‘The tricky thing, especially with nature-based options, is the challenge of permanent storage of carbon,’ said Spijker. ‘Once you submit carbon to ecosystems, they remain in the natural carbon cycle to a certain degree, but you don’t really know how much is stored and for how long.’
Observation from above and below
Monitoring techniques can help assess how much CO2 could be captured from the atmosphere and stored in the soil and plants. One of the project goals is therefore to incorporate different types of observations into models, to more realistically portray the potential of emission-removing solutions.
‘We use data from a combination of Earth observation techniques, including remote sensing (such as satellites) and also below-ground measurements (such as soil sampling) to measure the amount of carbon stored,’ said project coordinator Dr Jenny Lieu, an assistant professor at Delft University of Technology in the Netherlands.
LANDMARC is running 16 case studies across the world, where different activities like agroforestry in Spain and more sustainable rice production in Nepal will be monitored, to see how well they sequester carbon. The team plans to experiment with different combinations of monitoring techniques. Satellite data will be collected and analysed with algorithms they have developed, for example.
A tool to measure net climate impact on the ground
One of the outcomes of the project will be a carbon map tool, potentially also available as a phone app, that can quantify and monitor the impact of different land-based carbon removal activities on greenhouse gas emissions. It will use observations both from above, using satellites and drones, and on the ground, like soil sampling.
‘We’re aiming to combine several specialised Earth observation tools in a low-cost and user-friendly monitoring tool that considers a wide range of end users,’ said Dr Lieu. This means governments or land-use managers, for instance, will be able to enter site-specific data about the soil and vegetation on their land and get a reliable estimate of its net climate impact.
Large-scale CO2 removal
The potential of negative emission activities to slow down global warming also depends on whether they will be ready for use on an industrial scale in the next few decades. Many climate scenarios rely on this premise, but there are concerns over how feasible this will be. Technological solutions are still in their early stages at the moment, said Dr Bas van Ruijven, a researcher and group leader at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria.
Dr van Ruijven and his colleagues are therefore assessing feasibility concerns for different climate scenarios, as part of the ENGAGE project. For example, they will assess how greenhouse gas removal activities are expected to contribute. The team will also develop new climate mitigation scenarios. ‘Negative emission technologies play a large role in that part of the project,’ stressed Dr van Ruijven.
So far, the team has been comparing two different decarbonisation scenarios. The first aims to limit warming to below 2OC by 2100. In this case, the temperature target can be overshot in the first half of the century, but negative emissions would be essential later on to bring global temperatures back down.
In the second scenario, the goal is simply not to exceed the 2OC warming, which is more in line with the Paris Agreement. Carbon removal activities would play a role in reducing emissions more quickly in the short term. In the long term, they would mostly be needed to counteract remaining emissions from certain sectors such as aviation or industry, where it is hard to completely eliminate emissions.
Sooner is better: putting off action will have repercussions
In recent work, the team used models to investigate how each of these scenarios would impact land use in the future to better understand social and environmental consequences. They took into account several different factors: economic projections and population growth, along with their subsequent impact on energy use and greenhouse gas emissions.
Dr van Ruijven and his colleagues found that mitigation scenarios that focused on end-of-century scenarios, where temperatures were allowed to temporarily overshoot 2OC warming, had major consequences for land use after 2050. Shortages in food and irrigation water would be likely, as would higher food prices. ‘It’s a big call for more near-term efforts to bring emissions down faster,’ said Dr van Ruijven. ‘Otherwise you force future generations to use negative emission technologies at a larger scale.’
Additional policies will also be needed during the transition to net zero emissions to compensate for its social impact. Food subsidies may be necessary to help people on lower incomes, for example, if food prices rise.
‘Our work shows that deploying new technologies for CO2 removal will, however, be indispensable to achieve the goals of the Paris Agreement in both short- and long-term approaches, noted Dr van Ruijven. ‘Hopefully, our research will inspire governments to stimulate their development.’
The research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.