The new IPCC report Climate Change 2022: Mitigation of Climate Change has brought carbon removal to the centre stage of climate mitigation as an essential and unavoidable tool to achieve net-zero GHG emissions.

Every five to seven years, the IPCC publishes comprehensive scientific assessment reports. Their previous, Fifth Assessment Report (2014), provided the main scientific input to the Paris Agreement. Since then, the IPCC has published three Special Reports: on Global Warming of 1.5°, Climate Change and Land, and Ocean and Cryosphere.

The upcoming Sixth Assessment Report (AR6) consists of the three Working Group contributions (published) and a Synthesis Report (due in September 2022), which integrates the Working Group assessments and the three Special Reports (listed above) produced during the cycle.

Let’s have a closer look at the most recent contribution to AR6 that was published on 4 April 2022 – Climate Change 2022: Mitigation of Climate Change – and how this report is shaping the carbon removal narrative, terminology and categorisation.

Carbon removal definition – strong and consistent

The definition of carbon dioxide removal that the IPCC introduced in their Special Report on 1.5° has been kept the same in the new report: “CDR refers to anthropogenic activities that remove CO2 from the atmosphere and store it durably in geological, terrestrial, or ocean reservoirs, or in products.”

Narrative change – the three objectives of carbon removal

Whilst the Special Report on 1.5° listed two key objectives or roles for carbon removal, the 2022 Mitigation of Climate Change refines the language and introduces a third, near-term objective. This has featured in literature before – synthesising existing literature is what the IPCC reports do – and will undoubtedly play a strong role in the carbon removal advocacy space in years to come.

Here are the three roles of carbon removal outlined in the new IPCC report.

“CDR methods” wins the terminology competition

Today, there is no commonly agreed practice on how to refer to activities that remove CO2 from the atmosphere. CDR approaches, options, solutions, systems, techniques, measures and methods have often been used interchangeably. The IPCC Special Report on 1.5° mostly used “CDR measures”. The flagship report CDR Primer (2021) chose “CDR approaches” for their terminology and I’ve been using it ever since. The third instalment of the AR6, however, uses “CDR methods” almost consistently throughout the 2913 pages. Sounds great!

The term “negative emissions” is not interchangeable with carbon removal. It is used “only when referring to the net emissions outcome at a systems level (e.g., net negative emissions at global, national, sectoral or supply chain levels).” This is a practical approach and clarifies the relationship between carbon removal (an activity that removes CO2) and “net negative emissions” (describing negative carbon flows on systems-level).

Carbon removal categorisation – will the “nature vs technology” be finally sidelined?

The IPCC Special Report on 1.5° divides carbon removal methods based on the removal process into natural and chemical. This wasn’t widely adopted. Instead, the most common way of categorising carbon removal methods has been between natural vs technological, or at times natural vs mixed vs technological. Such categorisation is unhelpful for a wide range of reasons, including the fact that what is natural or technological, is still interpreted very differently by stakeholders.

The world of carbon removal methods is very broad. There is so much more than the usual suspects that have received the most attention so far. Many methods combine a wide range of solutions or technologies within them. I’m yet to see a take where emission reduction technologies are squeezed into natural vs technological categories. Why should we keep doing the same with carbon removal methods?

The new IPCC Report builds on the categorisation based on the removal process and on the timescale of storage as described below.

The categorisation is based on the role of CDR methods in the carbon cycle, i.e., on the removal process (land-based biological; ocean-based biological; geochemical; chemical) and on the timescale of storage (decades to centuries; centuries to millennia; ten thousand years or longer).

Let’s see if this taxonomy will be picked up more widely and used to replace the commonplace but less than ideal “nature vs technology”. From the communication perspective, it does make the picture more complex. However, it does an excellent job characterising the wide range of methods.

The two net-zeros

Net-zero greenhouse gas emissions can only be achieved after achieving net-zero CO2 emissions. I’ve written about it previously and it’s useful to have this clarified in writing in the new IPCC Report. A steep scale-up of removals is needed on the road to net-zero GHG emissions because one step on that path is achieving net-zero CO2 emissions. For example, for Europe to achieve climate neutrality by 2050, it will need to achieve net-zero CO2 emissions sometime around 2040.

“For most choices of GHG emissions metric, reaching net-zero GHG emissions requires net negative CO2 emissions in order to balance residual CH4, N2O and F-gas emissions. Under foreseen technology developments, some CH4, N2O and F-gas emissions from, e.g., agriculture and industry will remain over the course of this century. Net negative CO2 emissions will therefore be needed to balance these remaining non-CO2 GHG emissions to obtain net-zero GHG emissions at a point in time after net-zero CO2 has been reached in emissions pathways. Both the amount of net negative CO2 emissions and the time lag to reaching net-zero GHG depend on the choice of GHG emission metric.”

Working Group III contribution to the IPCC AR6, 2022​

Final Words

The new IPCC report Climate Change 2022: Mitigation of Climate Change has done what was expected – outlining how mitigation can address climate change, based on the most recent literature. Having this thorough analysis of literature is imperative for areas where many new solutions have emerged or developed further over the last decade. This report brought carbon removal to the centre stage of climate mitigation as an essential and unavoidable tool to achieve net-zero GHG emissions.

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