In 2024, planet Earth experienced unprecedented climate extremes, breaking a series of worrying records that unequivocally confirm the acceleration of global warming. The latest, 35th edition of the "State of the Climate" report, published as a supplement to the Bulletin of the American Meteorological Society (BAMS), provides a grim picture of a planet under increasing pressure. Greenhouse gas concentrations have reached new peaks, along with global land and ocean temperatures, sea level, and total ocean heat content. Data collected from a wide network of satellites, meteorological stations, ocean buoys, and field research paint a detailed and alarming diagnosis of our planet's health. At the core of this authoritative report, considered the most definitive annual assessment of the climate, are key data records provided by the European Space Agency (ESA) through its Climate Change Initiative (CCI).

A Planet in Fever: Record Temperatures and Unprecedented Ice Melt

The year 2024 will be remembered as the year in which glaciers suffered the largest annual mass loss since measurements began. This dramatic trend is a direct consequence of record-high temperatures and has far-reaching consequences, from raising global sea levels to threatening the supply of drinking water for billions of people who depend on glacier-fed rivers. ESA's Climate Change Initiative (CCI) plays a crucial role in monitoring these changes, transforming decades of satellite observations into consistent, long-term datasets on key climate variables. These data, covering everything from sea level, sea ice, and glaciers to permafrost and soil moisture, not only form the backbone of the "State of the Climate" report but also represent key evidence for international climate assessments and a stimulus for action.

Clement Albergel, head of ESA's Climate Applications and Science Department, emphasized the importance of these long-term records. "For more than a decade, our climate data have been contributing to the BAMS report, reflecting the commitment and expertise of our teams in delivering high-quality and reliable datasets from Earth observation," he stated. "These long-term records are crucial for providing clear evidence of how our planet's climate is changing. ESA's contribution this year again covered multiple components of the Earth system, and key satellite data helped document global climate conditions in relation to long-term trends." Specifically, the latest report used records on soil moisture, lake surface temperature, permafrost, land surface temperature, and stratospheric ozone.

Land of Extremes: From Record Drought to a Flooded Sahel

Satellite data on soil moisture revealed stunning contrasts across the globe in 2024. While regions like the Sahel recorded moisture levels twice as high as usual, leading to floods and changes in vegetation, much of the American continent faced severe drought conditions. The United States recorded record drought coverage affecting nearly half of the country, with devastating consequences for agriculture and ecosystems. These insights come from the CCI's soil moisture project, which uses data from microwave satellite sensors, including historical missions like ESA's ERS and the current SMOS mission. This data is vital for assessing drought and flood risks, as soil moisture directly affects everything from crop growth to the danger of wildfires.

Warming Lakes: A Silent Threat to Freshwater Ecosystems

Freshwater ecosystems have not remained immune to global warming. Satellite measurements from the CCI's lakes project revealed the highest recorded global lake surface temperature anomalies. More than half of the observed lakes showed anomalies greater than +0.5 °C compared to the 1995-2020 reference period. The project monitors the impact of warming on nearly 2000 freshwater lakes worldwide, providing scientists with key information on the effects of climate change on freshwater ecosystems and water resources. Warmer water can trigger algal blooms, reduce oxygen levels, and threaten the survival of fish populations, disrupting the delicate balance of these aquatic habitats.

Ticking Carbon Bomb: Permafrost Thaw is Accelerating

One of the most worrying trends concerns permafrost, the permanently frozen ground that covers large parts of the Arctic. New data from ESA's CCI permafrost project shows that the movement speed of rock glaciers in Central Asia has been continuously increasing since the 1950s, with a pronounced acceleration between 2010 and 2020. Rock glaciers, which consist of a mixture of ice, rocks, and debris, serve as important indicators of permafrost thermal conditions. Their accelerated movement is directly linked to the rise in air temperature in the region and provides further evidence that permafrost is rapidly responding to climate change. The Arctic permafrost stores nearly 1700 billion tons of frozen carbon, twice the amount currently in the atmosphere. Its thawing threatens to release vast quantities of methane and carbon dioxide, which could trigger a dangerous feedback loop that further accelerates global warming.

The Planet's Hot Spots: On the Edge of Human Endurance

The report also used results from the CCI's land surface temperature project, which identified extreme hot spots with surface temperatures above 60 °C on several continents. Using data from the Copernicus Sentinel-3 satellite at a resolution of 1 kilometer, the project provides crucial measurements in remote regions where meteorological stations are scarce. These data help scientists map areas where conditions are approaching the limits of human habitability and endurance. High land surface temperatures can dramatically affect the local climate, agriculture, and water availability, creating conditions unsuitable for life.

A Ray of Hope: The Ozone Layer Shows Signs of Recovery

Amidst a series of worrying news, the report did bring one positive development. Data from the CCI's ozone monitoring project showed encouraging signs. In 2024, stratospheric ozone levels in the Northern Hemisphere reached their highest level since satellite monitoring began in 1979, and in some regions, concentrations have returned to levels not seen since the 1960s. The Southern Hemisphere is also showing improvement, recovering from low ozone levels recorded between 2020 and 2022, which were the result of pollution from major Australian wildfires and volcanic eruptions. This recovery is a direct result of successful global cooperation and the implementation of the Montreal Protocol, proving that joint action can solve global environmental challenges.