Carbon Capture and Net Zero
In early October a press release from the Department for Energy Security and Net Zero confirmed that the UK government had made “up to £21.7 billion of funding available, over 25 years, to make the UK an early leader in 2 growing global sectors, CCUS and hydrogen” (DESNZ, 2024). The article was headed “Government reignites industrial heartlands 10 days out from the International Investment Summit”: the heartlands are in the Northwest and Northeast of England, centred on sites in Teesside and Merseyside, and the summit aims to drive UK economic growth by attracting private sector investment. Carbon Capture, Utilization and Storage (CCUS) is seen by many as “a critical tool in decarbonisation” and is “expected to support 50,000 good, skilled jobs as the sector matures in the 2030s”. The funding “will also help turbocharge the low carbon hydrogen sector by paving the way for the UK’s first large-scale hydrogen production plant, decarbonising vital industrial sectors.” CCUS and hydrogen are linked because CCUS technology can enable hydrogen production plants to significantly reduce their carbon footprints (Hydrogen UK, 2023; IEA, 2024). The DESNZ press release claimed that CCUS technology is “tried and tested” and has been “deployed across the globe for over 20 years.” The new projects will “create 4,000 new jobs, sustain important British industry, and help remove over 8.5 million tonnes of carbon emissions each year”.
The press
release provoked critical comment. Mike Childs, the head of policy at Friends
of the Earth was quoted as saying that the proposed investment in CCUS would “subsidise
the continued lifespan of the fossil fuel industry” and that taxpayers’ money
should go instead to properly funding “a home insulation scheme for those
unable to afford it”. Childs saw CCUS as one of the “false solutions peddled by
the fossil fuel industry” (Politics 2024).
Poynting and
Rowlatt (2024), writing for BBC News, also questioned the effectiveness and
value of the proposed scheme. They point out that while carbon capture and
storage technology “has been around for decades” the industry “currently makes
very little difference to global CO2 emissions.” Nevertheless, both the IPCC
and the UK’s Climate Change Committee “see the technology as part of efforts to
reach net zero.” The North Sea provides favourable geology for CO2 storage, and
the UK’s oil and gas industry offers a useful skills base. The proposed
investment could “help carbon capture to become cheaper in time” (as was the
case with wind and solar energy) “and help the UK to reach net zero, while also
securing jobs and investment.”
The role of carbon
capture and storage after reaching net zero has not been highlighted in comments
on the UK government’s proposals. If CCS/CCUS schemes are expected to have a
significant role beyond net zero, this could affect the assessment of whether
investment in them is justified, an issue that will be discussed below. A 2008 paper
on climate stabilization provides background and views that may still inform
opinion. It put the case that “human-induced climate warming will continue for
many centuries, even after atmospheric CO2 levels are stabilized” (Matthews and Caldeira, 2008). The authors noted the
importance given to stabilizing concentrations of greenhouse gases in the
atmosphere but pointed out that such stability does “not equate to a stable
global climate.” Instead, simulations showed that “global temperatures continue
to increase for many centuries beyond the point of CO2 stabilization.” It would
thus be necessary to decrease, rather than merely stabilize, greenhouse gas
levels. The paper refers to the “the very long lifetime of anthropogenic carbon
in the atmosphere … a substantial fraction [of which] will persist in the
atmosphere for several millennia”. The authors sought to demonstrate that “because
of the high heat capacity of the ocean, global temperatures may not parallel
decreases in atmospheric concentrations of greenhouse gases, but rather will
increase and remain elevated for at least several
centuries.” The situation described by Matthews and Caldeira could be used
to argue that carbon capture and storage will be needed “for at least several
centuries” to avoid continuing elevated temperatures. This would arguably add
weight to the UK government’s case for CCUS development, and so it is important
to ask whether the view presented in the 2008 paper still holds.
