I went to some Departmental talks recently and discovered that some of my colleagues are researchering possible carbon sequestration technologies. This could be very important, but appealing to negative emission technologies is often quite strongly criticised. The basic argument (which has some merit) is that presenting this as a possibility can provide policy makers with an argument for delaying action that might reduce emissions sooner.
Although I have some sympathy with these criticisms, I do have some issues with them. One is that it often involves criticising climate models that include negative emission pathways. The problem I have with this is that they seem to use “climate model” as a catch all for any kind of model associated with climate change. However, there are a large number of different models. Some are trying to understand how our climate responds to changes, and – typically – use concentration pathways. Others try to associate concentration pathways with emission pathways. Then there are others that try to understand the impact of various emissions pathways, how we could follow different pathways and, in some cases, if it is possible to actually do so. Given how easily what is said can be mis-interpreted, I generally think it would good to be clear about what type of models are actually being criticised.
The other issue I have relates to the idea that maybe we should avoid providing these pathways to policy makers. My view is that we should be very careful of selecting what information is presented. If there is a desire to understand what pathways might keep warming below 2oC, for example, and it turns out that many would require negative emission technology, then I think that this should be made clear. However, it should also be made clear that such technology does not yet exist (at scale, at least) and that there is a chance that it will never exist, on the required timescale at least. I don’t have much faith in policy makers myself, but if they can’t even get that it would be silly to base policy on technology that does not, and may never, exist, then we should probably just give up now.
What partly motivated this post, though, was a recent article that argues that we should not assume that land-based measures will save the climate. It’s pretty readable, so I would encourage you to do so and won’t say much more. It argues that negative emissions may either not be technological feasible, that they have unacceptable social and economic impacts, and that they may ultimately not be as effective as hoped. Therefore we should assume that it is unlikely to be a technology on which we can rely. I’ll leave you to make up your own minds, but I just wanted to quote the concluding remarks, as I think they do illustrate a crucial point.
If the expected negative emissions cannot ultimately be achieved, the decades in which society had allowed itself a slower, softer transition would turn out to be a dangerous delay of much-needed rapid emission reductions. Saddled with a fossil fuel-dependent energy infrastructure, society would face a much more abrupt and disruptive transition than the one it had sought to avoid. Having exceeded its available carbon budget, and unable to compensate with negative emissions, it could also face more severe climate change impacts than it had prepared for.
Update: Andy Skuce’s article ‘We’d have to finish one new facility every working day for the next 70 years’—Why carbon capture is no panacea is also worth reading. Kevin Anderson and Glen Peters also have an article called The trouble with negative emissions.