Has A Runaway
Greenhouse
Effect Begun?
By Norm Dixon
03 November, 2004
Green
Left Weekly
In
recent weeks, scientists have released two separate findings that indicate
the consequences of global warming due to the emission of greenhouse
gases primarily carbon dioxide (CO2) from the industrial
burning of fossil fuels may be far greater than previously estimated.
The new findings
underscore the need for governments around the world, in particular
the industrialised First World countries that are responsible for more
than 80% of past emissions and 75% currently, to take urgent action
to massively reduce the worlds industrial greenhouse gas emissions
by 60-80%.
Rajendra Pachauri,
chairperson of the United Nations Intergovernmental Panel on Climate
Change (IPCC), which pools the expertise of more than 2000 of the worlds
climate scientists, warned on October 25 that the greenhouse gas emission
reduction targets established in the 1997 Kyoto agreement do not go
far enough and far more radical solutions must be found.
Pachauri welcomed
the Russian parliaments October 22 ratification of the Kyoto agreement,
which will allow the treaty to come into legal force despite the refusal
by the worlds major polluter, the United States, to sign. However,
this mustnt lull us into thinking that the problem is solved,
Pachauri told Reuters. Kyoto is not enough. We have to look at
the problem afresh. The Kyoto treaty aims for a reduction in greenhouse
gas emissions of around 5% of 1990 levels, far short of the 60-80% over
the next 50 years necessary to arrest global warming.
The new evidence
on the pace of global warming suggests that world governments may have
even less time to act than previously estimated. The October 11 British
Guardian reported that CO2 in the atmosphere is at record levels and
increasing at an accelerating rate, while the September 23 edition of
Science revealed that glaciers in western Antarctica flowing into sea
are speeding up, indicating an increased level of melting.
The scientists who
make up the IPCC estimate that unless levels of greenhouse gases in
the atmosphere are stabilised by mid-century, Earths average temperature
will rise by up to 5.8°C by 2100. According to the IPCC figures,
if unchecked, CO2 levels in the air will be between 650 and 970 parts
per million (ppm). However, these estimates may be too conservative.
According to the
October 11 Guardian, measurements of average atmospheric CO2 levels
in 2002 and 2003 may confirm that the rate of CO2 accumulation is now
increasing at an alarming rate. Scientists at Hawaiis Mauna Loa
Observatory reported that average CO2 levels increased by 2.08 ppm in
2002, to 373.1 ppm, and by 2.54 ppm in 2003, to an average of 375.64
ppm. This is the first recorded example of the average CO2 level jumping
more than 2 ppm in two consecutive years. The average increase in the
CO2 level over the last few decades, reports the Guardian, has been
1.5 ppm. The current level of CO2 is the highest in at least 420,000
years!
Associated Press
reported earlier this year, on March 20, that scientists at Mauna Loa
Observatory had recorded the CO2 level in the atmosphere peaking at
a record of 379 ppm, compared to 376 ppm a year earlier and 373 ppm
in 2002.
The increase has
raised the spectre of a runaway greenhouse effect already
underway. Previous increases of CO2 levels of above 2 ppm 1973,
1988, 1994 and 1998 have coincided with the El Nino weather pattern
in the Pacific. However, this cannot explain the latest rises.
Weather scientist
Charles Keeling, who began measuring atmospheric CO2 at Mauna Loa in
1958, told the Guardian that 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 ... [The rise] could be a weakening of the Earths
carbon sinks, associated with world warming, as part of a climate change
feedback mechanism. It is cause for concern.
Piers Forster, senior
research fellow at the University of Readings department of meteorology,
added that if this is a rate change ... it will be of enormous
concern, because it will imply that all our global warming predictions
for the hundred years or so will have to be redone.
Friends of the Earths
Scotland head Duncan McLaren, speaking to Agence France Presse on October
11, demanded action to achieve the 60-80% reductions in industrial greenhouse
gas emissions required within 30 years: Instead of just keeping
our fingers crossed, these findings should send an urgent reminder to
governments everywhere of the urgent need to tackle the growing threat
of climate change.
