A recent study published in the journal Science Advances, conducted by researchers from the Rosenstiel School of Marine, Atmospheric, and Earth Science at the University of Miami, provides new evidence on the increase in Earth’s heat and its causes. The work concludes that the planet is accumulating more heat not due to the reduction of pollutant aerosols, as previously thought, but due to changes in cloud reflectivity and increased absorption of solar radiation.
What is Earth’s energy imbalance?
This parameter measures the difference between the solar energy the planet absorbs and the energy it returns to space. It is a key indicator for understanding climate evolution and the rate at which heat accumulates in the climate system.
Between 2003 and 2023, data shows that Earth accumulated around 0.51 watts more per square meter each decade, meaning the planet absorbs more energy than it releases. The emitted thermal radiation barely changed, reinforcing the idea that the increase comes from a greater entry of sunlight.
The role of aerosols
Traditionally, scientists had attributed part of the increase in energy imbalance to the reduction of aerosols —small suspended particles from natural and human sources. These particles reflect sunlight and promote cloud formation, reducing the energy trapped in the climate system.
However, the study concludes that in recent years their impact was practically null. Researchers analyzed two types of measurements:
- An aerosol index obtained by satellites, which measures the quantity and size of particles.
- The sulfate concentration, calculated from atmospheric models.
Both methods agreed on a pattern: decrease in aerosols in the northern hemisphere and increase in the southern hemisphere. This created a hemispheric compensation that neutralized the global effect.
Natural events and hemispheric compensation
In the northern hemisphere, the reduction of aerosols was mainly due to environmental laws that improved air quality in industrialized areas. In the southern hemisphere, however, natural events like the wildfires in Australia (2019-2020) and the eruption of the Hunga Tonga–Hunga Ha’apai volcano (2022) released large amounts of particles into the atmosphere.
This hemispheric “balancing act” explains why aerosols did not have a significant impact on the increase in global energy imbalance.
The true drivers of warming
The study’s authors, including Brian Soden and Chanyoung Park, emphasize that attention should focus on changes in cloud behavior and natural climate variability. The accumulated evidence indicates that interactions between aerosols and radiation or between aerosols and clouds have had an insignificant contribution to recent trends.
Park highlighted that this clarity favors better climate planning and more informed policy decisions: “While the northern hemisphere may experience some regional warming due to aerosol reduction, this does not translate into a significant global impact.”
Implications for science and climate policies
The study warns that climate models must more accurately incorporate natural sources of aerosols and their variability, to avoid overestimating the role of air pollution in global warming.
The main conclusion is that the increase in Earth’s energy imbalance is more explained by the reduction in cloud reflectivity and the greater absorption of solar radiation, rather than by aerosols.
This finding redefines the understanding of global warming and poses new challenges for climate research. The key is to study how changes in clouds reflect or absorb solar energy, and how natural climate variability influences this process.
Each advance in measuring and analyzing Earth’s energy imbalance allows for improved public communication, climate planning, and environmental policies, in a context where understanding the true forces behind warming is essential to facing the future.