A new analysis by NASA researchers confirms a significant change in the energy balance of the planet: Earth is reflecting less solar light back into space, especially in the northern hemisphere.
The earth reflects, from year to year, less and less light in space. Photo: Shutterstock
This decrease in the “brightness” of the planet, which has become measurable in the last two decades, could have direct consequences on the global climate, accelerating the heating and affecting the meteorological models on a scale.
According to the latest data provided by NASA, the Earth is reflecting less solar light back into space, a phenomenon that seems to be accentuated from year to year, especially in the northern hemisphere. This decrease in the ability of the planet to reflect solar radiation (an indicator known as Albedo) has been confirmed by a detailed analysis of the satellite data collected over the last 24 years.
A team of scientists led by Dr. Norman G. Loeb, a principal researcher at NASA Langley Research Center, conducted a comprehensive study to measure exactly the amount of radiant energy reflected by the Earth. According to PC Wold, research has combined multiple sources of data: incidental solar radiation measurements, the reflection of the terrestrial and ocean surface, but also the global balance of radiative energy.
Earth, an increasingly “dark” planet
The data has shown that, since 2001, the reflectivity of both hemispheres -nordic and southern has gradually decreased. In other words, less sunlight is sent back to space, and more is retained by the earth and oceans, contributing to the increase in global temperature.
Quantitatively, the earth is currently absorbing with 0.83 watts/square meter more solar energy per decade. The northern hemisphere is affected to a greater extent, with an additional absorption of 0.34 watts/square meter.
Although ocean and atmospheric currents redistribute some of this energy, the researchers have found that a net excess of 0.21 watts/square meter per decade remains, which contribute directly to regional and global heating.
“The change is measurable and worrying. The planet retains more energy than in the past, which has direct implications for the climate system,” support the authors of the study.
In the past, it has been assumed that natural balancing processes, such as the formation of clouds or the circulation of ocean currents, can compensate for regional radiation variations, but the new data suggest that these mechanisms become more and more ineffective, which causes an energy imbalance between the two hemispheres.
The main causes
Scientists have also identified the most important causes of this worrying phenomenon.
1. Melting ice and snow in Arctic regions
One of the main identified causes is the withdrawal of glacial cap. The surfaces covered with snow and ice, which have a high albedo, ie effectively reflect the sunlight, gradually disappear due to global warming, and in their place darker areas (liquid water, exposed soil) appear, which absorb much more solar energy.
This process creates a vicious circle: more absorption leads to more melting, which in turn leads to even more absorption.
2. Decreasing air pollution in industrialized areas
Paradoxically, the reduction of aerosol emissions (fine particles suspended in the air) in Europe, the United States and China as a result of anti-pollution regulations also had an unexpected effect. Thus, fewer aerosols in the atmosphere mean fewer clouds and, implicitly, a lower light reflection.
3. influences from the southern hemisphere
In the southern hemisphere, two major events temporarily influenced the radiative balance: on the one hand the vegetation fires, which released large amounts of aerosols, temporarily increasing the Albedo, and on the other hand, the eruption of the Hunga Tonga volcano, which also sent additional aerosols to the atmosphere, which increased the reflection for a short period.
With these elbows, the effects were transient and insufficient to counterbalance the trends observed globally.
More stored energy, more unstable climate
The modification of the Earth Albedo means, concretely, that the planet retains more thermal energy than it can redistribute or evacuated, so that especially the northern hemisphere, where the most populated and industrialized regions are, is to the risk of additional heating.
For areas such as Europe, North Asia and North America, this energy accumulation could lead to hotter, more unstable winters, prolonged droughts or, on the contrary, extreme precipitation.
“The change of solar reflection is a clear signal that we have to update the climatic models. It is a dynamic that can amplify other effects of the climatic changes already in progress.” say the researchers.
