Engineering the world
Posted by Science Oxford on June 15, 2011 | comments
A discussion at Science Oxford Live with Hugh Mortimer and David Frame (review by Blanka Sengerová).
In an interactive discussion with the audience at Science Oxford Live, David Frame and Hugh Mortimer (Research Scientist at the Rutherford Appleton Laboratory) introduced geo-engineering from the technical point of view, giving ample opportunity to all participants to ask questions and to pass comment on the ethical and moral issues associated with geo-engineering the world. Hugh Mortimer is a researcher in the STFC geo-engineering project – the only large scale project which is attempting to look at one of the possible solutions. David Frame has had a secondment in government and is interested in how science and technology interacts with policy, addressing questions such as “who could do this?”, “what mandate do we have to give them?”, or “what is the cost and benefit of a proposed scheme?”.
Geo-engineering was defined by the Royal Society as “deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change” (although some people have issues with the definition). This may involve one of two main approaches, either solar radiation reflection to reduce the amount of heat that reaches the earth’s surface, or carbon dioxide removal from the atmosphere to increase the amount of radiation that is re-reflected into space. In lay terms, the first approach is like turning the sun down a bit, the second involves hoovering up carbon dioxide to stop it from keeping the radiation close to the earth. To some extent, the latter approach, ‘sequestering’ carbon dioxide, occurs naturally so its extension has relatively lower uncertainties and risks, but conversely may only have a small effect on reducing global temperatures. Reflecting a small amount of radiation back into space, on the other hand, may be the only quick solution in the event of a major climate crisis. Critically, solar radiation management mitigates against only some of the problems of climate change and may create others, and the proposed solutions can be extremely expensive.
Figure 1: Possible technologies to address climate change (Royal Society).
Specifically, what were the approaches discussed in the context of both solar radiation management (SRM) and carbon dioxide removal (CDR)? They are illustrated above (Fig.1).
SRM measures
- Surface albedo (urban): making urbanised areas more reflective by painting surfaces white to reflect more sunlight. Potential problems raised by the audience included the sheer cost of the paint, as well as the environmental impact of making it (most paint is made from oil!). Also it would have to be re-done at regular intervals, as the white paint wouldn’t last too long.
- Surface albedo (desert): covering large amounts of desert with plastic to reflect the sun. What about the problem of covering such a large amount of earth with non-biodegradable material, said the audience…
- Cloud albedo means creating clouds to reflect back the sun’s heat.
- Space reflector: effectively putting a large mirror up in space. It would need to be about 700km x 700km, which is about the size of England and Wales… so the scale and cost is huge. This would reflect back some of the sunlight into space. What might the countries which already have low sunlight think of this?
- Stratospheric aerosols: putting sulphate particles into the stratosphere to block solar energy reaching the earth surface. It needs to be done at the equator where the reflectivity is higher. Will this cause acid rain, was the query from the audience. Actually, it shouldn’t because the sulphates would be put up high enough to spread globally whereas sulphates cause acid rain when at high concentrations locally.
CDR measures
- Biochar involves burning biomass before it rots (and so before it releases carbon dioxide) and converting it into charcoal. BECS is similar to this approach but involves burying the sequestrated carbon.
- Ocean fertilisation involves encouraging an algal bloom by seeding oceans with iron filings. Algae will take up carbon dioxide and when they die, they sink to the bottom of the ocean and sequestrate CO2 by taking it with them.
- Afforestation (planting more trees) is relatively cheap but has low effectiveness – it would take a very long time for carbon dioxide to be reduced solely by afforestation and, indeed, increasing forest regions also reduces the reflectivity of the earth, meaning that more of the sun’s radiation would be absorbed.
- Enhanced weathering means increasing the removal of carbon dioxide from the atmosphere by reacting it with minerals and storing it in the ocean.
- Carbon dioxide air capture is exactly what it says on the tin and means taking the CO2 from the air and storing it somewhere, possibly underground. CCS at source, meaning carbon capture and storage, is effectively the same thing but rather than applying to the air in general, it means catching and storing CO2 where it is produced, for instance at power stations.
And what were the various issues raised by the audience?
What happens if the stored carbon dioxide leaks out from where it is stored? Yes, there is potential for this to go wrong, with major ‘limnic‘ events when a sudden bubble of CO2 is released, potentially leading to deaths of animals and humans of asphyxiation.
