'Gap' in carbon removal: Countries' plans to remove CO2 not enough

New research involving the University of East Anglia (UEA) suggests that countries' current plans to remove CO2 from the atmosphere will not be enough to comply with the 1.5 ºC warming limit set out under the Paris Agreement.

Since 2010, the United Nations environmental organisation UNEP has taken an annual measurement of the emissions gap -- the difference between countries' climate protection pledges and what is necessary to limit global heating to 1.5 ºC, or at least below 2 ºC.

The UNEP Emissions Gap Reports are clear: climate policy needs more ambition. This new study now explicitly applies this analytical concept to carbon dioxide removal (CDR) -- the removal of the most important greenhouse gas, CO2, from the atmosphere.

The study, published today in the journal Nature Climate Change, was led by the Berlin-based Mercator Research Institute on Global Commons and Climate Change (MCC) and involved an international team of scientists.

"In the Emissions Gap Reports, carbon removals are only accounted for indirectly," said lead author Dr William Lamb, of the MCC Applied Sustainability Science working group.

"After all, the usual benchmark for climate protection pledges is net emissions, ie emissions minus removals. We are now making transparent the specific ambition gap in scaling up removals.

"This planetary waste management will soon place completely new requirements on policymakers and may even become a central pillar of climate protection in the second half of the century."

Co-author Dr Naomi Vaughan, of the Tyndall Centre for Climate Change Research at UEA, added: "Carbon dioxide removal methods have a small but vital role to play in achieving net zero and limiting the impacts of climate change.

"Our analysis shows that countries need more awareness, ambition and action on scaling up CDR methods together with deep emissions reductions to achieve the aspirations of the Paris Agreement."

According to the study, if national targets are fully implemented, annual human-induced carbon removals could increase by a maximum of 0.5 gigatonnes of CO2 (500 million tonnes) by 2030, and by a maximum of 1.9 gigatonnes by 2050.

This contrasts with the 5.1 gigatonne increase required in a 'focus scenario', which the research team depicts as typical from the latest Intergovernmental Panel on Climate Change (IPCC) assessment report.

There, global heating, calculated over the entire course of this century, is limited to 1.5 ºC, and a particularly rapid expansion of renewable energies and reduction of fossil emissions is depicted as the core climate protection strategy.

But, the focus scenario still relies on scaling up carbon removals. The gap for the year 2050 is therefore at least 3.2 gigatonnes of CO2 (5.1 minus a maximum of 1.9).

An alternative focus scenario, also derived from the IPCC, assumes a significant reduction in global energy demand, due to politically initiated behaviour changes as the core element of climate protection strategy.

Here, carbon removals would increase by a more modest amount: 2.5 gigatonnes in 2050. Fully implemented national targets would be close to sufficient when compared to this scenario, with a gap in 2050 of 0.4 gigatonnes.

The research team points out the problem of sustainability limits in scaling up carbon removals; for example, the associated land area demand will come to jeopardise biodiversity and food security. Nevertheless, there is still plenty of room for designing fair and sustainable land management policies.

In addition, novel carbon removal options, such as air filter systems, or 'enhanced rock weathering', have hardly been promoted by politicians to date.

They currently only remove 0.002 gigatonnes of CO2 per year from the atmosphere, compared to 3 gigatonnes through conventional options such as afforestation, and they are unlikely to significantly increase by 2030. According to the scenarios, they must become more prevalent than conventional options by 2010.

Since only 40 countries have so far quantified their removal plans in their long-term low emissions development strategies, the study also draws on other national documents and best-guess assumptions.

"The calculation should certainly be refined," said Dr Lamb. "But our proposal using the focus scenarios further opens the discourse on how much carbon removal is necessary to meet the Paris Agreement.

"This much is clear: without a rapid reduction in emissions towards zero, across all sectors, the 1.5 ºC limit will not be met under any circumstances."

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Consensus needed on when global warming reaches 1.5°C

Writing in the journal Nature ahead of COP28, a team of Met Office scientists has emphasised that -- surprisingly -- there is currently no formally agreed way of defining the current level of global warming relevant to the Paris Agreement.

They have proposed a solution.

While the global average temperature in a particular year is well-known, this will not be suitable as an indicator of whether the "Paris 1.5" has been breached or not, because the Paris Agreement refers to long-term warming, not individual years.

But no alternative has yet been formally agreed.

Without an agreement on what will count as breaching the Paris 1.5, there may be confusion and delay in responding.

Professor Richard Betts MBE, of the Met Office and the University of Exeter, is the paper's lead author.

He said: "Clarity on breaching the Paris Agreement guard rails will be crucial.

"Without an agreement on what actually will count as exceeding 1.5°C, we risk distraction and confusion at precisely the time when action to avoid the worst effects of climate change becomes even more urgent."

New indicators for global warming levels

Some of the current suggested metrics rely on long-term averages -- usually over two decades -- of annual global annual temperature.

Professor Betts added: "Using the average global temperature over the last 20 years would mean we would have to wait ten years to confirm whether the 1.5 °C ceiling has been reached: creating a decade of otherwise preventable delay.

"Today we are recommending an indicator combining the last ten years of global temperature observations with an estimate of the projection or forecast for the next ten years.

"If adopted, this could mean a universally agreed measure of global warming that could trigger immediate action to avoid further rises."

Using this suggested approach, the researchers found that the figure for the current global warming level is around 1.26°C, with an uncertainty range of 1.13°C to 1.43°C.

It is more likely than not one of the next five years will reach or even exceed 1.5°C above pre-industrial levels.

But even an anomalously warm year would not mean that we have reached the first of the Paris Agreement guard rails.

The Earth's climate system has a range of natural variability where the annual temperature fluctuates within small margins.

Professor Betts added: "Using an indicator of several years of observations and projections will smooth out the natural variation to reveal the underlying human-induced warming."

2023 global temperature

Provisional estimates of the global average surface temperature for 2023 suggest the year could be on track to be the warmest on record.

The year is likely to exceed the level reached in 2016; currently the warmest year on record.

2023 is expected to continue the run of the warmest years on record since 1850.

Beginning in 2015, the series includes years at both ends of natural climate variability.

Some years, like 2016 and 2023, will have been naturally warmer because of the influence of El Niño -- when a natural warming of parts of the tropical Pacific warms the planet temporarily by a small margin.

But the series also includes years which should have been naturally marginally cooler.

Professor Betts concluded: "The fact that the warmest years on record include both the highs and lows of natural climate variability is yet more evidence that climate change driven by human-induced greenhouse gas emissions dominates the recent climate record."

Global warming dashboard

To complement the newly proposed indicators, a new section has been added to the Met Office Climate Dashboard to illustrate the current level of global warming.

The 'Indicators of Global Warming' dashboard displays eight separate indicators as well as observed global mean temperature using Met Office HadCRUT5 data.

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