Blamed For Climate Change
By Richard Black
03 February, 2007
Global climate change is "very
likely" to have a human cause, an influential group of scientists
The Intergovernmental Panel
on Climate Change (IPCC) said temperatures were probably going to increase
by 1.8-4C (3.2-7.2F) by the end of the century.
It also projected that sea
levels were most likely to rise by 28-43cm, and global warming was likely
to influence the intensity of tropical storms.
The findings are the first
of four IPCC reports to be published this year.
"We can be very confident
that the net effect of human activity since 1750 has been one of warming,"
co-lead author Dr Susan Soloman told delegates in Paris.
The report, produced by a
team tasked with assessing the science of climate change, was intended
to be the definitive summary of climatic shifts facing the world in
the coming years. IPCC
The agency said that it would
use stronger language to assess humanity's influence on climatic change
than it had previously done.
In 2001, it said that it
was "likely" that human activities lay behind the trends observed
at various parts of the planet; "likely" in IPCC terminology
means between 66% and 90% probability.
Now, the panel concluded
that it was at least 90% certain that human emissions of greenhouse
gases rather than natural variations are warming the planet's surface.
They projected that temperatures
would probably rise by between 1.8C and 4C, though increases as small
as 1.1C (2F) or as large as 6.4C (11.5F) were possible.
In 2001, using different
methodology, the numbers were 1.4 (2.5F) and 5.8C (10.4F).
On sea level, there has been
a more fundamental debate.
Computer models of climate
do not generally include water coming into the oceans as ice caps melt.
So the IPCC had to decide whether to exclude this from its calculations,
or to estimate the effect of a process which scientists do not understand
well but which could have a big impact.
They used the former, more
conservative approach, projecting an average rise in sea levels globally
of between 28 and 43cm. The 2001 report cited a range of nine to 88cm.
As for climate change influencing
the intensity of tropical storms in some areas of the world, the IPCC
concluded that it was likely - meaning a greater probability than 66%
- that rising temperatures were a factor.
Dr Rajendra Pachauri, the IPCC chairman, said: "It is extremely
encouraging in that the science has moved on from what was possible
in the Third Assessment Report.
"If you see the extent
to which human activities are influencing the climate system, the options
for mitigating greenhouse gas emissions appear in a different light,
because you can see what the costs of inaction are," he told delegates
Achim Steiner, executive
director of the United Nations Environment Programme (Unep), said the
findings marked a historical landmark in the debate about whether humans
were affecting the state of the atmosphere.
"It is an unequivocal
series of evidence [showing that] fossil fuel burning and land use change
are affecting the climate on our planet."
He added: "If you are
an African child born in 2007, by the time you are 50 years old you
may be faced with disease and new levels of drought."
He said that he hoped the
IPCC report would galvanise national governments into action.
But a study published on
the eve of the IPCC report suggested that the international body's previous
reports may have actually been too conservative.
Writing in the journal Science,
an international group of scientists concluded that temperatures and
sea levels had been rising at or above the maximum rates proposed in
the last report, which was published in 2001.
The paper compared the 2001
projections on temperature and sea level change report with what has
The models had forecasted
a temperature rise between about 0.15C-0.35C (0.27-0.63F) over this
period. The actual rise of 0.33C (0.59F) was very close to the top of
the IPCC's range.
A more dramatic picture emerged
from the sea level comparison. The actual average level, measured by
tide gauges and satellites, had risen faster than the intergovernmental
panel of scientists predicted it would.
The IPCC's full climate science
report will be released later in the year, as will other chapters looking
at the probable impacts of climate change, options for adapting to those
impacts, and possible routes to reducing emissions of greenhouse gases.
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