Nature editorial on climate change.

Published in the latest edition of Nature, one of the most prestigious peer-reviewed scientific journals in the world.

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EDITORIAL

Time to act

Without a solid commitment from the world’s leaders, innovative
ways to combat climate change are likely to come to nothing.

It is not too late yet — but we may be very close. The 500 billion tonnes of carbon
that humans have added to the atmosphere lie heavily on the world, and the burden
swells by at least 9 billion tonnes a year (see page 1117). If present trends continue,
humankind will have emitted a trillion tonnes of carbon into the atmosphere well
before 2050, and that could be enough to push the planet into the danger zone. And
there is no reason to think that the pressure will stop then. The coal seams and tar
sands of the world hold enough carbon for humankind to emit another trillion tonnes
— and the apocalyptic scenarios extend from there (see page 1104).
Nations urgently need to cut their output of carbon dioxide. The difficulty of that
task is manifest: emissions have continued to rise despite almost two decades of rhetoric,
diplomacy and action on the matter. But that unhappy fact should not be taken
as a licence for fatalism. Governments have a wide range of pollution-cutting tools
at their command, most notably tradable permit regimes, taxes on fuels, regulations
on power generation and energy efficiency, and subsidies for renewable energy and
improved technologies. These tools can work if applied seriously — so citizens around
the world must demand that seriousness from their leaders, both within their individual
nations and in the international framework that will be discussed at the United
Nations Climate Change Conference in Copenhagen this December.

As essential as it is, however, simply agreeing to cut emissions will not be enough.
The fossil fuels burned up so far have already committed the world to a serious amount
of climate change, even if carbon emissions were somehow
to cease overnight (see page 1091). And given the
current economic turmoil, the wherewithal to adapt
to these changes is in short supply, especially among
the world’s poor nations. Adaptation measures will be
needed in rich and poor countries alike — but those that
have grown wealthy through the past emission of carbon
have a moral duty to help those now threatened by that
legacy (see page 1102).

The latest scientific research suggests that even a complete halt to carbon pollution
would not bring the world’s temperatures down substantially for several centuries.
If further research reveals that a prolonged period of elevated temperatures would
endanger the polar ice sheets, or otherwise destabilize the Earth system, nations may
have to contemplate actively removing CO2
from the atmosphere. Indeed, the United
Nations Intergovernmental Panel on Climate Change is already developing scenarios
for the idea that long-term safety may require sucking up carbon, and various innovators
and entrepreneurs are developing technologies that might be able to accomplish
that feat (see page 1094). At the moment, those technologies seem ruinously expensive
and technically difficult. But if the very steep learning curve can be climbed, then the
benefits will be great.

More radical still is the possibility of cooling the planet through some kind of ‘geoengineering’
that would dim the incoming sunlight (see page 1097). The effects of
such approaches are much more worrying than those of capturing carbon from the air,
however. The cooling from geoengineering would not exactly balance the warming
from greenhouse gases, which would cause complications even if the technology itself
was feasible — something for which the evidence has been circumstantial, at best.
But discussions about the possibilities offered by geoengineering could also lull the
world’s leaders into complacency — if they lead them to believe that the technology

“Even a complete halt
to carbon pollution
would not bring the
world’s temperatures
down substantially
for several centuries.”

1www.nature.com/nature Vol 458 | Issue no. 7242 | 30 April 2009
© 2009 Macmillan Publishers Limited. All rights reserved