Earth is getting darker, according to data from NASA satellites, and the results could tell us a lot about how climate change is affecting our planet.
The news of our darkening planet comes from a study that used 24 years' worth of satellite observations as part of the Clouds and the Earth’s Radiant Energy System (CERES) project.
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CERES satellites orbit Earth and gather information on how much light our planet reflects outwards into space, and how much this has changed over time.
The CERES satellites provide data that enables scientists to calculate 'Earth’s radiation budget' (ERB).
Earth's radiation budget is the amount of sunlight absorbed by Earth, and the amount of infrared energy emitted to space, and the disparity between these two values.
Using data from the CERES satellites, a study shows that between 2001–2024, Earth has been reflecting less sunlight, making it get darker and darker over time.
What's more, this decrease in reflectivity is more pronounced in the Northern Hemisphere than in the South.
The study shows there are three main causes.
Melting snow and ice is a key cause of Earth's darkening.
Snow and ice both reflect sunlight, and as they melt away, that's exposing more water and land, which are much darker materials that reflect less sunlight.
A good example of this is how much brighter a back garden or public park appears when it's covered in snow, compared to when it's not.
As temperatures rise, snow and ice cover is shrinking, exposing these darker surfaces that absorb more sunlight instead of reflecting it.
The second factor is aerosol pollution.
In the Northern Hemisphere, stricter environmental regulations have reduced aerosol pollution, which previously reflected sunlight.
That's one reason why the Northern Hemisphere is getting darker.
However, in the Southern Hemisphere, aerosol levels are increasing due to events like bushfires and volcanic eruptions, which reflect more sunlight.
To make matters worse, the Northern Hemisphere's clearer skies, free of the smog and smoke of yesteryear, are making things worse.
The smoggy conditions that once plagued our towns and cities actually helped reflect sunlight, but now clearer air is letting more sunlight and heat get in.
And it's not being reflected off the ground because of how much snow and ice has been melting over the past two decades.
Thirdly, the study says changes in cloud formation and properties are contributing to the differences in reflectivity between the Northern and Southern Hemispheres.
These changes are causing to an imbalance in the Earth's energy system, the Northern Hemisphere absorbing more heat than it reflects.
The study suggests climate models may need to be updated to account for these differences in reflectivity between the Northern Hemisphere and Southern Hemisphere.
Perhaps even more importantly, understanding these changes in Earth's reflectivity will help predict future climate patterns and enable scientists to more accurately assess the impacts of global warming.
Read the full paper at www.pnas.org/doi/10.1073/pnas.2511595122
