The world is at a critical juncture in the fight against climate change, and the eyes of the global community are on Belém, Brazil, where the United Nations COP30 climate change conference is taking place. This conference is a pivotal moment, as it brings together policymakers from around the globe to assess progress under the Paris Agreement and discuss the urgent need for climate action.
But here's where it gets controversial: the Amazon rainforest, once a powerful carbon sink, is now showing signs of distress. Satellite observations reveal a worrying trend—parts of the Amazon are no longer absorbing carbon dioxide as they once did, and in some areas, it has even become a net emitter of carbon. This transformation underscores the critical importance of continuous and reliable monitoring of greenhouse gas emissions worldwide.
The European Space Agency (ESA) is stepping up to provide the tools and data needed to tackle this challenge. Through its Earth observation missions, ESA is delivering independent, satellite-based evidence that holds nations accountable for their climate commitments. With decades of expertise in Earth observation, ESA offers transparent and reliable data, empowering countries to track their progress and strengthen their national climate action plans.
At the heart of ESA's efforts is its Climate Change Initiative, which generates long-term satellite-based datasets that meet the criteria for Essential Climate Variables. These records provide a solid scientific foundation for climate researchers worldwide, enabling them to develop effective mitigation and adaptation strategies. ESA's work extends further with projects like RECCAP-2 (Regional Carbon Cycle Assessment and Processes), which aims to support the implementation of the Paris Agreement by providing the necessary research and data.
One of the fundamental metrics that informs effective climate action is the global carbon budget. It determines the scale and urgency of the actions needed to limit global warming to 1.5°C above pre-industrial levels, as set out in the Paris Agreement. As of January 2025, the remaining carbon budget stands at approximately 235 gigatonnes. This budget could be exhausted within just six years at current emission rates, highlighting the urgency of the situation.
Understanding the carbon budget requires precise knowledge of two key factors: the amount of carbon absorbed by natural sinks, primarily oceans and land, and the emissions from fossil fuels and land-use change. While ocean carbon sinks are relatively well understood, accurately quantifying the land sink remains a challenge. Small-scale disturbances in tropical forests, typically below two hectares and difficult to detect, account for a significant portion of carbon loss, despite representing only 15% of the affected area.
The RECCAP-2 project uses satellite data to address this challenge, combining satellite observations with ground data and computer models to quantify carbon exchanges between the land and atmosphere. By doing so, it provides independent estimates of regional carbon budgets that can be compared with national inventories, offering a more comprehensive understanding of carbon dynamics.
The findings to date are alarming. The Amazon Basin, which accounts for 14% of global plant carbon uptake annually, lost 370 million tonnes of carbon between 2010 and 2020, with its south-eastern region bearing the brunt of this loss. This accelerating trend raises concerns about potential tipping points.
In the northern hemisphere, boreal and temperate forests, which cover 41% of the world's forest area, have undergone a fundamental shift. Once reliable carbon sinks, these forests have become net emitters of carbon since 2016, driven by increasing droughts, wildfires, and other climate-related stresses. Across Europe, forests have been absorbing about 10% of the EU's greenhouse gas emissions since 1990, but this uptake is declining due to harvesting, aging, drought, and disease, posing a significant challenge to the EU's climate neutrality goals by 2050.
Research also highlights the irreplaceable value of primary forests. While forest recovery offers hope, secondary and degraded forests regain only about a quarter of the carbon lost from deforestation. This underscores the critical importance of protecting old-growth forests, as their carbon storage capacity cannot be fully replaced by regrowth.
Perhaps most surprisingly, research has revealed that the majority of land carbon absorption over the past three decades has occurred in non-living reservoirs, such as soil, dead wood, and sediments. Only 6% of the 35 gigatonnes of carbon absorbed by land between 1992 and 2019 was stored in living vegetation. This insight emphasizes the need for comprehensive monitoring systems that capture the full spectrum of land carbon dynamics, including often-overlooked non-living carbon pools.
ESA's Earth observation missions are crucial in monitoring these changes. Missions like BIOMASS, EarthCARE, HydroGNSS, SMOS, and the Copernicus Sentinels provide critical climate data, tracking tropical forest carbon stocks, addressing cloud-related climate uncertainties, monitoring soil moisture, and continuously observing land surfaces, vegetation, oceans, ice sheets, and the atmosphere. The upcoming Copernicus Anthropogenic Carbon Dioxide Monitoring mission will specifically monitor carbon dioxide and methane emissions, assessing the effectiveness of emission-curbing policies on a national and global scale.
As nearly 200 countries gather in Belém, the stakes are incredibly high. The Global Stocktake, which occurs every five years under the Paris Agreement, will assess collective progress toward climate goals. Novel methods developed by the CCI RECCAP-2 team, based on Earth observation and atmospheric modeling, provide a means of comparing greenhouse gas inventories, promoting transparency, and measuring progress against empirical records.
ESA's Director of Earth Observation Programs, Simonetta Cheli, emphasizes the importance of regularly comparing inversion results with national greenhouse gas inventories to monitor the effectiveness of mitigation policies and track countries' progress toward their pledges.
The science is clear: climate action is urgent, and the tools for monitoring are in place. Thanks to ESA's satellites and projects like RECCAP-2, we can turn observations into actionable insights and determine whether our climate actions are making a difference. What remains is the political will to act, and to act now, to ensure a sustainable future for our planet.
