Environmental Engineering Reference
In-Depth Information
IPCC Critics and climate sceptics
The IPCC has its critics. Some accuse it, out of hand, of exaggerating global
warming. Others accuse the IPCC of producing reports that are too cautious
and too infrequent to keep up with the pace of climate change. The process by
which it produces its formal assessment reports on the state of climate change
- of which there have been four (1990, 1995, 2001 and 2007) - is curious. Its
working groups are a mix of scientists and government officials. The IPCC
claims that “because of its scientific and intergovernmental nature, the IPCC
embodies a unique opportunity to provide rigorous and balanced scientific
information to decision makers,” going on to confidently assert that “by endors-
ing the IPCC reports, governments acknowledge the authority of their scientific
content” and that “the work of the organization is therefore policy-relevant and
yet policy-neutral, never policy-prescriptive”. Nonetheless, it is a strange, hybrid
process in which the evidence comes from the scientists, but the conclusions
to be drawn from it, contained in “the summaries for policy makers”, are agreed
between the scientists and government officials.
The Fourth Assessment Report (AR4) of 2007 has also been criticized by among
others Joseph Romm, a former senior US Department of Energy official in the
Clinton Administration, of underestimating the potential positive-feedback
effects of climate change. There is a possibility that the Earth's rising tempera-
ture could release huge amounts of methane through the thawing of the Arctic
tundra which currently keeps it buried: it is but one of many vicious-circle sce-
narios in which a rising temperature precipitates events that, in turn, increase
the world's temperature even further.
James Hansen, head of the Goddard Institute for Space Studies in New York, has
suggested that the IPCC has underestimated the degree to which the world's
ice-caps are liable to melt - and, in turn, that they have underestimated sea-
level rise. Hansen criticized the IPCC's 2007 report for shrinking back, on this
occasion, from trying to evaluate possible dynamic responses of ice-sheets to
global warming, while at the same time issuing some very precise numbers
for estimated sea-level rises in the 21st century. Its full-range estimate is a rise
of between 18 and 59 cm and its mid-range estimate is between 20 and 43.
Hansen has complained that “the provision of such specific numbers for sea
level rise encourages a predictable public response that the projected sea
level change is moderate, and smaller than in the IPCC 2001 (AR3) report”. He
pointed out that it has led to “numerous media reports of 'reduced' sea-level
rise predictions”.
Some scientists who have contributed evidence to the IPCC have expressed
reservations about its emphases. Dr Chris Landsea, a US hurricane meteor-
ologist who had been involved in the IPCC's Third Assessment Report (2001),
pulled out of the Fourth Assessment in 2005, complaining that his peers were
trying to make too close a link between the frequency of hurricanes and cli-
mate change. (Significantly, however, he had no qualms in ascribing oceanic
and atmospheric warming over the last decades to the increases in GHG.)
