We Need to Talk More About Carbon Dioxide Removal

CO₂ emissions continue to rise, according to the Global Carbon Budget. The average temperature for 2024 was 15.1 degrees Celsius. This is a record high, and 1.6 degrees above pre-industrial levels (the average temperature for 1850-1900).

This means that 2024 was the first year with global warming exceeding 1.5 degrees.

Does 1.5 degrees sound familiar? In the Paris Agreement, the world's countries agreed to keep global warming to well below 2 degrees, ideally below 1.5 degrees. The purpose of limiting warming to 1.5 degrees is to avoid tipping points in the climate system, i.e., climate changes that cannot be reversed. Additionally, there can be significant differences in the damages caused by climate arming, such as due to extreme precipitation, by keeping global warming below 1.5 degrees instead of 2 degrees.

Most climate researchers, however, agree that the goal of 1.5 degrees has already become unrealistic after many years without emission cuts.

One of these climate researchers is Jörg Schwinger. He, along with his NORCE colleague Siv Kari Lauvset, has contributed to the Global Carbon Budget. He finds news about record hot years or months litle interesting.

– We know that, as long as we emit CO₂, it will get warmer. Without the variability in the Earth system, for example due to El Niño/La Niña, which makes one year occasionally colder than the previous year, every single year would be warmer than all the previous ones, thus 'record warm,' he says.

Schwinger prefers to talk about something he finds difficult to communicate: Carbon Dioxide Removal. Schwinger and other climate researchers use the abbreviation "CDR," and for simplicity, we will use it in this article as well.

A Hot Topic Among Climate Scientists

CDR is much discussed among climate researchers. CDR removes CO₂ from the atmosphere, either through nature-based solutions like afforestation or reforestation and ocean alkalinization, which enhances the ocean's ability to absorb CO₂, or through technological solutions like capturing CO₂ directly from the air, known as 'direct air capture'. But this will not save us from the climate crisis.

– People often have the idea that CDR can save us and therefore we don't need to do anything about our emissions. That's not the case. CDR is very expensive and has too little capacity to make a significant difference with today's emission levels. First, emissions must be reduced — something we should have started working on 30 years ago. The problem has accumulated over the last 30 years. The carbon budget for 1.5 degrees is almost used up. We have been asleep at the wheel. This is why we talk a lot about CDR, he states.

On one hand, CDR does not help in today's situation where emissions are as high as they are. But on the other hand, we know there are emissions that are difficult to avoid. This is where CDR becomes relevant.

– In a perfect world, we cut emissions so that in 20 years we have almost zero emissions. There will still be some emissions that are difficult to eliminate. For example, from cement production. Here, CDR will be relevant to use. But if we want to use it on a large scale in 20 years, we need to start researching it now and develop it, so it is 'fully researched' when we need to use it.

An Uncomfortable Situation

For every ton of CO₂ we emit, the temperature rises.

– Emissions of 1000 gigatons of carbon make the Earth approximately 1.65 degrees warmer. This temperature increase remains for a very long time. It's not like you emit CO₂ and then it gets warmer for a period and then it cools down by itself. Global warming is proportional to all accumulated CO₂ emissions. This means that we can emit a certain amount of CO₂ before we reach the 1.5 degree limit. Once that quota is used up, we will exceed that temperature, unless we reduce emissions to zero, explains Schwinger.

Emissions that are difficult to avoid occur, for example, when producing food and cement. During cement production, emissions occur because it is a chemical process that releases CO₂. There is hope that these types of emissions can be removed with CDR, either directly at the emission source with CCS (carbon capture and storage) or through other methods such as afforestation/reforestation, bioenergy combined with CCS, or ocean alkalinization.

– In areas that have been deforested, there is potential for tree planting. For example, the rainforest that has been deforested for food production. Here, it might be possible to plant trees again, and these trees can absorb CO₂. But then it becomes a question of food security. It might work on a small scale, but the question is whether it works on a large scale. Finally, it is a question of climate justice, since those living in tropical areas have not contributed much to carbon emissions historically.

Multiple Technologies Exist

Schwinger emphasizes that we are still in a phase where several different CDR technologies have been proposed to help solve the climate crisis. But it is too early to bet on one or two because we do not know which works best. We will likely need to use several CDR methods simultaneously. Schwinger himself is involved in two EU projects, OceanNETs and RESCUE, where he, along with colleagues, will simulate how much four different technologies can contribute to removing CO₂.

These include afforestation/reforestation, bioenergy combined with CCS, ocean alkalinization, and 'direct air capture' with permanent storage underground.

– We know that ocean alkalinization can work. For example, rivers and streams have been limed in Norway since the 1970s and 80s, primarily to protect ecosystems from the consequences of acid rain, but this also has the effect of the ocean absorbing more CO₂ while reducing ocean acidification. Ocean alkalinization is very expensive, and there are many questions related to it. The same applies to the other technologies. I think it will take a long time before one of these methods can be used to remove significant amounts of CO₂ from the atmosphere, concludes Schwinger.