Geoengineering Alone Will Not Slow Climate Change

The global countries will need to make more drastic changes to reduce their carbon dioxide emissions in order to meet the climate targets set in the Paris Agreement.

Relying solely on planting new trees and technological solutions such as geoengineering will not be enough to prevent global temperatures from rising to 2 °C, according to a new study.

“We can’t rely on geoengineering to meet the goals of the Paris Agreement,” states Helene Muri, a researcher from NTNU’s Industrial Ecology Programme, and one of the lead authors of a new article published in Nature Communications that analyzed different climate geoengineering projects in the context of reducing global warming.

The Earth’s average temperature is increasing. It has been proposed by the UN Intergovernmental Panel on Climate Change (IPCC) that this warming should be limited to less than 2 °C, and better yet to less than 1.5 °C. These climate targets were established in the 2015 Paris Agreement, which was endorsed by almost all nations.

Among the solutions being considered are different geoengineering options. These options involve intervening directly in the climate system of Earth so as to prevent the temperatures from rising as much as would otherwise occur owing to the increasing amount of atmospheric greenhouse gases. Geoengineering involves reducing the effect of the sun or reducing the CO₂ levels in the atmosphere.

Untested, uncertain, and risky

Is it possible to eliminate the atmosphere greenhouse gases with the aid of technology, or capture more amounts of CO₂ by planting a countless number of trees? Can more of the sun’s radiation be reflected by administering particles into the atmosphere?

Several techniques could help to limit climate change. But they’re still untested, uncertain and risky technologies that present a lot of ethical and practical feasibility problems.”

Helene Muri

In brief, the researchers say that there is a lack of understanding about these technologies as well as a lack of knowledge of what might occur if these are put to use.  

Stumbling blocks

For instance, when trees are planted, it triggers major political issues. A large section of forest land has been cut for growing food, which restricts the amount of acreage that can be reforested.

In addition, a recent study raised the question as to whether or not temperatures can be predictably lowered with additional forest land. NTNU and Giessen University provided data simulations which demonstrate that there may be a rise in temperatures, at least locally.

The use of biochar is another mitigation proposal. Biochar is a charcoal that can be tilled into the ground for storing carbon that otherwise would escape as CO₂ into the atmosphere. Here, the question is whether this can be performed on a sufficiently large scale to make a viable difference. There was hardly any consensus from the researchers.

How about spurring phytoplankton blooms to sequester carbon by adding nutrients to the sea? In this proposal, iron-poor regions of the ocean have to be fertilized.

Yet, there could be huge potential side effects, disturbing local nutrient cycles and possibly even boosting the production of another greenhouse gas, N₂O.

There is no clear idea yet. There are some possible solutions that might even do more harm than good. As a result, more discussion and learning are encouraged by the article authors.

NETs and airy plans

Negative emissions technologies, which are usually abbreviated as NETs allow atmospheric greenhouse gases, particularly CO₂, to be removed. While some of these recommended methods may work well on a global scale, they are very costly and the technology is still in its infancy.

Prototypes already exist for capturing carbon directly from the air. Although this technology shows immense promise, it would require a lot of energy and substantial infrastructure to become a reality.

In addition, cost estimates can range anywhere between $20 to over $1000 per ton of captured CO₂. If one considers that the global countries emitted over 40 billion tons of CO₂ in 2017, it readily becomes clear that it would be prohibitively expensive to fund this approach.

Regular refills would be needed to add particles to the air and perhaps drones or planes dedicated to the task. While this might appear to be a feasible concept, the side-effects are not clear. And thus this continues for one possibly grand proposal after another.

To sum up, these concepts are merely too little, too late - or too costly.

None of the proposed techniques can realistically be implemented on a global scale in the next few decades. In other words, we can’t rely on these technologies to make any significant contribution to holding the average temperature increase under the 2 degree C limit, much less the 1.5 degree limit."

Mark Lawrence, Lead Author

No substitutes for cutting emissions

The Paris Agreement’s 2 degree C goal could still be salvaged through emission reductions, but the challenge in meeting this objective is that the planet’s growing population, which has also witnessed a gradual increase in the standard of living, will need to lower the amount of greenhouse gases being released into the atmosphere compared to the present times.

Some form of geoengineering is included in most of the IPCC scenarios; this usually include bioenergy and afforestation, combined with capture and storage of carbon, particularly if the objective is to limit the rise in temperature to 1.5 degrees towards the end of this century.

Solutions other than clear-cut emissions reductions should not be relied upon, warn the researchers behind the study. Or else, technological solutions might be viewed as alternatives for reducing carbon emissions, which they are not.