institutions and policies. How has this happened, and what meanings of green and
forms of knowledge are included and excluded?
The two-degree safety barrier for climate change
In the last decade, the ‘two-degree safety barrier’ or ‘two-degree target’ has
become a dominant guiding concept in climate change debate and policy, reinforced again in the latest Intergovernmental Panel on Climate Change (IPCC)
report and associated policy and media commentary. The central idea is that any
increase in average global temperature should be limited to two degrees above a
baseline, the pre-industrial level in 1880. This is the maximum allowable warming
before human interference in the climate is deemed ‘dangerous’. Beyond it dire
consequences are predicted, including potentially significant losses of food
production, especially in Africa; high extinction risks for 20–30 per cent of species,
more severe droughts and floods, and an unstoppable loss of the Greenland ice
sheet, triggering escalating sea-level rises (Hansen et al., 2007; IPCC, 2013).
This ‘two-degree safety barrier’ offers an important message about the need for
green transformation:
an indication, as simple as it is compelling, of the physical limits to the volume
of greenhouse gases that can be dumped in the atmosphere [which] sets out
the breathtaking message that the world’s population must immediately begin
to make significantly less use of fossil energy sources or leave them in the
ground.
(Leggewie and Messner, 2012b, p128)
Yet there is nothing natural or immutable about the existence of such a safety barrier,
or that it should be set at two degrees. Rather, like previous green limits, this is
socially and politically constructed, and has a history. As Randalls (2010) and Tol
(2007) detail, it is rooted in the particular ways in which scientists and economists
developed heuristics and models from the 1970s to guide understanding and
decision-making about climate change. The two- degree figure was first pinpointed
by the economist W. D. Nordhaus in 1979, assuming that this was the limit of
the warming to have occurred naturally over the last 10,000 years. Through the
1980s, a series of integrated assessment modelling exercises, and the particular
assump tions they incorporated, helped to support the idea of limits and thresholds
to dangerous climate change, and two degrees in particular. It acquired growing
weight in policy circles, with a link between limits and averted danger enshrined
in Article 2 of the UN Framework Convention on Climate Change (UNFCCC,
1992). The proposition of two degrees as an actual policy target came in 1996
from the European Union (EU), backed by certain scientists and environmentalists.
It gained in visibility and policy institutionalization through the 2000s – for
instance, underpinning the UK’s 2008 Climate Change Act and included in the
2009 Copenhagen Accord. In UNFCCC conferences of parties (COP) in
Copenhagen (COP-15) and Cancun (COP-16) all parties to the UNFCCC
28 Melissa Leach
forms of knowledge are included and excluded?
The two-degree safety barrier for climate change
In the last decade, the ‘two-degree safety barrier’ or ‘two-degree target’ has
become a dominant guiding concept in climate change debate and policy, reinforced again in the latest Intergovernmental Panel on Climate Change (IPCC)
report and associated policy and media commentary. The central idea is that any
increase in average global temperature should be limited to two degrees above a
baseline, the pre-industrial level in 1880. This is the maximum allowable warming
before human interference in the climate is deemed ‘dangerous’. Beyond it dire
consequences are predicted, including potentially significant losses of food
production, especially in Africa; high extinction risks for 20–30 per cent of species,
more severe droughts and floods, and an unstoppable loss of the Greenland ice
sheet, triggering escalating sea-level rises (Hansen et al., 2007; IPCC, 2013).
This ‘two-degree safety barrier’ offers an important message about the need for
green transformation:
an indication, as simple as it is compelling, of the physical limits to the volume
of greenhouse gases that can be dumped in the atmosphere [which] sets out
the breathtaking message that the world’s population must immediately begin
to make significantly less use of fossil energy sources or leave them in the
ground.
(Leggewie and Messner, 2012b, p128)
Yet there is nothing natural or immutable about the existence of such a safety barrier,
or that it should be set at two degrees. Rather, like previous green limits, this is
socially and politically constructed, and has a history. As Randalls (2010) and Tol
(2007) detail, it is rooted in the particular ways in which scientists and economists
developed heuristics and models from the 1970s to guide understanding and
decision-making about climate change. The two- degree figure was first pinpointed
by the economist W. D. Nordhaus in 1979, assuming that this was the limit of
the warming to have occurred naturally over the last 10,000 years. Through the
1980s, a series of integrated assessment modelling exercises, and the particular
assump tions they incorporated, helped to support the idea of limits and thresholds
to dangerous climate change, and two degrees in particular. It acquired growing
weight in policy circles, with a link between limits and averted danger enshrined
in Article 2 of the UN Framework Convention on Climate Change (UNFCCC,
1992). The proposition of two degrees as an actual policy target came in 1996
from the European Union (EU), backed by certain scientists and environmentalists.
It gained in visibility and policy institutionalization through the 2000s – for
instance, underpinning the UK’s 2008 Climate Change Act and included in the
2009 Copenhagen Accord. In UNFCCC conferences of parties (COP) in
Copenhagen (COP-15) and Cancun (COP-16) all parties to the UNFCCC
28 Melissa Leach