The future of the Earth could rest on potentially dangerous
and unproven geoengineering technologies unless emissions of carbon dioxide can
be greatly reduced, a new study has found.
The report (published Sept. 1 by the Royal Society, the UK's national
academy of science) found that unless future efforts to reduce greenhouse gas
emissions are much more successful than they have been so far, additional
action in the form of geoengineering will be necessary to cool the planet.
However, the report identified major uncertainties regarding the effectiveness,
costs, and environmental impacts of geoengineering technologies.
"Reducing our greenhouse gas emissions is more
important than ever," said coauthor Ken Caldeira of the Carnegie
Institution's Department of Global Ecology, "but even with our best
efforts, the Earth is likely to continue warming throughout this century due to
inertia in the climate system. Cutting emissions can reduce but cannot
eliminate the risk of a climate emergency." Possible climate emergencies
include rapid collapse of the Greenland ice
sheet into the sea causing major sea level rise, a shift in rainfall patterns
causing massive global crop failures, or melting Arctic permafrost causing
catastrophic release of the powerful greenhouse gas methane.
Professor John Shepherd, who chaired the study said,
"It is an unpalatable truth that unless we can succeed in greatly reducing
CO2 emissions we are headed for a very uncomfortable and challenging
climate future, and geoengineering will be the only option left to limit
further temperature increases. Our research found that some geoengineering
techniques could have serious unintended and detrimental effects on many people
and ecosystems—yet we are still failing to take the only action that will
prevent us from having to rely on them. Geoengineering and its consequences are
the price we may have to pay for failure to act on climate change."
The report assesses the two main kinds of geoengineering
techniques—carbon dioxide removal (CDR) and solar radiation management (SRM).
CDR techniques address the root of the problem rising CO2—and so
have fewer uncertainties and risks, as they work to return the Earth to a more
normal state. They are therefore considered preferable to SRM techniques, but
none has yet been demonstrated to be effective at an affordable cost, with
acceptable environmental impacts, and they only work to reduce temperatures
over very long timescales.
SRM techniques act by reflecting the sun's energy away from
Earth, meaning they lower temperatures rapidly, but do not affect CO2
levels. They therefore fail to address the wider effects of rising CO2,
such as ocean acidification, and would need to be deployed for a very long
time. Although they are relatively cheap to deploy, there are considerable
uncertainties about their regional consequences, and they only reduce some, but
not all, of the effects of climate change, while possibly creating other
problems. The report concludes that SRM techniques could be useful if a threshold
is reached where action to reduce temperatures must be taken rapidly, but that
they are not an alternative to emissions reductions or CDR techniques.
"If we are confronted with a climate emergency and
decide we cannot tolerate any more warming, engineering some system to deflect
more sunlight back to space would likely be the primary option available to
cool the Earth quickly," said Caldeira. "Of course, we need to make
sure that tinkering with our environment in this way would not just cause
bigger problems. We need to study these options now so that we can understand
the pluses and minuses in case we need to deploy them."
Professor Shepherd added, "None of the geoengineering
technologies so far suggested is a magic bullet, and all have risks and uncertainties
associated with them. It is essential that we strive to cut emissions now, but
we must also face the very real possibility that we will fail. If 'Plan B' is
to be an option in the future, considerable research and development of the
different methods, their environmental impacts, and governance issues must be
undertaken now. Used irresponsibly or without regard for possible side effects,
geoengineering could have catastrophic consequences similar to those of climate
change itself. We must ensure that a governance framework is in place to
prevent this."
Full
report available here
Original
release
SOURCE: Carnegie Institution
