The amount of greenhouse gases in Earth's atmosphere hit a record high
in 2012, continuing an ever-faster rise that is driving climate change, the
U.N. weather agency said Wednesday.
"The concentrations are reaching once again record levels," Michel
Jarraud, who heads the World Meteorological Organization, told reporters in
Geneva
.
His organization released its annual report on greenhouse gases Wednesday,
showing that concentrations of carbon dioxide, methane and nitrous oxide all
broke fresh records in 2012.
Global concentrations of CO2, the main culprit in global warming, reached 393.1
parts per million last year, or 141% of pre-industrial levels--defined as
before 1750.
The report was released a day after the U.N. Environment Program warned the
chances of limiting the global temperature rise to two degrees Celsius (3.6
Fahrenheit) over pre-industrial levels were swiftly diminishing, and ahead of
U.N. climate talks that open in Warsaw next week.
The U.N.'s two-degree target is being chased through efforts to curb greenhouse
gas emissions, mainly caused by fossil-fuel burning to power industry,
transport and farming.
"The observations from WMO's extensive Global Atmosphere Watch network
highlight yet again how heat-trapping gases from human activities have upset
the natural balance of our atmosphere and are a major contribution to climate
change," Jarraud said.
Dave Reay, a carbon-management expert at the
University
of
Edinburgh
, said
that stabilizing greenhouse gas concentrations was the key to successful
climate negotiations, emissions regulations, and carbon markets rests.
"Despite the financial crash, and reduced emissions from some nations, the
global picture is one of carbon dioxide concentrations in our atmosphere
reaching a record-breaking high year after year," Reay added.
Some experts warn that unless more is done to rein in emissions, the world faces
potentially devastating effects such as more frequent megastorms, species
extinctions, water shortages, crop die-offs, loss of land to the rising seas as
glaciers and polar ice melt, and spreading disease.
"CO2 has a ratchet effect," said Peter Wadhams, professor of ocean
physics at the
University
of
Cambridge
.
"Its influence on the climate system lasts for about 100 years, so we will
be paying for our profligate use of fossil fuels for a long time to come--so
long, in fact, that we may well have now made it impossible for the planet to
avoid catastrophic global warming effects, even if we make a start now on
reducing CO2 emissions."
The atmospheric increase of CO2 from 2011 to 2012 was higher than the average
growth rate over the past 10 years, WMO said, stressing that the global
concentrations of CO2 last year were dangerously close to the symbolic 400
parts-per-million threshold.
That threshold was exceeded at several Arctic stations during the year, and the
global annual average CO2 concentration looks set to cross it in 2015 or 2016,
the U.N. agency said.
This level hasn't existed on Earth in 3 million to 5 million years, experts
say.
Concentrations of methane, meanwhile, were 260% of the pre-industrial level,
while nitrous oxide reached 120%.
The WMO report said that between 1990 and 2012 there was a 32% increase in
so-called "radiative forcing"--the warming effect on our
climate--because of heat-trapping gases.
CO2 accounted for 80% of this increase.
What is happening in the atmosphere is just part of the picture.
Only about half of the CO2 emitted by human activities remains in the
atmosphere, with the rest absorbed in the biosphere and in the oceans, the WMO
said.
Jarraud said the U.N.'s Intergovernmental Panel on Climate Change recently
sounded the alarm over gas concentrations.
"According to the IPCC, if we continue with 'business as usual,' global
average temperatures may be 4.6 degrees higher by the end of the century than
pre-industrial levels--and even higher in some parts of the world. This would have devastating
consequences," he said.