, 2015;Qu et al, 2015;Yuan et al, 2018) and active sensors (Cesana et al, 2019;Myers & Norris, 2015).…”

How accurately can the climate sensitivity to $$\hbox {CO}_{2}$$ be estimated from historical climate change?

“…This contrasts with the AOGCMs, in which we found evaluated from a single integration to be biased low by the presence of unforced variability (Appendix C), and comparably large values are attained only in the multimodel mean. We speculate that there are coupled atmosphere-ocean feedbacks which reinforce this SST pattern in the real world but are lacking in models (McGregor et al 2014(McGregor et al , 2018Raedel et al 2016;Yuan et al 2018;Liu et al 2018).…”

Relative Contributions of Atmospheric, Oceanic, and Coupled Processes to North Pacific and North Atlantic Variability

“…Weaker westerlies in the midlatitude NE Atlantic also reduce Ekman‐driven equatorward cold advection, warming the ocean by an amount even larger than that due to anomalous turbulent flux. The dominance of turbulent and oceanic fluxes in our observational analysis does not preclude the importance of cloud radiative anomalies for North Atlantic SST variations in particular seasons or on decadal timescales, as previous studies have found (Bellomo et al, ; Myers, Mechoso, & DeFlorio, ; Yuan et al, ; Yuan et al, ). But it does suggest that the leading pattern of interannual SST variability in the North Atlantic is almost entirely modulated by other processes.…”

“…There is abundant evidence from observational data and numerical model results that an atmosphere‐ocean coupled process consisting of a locally positive cloud radiative feedback over eastern subtropical and northern midlatitude oceans locally amplifies the magnitude and persistence of SST anomalies associated with the PDO and AMO (hereafter referred to as North Pacific variability and North Atlantic variability; Bellomo et al, , ; Brown et al, ; Burgman et al, , ; Clement et al, ; Deser et al, ; Myers, Mechoso, & DeFlorio, ; Norris et al, ; Yuan et al, , Yuan et al, ). This feedback acts to increase the damping timescale of SST anomalies.…”