IPCC AR5 looks into geoengineering science

Next week, Monday till Wednesday, climate experts from IPCC WGI, II & III will get together in Lima to discuss a possible inclusion of geoengineering measures in climate policy.

Although intended for participants only, the programme, including abstracts of keynote speeches, has leaked to the media. There’s not much new in the science, but it does provide some new insights into the geoengineering debate, and how it may one day close in to reach actual policy.

After a ‘framing’ plenary session, with an ‘overview on geoengineering in the context of assessment’ and speeches by the different IPCC Working Group co-chairs and University of Calgary’s David Keith, the programme offers three more plenary sessions, one focussing on Solar Radiation Management (SRM) – attempts to increase the Earth’s albedo – and the next on Carbon Dioxide Removal (CDR) geoengineering – measures aiming to actually lower the atmospheric concentration of CO2.

The third session is intended to investigate risks, timescales and geoengineering governance, with speakers including Catherine Redgwell, of University College London and Ken Caldeira, of Carnegie Institution for Science. This article does not include such political (& legal) implementation issues [as we hope to keep our focus on the climate science] but we do recommend taking a look at their respective abstracts – as they provide lots more food for debate.

‘SRM geoengineering in new IPCC report’

From Phil Rasch of the US Pacific Northwest National Laboratory, we learn that Working Group I for the IPCC’s 5th Assessment Report ‘will explicitly discuss the scientific issues’ of Solar Radiation Management (SRM) geoengineering in the 1st and 7th chapter. Rasch continues to present an overview of SRM examples and elaborates on the state of current research.

Interestingly, as his example of groups that look into technical feasibility, he refers to ongoing research in marine cloud geoengineering: “there are groups exploring technologies that might be used to make sea salt particles of the right size and quantity to be used to seed marine clouds over oceans” – hinting to recent concerns around the general effectiveness and even possible warming effect of this method, indeed related to the size of salt aerosols.

However the next speaker on SRM geoengineering, Thomas Peter of the Swiss Federal Institute of Technology, still lists cloud albedo enhancement, together with stratospheric aerosol albedo enhancement, as being “of particular interest, given potential advantages in terms of effectiveness, timeliness and affordability”.

Moral hazard vs action failure

Next Scott Barrett of Columbia University takes a remarkable stance with respect to the proclaimed ‘moral hazard’ of (SRM) geoengineering [that suggesting an alternative last-minute solution route to climate change may undermine international mitigation attempts]:

“While knowledge that geoengineering could be used to limit climate change in the future will likely influence emissions policy today, that effect need not be inefficient. If SRM were expected to work, and without harmful consequences, it would be desirable for countries to use it – and to ease up on their efforts to reduce emissions today.”

Barrett continues: “There are other reasons why too little effort will be devoted to reducing emissions, perhaps the main one being free riding. Moreover, since the costs of deploying SRM are low, the incentives to deploy it unilaterally or minilaterally will be strong.”

“We will tend to substitute more geoengineering for less emission reductions not because of moral hazard but because of [collective] action failure.”

Back to solving the actual CO2 problem

Nicolas Gruber from the ETH University in Zurich may defuse tensions, as he is the first to speak about CDR geoengineering, by listing ‘physical (deep sea CCS), chemical (DHS could be one key) and biological (like iron fertilisation)’ marine possibilities for lowering CO2 concentrations. Peter Cox, of the University of Exeter, does the same for chemical and biological CDR on land.

James Dooley, a PNNL colleague of Phil Rasch, looks at geological sequestration and ambient air CO2 capture, something that David Keith also researches. Both techniques require the implementation of CCS.

Dooley calls the geological option bioCCS. It is referred to by others as BECCS – Biomass Energy Carbon Capture and Storage, which sort of explains the general idea. Harvest sustainable biomass (for instance sea weed, from plantations), burn it in power plants, capture the CO2 and sequester it in deep geological formations.

Sooner BECCS than DACS

When biomass production sustainability requirements are met, international biomass trade (for instance pellets) should not be of specific concern, Dooley states. Large-scale production (expressed in energy production: ‘hundreds of exajoules’) ‘should be well under way’ at carbon prices approaching 100 dollars per tonne of CO2 – and that’s probably still less than the other CDR geoengineering option Dooley discusses, with ‘direct air capture,’ or DAC – although here price estimates range widely, between 30 to 1200 dollar per tonne of CO2, reflecting the great uncertainties around DAC. Dooley refers to a sequestration potential of ‘hundreds of millions to billions’ of tonnes of CO2 per year. That would place DAC’s potential in line with organic measures like biochar [biochar would be cheaper btw] – and hardly the secret weapon to achieving negative CO2 emissions.

Dooley seems to favour bioCCS (BECCS) over DAC geoengineering because of one other reason. Although both measures would produce carbon permits (allowing revenue) bioCCS also produces carbon free electricity, whereas DAC processes require energy.

Comparing bioCCS to DAC is an example of how discussing geoengineering proposals may lead to alternative, gradually improving ideas, which may go without side effects or simply prove more effective. However, bioCCS as well as DAC require full implementation of CCS and ‘would likely increase demand for deep geologic CO2 storage reservoirs.’

Dooley even takes climate and CO2 feedbacks into account and warns that both bioCCS and DAC – in a scenario of large-scale implementation with the aim of creating net global negative emissions over a period of decades – would need to also remove possible CO2 emissions from the oceans and terrestrial biosphere, until a new atmospheric equilibrium concentration is reached. [But that is in fact a general climate concern, not reserved for CDR geoengineering, and should also increase the sense of urgency around implementing emission reductions from fossil fuels or perhaps developing an SRM backup plan.]

The UN’s new scientific climate assessment report, IPCC AR5, will be released over the course of 2013 and 2014.

© Rolf Schuttenhelm | www.bitsofscience.org

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