The study “Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?”, led by climatologist James E. Hansen, warns of a significant acceleration in global warming in recent years. The researcher and his team question whether the United Nations and the general public are sufficiently informed about the severity of the situation. Published in February 2025, the report emphasizes that the global temperature increase is occurring at a faster rate than many previous scientific predictions had indicated.
Key findings
The study reveals that the global average temperature has risen by more than 0.4°C over the past two years, reaching a peak of +1.6°C in August 2024 compared to the reference period (1880-1920). This increase was partly driven by the El Niño climate phenomenon, but the magnitude of the warming was twice what would be expected for a moderately intense El Niño event, suggesting the presence of additional underlying factors.
Reduction of aerosols and increased solar radiation absorption: the explanation?
One of the hypotheses proposed to explain this acceleration in global warming is the reduction of atmospheric aerosol pollution. Aerosols, tiny particles suspended in the atmosphere, have a cooling effect by reflecting part of the sun’s radiation back into space.
The decrease in aerosol emissions due to stricter environmental policies and the transition to clean energy sources may have contributed to increased heat absorption by the planet.
This reduction in aerosols has a paradoxical effect: it improves air quality but may accelerate global warming by allowing more solar radiation to be absorbed by the Earth. The solution is not to return to polluting the atmosphere but to simultaneously reduce greenhouse gas (GHG) emissions and develop strategies to limit global temperature rise.
Impacts on polar regions and rising sea levels
The study highlights that polar regions are particularly vulnerable to climate change, with long-term global consequences. The accelerated melting of ice sheets in Greenland and Antarctica, combined with the influx of freshwater into the North Atlantic Ocean, could alter ocean current patterns and intensify extreme weather events. Meanwhile, rising sea levels pose an increasing risk to coastal cities worldwide, with severe economic and social implications for millions of people.
Challenges for cities and global impact
Cities, as major centers of economic and social activity, are at the forefront of climate change impacts. Rising urban temperatures, more frequent and intense heat waves, water shortages in many regions of the planet, and the risk of coastal flooding present significant challenges for local governments. However, beyond their heightened exposure to risks, the study notes that some cities are already implementing mitigation and adaptation measures, such as expanding green infrastructure, improving building energy efficiency, and strengthening urban drainage systems to cope with heavy rainfall.
Conclusions and Recommendations
The study “Global Warming Has Accelerated” reinforces the need for a coordinated global response, warning that without swift and effective measures, the impacts of climate change will become increasingly severe and difficult to reverse. It raises concerns about how the climate crisis is communicated to the public and international bodies, including the United Nations. The authors argue that:
- Climate science must be communicated more clearly and accessibly to ensure that both policymakers and the public understand the urgency of the problem.
- Current climate targets may be insufficient, as global warming is progressing faster than predicted.
- Immediate and more ambitious actions are needed to reduce greenhouse gas emissions, invest in renewable energy, and prepare cities and communities for the inevitable impacts of climate change.
The study was conducted by a team of 18 climate scientists, led by James E. Hansen, climatologist and former director of NASA’s Goddard Institute for Space Studies. The article was published on February 3, 2025, in the scientific journal Environment. The official presentation of the study took place on the same day during a publicly accessible webinar, where the authors discussed the main findings and implications of their research.
