Tue, May 14, 2013
- At the current rate of increase, the global
annual average CO2 concentration is set
to cross the 400 ppm threshold in 2015 or
2016
Observed concentrations
of carbon dioxide (CO2) in the atmosphere
have exceeded the symbolic 400 parts per
million (ppm) threshold at several stations
of the World Meteorological Organization's
Global Atmosphere Watch network. This is
a wakeup call about the constantly rising
levels of this greenhouse gas, which is
released into the atmosphere by fossil fuel
burning and other human activities and is
the main driver of climate change. Carbon
dioxide remains in the atmosphere for thousands
of years, trapping heat and causing our
planet to warm further, impacting on all
aspects of life on earth.
On May 9, 2013, the
daily mean concentration of carbon dioxide
in the atmosphere of Mauna Loa, Hawaii,
recorded a reading of 400.03 ppm, according
to the U.S. National Oceanic and Atmospheric
Administration. Mauna Loa is the oldest
continuous atmospheric measurement station
in the world and so is widely regarded as
a benchmark site in the Global Atmosphere
Watch.
Several other Global Atmosphere Watch stations
have also reported CO2 concentrations exceeding
the 400 ppm threshold during the seasonal
maximum. This occurs early in the northern
hemisphere spring before vegetation growth
absorbs CO 2.
The threshold was first
crossed at stations in the Arctic. A monthly
average value exceeding 400 ppm was registered
at Barrow, Alaska, USA (71.3N) for the first
time in April 2012, as well as at Alert,
in Canada (82.5N). From the beginning of
2013, measured CO 2. values at another GAW
Global station, in Ny-Ålesund, Norway,
(at 78.9N) also exceeded 400 ppm. This threshold
has now also been crossed at stations closer
to the Equator. Izaña, (Canary Islands,
Spain), reported daily mean values exceeding
400 ppm at the end of April 2013. This was
followed by Mauna Loa, which has been carrying
out measurements since 1958.
The Global Atmosphere
Watch coordinates observations of CO2 and
other heat-trapping gases like methane and
nitrous oxide in the atmosphere to ensure
that measurements around the world are standardized
and can be compared to each other. The network
spans more than 50 countries including stations
high in the Alps, Andes and Himalayas, as
well as in the Arctic, Antarctic and in
the far South Pacific.
Carbon dioxide is the
single most important greenhouse gas emitted
by human activities. It is responsible for
85% of the increase in radiative forcing
? the warming effect on our climate - over
the past decade. Between 11000 and 2011
there was a 30% increase in radiative forcing
because of greenhouse gases. Radiative forcing
is calculated relative to the pre-industrial
level of key greenhouse gases.
According to WMO's Greenhouse
Gas Bulletin, the amount of CO2 in the atmosphere
reached 390.9 parts per million in 2011,
or 140% of the pre-industrial level of 280
parts per million. The pre-industrial era
level represented a balance of CO2 fluxes
between the atmosphere, the oceans and the
biosphere. The amount of CO2 in the atmosphere
has increased on average by 2 parts per
million per year for the past 10 years.
At the current rate
of increase, the global annual average CO2
concentration is set to cross the 400 ppm
threshold in 2015 or 2016. http://www.esrl.noaa.gov/gmd/ccgg/trends/global.html.
