Update Saturday 11 May
According to NOAA measurements, CO2 reached
400.03 ppm on 9 May. Not so according to data held by
Scripps (399.73 ppm). The difference in the readings
would be due to different measurement times
during the day. NOAA uses the UTC system, while Scripps uses local Hawaiian
time. If Scripps were to use the UTC system, the concentration
would have been 400.08 ppm.

News from 2 May
The news of the upcoming record set to be broken within
the month of May (we currently stand at 399.5 ppm) was announced
by scientists who monitor daily data from the
Mauna Loa observatory, in the Hawaiian Islands, the
most important monitoring station in the world, active since
1958 when American scientist Charles David Keeling
began tracking the rise of CO2 in the atmosphere.

The Keeling curve
The first reading was 317 ppm. Today the Keeling
curve, made famous by Al Gore through the documentary "An
Inconvenient Truth", contains 55 years of readings taken on an hourly
basis at the summit of the Hawaiian volcano (shown in the small photo).

"This is another milestone reached by global warming
without anything being done about it," declared Jim Butler,
director of the global monitoring division of the Earth System Research
Laboratory at NOAA. "Ever more powerful storms,
droughts, rising sea levels. We are already
seeing the impacts of increasing CO2 in the atmosphere. How
much longer must we wait?"

By analysing air bubbles trapped in the ice caps and
glaciers of the Arctic Circle, scientists have
established that CO2 had never exceeded 300 ppm during the
800,000 years that preceded the industrial
revolution.

400 blows are still not enough
This is not the first time ever that a CO2 monitoring
station has recorded a value above 400 ppm. In
the past it has happened in the Arctic, where vegetation is
sparse and winds carry much of the gas emitted by neighbouring
countries. By contrast, the values recorded by the Mauna
Loa station are those closest to the global average.

According to Ralph Keeling, director of the CO2 programme at
Scripps and son
of the famous scientist after whom the curve is named, once
trees have completed their leafing and are able to
absorb more carbon dioxide, the concentration
will fall back below 400 ppm, but it will not be long
before this threshold is crossed permanently, even
in summer.

"The next target in emissions' sights is 450 ppm,"
Butler concluded. A result that could be reached in just 25 years if
nothing is done in the near term to reverse course.