Can we introduce a second use to the poly tunnels that are used on fields to grow fruit and vegetables and make them reflect some heat? Yes, it’s possible, but to change the reflectivity to a large enough extent, this would need to be done closer to the equator, where reflectivity of the earth’s surface is higher than closer to the poles.
Will a giant reflector reduce sunshine in places where there is already little of it? Yes, the sunshine would be reduced by about 1.5%, which could have major changes on, for instance, the hydrological cycle.
Why don’t we concentrate (funnel) the sun’s energy onto a solar panel instead of reflecting it back? This is something that’s being done in places already, for example in Spain. It is difficult at higher altitudes and does not address the change in global temperature.
What about the nature of unintended consequences, do we really know and can we test what all these alterations will do to the earth’s climate? Also, surely we can’t actually do a test without taking the plunge and starting the 30 year experiment and so cannot turn it back? Sensible point, and yes, wind-farms (for instance) might change the wind-flow pattern, affecting localised weather patterns. However, you could argue that burning fossil fuels at the rate we currently do is one massive experiment in progress, and all these suggested geo-engineering procedures are emergency ones. But it’s not all bad, and we can test some things (as is being done as part of this large scale geo-engineering research project), using for instance aeration chambers and stratospheric modelling techniques. So we might, after all, have some idea of what is safe and what is not.
Surely afforestation is the best way to go as it cannot cause any harm? Actually, planting forests can have issues in terms of land management and, indeed, trees aren’t very reflective so by planting lots of trees, the earth surface would be made more absorbing to energy.
Which of the proposed technologies, all of which sound rather sci-fi, are more mature at the moment and actually taken into practical use? This would be carbon capture and storage (CCS) at the moment.
How would stratospheric aerosols be put into practical use? Current ideas include the possible use of ballistic rackets to fire them upwards or the use of a tethered balloon (at 25km) to pump aerosols into the stratosphere in liquid form. And how might this affect the earth’s population? Since the approach of using stratospheric aerosols simulates volcanic eruptions, a suggestion from the audience was that the eruption of Krakatoa in AD535, as discussed by David Keys, may have exemplified what could happen. If that is true, people may die because of changes in the hydrological cycle.
To end with, there was a heated and lively discussion about the question of how far the solution of the climate change question is about the creation of a world democracy where everyone has a vote on what happens. Currently, the international political system arguably encourages gridlock because all countries have to sign up to a technology, with everyone having a veto. Clearly, as the discussions around the CO2emission reductions have shown, no country wants to share the burden of the negative impacts, with the biggest CO2 emitters choosing not to sign up to Kyoto. Part of the problem is what was referred to as NIMBYism and NIMTOism – “not in my backyard” and “not in my term of office”, respectively. Why should I have a wind-farm on my doorstep, and why should I force into law an unpopular measure if it is not going to get me re-elected in four years’ time?
This ran into arguments about whether people are inherently selfish and do not necessarily co-operate even if it is in their best interest (exemplified in the prisoner’s dilemma). When a new technology will affect their lives, they will always speak up and care less about the life of someone elsewhere in the world. Any geo-engineering technology will be difficult to push through because it will change lives, yet it appears that doing nothing may not be an option. It was suggested that the emerging economies, particularly China and India, are likely to play a key role in pushing on technology for mitigating climate change, with the developed (“northern”) countries possibly acting as an honest broker and perhaps as a regulator/consumer insisting on certain standards for exported products.
To reflect upon the discussion, it was certainly lively and thought-provoking. It is a bit depressing to think that as a species, we have such a bad track record of trying out things but finding out something has gone wrong far too late (someone exemplified this by the story of the snails of Tahiti, where biological control went awry) and it may lead us to wonder where all these mega-projects might lead to. Yet, someone else picked a positive story to finish on. In the 1800s, statisticians apparently calculated that London’s growth would soon be halted. The reason was that with its increasing size, the number of horse-drawn carriages needed to remove horse dung from the streets would increase, in turn increasing the dung so that eventually the dung could be not removed quickly enough. Yet, London did not drown in horse dung because someone invented a horse-less carriage. We are an inventive species and although we might not yet know how, there look to be a number of avenues to explore for mitigating the effects of climate change in future.
What do you think?