by Judith Curry
The economic models that are used to inform climate policy currently contain an unhealthy dose of wishful thinking. Technologies that remove carbon dioxide from the air are assumed in the models that avoid dangerous climate change – but such technologies do not yet exist and it is unclear whether they could be deployed at a meaningful scale. – Tim Kruger
I’m in the midst of a really interesting discussion on twitter with Silvio Funtowicz, and he pointed me to a superb article published last April in the Guardian (that I somehow missed), written by Tim Kruger. The title is Abandon Hype in Climate Models. Excerpts:
Most of the modelled emissions pathways limiting warming to 2 °C (and all the ones that restrict the rise to 1.5 °C) require massive deployment of Biomass Energy with Carbon Capture and Storage (BECCS). This involves growing biomass which is used to generate power and geologically sequestering the carbon dioxide produced. While the constituent steps of this process have been demonstrated, there are but a few, small, examples of the combined process.
There is a distinct lack of evidence to determine whether BECCS is technically feasible, economically affordable, environmentally benign, socially acceptable and politically viable at a material scale. Technically, there are serious doubts about the ability to sequester the vast quantities of carbon dioxide that are implied in the models. Economically, without a substantial carbon price, the costs would be much higher than competing power-generation technologies. Environmentally, growing such volumes of biomass would have profound effects on biodiversity. Socially, the use of land for BECCS would restrict agriculture – contributing to substantial increases in food prices; while politically, the issue seems so toxic that the Paris Agreement carefully avoided mentioning negative emissions at all.
For a technology to be deployable it needs not only to work, but also to possess a social licence to operate. For example, that Germany possesses the technical ability and financial means to build new nuclear power plants is not in question, but lacking the social and political will to do so makes the point moot.
Yet to model what you want to happen, rather than what there is evidence could happen, is to lose the thread of reality. It is redolent of a defeated leader issuing orders to armies that have long since ceased to exist – not so much vision, as delusion.
Should modellers be able to model what they like? Of course. Scenarios allow us to undertake useful thought experiments that provide us with the means to assess potentially novel approaches.
Some will defend the use of these technological imaginaries in IPCC scenarios by arguing that without them hopes of avoiding dangerous climate change are forlorn and that this would generate a degree of despair that would undermine the will to act.
But that is not the role of models. “Fake it ‘til you make it” may work as a tactic, but it is a lousy strategy. As the dust settles on the Paris Agreement and policymakers face up to the challenge of achieving the ambition set out by their leaders, we need to reflect on what actually needs to happen. Policymakers can only hope to develop realistic plans, if the basis on which they are making those plans is itself realistic. While the boundary between ambition and delusion may be not be entirely sharp, the inclusion of negative emissions amounting to 600-800 billion tonnes of carbon dioxide (equivalent to 15-20 years of current annual emissions) is clearly more than a stretch goal. For this reason, negative emission techniques should be excluded from the mitigation scenarios used by the IPCC unless and until there is sufficient evidence to warrant their inclusion and then only on a scale that is demonstrably realistic.
On the basis of such a comprehensive assessment, policy makers will then have to make an explicit decision either to invest in the necessary research, development and demonstration of the technologies or to explain how they propose to meet their ambitious targets without such interventions. Policymakers cannot be allowed to hide behind the vague language of the Paris Agreement (“achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases”).
In the absence of comprehensive research and indications of political feasibility, it seems prudent to exclude from the models what is currently magical thinking. Only by undertaking research will it be possible to determine whether today’s science fiction could be transformed into tomorrow’s science reality.
Nail — you have been squarely hit on the head.
There simply is no conceivable pathway to reducing CO2 concentrations (through emissions reductions or carbon sequestration) on the timescales put forth by the Paris Agreement. Until policy makers factor this into their plans, what they are doing is an extremely expensive and potentially dangerous scam.
Policy makers need to put forward more realistic plans for dealing with climate change that are technically, economically and socially viable. And while they’re at it, they can invest in understanding natural climate variability, so we can develop more realistic scenarios of how the climate might actually evolve over the 21st century