Hopes of keeping global warming below the
long-established target of two degrees above pre-industrial levels
are rapidly eroding, according to a collection of papers in two
Nature journals today.
That might sound like a gloomy backdrop to this week's
climate summit, convened by UN director-general Ban Ki Moon to
refocus world leaders' attention on climate action.
But chalking up the two degrees target as a political
failure is a "naive" way to look at climate ambition and could even
obstruct future negotiations, the authors argue.
Origin of two degrees
In 1992, the United Nations Framework Convention on
Climate Change (UNFCCC)
said the objective of
global climate policy should be to stabilise humans' influence on
the climate below the level at which it can be considered
Scientifically-speaking, there's no definitive
threshold beyond which climate change tips the balance into being
"dangerous". But as temperatures rise, so do the risks.
Curbing temperature rise to
two degrees above pre-industrial levels has become the
most widely accepted point beyond which climate change risks are
considered unacceptably high.
As the recent
report on climate change impacts from the
Intergovernmental Panel on Climate Change (IPCC) puts it:
"Increasing magnitudes of
warming increase the likelihood of severe, pervasive, and
irreversible impacts. Some risks of climate change are considerable
at 1 or 2°C above preindustrial levels … The precise levels of
climate change sufficient to trigger tipping points… remain
uncertain, but the risk ... increases with rising temperature".
A two degree limit has been a symbolic focus of
climate ambition for the past two decades - it is the limit
recommended by the UK's
Committee on Climate Change, for example.