Changes in Earth's Reflectance over the Past Two Decades

Πάλλη, Ε.; Goode, Philip R.; Montañés-Rodŕıguez, P.; Koonin, S. E.

doi:10.1126/science.1094070

Cited by 105 publications

(95 citation statements)

References 6 publications

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“…It is noticeable, however, that over the 1960-1984 period there is a general decrease in bright sunshine hours (a surface dimming), followed by a recovery from the mid-1980s till the present. These changes are consistent with the so-called 'global dimming' phenomena observed at other ground-based observatories worldwide from the 1960s to the mid1980s (Stanhill and Cohen, 2001;Liepert, 2002) and the 'global brightening' that followed, starting in the mid1980s (Pallé et al, 2004;Wild et al, 2005). Seasonal trends in sunshine hours are detailed in Table I. 3.2.…”

Section: Synoptic Cloud Observations At Ebrosupporting

confidence: 70%

Sunshine and synoptic cloud observations at Ebro Observatory, 1910–2006

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Πάλλη

et al. 2009

Intl Journal of Climatology

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ABSTRACT:The aim of this study is to characterize the evolution of the number of bright sunshine hours and cloudiness at Ebro Observatory. Sunshine and synoptic cloud observations, extending over almost a century, are available from the Ebro Observatory in the north-east of Spain. Here, we analyse these time series and find a strong decadal variability in the duration of bright sunshine hours since 1910, but without a statistically significant long-term trend. A comparison with sunshine records from other Spanish Mediterranean observatories was also performed to validate the Ebro time series over the shorter time interval for which comparison stations are available. At the same time, we find a monotonic increase in synoptic cloud amount since the 1920s. Time series of cloudiness at different heights are also available at Ebro in digital form dating from 1954, and their analysis allows us to interpret these results as a change in cloud type frequency, possibly coupled with changes in air transparency.

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Section: Synoptic Cloud Observations At Ebrosupporting

confidence: 70%

Sunshine and synoptic cloud observations at Ebro Observatory, 1910–2006

Curto

Also

Πάλλη

et al. 2009

Intl Journal of Climatology

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“…Observations of earthshine for example, have shown that clouds can induce a considerable daily variation A&A 548, A90 (2012) in the planetary signal. The amount of variability observed differs slightly among the observations (∼10% for Pallé et al 2004; ∼5% for Goode et al 2001, and a few percent for Cowan et al 2009). Cloud coverage and variability can also influence to a large degree the interpretation of the observations.…”

Section: Introductionmentioning

confidence: 79%

Looking for the rainbow on exoplanets covered by liquid and icy water clouds

Karalidi

Stam

Hovenier

2012

A&A

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Aims. Looking for the primary rainbow in starlight that is reflected by exoplanets appears to be a promising method to search for liquid water clouds in exoplanetary atmospheres. Ice water clouds, that consist of water crystals instead of water droplets, could potentially mask the rainbow feature in the planetary signal by covering liquid water clouds. Here, we investigate the strength of the rainbow feature for exoplanets that have liquid and icy water clouds in their atmosphere, and calculate the rainbow feature for a realistic cloud coverage of Earth. Methods. We calculate flux and polarization signals of starlight that is reflected by horizontally and vertically inhomogeneous Earth-like exoplanets, covered by patchy clouds consisting of liquid water droplets or water ice crystals. The planetary surfaces are black. Results. On a planet with a significant coverage of liquid water clouds only, the total flux signal shows a weak rainbow feature. Any coverage of the liquid water clouds by ice clouds, however, dampens the rainbow feature in the total flux, and thus the discovery of liquid water in the atmosphere. On the other hand, detecting the primary rainbow in the polarization signal of exoplanets appears to be a powerful tool for detecting liquid water in exoplanetary atmospheres, even when these clouds are partially covered by ice clouds. In particular, liquid water clouds covering as little as 10-20% of the planetary surface, with more than half of these covered by ice clouds, still create a polarized rainbow feature in the planetary signal. Indeed, calculations of flux and polarization signals of an exoplanet with a realistic Earth-like cloud coverage, show a strong polarized rainbow feature.

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“…The issue has arisen because of apparent inconsistencies among direct and indirect observational records of the Earth's reflected solar radiation. While Pallé et al [2004] looked at Earthshine data and found a steady decrease in the Earth's broadband reflectance from 1984 to 2000 followed by an increase between 2001, Wielicki et al [2005 found no trend in planetary broadband albedo from an analysis of CERES data coupled with other correlative satellite records from the Moderate Resolution Imaging Spectrometer (MODIS) [Justice et al, 1998] and Jason/TOPEX [Ducet et al, 2000]. This debate and additional problems encountered by researchers attempting to synthesize long-term climate records by harmonizing heterogeneous satellite instrument data [i.e., Hurrell and Trenberth, 1998] have led to the recognition of the critical importance of long-term measurement stability that is rigorously traceable to international standards for the assessment of changes in climate.…”

Section: Introductionmentioning

confidence: 99%

CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation

Feldman¹,

Algieri²,

Ong³

et al. 2011

J. Geophys. Res.

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[1] Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensively validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and poleward shifts in the subsidence zones and the storm tracks are all detectable along with large changes in snow cover and sea ice fraction. These findings suggest that the proposed NASA Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to measure shortwave reflectance spectra may help elucidate climate forcings, responses, and feedbacks.

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Changes in Earth's Reflectance over the Past Two Decades

Cited by 105 publications

References 6 publications

Sunshine and synoptic cloud observations at Ebro Observatory, 1910–2006

Sunshine and synoptic cloud observations at Ebro Observatory, 1910–2006

Looking for the rainbow on exoplanets covered by liquid and icy water clouds

CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation

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