Post date: Oct 22, 2013 4:18:15 PM
The most recent Intergovernmental Panel on Climate Change (IPCC) summary has brought the idea of geo-engineering – deliberate interventions designed to modify the regional or global climate – to the attention of policy-makers around the world. While most immediate reactions have focused on techniques for so-called ‘solar radiation management’ (SRM) - such as cloud brightening, or the injection of sulphate aerosols into the high atmosphere to reflect more sunlight - this is only one aspect of the issue.
Buried in the numerical analysis of the IPCC documents is a frightening admission that even in the most optimistic of these ‘consensus scenarios’ the world will need to deliver global net negative carbon emissions in the latter part of this century if we are to stand a decent chance of avoiding more than 2oC warming globally and the much more extreme regional consequences that would accompany such average warming.
There are reasons to believe that the IPCC’s consensus about the prospects for mitigation may be politically over-cautious, but we must look seriously at what is meant by global negative emissions. Such a trajectory means very large scale deployment of some or all of a family of techniques or technologies that remove greenhouse gases from the air (typically called ‘carbon dioxide removal’). Yet at a major conference in Oxford in August, I heard a succession of speakers raise concerns over the technical or economic viability of every one of these techniques – largely reflecting arguments I previously set out in my report on negative emissions techniques (NETs) for Friends of the Earth. Large scale afforestation, for example, might draw down carbon, but because it directly warms the planet’s surface, and makes it less reflective of sunlight, the net effect could still be further warming.
There are some NETs which might be adopted as ‘no-regrets’ options: restoring peatbogs, salt-marshes and mangrove swamps for example, or treating genuinely waste biomass – such as rice husks - with a ‘biochar’ process; or perhaps adopting ‘regenerative’ rotational grazing techniques to help re-establish vegetation and build soil carbon in drylands. These could all be deployed in ways that help with human development goals if developed with the full participation of local communities. But the likely scale of these ‘no regrets’ options is typically small, compared with the levels needed to compensate for all remaining emissions and ‘flip over’ the earth system to be a net sink – rather than source - of carbon before 2100, and they are receiving limited attention.
NETs fundamentally differ from SRM methods in that they address the root cause of climate change rather than masking or compensating for its effects, but they are also – if feasible at all – much slower to deploy at scale and take effect. There are three main classes of NETs which might be deployed at large scale – and none is without its negative impacts. Richard Branson has offered a $25 million prize for the demonstration of negative emissions at commercial scale. As yet it remains unclaimed, and most of the contenders face one of two major hurdles: the need for land or the need for energy.
Closest to deployment are technologies that apply end of pipe carbon capture and storage techniques to bio-energy (so called ‘BECCS’). This would mean that the carbon taken up by the fuel source when growing would be effectively permanently captured rather than released when the fuel was burnt. But as we have seen already, even relatively small demands for land for biofuels have led to serious risks for food security, overuse of water in water-scarce regions, and to a range of conflicts over land. Delivering large scale BECCS without undermining human development goals or other environmental interests such as biodiversity seems implausible. Sadly, it seems entirely likely that misplaced efforts will be made, exacerbating the impacts already caused by rich countries growing demand for biofuels.
Other possibilities for large scale NETs include ocean liming and direct air capture (DAC) – sometimes described as ‘artificial trees’). There are many different proposals for such technologies, but even taking the most optimistic assumptions about energy efficiency made by their promoters, they would make little sense if we had not first converted the whole global energy supply to low or zero carbon sources, and even then the impacts of adding maybe 10-30% more energy production to power NETs would be a major undertaking with potentially serious consequences for problems such as fuel poverty.
That such major implications are buried in the IPCC’s assumptions, rather than being openly debated, is worrying in itself. It largely reflects a rich-country framing of the climate problem, which sees accelerated mitigation as ‘politically unrealistic’. The favoured approaches to NETs also reflect the interests of the rich world, in developing approaches that rely on further colonisation of the natural biological productivity of the planet, and encourage the commercialisation of carbon capture through ‘enhanced oil recovery’ or through extension of carbon markets, with all the negative implications of such approaches.
It’s past time that more environment and development NGOs took a long hard look at this form of geo-engineering, and helped shape a course in which NETs could be deployed as a supplement to accelerated mitigation in ways that sustain and enhance human development.