Other Space Activities

Earth Radiation Budget

Last updated:Jul 18, 2025

Measurement Types

The Earth Radiation Budget describes the balance between incoming solar radiation and outgoing reflected, scattered, and emitted energy from Earth. This balance is key to understanding climate processes and change. Satellite-based radiometers provide essential global measurements to understand Earth’s radiation budget and its effect on the global temperature and climate.

Figure 1: Schematic of Earth’s radiation budget balance (Image credit: ESA)

The Earth Radiation Budget (ERB) refers to the balance between the energy the Earth receives from the Sun and the energy it emits back to space. The incoming solar energy is partly reflected by clouds, aerosols, and the surface, and partly absorbed by the atmosphere and Earth’s surface. In turn, the Earth emits longwave thermal radiation back to space. Even small changes in this balance can have significant impacts. Variations in solar irradiance, cloud cover, greenhouse gases, or surface albedo can all influence the Earth radiation budget. Long-term, continuous monitoring is therefore vital for understanding feedback mechanisms and predicting climate trends. The Global Climate Observing System (GCOS) recognised the importance of these measurements, defining Earth Radiation Budget and Surface Radiation Budget as Essential Climate Variables (ECVs). 1) 2)

Satellites provide the means of making continuous, global measurements of Earth’s radiation budget. The radiation budget is measured using radiometers and spectroradiometers hosted on a variety of missions. Instruments monitor seven main components, as summarised in Table 1. To cover these, sensors are designed to observe the full solar irradiance spectrum and reflected shortwave radiation with wavelengths between 0.2 μm and 4.0 μm, and emitted longwave thermal radiation at wavelengths 3 μm to 100 μm. 2) 3)

Table 1: Types of radiation considered in the Earth radiation budget 4) 5) 6)
Direction	Height	Wavelength	Description
Incoming (downwelling)	Top of atmosphere	Short-wave Irradiance	Solar radiation received at the top of the atmosphere
Outgoing (upwelling)	Top of atmosphere	Short-wave (0.2-4 µm)	Solar radiation reflected by Earth’s atmosphere and surface
Outgoing (upwelling)	Top of atmosphere	Long-wave (4-200 µm)	Radiation emitted by clouds and particles in Earth’s atmosphere
Incoming (downwelling)	Earth surface	Short-wave	Solar radiation received at the Earth’s surface
Incoming (downwelling)	Earth surface	Long-wave	Radiation emitted by the gases, aerosols and clouds of the atmosphere to the Earth's surface
Outgoing (upwelling)	Earth surface	Long-wave	Thermal radiation emitted by the Earth’s surface
Outgoing (upwelling)	Earth surface	Short-wave	Short-wave radiation reflected by the Earth’s surface

Radiometers typically measure radiance in a given direction and fluxes are then derived using knowledge of the radiation’s angular properties. Some advanced sensors also account for anisotropy and polarisation. High radiometric accuracy is required of around 1 W/m2.

Figure 2: Global maps of reflected and emitted radiation (Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)

Earth observation satellites play a vital role in monitoring the global energy balance by measuring the radiation entering and leaving the Earth system. Earth observation monitoring supports climate modelling, helps constrain uncertainties, and improves understanding of radiative processes across the atmosphere, land and ocean. Measurements also support regional studies, enabling analysis of climate impacts on agriculture, urban areas, and extreme events. With newer missions, the international community is striving to achieve higher levels of accuracy and precision, enabling detection of subtle radiative changes that reflect shifts in the global climate system.

Example Products

Outgoing Longwave Radiation (OLR)

Outgoing Longwave Radiation (OLR) refers to the energy emitted by the Earth into space. After shortwave solar radiation is absorbed by the Earth’s surface and atmosphere, the planet re-emits this energy as longwave radiation, primarily within the 4 μm - 100 μm wavelength range. This spectral region overlaps with absorption bands of greenhouse gases such as water vapour and carbon dioxide, making OLR a critical parameter for monitoring the greenhouse effect and global warming. 1) 7)

Satellite-based observations of OLR at the top of the atmosphere (TOA) are essential in studying Earth’s energy budget, climate research, and weather forecasting. TOA OLR data provide insight into surface-atmosphere interactions, cloud patterns, rainfall, and large-scale climate events like El Nino and monsoons. 8)

Figure 4: Composite image of seasonal variation in outgoing longwave radiation captured by CERES. These four maps highlight how TOA OLR changes across the globe throughout the year (Image credit: Image courtesy of the CERES Science Team at NASA Langley Research Center in Hampton, Virginia, USA)

