The world is watching as the United Nations COP30 climate conference unfolds in Belém, Brazil, with a spotlight on the Amazon rainforest, a symbol of both promise and worry in the battle against climate change. Once a vital carbon sink, the Amazon now shows worrying signs, with satellite data revealing a shift from carbon absorption to emission in certain areas. This transformation highlights the critical need for continuous, reliable monitoring of greenhouse gas emissions worldwide.
As policymakers from around the globe gather to assess progress under the Paris Agreement, which aims to limit global warming to 1.5°C, they require accurate, science-based information to verify climate actions and build resilience against the impacts of climate change. The European Space Agency (ESA) is providing this capability through its Earth observation missions, offering independent, satellite-based evidence for climate accountability.
ESA's Climate Change Initiative is central to this effort, generating long-term satellite datasets that meet the Essential Climate Variables defined by the Global Climate Observing System. These records provide a solid scientific foundation for climate researchers worldwide, informing effective mitigation and adaptation strategies. Through projects like Regional Carbon Cycle Assessment and Processes (RECCAP-2), ESA is delivering the research and data needed to support the implementation of the Paris Agreement.
A key metric in understanding effective climate action is the global carbon budget. With the Paris Agreement's goal, the remaining carbon budget stands at approximately 235 gigatonnes as of January 2025, which could be exhausted within six years at current emission rates. Understanding this budget requires precise knowledge of carbon absorption by natural sinks, primarily oceans and land, and emissions from fossil fuels and land-use change. While ocean carbon sinks are relatively well-understood, accurately quantifying the land sink remains a challenge, particularly with small-scale disturbances in tropical forests.
The RECCAP-2 project uses satellite data to address the challenge of understanding carbon storage and release across the planet's land surface. By combining satellite observations with ground data and computer models, the project quantifies land-atmosphere carbon exchanges and provides independent estimates of regional carbon budgets, which can be compared with national inventories. The findings reveal critical trends, such as the Amazon Basin's accelerating carbon losses, the shift from carbon sinks to sources in northern forests, and the decline in carbon uptake by European forests.
Research also highlights the irreplaceable value of primary forests, as secondary and degraded forests regain only a fraction of the carbon lost from deforestation. Additionally, the majority of land carbon absorption over the past three decades has occurred in non-living reservoirs, such as soil, dead wood, and sediments, emphasizing the need for comprehensive monitoring systems.
ESA's Earth observation missions, such as BIOMASS, EarthCARE, HydroGNSS, and SMOS, provide critical climate data by tracking tropical forest carbon stocks, addressing cloud-related climate uncertainties, monitoring soil moisture, and tracking changes in northern forest biomass. The Copernicus Sentinels continuously monitor land surfaces, vegetation, oceans, ice sheets, and the atmosphere, with the upcoming Copernicus Anthropogenic Carbon Dioxide Monitoring mission set to monitor carbon dioxide and methane emissions.
As nearly 200 countries gather in Belém, the Global Stocktake under the Paris Agreement will assess collective progress toward climate goals. Novel methods developed by the CCI RECCAP-2 team provide a means of comparing greenhouse gas inventories, promoting transparency and progress measurement against empirical records. ESA's Director of Earth Observation Programs, Simonetta Cheli, emphasized the importance of regularly comparing inversion results with national greenhouse gas inventories to monitor the effectiveness of mitigation policies.
The science is clear: climate action is urgent, and the tools for monitoring are in place. With ESA's satellites and projects like RECCAP-2, we can track the impact of climate actions. The question remains: will there be the political will to act, and act now?
