ESA’s Sentinel-1 detects retreating Arctic glaciers. As Arctic temperatures rise, glaciers that end at sea, particularly in places like Svalbard, are retreating rapidly and calving at a rapid rate. Arctic sea ice has also retreated to near-historic minimums in the Northern Hemisphere this summer, according to NASA and the National Snow and Ice Data Center (NSIDC).
Satellite data has proven that climate change is a climate crisis. 2024 was a record year, and not in a good way. In July, the Earth’s average temperature was the highest in 175 years, and July 22 in particular was the hottest day on record. Last summer was the hottest since 1880, this year’s hurricane season began with Beryl, the earliest Category 4 hurricane on record, and a report published in June confirmed that human-caused global warming had reached an all-time high.
But it’s not just the record-breakers making headlines that scientists are worried about. This year, glaciers are melting at an unprecedented rate because of all that human-caused heat, sea levels are rising irreversibly as a result of those melting glaciers, coastal communities are being devastated by storms made worse by that sea-level rise combined with high temperatures, and animals are being displaced from their homes because the Earth is changing too much, too fast. Just last month, we saw Hurricane Helene destroy towns and take lives — and its power was indeed linked to climate change.
It’s certainly hard to see facts laid out this way, especially given how much these paragraphs leave unsaid. But it does highlight something very important: at a fundamental level, it’s valuable that this information exists at all. Perhaps the single most limiting step in the fight against climate change is turning facts into actionable goals and, in turn, convincing politicians to start making serious changes to how our world is run. The climate crisis is a deceptively political issue, meaning that the Earth’s future depends on data — and, depending on how you look at it, that data depends on an unlikely source: space exploration.
The word “satellite” gets thrown around a lot these days, but in general terms it refers to any object sent into orbit around our planet to perform a specific task. We have communications satellites to make our cell phones work, navigation satellites to make Google Maps give us the right directions, and experimental satellites for pure science purposes, like this one that’s currently testing solar sail technology.
Among the satellites there are also climate satellites.
For example, there are satellites with spectrometers that can measure the concentration of carbon dioxide in our atmosphere, which is important because experts have found that atmospheric carbon dioxide levels are increasing primarily due to the burning of fossil fuels like coal and oil. More carbon dioxide in the atmosphere means an “enhanced” greenhouse effect, as the US National Oceanic and Atmospheric Administration (NOAA) calls it, and an enhanced greenhouse effect means rising global temperatures. To be clear, there is such a thing as “natural” climate change. But nature is not the primary driver of global warming right now.
This map shows sea level measured by the Sentinel-6 Michael Freilich satellite from June 5 to June 15, 2021. Red areas are regions where sea level is above normal, and blue areas are regions where it is below normal. NASA Earth Observatory
There are also many satellites, like NASA’s Landsat spacecraft, that can take images of how forests are shrinking as industry cuts them down to make way for commercial ventures. The images can also help track things like changing animal habitats, forced migrations of wildlife, and declining food supplies for certain species. There are also spacecraft with lasers that can help measure how quickly ice caps are melting. Others have synthetic aperture radars that show how our planet is responding to earthquakes, which could increase as the Earth warms.
Satellite gravimetry helps scientists measure the Earth’s gravitational influence – and, crucially, subtle changes in our planet’s gravitational field. Because gravity is directly related to objects of mass, this means the technique can pinpoint when ice mass is being lost, how ocean levels are rising, and even fluctuations in groundwater supplies. Satellites can see what we can’t see with our own eyes: changes in deep underground water storage that we would have to dig deep into the earth to observe.
The list goes on, with so much data available, scientists can exercise due diligence, gathering vast amounts of evidence for people in power to review before making climate-impacting decisions. At major climate meetings – the COP is perhaps the most famous – this evidence can be presented to officials as part of the case for change. Without information, communication is difficult.
However, satellite data is often useful in the short term as well.
For example, hurricane spotters help meteorologists predict where storms will strike—an important task because as the climate warms, such storms will inevitably become more intense and frequent—and methane emissions trackers can pinpoint where greenhouse gas hotspots are.
In a 2018 report, the US National Academies recommended that NASA build a series of spacecraft that would together form the Earth System Observatory (ESO). This observatory would be tasked with tracking the movements of our planet’s atmosphere, the formation of rain, the rise and fall of continents, and the ongoing movements of mass around the globe.
Sentinel-1 detects the retreat of Arctic glaciers. As temperatures in the Arctic rise, glaciers that end at sea, particularly in places like Svalbard, are retreating rapidly and calving at a rapid rate. The ESA-funded Space for Shore project is using radar data from the Copernicus Sentinel-1 mission to obtain precise annual information on glacier retreat and calving rates, particularly in areas like Kongsfjord where large glaciers are experiencing significant retreat.
Calving, the process by which ice breaks away from the end of a glacier, is a major driver of sea level rise and poses growing risks to coastal regions around the world. Understanding these processes, particularly in the Arctic, is important for predicting future impacts.
In a recent phase of the Space for the Coast project, a joint project between I-SEA (France) and NORCE (Norway), scientists used more than a thousand images from the Sentinel-1 mission to monitor in detail the evolution of coastal glaciers in Svalbard.