Cloud Fraction

Clouds are a major regulator of Earth’s energy balance. Depending on their altitude, type, and composition, they can either cool the planet by reflecting incoming solar radiation or warm it by absorbing and re-emitting longwave radiation from the surface. The degree to which clouds contribute to either effect depends on their spatial and temporal distribution. Cloud fraction (CF) is a fundamental parameter used to describe this distribution, representing the proportion of a given satellite image pixel or region that is covered by clouds. Accurate CF data is essential for understanding how cloud cover varies with geography, season, and climate patterns. 11) 12)

Because cloud properties and coverage fluctuate widely across space and time, satellite observations are crucial for monitoring them consistently on a global scale. Lidar and radar instruments, such as those onboard ESA and JAXA’s EarthCARE, provide vertical profiles of the atmosphere, investigating the structure and dynamics measurements of clouds and aerosols and their effect on radiation. 13)

Related Missions

EarthCARE

Launched on 28 May 2024, EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) is a joint mission by ESA and JAXA designed to improve climate and weather models by investigating cloud-aerosol-radiation interactions. The satellite carries four instruments that contribute to radiation budget measurements. The Multi-Spectral Imager (MSI) is a radiometer that collects visible and near-infrared cloud and aerosol data, while the Broad-Band Radiometer (BBR) measures TOA radiation. These are supported by the Atmospheric Lidar (ATLID) and the Cloud Profiling Radar (CPR), which together provide detailed vertical profiles of aerosols and clouds.

Copernicus: Sentinel-5

With the precursor instrument launched in 2017 as part of the European Copernicus programme, Sentinel-5 is an instrument developed by Airbus Defence and Space and jointly operated by ESA and the European Commission. It carries the UVNS (Ultraviolet/Visible/Near Infrared/Short-Wave Infrared) spectrometer, a passive pushbroom instrument designed to monitor the chemical composition of Earth’s atmosphere. Sentinel-5 measures trace gases such as ozone, methane, and nitrogen dioxide across six spectral channels ranging from Ultraviolet (UV) to Short-wave Infrared (SWIR).

SIMBA (Sun-earth IMBAlance)

Launched in September 2020, the SIMBA (Sun-earth IMBAlance) satellite was developed by the Royal Meteorological Institute of Belgium, the University of Leuven, and ISIS of the Netherlands in collaboration with ESA. It carried a miniaturised radiometer instrument designed to measure Earth’s radiation budget and total solar irradiance. The mission operated until December 2022.

Terra/Aqua

Aqua (launched in 2002) and Terra (launched in 1999) are NASA-led missions under the Earth Observing System (EOS), with international collaboration from agencies including JAXA (Japan), INPE (Brazil), and CSA (Canada). Both satellites carry the Clouds and the Earth’s Radiant Energy System (CERES) instrument, which measures reflected solar and emitted thermal radiation to characterise the Earth’s radiation budget. Each radiometer operates across three spectral channels: one in the visible-near infrared (NIR) to SWIR range (0.3 μm - 5.0 μm), used to measure reflected solar radiation with an accuracy of 1%; one in the atmospheric window region (8.0 μm - 12.0 μm) for detecting Earth-emitted longwave radiation, including contributions from water vapour; and a total channel spanning 0.35 μm - 125 μm, which captures both reflected and emitted radiation with a measurement accuracy of 0.3%. The satellites also carry the MODIS (Moderate-Resolution Imaging Spectroradiometer) instrument, which provides data on cloud and aerosol properties. MODIS operates across 36 spectral bands from the visible to the long-wave infrared. It retrieves cloud optical thickness and particle size at spatial resolutions between 250 m and 1 km, and aerosol concentrations at spatial resolutions between 5 km and 10 km.

Terra: Read more

Aqua: Read more

Joint Polar Satellite System (JPSS)

The Joint Polar Satellite System (JPSS) is a collaborative programme between NOAA and NASA, designed to support global weather forecasting and extreme events monitoring. JPSS-1 (NOAA-20) and JPSS-2 (NOAA-21) were launched in 2017 and 2022 respectively, with additional satellites planned. JPSS-1 carries the Cloud and the Earth’s Radiant Energy System (CERES) instrument (the same as carried on Terra & Aqua).

