All of our options for keeping warming below 2C above
pre-industrial temperatures now involve capturing carbon dioxide
and storing it underground - a technology that doesn't yet exist on
a large scale, according to new research.
published today in Nature Communications, argues that 'negative
emissions' alone, in the absence of conventional mitigation,
are unlikely to achieve the 2C goal.
And in all but the most optimistic cases, staying
below 2C requires capturing and storing carbon in amounts that
exceed the capabilities of current technology, say the
Ahead of a major international climate summit in
Paris, the study makes an interesting contribution to the debate
about the role of negative emissions in meeting the 2C target.
In December, global leaders will gather in Paris to
agree a deal for capping global temperature rise at 2C above
pre-industrial levels - the internationally
For any given temperature target, there is a finite
amount of carbon that can be burned before the chances of staying
below that target become minimal. This is known as a
In its latest
report, the Intergovernmental Panel on Climate Change (IPCC)
said that to have a reasonable chance of staying below 2C, total
emissions from all human activity must not exceed 1,000bn tonnes of
carbon (or gigatonnes of carbon, GtC).
The world is currently not on course to meet this
target and there are two options for how to get ourselves back on
track, says today's paper.
The first is to produce fewer emissions, which means
burning fewer fossil fuels. This is what's commonly referred to as
The other is to capture fossil fuel emissions before
they enter the atmosphere, or to suck them directly out of the air
- a technique known as carbon dioxide removal. A third possibility
sometimes proposed is to artificially engineering parts of the
climate system, such as the oceans, to take up more carbon.
Collectively, the new paper calls these "negative
(Note that this is not shorthand for what the IPCC
refers to as "net negative emissions". In its latest report, the
said: "Net negative emissions can be achieved when more GHGs
are sequestered than are released into the atmosphere (e.g., by
using bio-energy in combination with carbon dioxide capture and
Laboratory studies help progress the field of
carbon storage, by characterising the chemical signatures that
result when certain types of rocks are exposed to carbon
dioxide. Credit: Idaho National Laboratory | Flickr