Large-Scale Climate Interventions: Carbon Dioxide Removal and Solar Radiation Management - Book Chapter

[Geoengineering News]

https://link.springer.com/chapter/10.1007/978-3-031-82869-0_11

Authors: Walker Raymond Lee, Douglas MacMartin & Amanda Borth 

23 August 2025

Abstract

Chapter 11 explores the question: is anthropogenic climate change fixable? This exploration considers whether large-scale human interventions can mitigate the effects of human-induced increases in atmospheric greenhouse gas concentrations, with a focus on two potential strategies: carbon dioxide removal (CDR) and solar radiation management (SRM). Both of these strategies are designed to eliminate the present imbalance in Earth’s energy budget. CDR directly offsets carbon emissions, but present technologies are not well-developed or economically feasible at the necessary scale. SRM is designed to alter Earth’s energy balance, either by reducing the amount of incoming solar radiation (e.g., by increasing the abundance of certain types of clouds) or by increasing the amount of long-wavelength radiation that escapes the atmosphere (by reducing the abundance of other types of clouds). Implementing SRM is likely to have unintended and potentially unwanted consequences on natural systems and human societies. Much more research – and consultation with potentially impacted groups – is needed before large-scale implementation of either CDR or SRM.

Key Take-Away Points

It is very likely that carbon emissions will cause global warming to exceed the 1.5 °C threshold prescribed by the 2015 Paris Climate Agreement. Based on recent emissions trends, the planet is on track for 2–4 °C of warming by the year 2100.

The surface temperature of the Earth is determined largely by the planet’s energy balance: the fluxes of radiation into and out of the Earth system. The two main components of the energy balance are the shortwave energy from the Sun and the longwave energy emitted by the Earth.

Carbon emissions warm the planet by reducing the amount of longwave radiation that can leave the planet, and this is causing surface temperatures to rise.

Any proposed attempt by humans to modify the Earth’s energy balance in order to cool the planet would be a climate intervention or geoengineering. Climate intervention proposals fall into two broad categories: carbon dioxide removal (CDR) and solar radiation management (SRM).

CDR proposals aim to remove carbon dioxide from the atmosphere through photosynthesis or through chemical reactions that produce carbonate compounds.

CDR directly offsets carbon emissions, and at a large enough scale, CDR could reduce or eliminate global warming. However, the technologies are immature and often compete with each other (e.g., for land), and there is currently no technology that can be implemented economically at the necessary scale.

SRM aims to alter the Earth’s energy balance by scattering particles into the atmosphere. Stratospheric aerosol injection (SAI) and marine cloud brightening (MCB) would reduce the amount of sunlight reaching the surface, while cirrus cloud thinning (CCT) would increase the amount of longwave energy leaving the atmosphere.

SRM would cool the planet, but it would not directly counteract the mechanism by which carbon emissions warm the planet, and therefore “global warming + SRM” would not produce the same climate state as “reduced greenhouse gas emissions”. SRM would have unintended and possibly unwanted consequences, which could include changes to circulation and precipitation patterns and impacts to ecosystems.

The three proposed methods of SRM are understood to varying degrees, but any of them would introduce a host of physical, political, and ethical complications.

Substantially more research is required to determine the roles that CDR or SRM could play in responding to climate change.

To make informed decisions, it is essential that entities with decision-making power, such as governments and corporations, engage with publics, stakeholders, and communities directly impacted by climate intervention decisions.

Source: Springer Nature Link