Surprise CO2 Rise May Speed Up Global Warming
By Michael McCarthy
11 October 2004
The Independent
The
rate at which global warming gases are accumulating in the atmosphere
has taken a sharp leap upwards, leading to fears that the devastating
effects of climate change may hit the world even sooner than has been
predicted.
Atmospheric levels
of carbon dioxide (CO2 ), the principal greenhouse gas, have made a
sudden jump that cannot be explained by any corresponding jump in terrestrial
emissions of CO2 from power stations and motor vehicles - because there
has been none.
Some scientists
think instead that the abrupt speed-up may be evidence of the long-feared
climate change "feedback" mechanism, by which global warming
causes alterations to the earth's natural systems and then, in turn,
causes the warming to increase even more rapidly than before.
Such a development
would mean the worldwide droughts, agricultural failure, sea-level rise,
increased weather turbulence and flooding all predicted as consequences
of climate change would arrive on much shorter time-scales than present
scenarios suggest, and the world would have much less time to co-ordinate
its response.
Only last month,
Tony Blair expressed anxiety that global warming's dire effects would
arrive not just in his children's lifetime, but in his own, and would
"radically alter human existence".
The feedback phenomenon
has already been predicted in the supercomputer models of the global
climate on which the current forecasts of warming are based. A key aspect
is the weakening, caused by the warming itself, of the earth's ability
to remove huge amounts of CO2 from the atmosphere by absorbing it annually
in its forests and oceans, in the so-called carbon cycle. (The forests
and oceans are referred to as carbon "sinks".)
Hitherto, however,
that weakening has been put decades into the future.
The possibility
that it may be occurring now is suggested in the long run of atmospheric
CO2 measurements that have been made since 1958 at the observatory on
the top of Mauna Loa, an 11,000ft volcano in Hawaii, by the American
physicist Charles Keeling, from the University of California at San
Diego.
When he began, Dr
Keeling, who is still in charge of the project and who might be said
to be the Grand Old Man of CO2 , found the amount of the gas present
in the atmosphere to be 315 parts per million by volume (ppm); today,
after the remorseless increase in emissions from power stations and
motor vehicles over the past four and a half decades, the figure stands
at 376ppm.
This growth is what
most scientists believe is causing the earth's atmosphere to warm up,
as the increasing CO2 retains more and more of the sun's heat in the
atmosphere, like the panes of a greenhouse.
But the worry now
is not merely the swelling volume of CO2 but the sudden leap in its
increase rate. Across all 46 years of Dr Keeling's measurements, the
average annual CO2 rise has been 1.3ppm, although in recent decades
it has gone up to about 1.6ppm.
There have been
several peaks, all associated with El Niño, the disruption of
the atmosphere-ocean system in the tropical Pacific Ocean that causes
changes to global weather patterns. In 1988, for example, the annual
increase was 2.45ppm; in 1998, 2.74ppm; both were El Niño years.
Throughout the series
those peaks have been followed by troughs, and there has been no annual
increase in CO2 above 2ppm that has been sustained for more than a year.
Until now.
From 2001 to 2002,
the increase was 2.08ppm (from 371.02 to 373.10); and from 2002 to 2003
the increase was 2.54ppm (from 373.10 to 375.64). Neither of these were
El Niño years, and there has been no sudden leap in emissions.
The greater-than-two
rise is also visible in two separate sets of CO2 measurements made by
America's National Oceanic and Atmospheric Administration, at Mauna
Loa and other stations around the world.
At the weekend,
Dr Keeling told The Independent the rise was real and worrying as it
might indeed represent the beginnings of a feedback.
He said it might
be associated with the Southern Oscillation, a pattern of high and low
atmospheric pressure previously always associated with El Niños,
or it might be something new.
"The rise in
the annual rate of CO2 increase to above two parts per million for two
consecutive years is a real phenomenon," Dr Keeling said.
"It is possible
this is merely a reflection of the Southern Oscillation, like previous
peaks in the rate, but it is possible it is the beginning of a natural
process unprecedented in records.
"This could
be a decoupling of the Southern Oscillation from El Niño events,
which itself could be caused by increased CO2 in the atmosphere; or
it could be a weakening of the earth's carbon sinks. It is a cause for
concern."
Leading British
scientists and environmentalists agree. "If this is a rate change
[in the CO2 rise], of course it will be very significant," said
Dr Piers Forster of the meteorology department of the University of
Reading. "It will be of enormous concern, because it will imply
that all our global warming predictions for the next 100 years or so
will have to be redone. If the higher rate of increase continues, things
will get very much worse. It will makes our predicament even more catastrophic."
Tom Burke, a former
government adviser on green issues who is now an academic and environmental
adviser to business, said: "This series of CO2 measurements is
the world's climate clock, and it looks as if it may be ticking faster,"
"That means
we are running out of time to stabilise the climate. Governments and
business will both have to invest dramatically more if we are to avoid
the global warming catastrophe that Tony Blair has warned against."