MetOp (Meteorological Operational Satellite Program of Europe) / MetOp Second Generation

The MetOp programme, developed jointly by ESA and EUMETSAT, delivers meteorological data for weather forecasting and climate monitoring. MetOp-A launched in 2006 and was followed by MetOp-B in 2012 and MetOp-C in 2018. Each satellite carries a suite of instruments that include the AVHRR/3 sensor, which provides global imagery and data on sea surface temperature, cloud cover, and radiation budget; the IASI interferometer, providing infrared sounding for clouds, radiation, and trace gases; and the MHS (Microwave Humidity Sounder). MHS is a quasi-optical heterodyne radiometer that monitors microwave emissions from the surface and atmosphere. It operates across five channels and captures data on humidity, water vapour, and cloud properties.

MetOp is followed by MetOp Second Generation (MetOp-SG). The MetOp-A series of three missions carry IASI New Generation (IASI-NG) and the Microwave Sounder (MWS), as well as hosting the Sentinel-5 payload.

MetOp: Read more

MetOp-SG: Read more

MTG-S

MTG-S (Meteosat Third Generation-Sounder) is part of the MTG mission, a collaboration between ESA and EUMETSAT to support weather forecasting and atmospheric studies. It consists of two satellites that carry the IRS (Infrared Sounder) instrument. IRS is a hyperspectral infrared sounder that measures vertical structures of atmospheric temperature, humidity and wind. It operates in two spectral bands (LWIR at 8.26 μm - 14.70 μm and MWIR at 4.44 μm - 6.25 μm) with a spatial resolution of 4 km.

TRUTHS

TRUTHS (Traceable Radiometry Underpinning Terrestrial-and Helio-Studies) is a planned climate mission led by UKSA to measure Earth’s radiation imbalance. The mission’s main payload HIS (Hyperspectral Imaging Spectrometer) will measure both incoming and Earth-reflected solar radiation. HIS will operate over two spectral ranges (320 - 400 nm and 400 - 2450 nm), with a swath of 100 km and spatial resolution of 50 - 100 m, and will enable accurate retrieval of top of the atmosphere reflectance.

ERBS

ERBS (Earth Radiation Budget Satellite) was a three-satellite mission, and was first launched by NASA in 1984 as part of the Earth Radiation Budget Experiment (ERBE). It measured both reflected shortwave and emitted longwave radiation from the Earth, contributing to understanding how solar energy is absorbed and re-emitted.

References

1) NASA, “The Earth's Radiation Budget,” URL: https://science.nasa.gov/ems/13_radiationbudget/

2) EO HANDBOOK, “Earth Radiation Budget Radiometers,” CEOS, URL: https://eohandbook.com/cop21/capabilities/sat_earth_obs_earth_rad_budget.html

3) EO HANDBOOK, “Atmosphere,” CEOS, URL: https://eohandbook.com/eohb2012/earth_observation_plans_atmosphere.html

4) Global Climate Observing System (GCOS), “Surface Radiation Budget,” URL: https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/surface-radiation-budget

5) Global Climate Observing System (GCOS), “Earth Radiation Budget,” URL: https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/earth-radiation-budget

6) THE CEOS DATABAS, “ABI Instrument,” URL: https://database.eohandbook.com/database/instrumentsummary.aspx?instrumentID=870

7) ESA, “Climate and outgoing radiation,” URL: https://www.esa.int/Applications/Observing_the_Earth/FutureEO/FORUM/Climate_and_outgoing_radiation

8) Kim, B.-Y., et al., “Retrieval of outgoing longwave radiation at top-of-atmosphere using Himawari-8 AHI data,” Remote Sensing of Environment, vol. 204, pp. 498-508, 2018, URL: https://www.sciencedirect.com/science/article/pii/S0034425717304698

9) Scientific Visualization Studio NASA, “Monthly Outgoing Longwave Radiation,” 23 October 2013, URL: https://svs.gsfc.nasa.gov/30368/

10) CERES NASA, “The Best of CERES,” URL: https://ceres.larc.nasa.gov/resources/images/

11) Earth Observatory NASA, “Cloud Fraction,” URL: https://earthobservatory.nasa.gov/global-maps/MODAL2_M_CLD_FR

12) Kassianov, E., Long, C., and Ovchinnikov, M., “Cloud Sky Cover versus Cloud Fraction: Whole-Sky Simulations and Observations,” Journal of Applied Meteorology, 2005, URL: https://journals.ametsoc.org/view/journals/apme/44/1/jam-2184.1.pdf

13) ESA, “EarthCARE goes live with data now available to all,” 16 January 2025, URL: https://www.esa.int/Applications/Observing_the_Earth/FutureEO/EarthCARE/EarthCARE_goes_live_with_data_now_available_to_all