The changing nature of Earth's reflected sunlight

Abstract

The increased rate of sea-level rise suggests that Earth's energy imbalance is also increasing over time. This study assesses whether 20 years of direct observations of this energy imbalance from Earth-orbiting satellites support the existence of a real trend in this imbalance and the components of it and finds. Changes to the imbalance observed are found to be consistent across multiple sources of observations. The majority of recent studies now clearly point to this energy imbalance being positive, while forced by increasing greenhouse gas concentrations in the atmosphere, being amplified significantly by decreases to the amount of sunlight reflected by Earth to space. Here, we show that the global changes observed appear largely from reductions in the amount of sunlight scattered by Earth's atmosphere. These reductions, in turn, are found to be almost equally split between reduced reflection from the cloudy and clear regions of the atmosphere, with the latter being suggestive of reduced scattering by aerosol particles over the observational period. Climate models, however, show an almost exclusive response from clouds, and a slightly exaggerated darkening of the surface. Thus, models that match the global shortwave change do so for the wrong reasons.

Connecting Hemispheric Asymmetries of Planetary Albedo and Surface Temperature

“…This phenomenon was first observed decades ago and confirmed with greater precision with the now 21‐year long record of the Clouds and Earth's Radiant Energy System (Loeb et al., 2009; Vonder Haar & Suomi, 1971; Wielicki et al., 1996). Over the last 20 years, both hemispheres experienced exactly the same trend in planetary albedo (e.g., Hartmann & Ceppi, 2014; Jönsson & Bender, 2022; Raghuraman et al., 2021; Stephens et al., 2022; Stevens & Schwartz, 2012). Even after 50 years of research, we do not know whether and if so, how the climate system maintains this symmetry or whether it is a random product of the data record or a function of the current spatial patterns of surface albedo, clouds, aerosols, and changes therein over the last couple of decades.…”

The response of hemispheric differences in Earth’s albedo to CO2 forcing in coupled models and its implications for shortwave radiative feedback strength

“…While there is no known physical mechanism or explanation for the observed hemispheric albedo symmetry, it is important to pose the question: what would a mechanism for maintaining a hemispheric albedo symmetry entail for climate? Given that there is no observed trend in the hemispheric difference in albedo despite changes in the global radiative energy balance and despite global changes in albedo (Stephens et al, 2022), the hemispheric symmetry is at least over this period robust. In this study, we investigate the implications for Earth's climate if its albedo is forced out of its current hemispheric symmetry due to warming processes, to guide an exploration of possibilities for changes in the global cloud distribution in a changing climate.…”

Global Radiative Flux Profile Data Set: Revised and Extended

“…provides an additional evaluation of FH, especially since the anomalies shown are relative to each data sets own record average. The longer FH record suggests that the recent increase in SWnet (decreased albedo, see also Goode et al, 2021;Stephens et al, 2022) may not be a trend but a longterm variation. However, the magnitude of the recent changes in LWnet in FH (decreased emission from about 2005 to 2012 and increased emission to 2017) is more than twice as large as shown in the CERES record.…”