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The rise and rise of greenhouse gases
the VoluMe oF greenhouse gases causing global
warming has risen to new highs, the UN World
Meteorological Organisation (WMO) says, warning it is
becoming increasingly unlikely the world can limit rising
temperatures to UN-backed targets.
Pointing out that the worst warming gases – carbon dioxide
(CO2), methane, and nitrous oxide – had all reached new highs in
recent years, the agency’s Secretary-General Michel Jarraud said
“it is getting increasingly unlikely” that a UN-backed pledge to
limit global warming to 2°C (3.6° Fahrenheit) could be achieved.
“Between 1990 and 2011, there was a 30% increase in
radiative forcing – the warming effect on our climate – because
of carbon dioxide and other heat-trapping long-lived gases,” the
Levels of CO2
– the single most important man-made
contributor to climate change – rose to 390.9 parts per million
(ppm) in 2011, which is 2.0 ppm higher than in 2010, reported
the WMO. In April 2012, CO
levels were recorded as reaching
almost 400 ppm (399.72), the first time they have reached this
level in three million years.
CO2 levels are at more than 140% of the pre-industrial level
(before 1750), with about 375 billion tonnes of carbon released
into the atmosphere as CO2 in the past 260 years.
“ These billions of tonnes of additional CO2 in our atmosphere
will remain there for centuries, causing our planet to warm
further and impacting on all aspects of life on earth,” Jarraud
said in a statement. “Future emissions will only compound the
situation,” he added.
Taking the long view on data to smooth out year-on-year
anomalies, the WMO showed that while CO2 in the atmosphere
increased on average 1.5 ppm during the 1990s, the average
annual hike from 2000 to 2010 stood at 2.0 ppm. “So it’s not
just increasing, it’s increasing exponentially,” WMO scientific
officer Oksana Tarasova told reporters.
Jarraud, meanwhile, pointed out that so-called ‘carbon sinks’,
including oceans, have until now absorbed nearly half of the
CO2 emitted by humans, but stressed that “this will not
necessarily continue in the future.”
The level of atmospheric methane (CH4), the second most
important greenhouse gas after CO2
, has also reached new
highs at 1,813 parts per billion (ppb). This is 259% of the
pre-industrial level, the WMO said, blaming mainly human
activities like fossil fuel exploitation, cattle breeding, rice
agriculture, landfills and biomass burning.
As a greenhouse gas, methane is estimated by the
Intergovernmental Panel on Climate Change to be between
21–23 times the potency of CO2
Also worrying was the increase in nitrous oxide (N2O) levels,
the WMO said, since its impact on climate is almost 300 times
greater than that of carbon dioxide.
The gas, emitted into the atmosphere from natural and
artificial sources, also plays an important role in the
destruction of the ozone layer, which protects the Earth
from harmful ultraviolet rays.
According to the WMO, the atmospheric concentration of
nitrous oxide in 2011 was about 324.2 ppb, which is up 1.0 ppb
from 2010, and at 120% of pre-industrial levels.
– A F P and staff writers
the Australian picture
ACCORDING TO 2010 data from the Department
of Climate Change and Energy Efficiency, Australia
produces only about 1.5% of the world’s greenhouse gas
emissions. However, per capita, Australia is one of the
world’s worst polluters, with emissions of about 24.4
tonnes carbon dioxide equivalent (CO2e) per person –
more than four times the world average.
Australia’s greenhouse gases emissions are mainly
(about 74%) in the form of CO2
, most of which are
generated by the energy sector. Methane accounts for
a further 20%, with nitrous oxide making up most of
The main human activities increasing the amount of
carbon dioxide in the atmosphere are:
n electricity production (involving the combustion of
fossil fuels, which releases CO2)
n transport (motor vehicles, trains and planes all burn
fuel, which releases CO2)
n land clearing (when forests are cleared, there are
fewer trees to store carbon and to convert CO2 during the
process of photosynthesis).
For methane emissions, the main contributing activities
are livestock production (since livestock, such as cattle
and sheep, produce methane during their digestion
process) and mining for fossil fuels, which releases
methane. Nitrous oxide, the third major greenhouse gas,
mainly comes from the production and application of
nitrogen fertilisers, which are used to help crops grow.
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