- An unexplained and unprecedented rise in carbon dioxide
in the atmosphere two years running has raised fears that the world may
be on the brink of runaway global warming.
- Scientists are baffled why the quantity of the main greenhouse
gas has leapt in a two-year period and are concerned that the Earth's natural
systems are no longer able to absorb as much as in the past.
- The findings will be discussed tomorrow by the government's
chief scientist, Dr David King, at the annual Greenpeace business lecture.
- Measurements of CO2 in the atmosphere have been continuous
for almost 50 years at Mauna Loa Observatory, 12,000ft up a mountain in
Hawaii, regarded as far enough away from any carbon dioxide source to be
a reliable measuring point.
- In recent decades CO2 increased on average by 1.5 parts
per million (ppm) a year because of the amount of oil, coal and gas burnt,
but has now jumped to more than 2 ppm in 2002 and 2003.
- Above or below average rises in CO2 levels in the atmosphere
have been explained in the past by natural events.
- When the Pacific warms up during El Niño - a disruptive
weather pattern caused by weakening trade winds - the amount of carbon
dioxide rises dramatically because warm oceans emit CO2 rather than absorb
- But scientists are puzzled because over the past two
years, when the increases have been 2.08 ppm and 2.54 ppm respectively,
there has been no El Niño.
- Charles Keeling, the man who began the observations in
1958 as a young climate scientist, is now 74 and still working in the field.
- He said yesterday: "The rise in the annual rate
to above two parts per million for two consecutive years is a real phenomenon.
- "It is possible that this is merely a reflection
of natural events like previous peaks in the rate, but it is also possible
that it is the beginning of a natural process unprecedented in the record."
- Analysts stress that it is too early to draw any long-term
- But the fear held by some scientists is that the greater
than normal rises in C02 emissions mean that instead of decades to bring
global warming under control we may have only a few years. At worst, the
figures could be the first sign of the breakdown in the Earth's natural
systems for absorbing the gas.
- That would herald the so-called "runaway greenhouse
effect", where the planet's soaring temperature becomes impossible
to contain. As the icecaps melt, less sunlight is refected back into space
from ice and snow, and bare rocks begin to absorb more heat. This is already
- One of the predictions made by climate scientists in
the Intergovernmental Panel on Climate Change is that as the Earth warms,
the absorption of carbon dioxide by vegetation - known as "carbon
sink" - is reduced.
- Dr Keeling said since there was no sign of a dramatic
increase in the amount of fossil fuels being burnt in 2002 and 2003, the
rise "could be a weakening of the Earth's carbon sinks, associated
with the world warming, as part of a climate change feedback mechanism.
It is a cause for concern'.'
- Tom Burke, visiting professor at Imperial College London,
and a former special adviser to the former Tory environment minister John
Gummer, warned: "We're watching the clock and the clock is beginning
to tick faster, like it seems to before a bomb goes off."
- Peter Cox, head of the Carbon Cycle Group at the Met
Office's Hadley Centre for Climate Change, said the increase in carbon
dioxide was not uniform across the globe.
- Measurements of CO2 levels in Australia and at the south
pole were slightly lower, he said, so it looked as though something unusual
had occurred in the northern hemisphere.
- "My guess is that there were extra forest fires
in the northern hemisphere, and particularly a very hot summer in Europe,"
Dr Cox said. "This led to a die-back in vegetation and an increase
in release of carbon from the soil, rather than more growing plants taking
carbon out of the atmosphere, which is usually the case in summer."
- Scientists are have dubbed the two-year CO2 rise the
Mauna Loa anomaly. Dr Cox said one of its most interesting aspects was
that the CO2 rises did not take place in El Niño years. Previously
the only figures that climbed higher than 2 ppm were El Niño years
- 1973, 1988, 1994 and 1998.
- The heatwave of last year that is now believed to have
claimed at least 30,000 lives across the world was so out of the ordinary
that many scientists believe it could only have been caused by global warming.
- But Dr Cox, like other scientists, is concerned that
too much might be read into two years' figures. "Five or six years
on the trot would be very difficult to explain," he said.
- Dr Piers Forster, senior research fellow of the University
of Reading's Department of Meteorology, said: "If this is a rate change,
of course it will be very significant. It will be of enormous concern,
because it will imply that all our global warming predictions for the next
hundred years or so will have to be redone."
- David J Hofmann of the US National Oceanic and Atmospheric
Administration centre, which also studies CO2, was more cautious.
- "I don't think an increase of 2 ppm for two years
in a row is highly significant - there are climatic perturbations that
can make this occur," he said. "But the absence of a known climatic
event does make these years unusual.
- "Based on those two years alone, I would say it
was too soon to say that a new trend has been established, but it warrants