240
WE ARE SEEING
THE BEGINNINGS
OF A RAPIDLY
CHANGING PLANET
THE KEELING CURVE
T
he Keeling Curve, named
after Charles Keeling, an
American scientist, charts
the daily record of atmospheric
carbon dioxide (CO 2 ), measured in
parts per million by volume (ppmv),
in a series dating back to 1958.
It shows two things: the natural
seasonal respiration of Earth and
the year-on-year rise in atmospheric
CO 2. Atmospheric CO 2 is significant
because carbon dioxide is the most
important of the greenhouse gases,
which trap warmth in Earth’s
atmosphere. More molecules of CO 2
and other greenhouse gases causemore heat to be trapped, leading to
an overall increase in temperature
and global climate change.Measuring CO 2 levels
Since the start of the Industrial
Revolution in the late 1700s, human
activity has produced increasing
emissions of CO 2. This is largely
due to burning fossil fuels, while
forest clearance for agriculture and
development has resulted in less
vegetation absorbing CO 2 through
photosynthesis. Many scientists
once believed that excess CO 2
would be absorbed by the oceans.
Others disagreed, but there was
little hard evidence either way.
Charles Keeling was not the
first to propose a link between
atmospheric warming and CO 2
emissions. Others had measured
CO 2 levels but had produced only
“snapshots” in time rather than a
long-term dataset. Keeling knew
that a long study was needed to
prove the link. In 1956, he took up
a post at the Scripps Institution of
Oceanography in San Diego,
California, and obtained funds to
establish CO 2 monitoring stations
at remote locations 9,843 ft (3,000 m)
up on Mauna Loa, Hawaii, and at
the South Pole. By 1960, KeelingIN CONTEXT
KEY FIGURE
Charles Keeling (1928–2005)BEFORE
1896 The Swedish chemist
Svante Arrhenius is the first
to estimate the extent to
which atmospheric CO 2 could
increase Earth’s temperature.1938 Comparing historic
temperature data and CO 2
measurements, the British
engineer and scientist Guy
Stewart Callendar concludes
that the increase in CO 2 is
responsible for the warming
of the atmosphere.AFTER
2002 The European Space
Agency’s ENVISAT satellite
begins to produce up to 5,000
readings of greenhouse gases
every day.2014 NASA’s Orbiting Carbon
Observatory generates up to
100,000 high-precision
measurements daily.We were witnessing for
the first time nature’s
withdrawing CO 2 from the
air for plant growth during
summer and returning it
each succeeding winter.
Charles KeelingUS_240-241_Keeling_Curve.indd 240 17/12/2018 14:33