What Is Climate Engineering?
Climate engineering (CE), also known as geoengineering or climate intervention, is generally defined as the deliberate intervention in Earth systems to counteract climate change. Climate engineering remains hypothetical at this point; while research is underway on the science, governance, and ethics of climate engineering, there are currently no efforts to engineer the climate.
Proposed methods of climate engineering is typically divided into two very different kinds of interventions: solar geoengineering and carbon dioxide removal.
What Is Solar Geoengineering?
Solar geoengineering, also known as solar radiation management (SRM), is a proposed method for cooling the planet by reflecting a small fraction of incoming sunlight back into space before it can warm the Earth. This could temporarily slow or even reverse global warming, although using solar geoengineering without reducing greenhouse gas emissions carries severe risks. Solar geoengineering would not directly reduce carbon dioxide levels in the atmosphere, although it could have some indirect effects that could slow the rise in atmospheric levels of carbon dioxide. Prominent proposals for implementing solar geoengineering include injecting tiny particles into the upper atmosphere (stratospheric aerosol injection) or brightening the skies over the open ocean (marine cloud brightening or marine sky brightening).
What Is Carbon Dioxide Removal?
Carbon dioxide removal (CDR) would remove carbon dioxide from the atmosphere and lock it away for decades, centuries, or millennia. This could permanently reduce or even reverse global warming, although CDR is too slow-acting and expensive to make a significant long-term difference unless humanity dramatically reduces its greenhouse gas emissions. Technologies for implementing CDR are sometimes called negative emissions technologies (NETs). Some prominent ideas for NETs include planting massive new forests (afforestation), capturing and sequestering carbon from biomass-fired power plants (bioenergy with CCS or BECCS), spreading crushed rocks over land or the surface of the sea to absorb carbon dioxide from the air or water (enhanced weathering), and building machines that would suck carbon dioxide directly out of the atmosphere and bury it (direct air capture). Similar methods for capturing and storing other greenhouse gases, such as methane, are known as greenhouse gas removal.
What Role Might Climate Engineering Play in Climate Policy?
While some researchers hope that some kind of climate engineering might be a useful addition to the climate policy toolkit, there is a strong consensus that climate engineering is not a suitable replacement for cutting greenhouse gas emissions. Thus, reducing our greenhouse gas emissions and adapting to climatic changes must remain the top priority in climate policy.
Climate engineering remains controversial both because of significant scientific and technological uncertainty and because of the governance challenges and ethical concerns involved in research and any potential deployment.