Last week, more than 260 researchers convened in Milan to discuss the opportunities, challenges and risks involved in scaling “carbon dioxide removal” (CDR) to help curb climate change.
The conference – held on the campus of the Politecnico di Milano – is the fourth in a series, with previous editions held in Oxford, UK in 2024 , and Gothenburg, Sweden in 2018 and 2022.
A broad range of academics – from forests, oceans and soils experts through to social and political scientists – discussed the co-benefits and trade-offs involved in drawing down CO2 from the atmosphere at scale, as well as the ways policy could drive CDR deployment.
Dr Soheil Shayegh , director of the industrial and planetary carbon cycle programme at the Euro-Mediterranean Center on Climate Change (CMCC), told Carbon Brief the idea behind the conference was to “bring scientists together to convey a message to policymakers about where the technology stands”.
He continued: “We should be very clear that there still are huge uncertainties about the effectiveness of lots of this CDR technology – are they marketable or not? But what is clear for us is the need for CDR.”
Dr Morgan Edwards , the lead author of the recently published “ state of CDR report ”, told delegates that meeting the Paris Agreement’s 1.5C goal by the end of this century would require CDR to “scale up rapidly” from 2.2bn tonnes of CO2 (GtCO2 per year) today to 8.8GtCO2 by 2050.
She added: “We need to see an upscaling in ambition over the next few years to get on a track consistent with these long-term scenarios.”
Below, Carbon Brief summarises the key talking points at the conference.
Overshoot
The removal of carbon from the atmosphere is seen as crucial to compensate for the emissions from human activities that are difficult to decarbonise – for instance, those generated in aviation and agriculture.
This, scientists have emphasised , must come in addition to steep emissions cuts.
CDR has another role, which is as a mechanism to return average global warming to 1.5C above pre-industrial levels, in the likely event that the Paris Agreement ’s temperature target is exceeded.
The Milan conference comes after 2024 was the first single year to breach the 1.5C target and as scientists have projected that the Paris Agreement’s 1.5C target – typically interpreted in terms of a 20-year average – could be exceeded by the end of this decade .
Prof Sabine Fuss , head of research department at the Potsdam Institute for Climate Impact Research (PIK) told Carbon Brief the likely breach of the 1.5C limit means the CDR research agenda was getting “even bigger” as the world would need to contend with “even larger scales” of CDR. She added:
“Some of the things that we were worrying about already in a net-zero context are getting even more pertinent. Also, [we need to think about] what will happen under climate change. A lot of [CDR approaches] may not be super resilient if we’re facing higher temperatures and more disturbances. Think about forests.”
Prof Massimo Tavoni , scientific director of the RFF-CMCC European Institute on Economics and the Environment , described the prospect of returning temperatures to 1.5C with CDR as the “biggest Earth restoration project ever”.
Speaking in the plenary, Tavoni said the concepts of “overshoot” and “CDR” were “closely connected, but not the same thing”.
Broadly speaking, there have been three “phases” of overshoot research, Tavoni said:
1995 to 2005: a period where overshoot was not “seriously considered”, he argued. It was during this period that researchers first explored scenarios that would “now be classified as overshoot pathways” and “set out CO2 removal as a mechanism” for stabilising the climate, he said.
2005 to 2015: the age when “overshoot was discovered”, according to Tavoni. At this time, he said, “[climate] ambition was rising and emissions were also rising, which led to the incorporation of CDR in the models”.
2015 to the present day: an “age of reckoning” where overshoot has become “formally entangled” in the scenarios created by the climate community due to the “absolute need for overshoot and CDR to achieve [temperature] targets in the face of growing CO2 concentration”.
Tavoni noted that all of the new emissions scenarios set out ahead of the seventh phase of the Coupled Model Intercomparison Project (CMIP7) – unveiled in April – exceeded the 1.5C limit.
(CMIP is a global initiative that coordinates the work of dozens of climate modelling centres around the world, recommending a common set of model experiments that can collectively shed light on the climate and how it could change.)
Half of the CMIP7 scenarios, Tavoni said, first “overshoot” the 1.5C goal and then “return back”.
The indicative global temperature rise under these seven scenarios is shown in the chart on the right below.
(For more on CMIP7 and the emissions scenarios, see Carbon Brief’s recent guest post ).
The greenhouse gas emissions f…
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