NETs a goal?

Progress on tackling climate change remains slow. Yet another UN summit approaches with little hope of a just solution to the interminable debate over which nations should cut emissions and by how much. Climate deniers and vested interests have been having a field day, cultivating doubt, and cheerleading for alternative 'cheaper' responses to climate change, rather than cutting emissions by investing in clean energy, energy conservation and public transport.

Twenty years ago they used to claim that even if the climate were changing it would be cheaper for humanity to adapt to those changes than to cut emissions. Today the vogue is for 'geo-engineering' options – deliberately intervening in the climate in an effort to cool the planet. But the scientists researching geo-engineering options are almost without exception convinced that climate change is real, that we must cut emissions dramatically and fast – but that we may need geo-engineering interventions too if we are to avoid dangerous climate change.

This highlights what economists call 'moral hazard': the idea that if someone believes they are insured against failure, they will take bigger risks (rather like the banks in the last decade). In this case the moral hazard is that if politicians believe we can prevent dangerous climate change with geo-engineering alone, they will not take potentially costly or politically difficult decisions to cut emissions: and of course the deniers will do their best to encourage such a belief.

So why have I just published a report looking at 30 potential geo-engineering options? Well, there are several reasons.

First, we need to distinguish between different sorts of geoengineering. Most techniques fall into one of two categories: solar radiation management (SRM) which aims to influence temperatures directly; or Negative Emissions Technologies (NETs) which remove carbon dioxide from the environment. Even though each group includes a diverse mix of techniques, the differences between the groups are probably even more significant. SRM measures are typically more risky, but may possibly be deployed fairly swiftly. NETs are largely less risky, but slower to take effect.

So as options for policymakers they need distinct consideration. In particular, while further research into SRM approaches is probably justified, appropriate NETs already need support for development and deployment. It may even be justifiable to categorise NETs and SRM as different climate policy responses altogether, as the differences between NETs and SRM may be larger than those between NETs and mitigation.

Second, we need to be better informed about all these options – in particular if most people making claims about geo-engineering have an interest in their own pet technique, then we can expect those claims to show 'promoter bias': and imply that the technique is cheaper, less risky, more effective and fairer than an objective review might conclude. In particular we need to know what the limits are to their use: whether those arise from side effects (such as impacts on rainfall patterns), from the supply of inputs (such as biomass) or from the capacity to store captured carbon dioxide.

So my report deliberately focuses on NETs, assessing them against several criteria, including capacity, cost, technical readiness, side effects and accountability. It highlights no-regrets options such as wetland restoration, and also larger scale potential which merits investment in further development – such as carbon capture on sustainable bioenergy, or direct air capture of carbon dioxide. Although such techniques are likely to remain more expensive than mitigation, as a result of twenty years of procrastination it appears we will need them too, and soon. In other words NETs should constitute a separate, albeit subsidiary, goal of climate policy.

My report can be downloaded here.