Is 1.5 degrees a scientifically realistic target?
- 13 Jun 2011, 17:00
- Christian
We are currently half way through an interim meeting of the UN's
Framework Convention on Climate Change (UNFCCC), the body that is
supposed to be negotiating a sensible global climate deal. And once
again, the disconnect between scientific and political reality is
startlingly apparent.
As the world struggles towards some sort of agreement, the
discussion about what shape a deal should take - and even what it
should be aiming for - continues. The Copenhagen
Accord [pdf], which the UNFCCC agreed to 'take note of' at the
end of 2009, recognized
"the scientific view that the increase
in global temperature should be below 2 degrees Celsius".
But at the beginning of last week, the executive secretary of
the UNFCCC, Christina Figueres,
went on the record saying
"Two degrees is not enough - we should
be thinking of 1.5C. If we are not headed to 1.5C we are in big,
big trouble."
Small island states - aware that their survival is threatened by
climate change - have made repeated calls in the negotiations for
the world to commit to keeping temperatures to 1.5 degrees above
pre-industrial level. But their call has largely fallen on deaf
ears.
This is perhaps unsurprising given that its taken 20 years to
get the world to commit to two degrees as a target, even in
principle. But it is worth pointing out how far away from the
current scientific reality the 1.5 degree target is.
Figueres' statement coincided with an IEA assessment
that global emissions from the power sector are at an all-time high
- as assessment which suggests
that if current trends in emissions continue, a four degree rise by
the end of this century looks likely.
A
recent policy briefing from the Grantham institute and the Met
Office detailed the challenges implicit in a 1.5 degree target,
concluding that temperatures will now almost inevitably rise above
1.5 degrees. The best we can hope for, they suggest, is that with
rapid emissions cuts it may be possible to end up with temperatures
less than 1.5 degrees above pre-industrial - but only if
temperatures 'peak and decline' following rapid cuts in
emissions.
To have a more than 50% chance of achieving this, the report
suggested immediate and very rapid emissions cuts would be
necessary. The authors however note that
'The feasibility of such rapid rates of
emissions reductions is an area of active debate.'
There are also large scientific uncertainties about the
feasibility of whether it is possible to 'overshoot' on temperature
rise - possibly for up to 100 years - and then bring temperatures
down again.
Without putting too much weight on one study, this kind of
essentially fairly simple budgeting analysis shows that two degrees
is in danger of becoming a 'best case' scenario, rather than the
'must not be crossed' limit it still occupies in much of the
discussion on this issue.
And that raises some pretty fundamental questions about the
framing of a lot of current climate geopolitics from politicians
and advocates. It may be that a fixation on 2 degrees and less
is in danger of missing the increasingly obvious - that staying
under even that limit already requires a great deal of extra
ambition and delivery on emissions cuts, as well as a modicum of
luck. Despite the fervent wishes of diplomats, activists and
affected people around the world, the basic science of climate
change isn't going to change anytime soon.