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projections found that: ‘The data now available raise
concerns that the climate system, in particular sea
level, may be responding more quickly than climate
models indicate.’ 3 Numerous examples can now be
cited of shifts in climate and ecological systems that
reflect these recent changes. They include the more
rapid melting of Antarctic ice and increased
hurricane and cyclone activity.
The message emerging from the climate science
community is that the chance of keeping
temperatures no more than 2°C above pre-industrial
levels – the guardrail over which organisations
including the European Commission agree
constitutes ‘dangerous climate change’ – is at best
low. 4 Indeed, one recent study states that if GHG
emissions were frozen at 2005 levels, we are
already committed to 2.4°C warming (within a range
of 1.3°C-4.3°C) above pre-industrial levels. 5 Recent
research raises the prospect of rapid and dangerous
climate change at levels of 4°C and beyond above
current levels. 6
A downward revision of thresholds for
significant impacts relative to global
temperature rise
At the same time that scientists are projecting
the increased likelihood of higher-end climate
change, research is also suggesting that harmful
impacts linked to this change could be felt at lower
levels of temperature rise than was previously
expected. In 2008, an update was produced for the
IPCC’s ‘Reasons for Concern’ assessment, which
was originally developed eight years earlier. 7 More
commonly known as the ‘burning embers diagram’,
the assessment reflects an understanding of the
potential impacts associated with different levels of
global temperature rise on five factors thought to
represent key risks linked to a changing climate. The
five reasons for concern are:
● risk to unique and threatened species;
● risk of extreme weather events;
● risk of large-scale discontinuities (for example
disruption to the Gulf Stream);
● aggregate damages (principally measured in
monetary terms); and
● the spatial distribution of impacts.
Comparison of the updated burning embers
diagram against the original demonstrates that in
the case of each reason for concern, the risk of
negative impacts is now greater at lower levels of
global temperature rise. This risk is assessed as
‘substantial and severe’ for all five reasons for
concern at a global mean temperature rise of just
less than 3°C above 1990 levels, and in three cases
at a level around 1°C above this baseline. Given the
recent projections for a temperature rise of 4°C and
beyond, 6 the magnitude of the risks associated with
climate change become clear.
Greater appreciation of the complexity of the
global climate system
A key reason that the prognosis from climate
scientists is looking increasingly worrying relates to
a greater appreciation of the complexity of the
global climate system. The notion that humans may
be able to control the global climate is likely to be
misplaced, and instead the chances are that the
climate will govern our behaviour, as it has done for
millennia. The biophysical processes influencing the
global climate are not fully understood, which
challenges the ‘dose-response’ relationship
approach around which climate policy is framed.
‘Comparison of the updated
burning embers diagram
against the original
demonstrates that in the case
of each reason for concern, the
risk of negative impacts is now
greater at lower levels of
global temperature rise’
An appreciation of the complex and non-linear
processes involved calls into question the idea that
we can ‘stabilise’ the climate through achieving a
defined level of emissions reduction. 8 Central to this
is the issue of positive feedback loops, which work
to intensify a variable or process. They may not be
positive or desirable in terms of their impact, which
is the case with climate science, where positive
feedbacks are increasing GHG emissions and
intensifying climate change impacts. Examples
include the melting of the polar ice sheets and the
replacement of reflective ice with sea and/or land
which absorbs solar radiation, leading to further
warming; and tundra melt with associated release
of methane, which is a far more potent GHG than
carbon dioxide.
Evidence of rapid carbonisation of economies and
societies
The failure of the 2009 Copenhagen Summit
(COP15) to reach a common consensus on
reducing GHG emissions means that post-2012,
after the end of the current commitment period of
the Kyoto Protocol, there will be no global
mechanism in place for managing GHG emissions.
Although some commentators argue that top-down
mechanisms such as this may not be the most
appropriate way of managing emissions, the policy
vacuum that we find ourselves in at all scales is
associated with a period of unprecedented global
carbonisation.
Town & Country Planning June 2011 : GRaBS Project – INTERREG IVC; ERDF-funded 253