Memorandum 146
Submission from Dan Lunt, School of Geographical
Sciences, University of Bristol
- Several geoengineering schemes have recently
been proposed to mitigate against global warming.
- Current understanding related to the possible
efficacy, side-effects, and cost-effectiveness of these schemes
is extremely low.
- Before large sums of money are invested
into any of these schemes, they need to be thoroughly assessed
in a coherant national program of research.
1. There is almost universal consensus that
"dangerous" climate change must be avoided. However,
without radical changes in energy sources and usage and global
economies, it seems highly likely that we will start to experience
unacceptably damaging and/or societally disruptive global environmental
change later this century.
2. Geoengineering (the "intentional
large-scale manipulation of the environment") has been considered
for the mitigation of such dangerous climate change in response
to elevated anthropogenic greenhouse gases, at least in conjunction
with other mitigation strategies. Various such schemes have been
proposed, such as the removal of CO2 from the atmosphere by locking
it up in terrestrial biomass, pumping it into the deep ocean,
or injecting it into geological formations, or manipulation of
the energy budget of the climate system by the injection of sulphate
aerosols into the atmosphere, construction of a space-based "sunshade",
or modifications to the land and/or ocean surface to reflect more
sunlight back to space.
3. However, many of the geoengineering schemes
proposed remain un-quantified in their impact, and some are extremely
unlikely to work at all. All may give rise to undesirable climatic
side-effects and have hidden "costs", both economic
and environmental. This was highlighted in a recent study[6]
carried out at the University of Bristol, where a state-of-the-art
climate model was used to assess the climatic impact of a space-based
sunshade. Previously, it was widely assumed that such a geoengineering
scheme could revert climate back to a "pre-industrial"
state. However, this study found that although the impact of CO2
emissions would be reduced, it was inevitable that there would
still be a residual climate change of considerable magnitude,
resulting in the loss of Arctic sea-ice. Additionally, such schemes
leave other CO2-related problems, such as ocean acidifcation,
completely unaddressed.
4. That study, examining just one particular
method of geoengineering, highlights the fact that we currently
have insufficient scientific information to adequately support
the debate we need to have. A DEFRA Discussion Paper circulated
earlier this year perfectly illustrates the high-level interest,
yet also the critical need for a more reliable quantitative understanding
of the benefits, risks, and costs, together with an ethical perspective.
5. Before any geoengineering scheme is implemented,
or substantial funds are invested in geoengineering technologies,
we would recommend the funding of a national program designed
explicitly to improve current understanding of the efficacy, side-effects,
practicality, economics, and ethical implications of geoengineering.
This would bring together climate scientists, engineers, economists,
and philosophers. Of course, such a program would complement similar
investigations into the economics and practicality of other mitigation
and adaption strategies, such as improved energy efficiency, reduced
energy use, and more energy production from renewable sources.
October 2008
6 Lunt, DJ, A Ridgwell, PJ Valdes, and A Seale (2008),
Sunshade World: A fully coupled GCM evaluation of the climatic
impacts of geoengineering, Geophys Res Lett, 35, L12710, doi:10.1029/2008GL033674. Back
|
