Our planet is facing an unprecedented climate and environmental crisis, the pace and scale of which are rapidly accelerating. In 2024, the Earth's global surface temperature exceeded 1.5°C above pre-industrial levels for the first time., while the rate of heat gain from human activities is increasing. These changes are causing rapid transformations across the entire Earth system – atmosphere, oceans, cryosphere and biosphere – leading to accelerated global sea level rise and an intensification of the water cycle. Every region of the world is facing escalating adverse and severe impacts.

Observations of the Earth from space have transformed our ability to study the Earth as an interconnected system. We are no longer limited to geographically dispersed measurements of individual components. Remote sensing from space using satellites of the European Space Agency (ESA) and the European Commission's Copernicus programme (Sentinel satellites) provides essential data for understanding and addressing these challenges. These observations play a key role in closing knowledge gaps in climate science, diagnosing processes, refining our understanding of the Earth system and increasing confidence in future predictions. They also help inform our responses to a changing climate.

ESA satellites have made breakthrough discoveries in four main Earth science thematic areas: atmosphere, polar regions, oceans and land. In the atmosphere, the Aeolus mission, the first satellite specifically designed to measure wind profiles, has significantly improved the accuracy of weather forecasts, even nine days ahead, and provided insight into the atmospheric dynamics that drive climate patterns. The Sentinel-5P satellite, with its TROPOMI instrument, allows monitoring of global concentrations of pollutants such as nitrogen dioxide (NO2), a major contributor to air pollution from transport and industry. During the COVID-19 lockdowns, TROPOMI recorded a dramatic drop in NO2 levels in cities, providing compelling evidence of the human impact and how targeted measures can lead to improvements in air quality. The same TROPOMI instrument on Sentinel-5P also allows monitoring of global concentrations of methane. Methane is a greenhouse gas more than 80 times more potent than carbon dioxide in the short term and a significant contributor to global warming. TROPOMI can identify methane “super-emitters” (local sources with high concentrations of emissions) from the oil and gas sector, landfills and coal mines, enabling regulators and industry to respond quickly to previously unknown sources of leaks and emissions.

In the polar regions, satellite radar altimetry, starting with missions such as ERS-1 and then CryoSat-2, has provided a 33-year record of the mass balance of the large ice sheets of Greenland and Antarctica. Before these satellites, we had little idea of how these ice masses evolve, and satellites now allow us to quantify their contribution to sea level rise with unprecedented precision. In the Arctic, which is warming four times faster than the global average, CryoSat-2 and SMOS provide key data on sea ice loss and thickness. The satellite data have shown significant thinning of multi-year ice, which is essential for refining global and regional climate models and predicting the future of the Arctic.

For the oceans, satellite altimetry has revolutionized our understanding of the oceans, providing near-global observations of sea level. Satellites such as TOPEX/Poseidon, Jason and Sentinel-6, combined with ESA missions, have revealed global sea level rise of more than 3.4 mm per year on average and have shown that sea level rise is uneven. These data, combined with tide gauge data, track the acceleration of sea level rise since the late 1960s. Satellite missions such as GOCE have enabled unprecedented precision measurements of the Earth's gravitational field and, combined with altimetry, have revealed complex global patterns of ocean currents, furthering our understanding of their impact on climate.

On land, ESA satellites are changing our view of the world's forests. Forests absorb vast amounts of carbon dioxide, but deforestation and degradation can turn them into carbon sources. Satellites such as Envisat, Sentinel-1, Sentinel-2 and SMOS provide detailed maps that reveal forest growth, biomass and carbon storage. Future missions such as Biomass promise an even deeper understanding of forest dynamics and the global carbon cycle. Earth observation has also revolutionised our understanding of the water cycle. Missions such as SMOS were the first satellites to measure soil moisture from space, improving the forecasting of droughts, forest fires and floods. Integrating data from Sentinel and SMOS satellites allows for the creation of water cycle models that help planners better manage water resources and prepare for future climate scenarios.

The twelve scientific achievements presented in the resource, which provide vital information for society, would not have been possible without European cooperation, leadership and support for innovative space-based Earth observations. Satellite observations, together with in-situ data and modelling, form a vital basis for informed decision-making on how to address and adapt to the profound changes that humanity is driving within the Earth system. There has never been a more critical time to support ESA's Earth observation programme and its ability to deliver essential scientific knowledge. Many scientific challenges still remain, underlining the need to continue developing new satellites. With the combined efforts of the Earth Explorers, Copernicus and national missions, Europe has established itself as a global leader in satellite-based Earth observation. Spring