Hausfather (2021)
refers to media reports claiming that the world is facing inevitable future
warming regardless of decisions made today and states his view that when carbon
dioxide emissions reach zero, warming is likely to “more or less” stop. He
argues that two concepts have been confused: “a world where CO2 levels in the
atmosphere remain at current levels; and a world where emissions reach net-zero
and concentrations begin to fall.” Earlier climate models did not account for biogeochemical
cycles (including the carbon cycle) and so “could not effectively translate
emissions of CO2 into atmospheric to CO2 concentrations”. Models based on atmospheric
CO2 remaining at current levels predicted additional warming of 0.4C to 0.5C as
ocean temperatures rose towards equilibrium with the atmosphere. By contrast
work published in 2010 predicted no increase in temperature after a sudden fall
to net zero CO2 emissions. Hausfather believes that this stabilisation of
temperature would occur because two opposing factors approximately cancel each
other: most excess atmospheric heat goes into the oceans, but as they continue
to warm they will absorb less heat from the atmosphere, tending to make its
temperature continue to rise; however land and ocean both absorb CO2 from the
atmosphere, and under conditions of net zero emissions atmospheric CO2 will
fall, tending to lower atmospheric temperature. The two opposed tendencies are
initially roughly equal in their effects, but over many centuries of net zero emissions
“carbon sinks would become dominant and global temperatures would eventually
fall”. Modern climate models that include carbon cycle dynamics are known as
Earth system models (ESMs) and Hausfather cites the results of a 2019 study on
a set of different ESMs predicting what would happen if “global emissions
suddenly ceased after the world had emitted a total 3667 Gigatons of CO2 (or
1000 Gigatons of carbon)”. The predicted change in average surface temperature
after fifty years from fifteen simulations lay within a range of approximately
plus or minus 0.3 C, with the majority predicting near zero change. These
simulations focus on the effects of CO2, but other recent studies have included
combinations of CO2 and other greenhouse gasses and also aerosols which mostly have
a cooling effect. These lead to estimates for temperature change in 2100 of between
plus 1.75 C to plus 0.86 C relative to temperatures in 1880-89.
Our long-term
evaluation of carbon capture techniques, and hence what we think we should pay
for them, depends among other things on the competence of the predictive simulations
we use, the inputs we give them, and the temperature rise above the 19th
century baseline that we are prepared to accept, whether permanently or
temporarily. The issues surrounding long-term climate targets are discussed by King
et al. (2022) in a comment paper entitled ‘Preparing for a post-net-zero world’.
Assuming the will and the ability to set a target global temperature, its value
“will depend on whether the priority is to protect the world’s people or to
limit the long-term damage of human activities on ecosystems, the cryosphere
and other Earth systems that determine Earth’s suitability for human
civilization.” The authors point out that these aims may not be mutually
exclusive, but that at present “we do not understand their relationships to each other.” While the
target of a future climate akin to pre-industrial conditions may be a justifiable
aim, there are at present few robust simulations “with net-zero or net-negative
greenhouse gas emissions, despite their clear policy relevance.” The Paris Agreement
“makes no explicit provision for a world beyond net-zero emissions, which
raises the question of the global decision-making process that would apply and
opens the door to competing viewpoints.” The authors call for “efforts to
understand how our greenhouse gas emissions in the next decade may have long-term
consequences in a future cooling planet under net-negative global greenhouse gas
emissions.” Their argument suggests that we should view plans for investment in
CCUS such as those recently put forward by DESNZ and the UK government in a
broader perspective than at present.
References
DESNZ, 2024,
Government reignites industrial heartlands 10 days out from the International
Investment Summit, DESNZ Press Release, 4 October 2024, online, accessed 10
October 2024
Hausfather,
2021, Explainer: Will global warming ‘stop’ as soon as net-zero emissions are
reached? Carbon Brief, online, accessed 16 October 2024
Hydrogen UK,
2023, CCUS-Enabled Hydrogen Production Report, Hydrogen UK, online, accessed 16
October 2024
https://hydrogen-uk.org/wp-content/uploads/2023/09/HUK-CCUS-Enabled-Hydrogen-Production.pdf
IEA, 2024, A
new era for CCUS, IEA, online, accessed 11 October 2024
https://www.iea.org/reports/ccus-in-clean-energy-transitions/a-new-era-for-ccus
King, A. et
al, 2022, Preparing for a post-net-zero world, Nature Climate Change,
online, PDF accessed 18 Oct. 2024
https://drive.google.com/file/d/1mS2AjjAoCtNARmBpMLu49i32EPPOECmI/view?pli=1
Matthews and
Caldeira, 2008, Stabilizing climate requires near-zero emissions, Geophysical
Research Letters, Volume35, Issue4, online, accessed 17 October 2024
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2007GL032388
Politics,
2024, UK to pledge £22bn funding for carbon capture and storage projects –
Friends of the Earth reaction, Politics.co.uk, online, accessed 7 October 2024
Poynting, M.,
and Rowlatt, J., 2024, Will carbon capture help the UK tackle climate change?
BBC News, 4 October 2024, online, accessed 17 October 2024
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