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Satellites hold the key to climate monitoring

Certain climate parameters, like reflected solar flux and infrared radiation emitted by Earth and its atmosphere, can only be measured from space. These are key data for understanding how the climate system works.
Satellites have therefore become essential tools as a result of their ability to acquire highly precise measurements all over the planet, complementing readings taken on the ground.

Systematic global data

Satellites deliver uniform (acquired by the same instrument all over the globe), repetitive (over long time-series) data acquired automatically for climatology research.
The value of space to climate research is therefore clear and is driving the space policy that CNES is pursuing at European and international level.

A reserve created for reindeer in Sakha (Yakutia)

The Russian Republic of Sakha (Yakutia) has the fourth largest population of reindeer in the world, numbering more than 200,000. Global climate change and the development of the mining industry are modifying this species’ migratory habits. According to CNES subsidiary CLS, between 2010 and 2016 its winter pastures were 100 km further south than from 1980 to 1990. Data on its movements sent by Argos transmitters fitted to 50 wild reindeer helped local authorities to take protective measures. A nature reserve inside the new winter pasture area has notably been created in the North-West of Sakha.

CLS data

25 years of excellence in altimetry

The initially experimental series of oceanographic altimetry satellites has accomplished great successes with TOPEX/Poseidon and Jason-1, Jason-2 and Jason-3. These results have led CNES and NASA to perpetuate their 25-year partnership of excellence with the Surface Water and Ocean Topography mission (SWOT). From 2012, this new satellite will be able to observe deep and coastal oceans, delivering the most detailed large-scale data ever.

CNES’s satellite altimetry expertise is benefiting most international missions in this field. Indeed, French firms like Thales Alenia Space, CLS and Mercator Ocean are today European and even world leaders in altimetry.

Calculating pollution drift

Every year, 180,000 radar images are received by the teams at Vigisat, a station acquiring high-resolution radar satellite imagery operated by CNES subsidiary CLS. These images are used to detect pollution, traffickers, illegal fishing boats and polluting algae. Once the polluters have been identified, CLS’s teams alert the relevant authorities and run simulations to see where the pollution is likely to drift. For example, in 2016 oil slicks were detected over an area of 25 km in the Mozambique Channel. These slicks ended up fouling 200 km of Mauritania’s beaches. Investigations eventually identified an oil rig as the source of the pollution. To calculate pollution drift, scientists look at ocean currents using data from altimetry satellites like the Jason series, SARAL and Sentinel-3.

CNES - A climate-driven space agency

The New Delhi Déclaration, which came into effect on 16 May 2016, is a testament to the importance of space assets supporting efforts to curb climate change. On CNES’s initiative, the world’s 60 space agencies committed to put in place a common system for measuring atmospheric concentrations of greenhouse gases. This international and independent system is intended to provide a transparent benchmark to encourage nations to reduce their greenhouse gas emissions.
The role of space agencies in preserving Earth’s climate was also confirmed by work in 2016, for example at the IAC in Guadalaraja and the COP22 in Marrakesh, where CNES was present.
CNES is thus establishing itself as a climate-driven space agency.

Two new satellites to study greenhouse gases

Methane (CH4), the second most important greenhouse gas, remains poorly understood. The French-German MERLIN satellite to be launched in 2021 is set to enable major advances in our ability to analysis Earth’s carbon budget. Day and night, at all latitudes and in all seasons, it will fire its laser at the planet’s surface to detect sources and sinks of methane.
CNES is also developing the MicroCarb satellite to study emissions of carbon dioxide (CO2) and gain fresh insights into the mechanisms driving global warming. Scheduled to launch in 2020, MicroCarb will characterize surface fluxes of carbon gas to better anticipate future evolutions.

30% increase in sea level rise

Since the start of the 1990s, mean sea level has risen 8 cm as ocean waters have expanded and continental ice has melted as a result of a warming climate. Over the last decade, sea level rise has increased 30% due to the acceleration of ice melt in Greenland.

