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

Loeb, Norman G.; Wang, H.; Allan, Richard P.; Andrews, Timothy; Armour, Kyle C.; Cole, Jason N. S.; Dufresne, Jean‐Louis; Forster, Piers M.; Gettelman, Andrew; Guo, Huan; Mauritsen, Thorsten; Ming, Yi; Paynter, David; Proistosescu, Cristian; Stuecker, Malte F.; Willén, Ulrika; Wyser, Klaus

doi:10.1029/2019gl086705

Cited by 51 publications

(87 citation statements)

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“…It stresses the importance of testing the ability of numerical models of the climate system to reproduce the observed relationships analyzed in this study. A recent comparison of CERES observations with simulations from the latest generation of general circulation models with parameterized convection (Loeb et al., 2020) shows that when forced by observed SSTs, climate models reproduce the observed evolution of TOA LW or NET radiative fluxes less well than the evolution of TOA SW fluxes (when considering monthly deseasonalized anomalies, the correlation between simulations and observations ranges across models from 0.096 to 0.32 for N lw , and from 0.25 to 0.38 for N ). Since in observations the variability of deep convective organization arises mostly from the mesoscale (section 3) and influences the radiation budget mostly in the LW (Table 1), the poor ability of climate models to reproduce observed monthly anomalies of N lw might partly arise from their absence of representation of mesoscale convective organization.…”

Section: Summary and Discussionmentioning

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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Section: Summary and Discussionmentioning

confidence: 99%

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

et al. 2020

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“…There is consistent variability between CERES and ERA5 before 2013 (r ≥ 0.77) but ERA5 does not capture the increase in NET and ASR after this (Fig. 1a, c) (Loeb et al 2020); the reason behind this merits further investigation. The trends of NET, ASR and OLR from each data set and correlations between DEEPC and other data sets over 1985-2000 and 2001-2014 are listed in Table 2 for reference.…”

Section: Global Mean Toa Radiation Fluxes and Their Variability Sincementioning

confidence: 93%

Variability in the global energy budget and transports 1985–2017

et al. 2020

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The study of energy flows in the Earth system is essential for understanding current climate change. To understand how energy is accumulating and being distributed within the climate system, an updated reconstruction of energy fluxes at the top of atmosphere, surface and within the atmosphere derived from observations is presented. New satellite and ocean data are combined with an improved methodology to quantify recent variability in meridional and ocean to land heat transports since 1985. A global top of atmosphere net imbalance is found to increase from 0.10 ± 0.61 W m−2 over 1985–1999 to 0.62 ± 0.1 W m−2 over 2000–2016, and the uncertainty of ± 0.61 W m−2 is related to the Argo ocean heat content changes (± 0.1 W m−2) and an additional uncertainty applying prior to 2000 relating to homogeneity adjustments. The net top of atmosphere radiative flux imbalance is dominated by the southern hemisphere (0.36 ± 0.04 PW, about 1.41 ± 0.16 W m−2) with an even larger surface net flux into the southern hemisphere ocean (0.79 ± 0.16 PW, about 3.1 ± 0.6 W m−2) over 2006–2013. In the northern hemisphere the surface net flux is of opposite sign and directed from the ocean toward the atmosphere (0.44 ± 0.16 PW, about 1.7 ± 0.6 W m−2). The sea ice melting and freezing are accounted for in the estimation of surface heat flux into the ocean. The northward oceanic heat transports are inferred from the derived surface fluxes and estimates of ocean heat accumulation. The derived cross-equatorial oceanic heat transport of 0.50 PW is higher than most previous studies, and the derived mean meridional transport of 1.23 PW at 26° N is very close to 1.22 PW from RAPID observation. The surface flux contribution dominates the magnitude of the oceanic transport, but the integrated ocean heat storage controls the interannual variability. Poleward heat transport by the atmosphere at 30° N is found to increase after 2000 (0.17 PW decade−1). The multiannual mean (2006–2013) transport of energy by the atmosphere from ocean to land is estimated as 2.65 PW, and is closely related to the ENSO variability.

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“…Specifically, the observational studies of Zhou et al (2016) evidence for a pattern effect in the satellite records of cloud cover and TOA radiation as well as in atmospheric reanalysis fields of tropospheric stability. Importantly, GCMs appear to be able to capture the essential physical mechanisms linking SST patterns to radiative response (Loeb et al, 2020), providing confidence in the theory behind the pattern effect and the use of models to estimate how radiative feedbacks may change with evolving warming patterns (section 4.2.1).…”

Section: Transitioning From S Hist To Smentioning

confidence: 99%

An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence

Sherwood

Webb

Annan³

et al. 2020

Reviews of Geophysics

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We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO 2 , characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes. Plain Language Summary Earth's global "climate sensitivity" is a fundamental quantitative measure of the susceptibility of Earth's climate to human influence. A landmark report in 1979 concluded that it probably lies between 1.5°C and 4.5°C per doubling of atmospheric carbon dioxide, assuming that other influences on climate remain unchanged. In the 40 years since, it has appeared difficult to reduce this uncertainty range. In this report we thoroughly assess all lines of evidence including some new developments. We find that a large volume of consistent evidence now points to a more confident view of a climate sensitivity near the middle or upper part of this range. In particular, it now appears extremely unlikely that the climate sensitivity could be low enough to avoid substantial climate change (well in excess of 2°C warming) under a high-emission future scenario. We remain unable to rule out that the sensitivity could be above 4.5°C per doubling of carbon dioxide levels, although this is not likely. Continued ©2020. American Geophysical Union. All Rights Reserved.

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

Cited by 51 publications

References 58 publications

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

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

Variability in the global energy budget and transports 1985–2017

An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence

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