Environmental Engineering Reference
In-Depth Information
change. The IPCC published findings throughout the 1990s and 2000s and, although
they have been debated vigorously, a scientific consensus has slowly emerged (though
this has not stopped some governments from attempting to influence the language
of its assessment reports to express a rather more cautious and conservative viewpoint).
In 2002, Julian Borger of
The Guardian
reported that the US Bush administration,
with the oil company Exxon-Mobil, had secretly worked to remove the head of the
IPCC Robert Watson to make way for another person less likely to call for radical
mitigating action. Watson was replaced by the Indian railway engineer and
environmentalist Dr Rajendra Pachauri. Fred Pearce (2002), writing in
New Scientist
,
reported that the US may have threatened to withdraw funding from the IPCC if
there had not been change at its head, causing fears that the IPCC process had been
compromised by this apparent politicization. The IPPC's conservatism was again
highlighted in 2007, when Professor Stefan Rahmstorf and his team from the Potsdam
Institute for Climate Impact Research in Germany suggested that the IPCC's Third
Assessment Report, published in 2001, had underestimated sea-level rise by some
59 per cent. Rahmstorf used observational data, believing that computer models of
the climate significantly underestimated the sea-level rises that had already taken
place. The picture becomes increasingly detailed as additional reports finally reach
the public sphere. According to Smith
et al
.'s (2007) climate modelling system, there
may be a slowdown in global warming until about 2009, but then it will again
increase, with 'at least half of the years after 2009 predicted to exceed the warmest
year currently on record'.
Early in 2007 the IPCC issued the first of four major assessment reports.
Significantly, its language and predictions were much stronger than six years earlier,
with it concluding that it was at least 90 per cent certain that human-induced emissions
of greenhouse gases (GHGs) rather than any natural variations are the cause of global
warming. This was up from 6 per cent stated in the Third Assessment report in 2001.
By 2013, with the publication of the Fifth Assessment Report (AR5), the level of
certainty had climbed to 95 per cent, with global warming likely to exceed the
generally recognized danger level of 2°C, or between 3 and 4°C in Australia, by
2100. Sea levels are likely to rise by up to 1 metre if CO
2
emissions remain below
500ppm (parts per million) but up to 3 metres if CO
2
concentration is between 700
and 1,500ppm. Many millions of people live near sea level and a sea-level rise
approaching one metre would endanger many cities including London, New York,
Shanghai, Venice, Sydney, Miami and New Orleans (Gillis, 2013). The risk of the
Earth warming by 6°C is just 1 per cent but, as the Global Challenges Foundation
noted, such a percentage risk would mean something like 500,000 fatal plane crashes
every year if such a prediction was applied to the global aviation industry.
A large fraction of anthropogenic climate change resulting from CO
2
emissions
is irreversible on a multi-century to millennial time scale, except in the case of
a large net removal of CO
2
from the atmosphere over a sustained period. Surface
temperatures will remain approximately constant at elevated levels for many
centuries after a complete cessation of net anthropogenic CO
2
emissions. Due
to the long time scales of heat transfer from the ocean surface to depth, ocean
warming will continue for centuries. Depending on the scenario, about 15 to
40% of emitted CO
2
will remain in the atmosphere longer than 1,000 years.
(IPCC WGI AR5, 2013: 20)
