Observational Evidence for Two Modes of Coupling Between Sea Surface Temperatures, Tropospheric Temperature Profile, and Shortwave Cloud Radiative Effect in the Tropics

Fueglistaler, S.

doi:10.1029/2019gl083990

Cited by 53 publications

(67 citation statements)

References 42 publications

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“…The method consistently overestimates the change in TOA flux over the Southern Ocean and North Atlantic, and so overestimates the sensitivity. The method finds that that there are significant negative nonlocal feedbacks associated with regions of tropical convection, and that the reduction in the share of warming that occurs in these regions over time contributes to an increase in the global feedback with time in these models, consistent with recent studies (Andrews and Webb 2017;Ceppi and Gregory 2017;Dong et al 2019;Fueglistaler 2019).…”

Section: Discussionsupporting

confidence: 84%

“…Since warming in different regions sets off radiative feedbacks of different strengths, the inconstancy of the climate feedback is likely caused by the change in the spatial pattern of warming with time (Winton et al 2010;Armour et al 2013). Since the temperature pattern associated with internal variability differs from the forced response, we should expect the climate feedback associated with each to differ (Dessler 2013;Colman and Hanson 2017), and in fact the climate feedback appears to vary across the historical record (Gregory and Andrews 2016;Fueglistaler 2019). The climate feedback may vary between historical and future warming (Zhou et al 2016;Proistosescu and Huybers 2017;Andrews et al 2018), although the importance of this effect may be modest (Lewis and Curry 2018).…”

Section: Introductionmentioning

confidence: 99%

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Spatial Radiative Feedbacks from Internal Variability Using Multiple Regression

2020

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The sensitivity of the climate to CO2 forcing depends on spatially varying radiative feedbacks that act both locally and nonlocally. We assess whether a method employing multiple regression can be used to estimate local and nonlocal radiative feedbacks from internal variability. We test this method on millennial-length simulations performed with six coupled atmosphere–ocean general circulation models (AOGCMs). Given the spatial pattern of warming, the method does quite well at recreating the top-of-atmosphere flux response for most regions of Earth, except over the Southern Ocean where it consistently overestimates the change, leading to an overestimate of the sensitivity. For five of the six models, the method finds that local feedbacks are positive due to cloud processes, balanced by negative nonlocal shortwave cloud feedbacks associated with regions of tropical convection. For four of these models, the magnitudes of both are comparable to the Planck feedback, so that changes in the ratio between them could lead to large changes in climate sensitivity. The positive local feedback explains why observational studies that estimate spatial feedbacks using only local regressions predict an unstable climate. The method implies that sensitivity in these AOGCMs increases over time due to a reduction in the share of warming occurring in tropical convecting regions and the resulting weakening of associated shortwave cloud and longwave clear-sky feedbacks. Our results provide a step toward an observational estimate of time-varying climate sensitivity by demonstrating that many aspects of spatial feedbacks appear to be the same between internal variability and the forced response.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Spatial Radiative Feedbacks from Internal Variability Using Multiple Regression

2020

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“…Previous research has shown that on interannual, decadal, and longer time scales, EIS depends on the spatial pattern of surface temperatures, especially on the temperature difference between warm convective areas and the rest of the tropics (Ceppi & Gregory, 2017; Fueglistaler, 2019; Qu et al., 2015; Zhou et al., 2016). Monthly EIS anomalies are positively correlated ( R = 0.54) with anomalies of the SST # index proposed by Fueglistaler (2019) (defined as the surface temperature difference between the 30% warmest waters minus the tropical average SST), thus suggesting that EIS variations are partly controlled by the spatial pattern of surface temperature. We also note a strong anticorrelation between EIS and relative humidity in the free troposphere (Table 1).…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The analysis of satellite observations has confirmed that for given conditions of large‐scale circulation and surface temperature at the regional scale, situations associated with an enhanced convective aggregation are associated with decreased humidity, decreased upper‐level cloudiness, increased outgoing longwave radiation (OLR), and decreased planetary albedo (Holloway et al., 2017; Stein et al., 2017; Tobin et al., 2012, 2013). However, these relationships might be affected by variations of sea surface temperatures (SSTs) and large‐scale atmospheric circulations (Fueglistaler, 2019; Zhang & Fueglistaler, 2019). It also remains an open issue as to whether the radiative influence of changes in convective aggregation is significant compared to that of other well‐established controlling factors such as the lower tropospheric stability.…”

