This data visualization shows the area and shape of
the ozone hole on September 18, 2026, the day of its annual maximum extent.
Scientists define the ozone hole as the area in which ozone concentrations drop
below the historical threshold of 220 Dobson units.
NASA Earth Observatory/Lauren Dauphin
This
story is an update to the Antarctic ozone hole feature in our World of Change series, which documents how Earth changes over months, seasons, and years.
The stratospheric ozone layer protects
life on Earth by absorbing ultraviolet light, which damages DNA in plants and
animals (including humans) and leads to sunburns and skin cancer. Prior to
1979, scientists had not observed atmospheric ozone concentrations below 220 Dobson Units. But in 1985, British
Antarctic Survey scientists using ground-based measurements at Halley Research
Station reported that Earth’s natural sunscreen was thinning dramatically over
Antarctica each spring. NASA satellite instruments revealed the continental
scale of this Antarctic ozone thinning, and it came to be known as the ozone
hole.
The data visualizations below show the
ozone hole each year from 1979 through 2026 (no data are available for 1995).
The measurements were made from 1979-2004 by the TOMS (NASA’s Total Ozone Mapping
Spectrometer) instruments on Nimbus-7 and several additional satellites; from
2005-2011 by the OMI (Ozone Monitoring Instrument) on the Aura satellite; from 2012-2025 by the OMPS (Ozone Mapping and Profiler Suite) on
the Suomi NPP satellite; and in 2026 by the OMPS on the NOAA-20 satellite. Red and yellow areas
indicate the ozone hole.
As the images show, the word hole isn’t
literal; no place is empty of ozone. Scientists use the word hole as a metaphor
for the area in which ozone concentrations drop below the historical threshold
of 220 Dobson Units. Using this metaphor, they can describe the hole’s area and
depth. These maps show the state of the ozone hole each year on the day of
maximum depth—the day the lowest ozone concentrations were measured.
The
series begins in 1979. The maximum depth of the hole that year was 194 Dobson
Units (DU)—not far below the previous historical low. For several years, the
maximum depth stayed in the 190s, but then rapidly grew deeper: 173 DU in 1982,
154 in 1983, 124 in 1985. By 1991, a new threshold was passed, as the ozone
concentration fell below 100 DU for the first time. Since then, concentrations
below 100 DU have become more common. The deepest ozone hole occurred in 1994,
when concentrations fell to just 73 DU on September 30.
Records in depth and area have never
occurred in the same year (the largest ozone hole occurred in 2006), but the
long-term trend in both characteristics is consistent: from 1980 through the
early 1990s, the hole rapidly grew in area and depth. In the early years of the
21st century, annual ozone holes roughly stabilized (see NASA
Ozone Watch for annual averages). Year-to-year
fluctuations in area and depth are caused by variations in stratospheric
temperature and circulation. Colder conditions result in a larger area and lower ozone values in the core of the
hole.
That was the case in 2026, when an
unusually strong Antarctic polar vortex created ideal conditions for ozone
depletion over a large area. Measured by its mean size from September 7 to
October 13, which is peak ozone depletion season, the 2026 hole was the seventh largest in 48 years of monitoring. However, it was not as deep as other large holes on record. The map at
the top of this page shows the hole on September 18, the day of its annual
maximum area.
The ozone hole opened the world’s eyes
to the global effects of human activity on the atmosphere. Scientists learned
that chlorofluorocarbons (CFCs)—long-lived chemicals that had been used in
refrigerators and aerosol sprays since the 1930s—had a dark side. In the layer
of the atmosphere closest to Earth (the troposphere), CFCs circulate for
decades without degrading or reacting with other chemicals. When they reach the
stratosphere, however, their behavior changes. In the upper stratosphere
(beyond the protection of the ozone layer), ultraviolet light causes CFCs to
break apart, releasing chlorine, a very reactive atom that repeatedly
catalyzes ozone destruction.
The global recognition of the
destructive potential of CFCs led to the 1987 Montreal Protocol, a treaty phasing out the consumption and production of ozone-depleting
chemicals. Scientists estimate that about 80 percent of the chlorine in the stratosphere today comes
from human, not natural, sources. Human-produced bromine compounds, which are
far less abundant but much more destructive to ozone, also contribute to the
Antarctic ozone hole.
Models suggest that the
concentration of chlorine and other ozone-depleting substances in the
stratosphere will not return to pre-1980 levels until later in the 21st
century. In 2018, scientists reported the first direct
satellite evidence of ozone recovery, observing a 20 percent decrease in ozone
depletion during the Antarctic winter months from 2005 to 2016. In 2019,
abnormal weather patterns in the upper atmosphere over Antarctica dramatically
limited ozone depletion, leading to the smallest hole since 1982—illustrating
the impact of year-to-year variations in the meteorology of the Antarctic
stratosphere. Scientists estimate that the Antarctic ozone layer will return to
1980 levels in the 2070s.
NASA Earth Observatory images by Lauren Dauphin, using data from NASA Ozone Watch.
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