Scientists Warn of Future Risks as Earth Has Been Getting Darker Over the Past 20 Years
The atmosphere across Earth is constantly changing, shaped by natural forces and human activities. While we have already seen changing climate patterns, evolving landscapes, and growing urbanization changing the planet’s surface, a new phenomenon has now come to light. In the past two decades, scientists have noticed that the Earth is gradually getting darker with each passing year. The change in sunlight is more prominently observed in the Northern Hemisphere when compared to the Southern Hemisphere. The researchers analyzed the difference in sunlight between 2001 and 2024, and the findings of the research were published in the journal Proceedings of the National Academy of Sciences.
The satellite data was studied by a team of researchers at NASA’s Langley Research Center in Virginia, as reported by Phys.org. The authors wrote, “On average, the Southern Hemisphere gains radiative energy at the top of the atmosphere while there is a net loss in the Northern Hemisphere.” Earlier research suggested that winds and ocean currents balanced the energy between the two hemispheres. But the new study now shows that they haven’t fully done so in the last 20 years. Additionally, the imbalance also happens because the warmer Northern Hemisphere releases more heat into space, even though both hemispheres absorb almost the same amount of sunlight.
It is because of a change in Earth’s albedo, which means the amount of sunlight that the surface reflects. Bright surfaces like ice and snow reflect a lot of sunlight into space, while darker surfaces like rock or water absorb more of it. In this case, as the study explains, the northern hemisphere has been losing sea ice and snow cover over time due to the rapidly changing climate and increasing global temperatures. This leads to more sunlight being absorbed instead of being reflected, making the planet darker.
Furthermore, tiny particles in the air, called aerosols, also play a big role in this change. They help in the formation of the clouds that reflect sunlight. In the north, pollution controls have reduced these particles, so there are fewer clouds to bounce light back. However, in the south, tragic incidents like Australia’s bushfires and several volcanic eruptions added more aerosols to the environment, increasing the cloud formation there. Despite this, the recent study has indicated that clouds may not be able to fully balance the differences between the two hemispheres.
As reported by CBC, Zeke Hausfather, a popular research scientist, also spoke about the change in cloud reflectivity previously and said, "I think that we see such a clear change in cloud cover and cloud reflectivity is a little surprising. I hadn't looked at that data recently and realized just how big the signal we are starting to see, and that certainly is worrying." Meanwhile, the planet’s growing darkness is also causing it to hold onto more heat, which is speeding up the pace of global warming. This adds to the list of other concerning situations on top of the threats already caused by burning fossil fuels and rising pollution levels.
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