By analysing Sentinel-1 data from 2015 to 2023, the team mapped glacier front lines and measured calving activity during the summer months on Svalbard, when calving intensity peaks.
Kronebreen Glacier Front. ESA
Sentinel-1, part of the European Union’s Copernicus programme, uses synthetic aperture radar (SAR) technology to collect high-resolution data in challenging Arctic conditions, providing continuous year-round monitoring of these critical glaciers.
The key finding of the analysis is the annual extent of the ice fronts. By examining images taken between July and September, the researchers identified summer ice fronts as areas where the glacier extent is maintained 95% of the time during these months.
In addition, by detecting radar reflections from floating icebergs and ice floes, they developed a summer calving intensity index: summers with higher rates of icebergs and ice floes (a term for smaller pieces of ice that break off from glaciers) indicate more active calving and faster glacier retreat, which are key indicators of glacier health and stability.
As the next addition to the Sentinel-1 mission, Sentinel-1C will provide enhanced radar imaging capabilities and improved continuity for critical climate research. With its advanced technology, Sentinel-1C will enhance our ability to collect detailed year-round data on glacier front lines, calving rates, and ice-ocean interactions, even in challenging Arctic conditions.
Arctic sea ice has retreated to a near-historic minimum in the Northern Hemisphere this summer, according to researchers from NASA and the National Snow and Ice Data Center (NSIDC). The decline continues a decades-long trend of shrinking and thinning ice cover in the Arctic Ocean.
The amount of frozen seawater in the Arctic fluctuates throughout the year as ice melts and builds up between seasons. Scientists map these fluctuations to build a picture of how the Arctic is responding over time to warmer air and sea temperatures and longer melt seasons. Over the past 46 years, satellites have observed consistent trends of more melting in the summer and less ice formation in the winter.
Tracking sea ice changes in real time has revealed a wide range of impacts, from losses and changes in polar wildlife habitat to impacts on local Arctic communities and international trade routes.
Arctic sea ice extent has dropped to a minimum of 1.65 million square miles (4.28 million square kilometers) this year. That’s about 750,000 square miles (1.94 million square kilometers) below the 1981–2010 late-summer average of 2.4 million square miles (6.22 million square kilometers). The difference in ice cover covers an area larger than the state of Alaska. Sea ice extent is defined as the total area of the ocean with an ice concentration of at least 15 percent.
This year’s minimum remained above the all-time low of 1.31 million square miles (3.39 million square kilometers) set in September 2012. While sea ice extent can fluctuate from year to year, it has been trending downward since satellite ice records began in the late 1970s. Since then, sea ice has been lost at a rate of about 30,000 square miles (77,800 square kilometers) per year, according to the NSIDC.
Scientists are currently measuring sea ice extent using data from passive microwave sensors on satellites as part of the U.S. Defense Weather Satellite Program, as well as additional historical data from the Nimbus-7 satellite, a joint operation between NASA and the National Oceanic and Atmospheric Administration (NOAA).
This data visualization image shows the minimum extent of Arctic sea ice on Sept. 11, 2024. The yellow boundary shows the minimum extent averaged over the 30-year period from 1981 to 2010. NASA/Trent L. Schindler
Nathan Kurtz, director of NASA’s Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, noted that sea ice is not only melting, it’s getting younger.
“Today, the vast majority of the ice in the Arctic Ocean is thinner, first-year ice that is less able to survive the warmer months. There is much, much less ice that is three years old or older,” Kurz said.
Ice thickness measurements collected by space-based altimeters, including NASA’s ICESat and ICESat-2 satellites, have shown that much of the oldest, thickest ice has already been lost. New research from NASA’s Jet Propulsion Laboratory in Southern California shows that in the central Arctic, far from the coasts, autumn sea ice is now about 4.2 feet (1.3 meters) thick, down from a peak of 8.8 feet (2.7 meters) in 1980.
Sea ice in the planet’s southern polar regions was also low in 2024. Around Antarctica, scientists are tracking near-record low sea ice levels at a time when it should have been growing rapidly during the Southern Hemisphere’s darkest, coldest months.
The ice around the continent is on track to total just over 6.6 million square miles (16.96 million square kilometers). The average maximum extent between 1981 and 2010 was 7.22 million square miles (18.71 million square kilometers).
The slight increase in 2024 continues a recent downward trend. Before 2014, Antarctic sea ice was growing slightly, at a rate of about 1% per decade. After the 2014 spike, ice growth slowed sharply. Scientists are working to understand the cause of this change. The repeated loss hints at a long-term shift in conditions in the Southern Ocean, likely driven by global climate change.
“While Arctic sea ice changes have been dramatic for decades, Antarctic sea ice has been relatively stable. But that has changed,” said Walt Meyer, a sea ice specialist at NSIDC. “It looks like global warming has arrived in the Southern Ocean.”
In both the Arctic and Antarctic, ice loss is exacerbating ice loss. That’s because while bright sea ice reflects most of the sun’s energy back into space, open ocean water absorbs 90% of it. As more ocean is exposed to sunlight, water temperatures rise, further slowing sea ice growth. This cycle of increased warming is called the ice-albedo feedback.
Overall, the loss of sea ice is leading to warmer temperatures in the Arctic, where temperatures have risen about four times the global average, Kurz said.