Section: Introductionmentioning

confidence: 99%

Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

et al. 2020

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This study analyzes the observed monthly deseasonalized and detrended variability of the tropical radiation budget and suggests that variations of the lower-tropospheric stability and of the spatial organization of deep convection both strongly contribute to this variability. Satellite observations show that on average over the tropical belt, when deep convection is more aggregated, the free troposphere is drier, the deep convective cloud coverage is less extensive, and the emission of heat to space is increased; an enhanced aggregation of deep convection is thus associated with a radiative cooling of the tropics. An increase of the tropical-mean lower-tropospheric stability is also coincident with a radiative cooling of the tropics, primarily because it is associated with more marine low clouds and an enhanced reflection of solar radiation, although the free-tropospheric drying also contributes to the cooling. The contributions of convective aggregation and lower-tropospheric stability to the modulation of the radiation budget are complementary, largely independent of each other, and equally strong. Together, they account for more than sixty percent of the variance of the tropical radiation budget. Satellite observations are thus consistent with the suggestion from modeling studies that the spatial organization of deep convection substantially influences the radiative balance of the Earth. This emphasizes the importance of understanding the factors that control convective organization and lower-tropospheric stability variations, and the need to monitor their changes as the climate warms. Plain Language Summary Anomalies of the tropically averaged radiative balance determine the time variations of the tropical climate. The stability of the lower atmosphere has been shown to influence this balance because increased stability favors the formation of low-level clouds and the reflection of solar radiation to space. Modeling studies have suggested that the spatial distribution of deep convection, especially the degree of clustering of deep clouds, could also impact humidity and cloud coverage, and thus the radiative balance of the Earth system. However, the relationships between cloud clustering, humidity, and the radiation budget have never been observed at the scale of the tropics. By analyzing long time series of satellite observations, we show that monthly variations of lower-atmospheric stability and convective clustering are both strongly correlated with variations of the radiative cooling of the tropics and that their contributions to the modulation of the radiation budget are complementary and equally important. These observational results thus confirm modeling inferences and emphasize that to predict the future of our climate, it will be necessary to determine how the stability and the clustering of deep convection will change with warming.

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“…The formulation of the parameter used here follows the work of Flannaghan et al. (2014) and Fueglistaler (2019), and is deliberately oblivious to the geographic pattern of SSTs as the specific geographic location of deep convection is secondary to this problem. The approach is on safe theoretical grounds in the tropics (see also Y. Zhang & Fueglistaler, 2020) and observations of tropical SSTs, atmospheric temperature and top‐of‐atmosphere radiative fluxes are consistent with expectations (Fueglistaler, 2019).…”

Section: Introductionmentioning

confidence: 99%

The Peculiar Trajectory of Global Warming

Fueglistaler

Silvers

2021

JGR Atmospheres

Self Cite

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The large range in equilibrium climate sensitivity (the global average temperature change following a doubling of atmospheric CO 2) of 1.5°-4.5° reported in IPCC AR5 (IPCC, 2013) persists and is even wider (but see also assessment by Sherwood et al. (2020)) in the most recent Coupled Model Intercomparison Project, Phase 6 (CMIP6) simulations (Zelinka et al., 2020). This introduces uncertainty regarding the urgency of introducing measures to curb CO 2 emissions to limit global warming to specified targets, such as a global temperature increase relative to preindustrial times of no more than +1.5°C or +2°C (IPCC, 2018). The period since the late 1970s is arguably the best suited to provide observational constraints on the sensitivity of present climate due to both the availability of truly global observations provided by satellites, and to less uncertainty in atmospheric aerosol than in earlier decades (Anderson et al., 2003; Jimenez-de-la Cuesta & Mauritsen, 2019; Kiehl, 2007). However, it has been recognized that the cloud radiative feedback may have evolved unexpectedly, providing a strong negative feedback in particular over this best-observed period (

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Observational Evidence for Two Modes of Coupling Between Sea Surface Temperatures, Tropospheric Temperature Profile, and Shortwave Cloud Radiative Effect in the Tropics

Cited by 53 publications

References 42 publications

Spatial Radiative Feedbacks from Internal Variability Using Multiple Regression

Spatial Radiative Feedbacks from Internal Variability Using Multiple Regression

Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

The Peculiar Trajectory of Global Warming

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