CNES has been measuring this rise since 1992 thanks to the high-precision French-U.S. TOPEX/Poseidon, Jason-1, Jason-2 and Jason-3 satellite altimetry missions, and the French-Indian SARAL/AltiKa mission. Their observations are a precious aid in validating climate models simulating future sea level rise for the decades ahead.

Blue gold measured with millimetre accuracy

One of the key challenges facing the world today is universal access to water, notably drinking water, and sanitation. Only 1.5% of all rainwater is collected and used. In response, CNES is involved in a range of missions including Sentinel-1, Sentinel-2 and Sentinel-3, Pleiades, Megha-Tropiques and soon SWOT.
SWOT will supply highly precise data on surface water (discharges and levels of the world’s lakes, flood zones and rivers). This mission will enable closer monitoring of river networks and regional freshwater resources in the context of a changing climate. It will also help to improve flood prediction systems and with floodplain mapping after a flood.

Improving climate prediction

For the last 10 years, the IASI instrument developed by Eumetsat and CNES has been monitoring the composition of Earth’s atmosphere. IASI is designed to improve medium-range weather forecasting. Besides key climate change parameters like temperature and humidity, IASI measures more than 25 atmospheric components with a high degree of precision. It thus maps pollution by detecting daily the gases present in the atmosphere (ozone, carbon monoxide, carbon dioxide and methane). The programme will be pursued with the follow-on New Generation instrument (IASI-NG) to be launched aboard the European MetOp-SG weather satellites in 2021.

Studying the impact of aerosols on climate

The atmosphere contains tiny solid or liquid particles in suspension, called aerosols. Several million tonnes of these aerosols are emitted every year from both natural sources (volcanic ash, desert dust, burning biomass, etc.) and human sources (industrial smoke stakes, exhaust fumes, etc.). Aerosols play a key role in cloud formation and have a very big impact (direct and indirect, via their effects on clouds) on Earth’s radiation budget and climate. For all these reasons, it’s vital to study their spatial and temporal distribution, their evolution and their physical, radiative and optical properties, in the context of a changing climate. CNES is contributing significantly to such studies, notably through the Parasol (2004-2013), Calipso (2006-), IASI (2006-) and IASI-NG (2021-) missions.

Forecasting intense precipitation

CNES is involved in a number of missions that are key to understanding the water cycle, like for example SMOS studying soil moisture or, more recently, Megha-Tropiques. Launched in 2011, this French-Indian satellite is operating in a specific non-Sun-synchronous orbit that allows it to revisit the intertropical belt several times a day. Megha-Tropiques is an essential link in the international GPM (Global Precipitation Mission) constellation that has fostered a wealth of applications. Its data are assimilated in real time in numerous operational weather-forecasting models, bringing real benefits for forecasting cyclones and intense precipitation events. Initially designed to last 3 years, the mission has been extended to 2020 to meet the needs of scientists and weather services.

The advantages of altimetry

Altimetry is also helping to monitor mean sea level and highlight exchanges between land surface and ocean waters (notably during El Niño and La Niña episodes).

Le CNES remercie tous les partenaires qui nous ont aidés à concevoir les contenus de cette exposition :

  • CLS, Collecte Localisation Satellite -
  • Novacom Services –
  • Altamira Information –
  • I-Sea –
  • Sertit –
  • Cospas/Sarsat –
  • Cité de l’Espace –
  • EuropaCorp / VALERIAN S.A.S –
  • Editions Dargaud –
  • Nexeya –
  • Safran Aircraft Engines –


  • Conception et réalisation du Pavillon : Olivier Bertrand,
  • Matériels audiovisuel et sonore : Eurydice,
  • Conception graphique, intégration et développement Data visualisation : Nun Design -
  • Recherche iconographique et travaux photos : Labo Photon -
  • Production audiovisuelle : Black Bear -, SapiensSapiens -, AnimaViva -, Arbracam Production Numérique -
  • Production multimédia Holopyramide : L’œil du Chat -
  • Traduction : Boyd Vincent