Light Pollution Is Stealing the Stars Faster Than Anyone Realized

A Sky That Dims With Every Generation

A child who can count 250 stars from home may be able to see fewer than 100 from that same spot by age eighteen. The stars themselves won't have moved. The difference will be the artificial light scattered through Earth's atmosphere between them and the observer. That sobering projection is not science fiction — it comes directly from one of the largest human-powered sky surveys ever conducted.

Researchers investigated the change in global sky brightness from 2011 to 2022 using 51,351 citizen scientist observations of naked-eye stellar visibility. The number of visible stars decreased by an amount explained by an increase in sky brightness of 7 to 10% per year in the human visible band — an increase faster than what emissions data from satellites had indicated. The gap between what orbiting instruments detect and what human eyes actually experience turns out to be enormous.

Why Satellites Have Been Missing the Picture

After devising a new method to convert observations into estimates of skyglow change, the authors found that the loss of visible stars reported by Globe at Night indicates an increase in sky brightness of 9.6% per year over the past decade — much greater than the roughly 2% per year global increase in surface brightness measured by satellites. That's a fivefold difference, and it has major implications for how seriously the problem has been taken by policymakers.

The reason satellites have been so far off comes down to the nature of modern lighting. Satellites primarily measure light emitted vertically, either directly or via reflection, and are blind to light in the bluer, short wavelengths. Ground observations also capture light emitted horizontally — from lit building facades, digital billboards, and light escaping windows — and the human eye sees light across a broader spectrum. Since human eyes are more sensitive to shorter wavelengths at nighttime, LED lights have an outsized effect on our perception of sky brightness, a factor satellites simply cannot account for.

A Crisis Hiding in Plain Sight

Researchers estimated that sky brightness at participants' locations was increasing by an average of 9.6% each year — equivalent to more than a fourfold increase across eighteen years. This is equivalent to a doubling of the night sky's brightness in less than eight years. For context, scientists estimated that carbon dioxide, the primary contributor to climate change, is growing at 2% per year globally — doubling every 30 years. Light pollution is accelerating at a pace that dwarfs even that benchmark.

The 2016 World Atlas of Artificial Night Sky Brightness estimated that more than 80% of humanity already lived under light-polluted skies, with the Milky Way hidden from more than one-third of the world's population — including about 60% of Europeans and nearly 80% of North Americans. That loss is not limited to city centres. Artificial light can scatter and create domes visible hundreds of kilometres from its source, meaning a landscape that appears dark at ground level may still have a brightened sky above it.

What Comes Next

The researchers drew a pointed conclusion: current lighting policies, such as the widespread use of LEDs, have not brought about any improvement, at least on a continental level, despite growing awareness of light pollution. Increasing sky brightness is a sign that we are doing lighting wrong — wasting energy inefficiently, wasting money, exacerbating climate change, and increasing environmental impacts.

Researchers believe the global average change of +9.6% per year is actually an underestimate of the true rate, since regions with high rates of economic growth — where lighting is expanding fastest — are under-sampled in the Globe at Night data. Despite high confidence in approaches known to reduce light pollution, the researchers concluded that current efforts don't seem to be working, and failure to cut back on wasted outdoor light at night can have real impacts on communities. For the first time in human history, an entire generation may grow up never truly knowing a dark sky — not because the universe changed, but because we left too many lights on.