Planetary warming is accelerating at an unprecedented pace, and critical climate indicators are deteriorating, according to an annual study by more than 70 scientists, including contributors to the United Nations Intergovernmental Panel on Climate Change (IPCC). The report, published in the journal Earth System Science Data, highlights growing concerns over the state of global warming and warns that funding cuts to Earth observation systems threaten the ability to monitor these changes effectively.

Global average temperatures reached approximately 1.39 degrees Celsius above preindustrial levels in 2025, with 1.37 degrees attributed to human activity, the researchers found. This warming trajectory suggests the 1.5-degree Celsius threshold, identified in the 2015 Paris Agreement as critical to limiting climate damage, could be crossed as early as 2030. The study stressed that the world is accumulating heat at a rapidly increasing rate, deepening Earth’s energy imbalance—the difference between energy absorbed and radiated back into space—which has doubled in recent decades.

The research attributes the accelerated warming primarily to record-high greenhouse gas emissions, particularly carbon dioxide (CO2), combined with a reduction in aerosol pollution that previously had a cooling effect by reflecting sunlight. Although emissions growth is slowing, scientists warn that the remaining “carbon budget,” or the allowable CO2 emissions to stay below 1.5 degrees Celsius of warming, may be exhausted within three years.

The report also documented significant changes in ocean conditions, including a global mean sea-level rise of approximately 23 centimeters since 1901, now increasing at nearly 3.84 millimeters per year, driven by melting land ice and thermal expansion of warming seawater. Marine heatwaves, newly incorporated into this year’s study, have more than tripled since 1991, averaging 65 hot days in 2025.

The Indicators of Global Climate Change initiative, launched in 2023, aims to provide continuous updates on the planet’s climate health between major IPCC assessments, with the next scheduled report in 2028 or 2029. This effort depends on extensive global data collected via satellite and various in situ instruments such as weather stations, buoys, ships, and weather balloons.

However, the study cautioned that geopolitical conflicts, a global energy crisis, budgetary pressures, and shifts in U.S. policy—highlighted by former President Donald Trump’s administration reducing the deployment of deep-sea instruments—pose serious risks to sustaining these observation networks. These in situ measurements are deemed vital for understanding ocean heat absorption and its implications for weather and circulation patterns.

Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, emphasized the importance of maintaining these on-site observations for accurate climate monitoring. She also noted declines in observational capacity across Africa, the western Pacific, and South America, and pointed to recent defunding of atmospheric observation flights in the United Kingdom.

The report underscored the erosion of funding for global monitoring bodies such as the UN’s World Meteorological Organization and the Global Climate Observing System (GCOS), both crucial for maintaining consistent, long-term climate data collection. Scientists warned that without sustained investment and international cooperation, the ability to track critical climate changes and inform timely policy responses will be severely compromised.