Negative emissions: a special issue of Climatic Change with the contribution by CMCC

What is the role of future technologies, which eliminate more CO2 from the atmosphere than is absorbed in the natural carbon cycle? Climatic Change, a prestigious journal, has devoted a special issue to this topic, which is extensive in multidisciplinary analyses regarding the potential negative impact of emissions on the management of climate change in the coming decades. However, those who think that these technologies will enable us to continue emitting greenhouse gases at the same pace that we have been used to for half a century will have to revise their assessments. CMCC has made a vital contribution to this important publication: Massimo Tavoni and Professor Socolow from Princeton University have edited the entire special edition. Tavoni and Chen Chen are also the co-authors of an article regarding the effects of the application of special technologies to remove CO2 from the atmosphere. Marcello Vichi, Antonio Navarra, and Pier Giuseppe Fogli have endorsed a study on the adaptation of the natural carbon cycle through the application of geoengineering techniques.

If the excess greenhouse gases in the atmosphere are responsible for climate change, there are essentially two solutions to ensure that in the coming decades the concentration of these substances decreases: to produce smaller quantities and second, to study and use methods to remove more CO2 from the atmosphere than is absorbed through the natural carbon cycle in the oceans, vegetation and soil. A second option is referred to as “negative emissions”; the systems which allow some greenhouse gases to be absorbed, reducing their concentration in the atmosphere and therefore the effects on the climate.

The prestigious journal, Climatic Change, has devoted a special issue to negative emissions, with a particular focus on the integrated work of modeling experts whose studies analyze mathematical models for the integrated assessment of possible future scenarios. This issue also highlights scientists whose analyses focus on the specific effects of the CO2 removal systems from various viewpoints of different disciplines.

Edited by Massimo Tavoni (Euro-Mediterranean Centre on Climate Change – CMCC), and Robert Socolow (Princeton University), this collection brings together contributions which consider the objectives of the concentration of greenhouse gases that are in line with an increase in the average temperature of the Earth’s surface between 2 and 2.5 °C, and analyze the possible results of CDR strategies (Carbon Dioxide Removal). After having presented assessments on what we can expect from the application of such methods in the scenarios considered, the authors of the following articles address the issue from the viewpoints of ecology, the study on the carbon cycle, chemical engineering, and political science. The result is a multidisciplinary analysis that sheds light on many aspects of the complex issue. This might be a bit of disappointment for those who believe that the problem of having to reduce greenhouse gas emissions over the next few decades can be overcome only with CDR technologies.

From the studies presented in the special issue written by Tavoni and Socolow, it follows that, when considering emission reduction strategies that require commitments to be made in the early decades of the century in order to maintain a CO2 equivalent (CO2e) concentration at the end of the century, the models show that a high decarbonization of global economy is needed, particularly in the energy sector.

CDR methods and technologies appear to be competitive only further down the road, for instance, when, as a consequence of implementing conventional mitigation strategies, a considerable part of the emission reduction is reached. In fact, these techniques appear to be effective only after the surplus of CO2 emissions from fossil fuels has been eliminated to a large extent. Even in this case, the reduction of concentration would progress very slowly (approximately 1 ppm l a year, which means that to lower the concentration of 550 ppm CO2e to 450 ppm, it would take about a century).

Finally, in this Climatic Change issue, it is clear from the research analyses that climate change research cannot forgo the multidisciplinary dimension, which combines different and necessary viewpoints for the study of such complex issues.  In this volume, in fact, the interdisciplinary dimension in the collection explains how the CDR technologies can play an effective role when integrated with other mitigation strategies that aim to reduce greenhouse gas emissions. Alternatively, the benefits produced by the removal of carbon dioxide from the atmosphere might be overcome by negative consequences on environmental and social conditions, such as the overexploitation of soil and water resources or the release of CO2 from the oceans.

The Italian contribution to CMCC’s special issue of Climatic Change “Carbon Dioxide Removal from the Atmosphere: Complementary Insights from Science and Modeling”

The article, “Adjustment of the natural ocean carbon cycle to negative emission rates” is devoted to the second topic, written by CMCC scientists: Marcello Vichi, Antonio Navarra and Pier Giuseppe Fogli. The authors use a series of Earth System Models to study the adaptation of the natural carbon cycle to CDR simplified strategies that take into account the objective value of fixed atmospheric CO2, or a defined negative annual amount of emissions so as to achieve a given reduction of CO2 in the atmosphere. The simulations show that the removal of CO2 from the atmosphere through CDR would result in the release of CO2 from the oceans, and therefore the effectiveness of strategies for negative emissions would decrease, thus increasing the need for CO2 removal from the atmosphere.

The simulations also show that the actions of CDR must always consider an extra release of anthropogenic carbon from the ocean accumulated by previous emissions and therefore necessarily increases the need for the removal of CO2 from the atmosphere, which has to be planned.

Chen Chen and Massimo Tavoni (both CMCC), in the article entitled “Direct air capture of CO2 and climate stabilization: A model-based assessment” focus their attention on a specific method of CDR: the direct capture of CO2 from the air by chemical processes. By using the WITCH model, which integrates the aspects of energy, economics and the climate, the authors analyze the long-term prospects of this particular system of removing CO2 from the atmosphere in two different scenarios evaluating their effects on energy markets, on the implementation of socio-economic low-carbon content and the strategies used to reduce the concentration of greenhouse gases in the atmosphere.

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