What did the 2011–2022 study measure?

It combined volunteer reports of naked-eye limiting magnitude—the faintest stars a person could see—with Sky Quality Meter measurements. The AAS account says Globe at Night collects both kinds of observation, so the study addresses changing visible conditions from the ground.

Why We Can't See the Milky Way: The Skyglow Problem

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The light between us and the stars

A bright sky can look empty even when the stars are still there. The problem is contrast: faint celestial light becomes difficult to distinguish against a brighter background. Skyglow is the artificial brightening of that background, caused by light scattered through the atmosphere. Our explanation of light pollution separates this sky-wide effect from the glare of an individual lamp.

That distinction matters. Blocking a streetlamp from your eyes can make observing more comfortable, but it does not remove the light already scattered across the sky. The obstacle can extend beyond the fixture you can point to. Looking away from a bright road and escaping the glow of a built-up area are different things.

AI-generated comparison of an orange urban sky and a dark desert sky with the Milky Way visible — AI-generated illustration of contrasting sky conditions; these are not measured before-and-after views of the same place.

The Milky Way's faint band makes the loss easy to recognize. A sky can retain conspicuous stars while losing the background detail that makes the galaxy visible. Seeing a few stars overhead therefore tells you much less than you might hope about how much of the night remains visible.

What the 2016 atlas actually tells us

The World Atlas of Artificial Night Sky Brightness gave the loss a global scale. Its published estimate put more than 80% of the world's population under light-polluted skies.^[2] That is a broader category than a sky bright enough to hide the Milky Way, so the two figures should not be treated as interchangeable.

The Milky Way estimate was more specific: more than a third of humanity overall, including 60% of Europeans and nearly 80% of North Americans.^[1] These are findings from the atlas published in 2016. They are not a fresh census of what people can see tonight.

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Population-level estimates cannot settle the question for a particular observing spot. They describe the scale of a shared problem; evaluating an individual sky is a separate task. The Bortle scale is useful background for thinking about visible sky conditions.

Why the later study found a faster change

A study published in 2023 asked a different question: how was the visible sky changing? Using observations from 2011–2022, Christopher Kyba and colleagues inferred an average annual increase in light pollution of 9.6%, with 10.4% for North America, as reported by the American Astronomical Society.^[3]

The estimates came from Globe at Night observations of naked-eye limiting magnitude: the faintest stars people could make out. The programme collects these estimates alongside Sky Quality Meter measurements.^[4] That makes the observer's view central to the evidence.

The AAS account contrasted this result with satellite-based studies reporting a roughly 2% annual global increase. It also identified a limitation of the satellite instruments discussed: their wavelength range missed short-wavelength emissions characteristic of modern white LEDs.^[5] Measurements looking down at emitted light and observations of stars from the ground do not capture precisely the same thing.

That is why I would keep both the method and the dates beside the headline number. The 9.6% estimate describes the study period and its observations. It is not a measured annual rate for every town, and carrying it forward to the present would require newer evidence.

A loss of view, with a local answer

Put together, the research tells a coherent story. The atlas describes the reach of artificial sky brightness at the time of its publication. The later observer-based study documents change over its stated measurement period.

A split-scene aerial view showing a light-polluted city skyline under orange sky glow on the left, transitioning to a pristine dark sky with the Milky Way visible on the right, illustrating what is light pollution and its visual impact on the night sky

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For someone who wants to see the galaxy, places to see the Milky Way are the practical next question. But the wider issue remains at home: the quality of the sky above a populated place is something worth examining in its own right.

The galaxy has stayed overhead; the conditions of the view are ours to change.

Sources

arxiv.org — 1609.01041 (opens in a new tab)
“The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans.”
arxiv.org — 1609.01041 (opens in a new tab)
“This atlas shows that more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies.”
aas.org — Rapid brightening night skies globally recent results citizen science and (opens in a new tab)
“Kyba et al. (2023) studied the NELM estimates and based on these data inferred a global average increase in the light pollution of 9.6% (10.4% in North America) per year between 2011 and 2022.”
aas.org — Rapid brightening night skies globally recent results citizen science and (opens in a new tab)
“This program collects estimates of naked-eye limiting magnitude (NELM) and Sky Quality Meter measurements submitted by volunteers around the world. Contributions typically exceed some 10,000 to 30,000 observations per year with more than a quarter of a million data points from 180 countries over the last 17 years.”
aas.org — Rapid brightening night skies globally recent results citizen science and (opens in a new tab)
“This is a much larger increase than has been reported by studies using only satellite remote sensing observations of light emissions (Kyba et al. 2017, Sanchez de Miguel 2017), which had found a roughly 2% per year increase on a global average basis. Satellite instrumentation is focused on wavelengths of 500-900 nm, which misses short-wavelength optical emissions characteristic of modern white light-emitting diodes (LEDs),”

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