Diversification reduces risk. That’s the spirit of one of the key takeaways from a new study led by scientists at the Department of Energy’s Pacific Northwest National Laboratory. An effective path to limiting global warming to 1.5°C by the end of this century will likely require a combination of technologies that can pull carbon dioxide out of the Earth’s atmosphere and oceans.
The authors warn that over-reliance on any method of carbon removal could lead to undue risk. We would most likely need them all to remove the necessary amount of carbon dioxide — 10 gigatonnes per year — to secure just 1.5 degrees of warming by 2100.
New work published today in the journal The nature of climate change, identifies the carbon removal potentials of six different methods. They range from restoring deforested land to spreading crushed rock across the landscape, a method known as enhanced weathering.
This study represents the first attempt to integrate all CO2 removal approaches recognized by US legislation into a single integrated model showing how their interactions can be measured on a global scale. It does so while showing how these approaches can affect factors such as water use, energy demand, or available cropland.
The authors explore the potential of these decarbonisation methods by modeling decarbonization scenarios: a hypothetical future that shows the kind of interactions that could emerge if the technologies were deployed under different conditions. They are exploring pathways, for example, where no climate policy is in place (and warming rises to 3.5 degrees as a result).
The second pathway shows how much carbon must be removed using technologies within an ambitious policy framework in which carbon emissions are constrained to net zero by mid-century and net negative by the end of the century to cap the end of the century. Horn warming to less than 1.5 degrees.
The third scenario follows the same emissions trajectory but is combined with behavioral and technological changes, such as reduced material consumption and faster electrification. In this scenario, these societal changes translate into lower overall emissions, which helps reduce the amount of remaining greenhouse gas emissions that must be offset by decarbonization to achieve the 1.5° target.
To achieve this goal – the original goal of the Paris Agreement – the authors found that approximately 10 gigatonnes of carbon dioxide must be removed annually. This amount remains the same even if countries increase their efforts to reduce carbon dioxide emissions from all sources.
“Getting us back to 1.5 degrees by the end of the century will require a balanced approach,” said lead author PNNL scientist Jay Foreman, whose work stems from the Joint Global Change Research Institute. “If one of these technologies fails to deliver or scales up, we don’t want too many eggs in that basket. If we use a globally diverse set of decarbonization strategies, we can mitigate risks while mitigating emissions.”
Some technologies are expected to contribute significantly, with the potential to remove several gigatonnes of carbon dioxide per year. Others offer less, but still remain to play an important role. For example, improved weathering could remove up to four gigatonnes of carbon dioxide annually by mid-century.
Under this method, finely ground rocks spread over farmland convert carbon dioxide in the atmosphere into carbonate minerals on the ground. It is among the most cost effective methods identified in the study.
By comparison, direct ocean capture through carbon storage, where carbon dioxide is stripped from seawater and stored underground, would likely remove much less carbon. According to the authors, this emerging technology is very expensive in and of itself. However, pairing this method with desalination plants in regions where the demand for desalinated water is high can lower the cost while providing more meaningful carbon reductions.
In addition to the above removal methods, technologies under study include biochar, direct air capture with carbon storage, and bioenergy combined with carbon capture and storage.
Each of the technologies that has been designed brings unique advantages, costs and consequences. Many of these factors are associated with specific regions. The authors point to sub-Saharan Africa as an example, where biochar, enhanced weathering and bioenergy with carbon capture and storage can contribute to significant reductions.
However, the authors found that much more work is needed to address greenhouse gases other than carbon dioxide, such as methane and nitrous oxide. Many of these are non-CO2 The gases are several times more powerful while at the same time more difficult to target than carbon dioxide.
While some of the removal methods examined in the new paper are well-studied, their interactions with other, newer methods are not clearly understood. The work comes from the Joint Institute for Global Change Research, a partnership between PNNL and the University of Maryland where researchers explore interactions between human, energy, and ecosystems.
Their work focuses on anticipating the trade-offs that may flow from a range of potential decarbonization scenarios. The authors seek to better understand how these approaches interact so that policymakers are informed in their decarbonization efforts.
“This study underscores the need for further research on carbon dioxide removal approaches and their potential impacts,” said corresponding author and PNNL scientist Haewon McJeon. “While each approach has its own unique benefits and costs, a variety of CO2 removal approaches are essential to effectively address climate change. By better understanding the potential impacts of each approach, we can develop a more comprehensive and effective strategy for reducing greenhouse gas emissions and reducing global warming.” Global Warming “.
In addition to Fuhrman and McJeon, PNNL authors include Candelaria Bergero and Maridee Weber. Seth Monteith and Frances M. Wang from ClimateWorks, as well as Andres F. Clarens, Scott C. Doney, and William Shobe from the University of Virginia, contributed to this work. This work was supported by ClimateWorks, the Alfred P. Sloan Foundation, and the University of Virginia’s Environmental Resilience Institute.