Predictions about
the rate of CO2 accumulating in the atmosphere might not be the only
estimates that have to be revised. Based on the IPCCs present
forecasts, global warming triggered by unchecked greenhouse gas emissions
will cause a sea level rise of between 20 centimetres and almost 1 metre
by the end of the century. However, the IPCCs prediction is based
on an assumption that the polar ice caps will not melt significantly.
However, according
the September 23 journal Science, NASA researchers have found that six
vast glaciers in the west Antarctic are flowing into the Amundsen Sea
at a rate up to 25% faster than in the 1970s. The Pine Island Glacier
is entering the ocean at a rate of six metres a day and as more enters
the sea, the remainder speeds up further. Glaciologists told Science
that within five years, 700 square kilometres of the thick Pine Island
Glacier alone will be floating (and melting) in the ocean.
According to Eric
Rignot, a glaciologist at NASAs Jet Propulsion Laboratory, should
the six glaciers completely melt, they alone will cause the worlds
sea level to rise by more than a metre. Researchers using ice-penetrating
radar also found that the glaciers are on average 430 metres thicker
than previously thought, meaning they are dumping considerably more
fresh water into the ocean.
One reason why Antarctic
glaciers are entering the sea at a much faster rate is because floating
500-metre ice shelves, which significantly slow the entry of the glaciers
into the sea, have begun to collapse and melt. Antarctica has warmed
by an average 2.5°C since the 1940s, and winter temperatures have
jumped by almost 5°C.
The Larsen A ice
shelf suddenly collapsed in 1995. The Wilkins Ice Shelf is shrinking.
In 2002, the 3400-square kilometre Larsen B shelf at least 12,000
years old and up to 70 storeys thick disintegrated into the Weddell
Sea in the space of a few months (satellites images of the collapse
are available at <http://nsidc.org/iceshelves/larsenb2002/animation.html>).
The calving of monster
icebergs is now common. Ted Scambos, an expert from the University of
Colorados National Snow and Ice Centre, found that after Larsen
Bs collapse, nearby glaciers began entering the sea up to eight
times faster than previously.
According to NASAs
Robert Thomas, the ice shelves are melting rapidly and have been thinning
at the rate of 10 to 15 metres a year since the 1990s. The rate of thinning
today is double that in the 1990s, he added.
The Larsen and Wilkins
ice shelves are relatively insignificant in Antarctic terms, but their
demise may indicate that similar processes may be underway on the massive
Ross and the Filchner-Ronne ice shelves. Ice-shelf thinning could
be happening elsewhere in the Antarctic, but we just dont know,
Scambos told Science.
The Ross and the
Filchner-Ronne ice shelves prevent the gigantic land-based Western Antarctic
Ice Sheet from rapidly entering the ocean and melting. The Western Antarctic
Ice Sheet, the smaller of Antarcticas two vast ice sheets, contains
a mind-boggling 3.2 million cubic kilometres of ice, about 10% of the
worlds total ice enough to raise the sea level six metres.
(If the more secure Eastern Antarctic Ice Sheet melted, the sea would
rise more than 60 metres!)
Within the western
sheet are five ice streams enormous glaciers more than 50 kilometres
wide and one kilometre thick. The Ross Ice Shelf floating ice
nearly the size of New South Wales and the similarly sized Filchner-Ronne
Ice Shelf prevent them sliding into the sea where they would rapidly
melt.
The West Antarctic
Ice Sheet may have melted at least once before, between 110,000 and
130,000 years ago, causing the sea level to rise about five metres higher
than todays level. An article in the August 1995 Scientific American
pointed out that the five-metre rise was followed by a 10-metre decrease
all in the space of 100 or so years!
The May 2002 edition
of Science reported that researchers from the Oregon State University,
the University of Toronto and the University of Durham in Britain had
found that a massive and unusually abrupt 23-metre rise in the sea level
about 14,200 years ago was caused by the partial collapse of both major
ice sheets in Antarctica. The sea level took just 500 years to reach
that height.