Can we still limit warming to two degrees?
- 03 Dec 2012, 17:15
- Roz Pidcock
Without a new "radical plan", the world is unlikely to meet the
target of two degrees of warming, according to a new study. As
energy secretary Ed Davey joins negotiators at the UN climate talks
in Doha, he seems optimistic that mustering enough political could
still put the world back on track. But the new research suggests
that two degree target is moving further out of reach.
Two degrees of warming
The official target of the United Nations Framework Convention
on Climate Change (UNFCCC) is that to avoid serious climate change,
global mean temperature rise should not exceed two
degrees Celsius above pre-industrial levels.
new study in Nature Climate Change yesterday says that without
a radical overhaul of emission reduction policies, it's very
unlikely we'll hit that two degree target.
The researchers plotted carbon dioxide emissions since 1980
against the emissions scenarios the Intergovernmental Panel on
Climate Change (IPCC) uses to estimate how fast greenhouse gas
emissions could rise in the future.
The analysis included the most recent set of scenarios - called
Representative Concentration Pathways (RCPs) -
which are the basis for the next round of projections in 2013.
Falling off course
The research shows carbon dioxide emissions increased from 6.1
billion tonnes in 1990 to 9.5 billion tonnes in 2011 - an increase
of 25 per cent. The rate of increase is growing too - from 1.9 per
cent per year in the 1980s to 3.1 per cent per year since 2000. The
researchers estimate emissions in 2012 will be 2.6 per cent above
2011 levels, 58 per cent higher than in 1990.
All of this means that current emissions are tracking the most
pessimistic IPCC scenarios. The highest RCP - known as RCP8.5 -
suggests four degrees warming by 2100. We wrote more about what
a four degree world could look like here.
Limiting warming to two degrees needs "immediate significant and
sustained global mitigation", the researchers say. This echoes the
conclusions of three
recent reports from the United Nations Environment Programme,
the World Bank and the World Meteorological Organisation.
Current emissions are tracking the IPCC scenarios that lead
to the most warming. RCP8.5 (red) is the most pessimistic of the
new RCP scenarios, which projects four degree warming by 2100.
Peters et al. (2012)
The release of this new study coincides with UN climate talks in
Doha. There, negotiators are discussing a replacement for the Kyoto
Protocol that will legally oblige all nations to curb greenhouse
But media coverage of the new study suggests that hopes aren't
high. The BBC,
The Guardian all report the concerns of co-author of the study
Corinne Le Quéré, director of the Tyndall Centre for Climate Change
Research. She says:
"[W]ith emissions continuing to grow,
it's as if no-one is listening to the scientific community...I am
worried that the risks of dangerous climate change are too high on
our current emissions trajectory. We need a radical plan."
Ahead of his arrival in Doha today, the UK energy and climate
change secretary Ed Davey sounded hopeful. He told the
"Two degrees is still within reach if we
can muster the political will."
So where do we go from here?
Staying below two degrees is unlikely but not impossible, says
the new study. The most ambitious of the new IPCC scenarios
(RCP3-PD) suggests it's possible to limit warming to 1.5 degrees
This scenario will depend on technologies that permanently remove
carbon dioxide from the atmosphere - resulting in negative
emissions. Such technologies could include carbon capture and
storage (CCS) from fossil fuels and biomass.
But relying on negative emissions is risky because it depends on
the large-scale roll out of emerging CCS technologies, say the
researchers. One of the less ambitious scenarios - called RCP4.5 -
suggests that the two degrees could be hit without negative
emissions, relying instead on changes in fuel use and energy
As the study highlights, some developed countries have
successfully reduced their carbon output this way. The UK, Denmark
and the US have had several periods since the 1970s in which they
reduced emissions by one to two percent per year by substituting
gas for coal or oil. Belgium, France and Sweden reduced emissions
by 4-5 per cent over a ten year period by moving from oil to
Big emitters, big responsibility
But a two degree temperature rise is still at the optimistic end
of RCP4.5 and would require early action by the biggest emitters to
work, says the new study. Together the US, China, the European
Union and India are responsible for nearly half of all global
emissions. As Le Quéré told the
"China is dominating the global rise in
emission that's for sure. The rich countries on the other side are
decreasing a little bit - one to three per cent per year - but not
enough to offset the growth in the developing world"
The Global Energy Assessment (
GEA), released last week by the International Institute for
Applied Systems Analysis in Austria, echoes the need for
technological innovations in energy efficiency and carbon capture,
as well shifts in energy sources. The GEA also highlights the
success of bottom-up initiatives like Sustainable Energy
For All, which are helping developing countries move away from
burning biomass toward less polluting energy sources.
The message from the new study is the biggest emitters should
lead by example and kickstart global mitigation, encouraging other
nations to follow suit. As the researchers say in the study:
"If similar energy transitions are
repeated over many decades in a broader range of developed and
emerging economies, the current emissions trend could be pulled
So current negotiations don't look on track to deliver the
emissions targets necessary to limit warming to the two degree
target, unless radical changes are set in motion - a sentiment Ed
Davey echoed as he set off for Doha. But are they right to
emphasise the top-down negotiations? As the GEA highlights,
mobilising bottom-up commitments to developing new energy pathways
could play a significant role in limiting global emissions.