Geoengineering

Geoengineering is large-scale intervention in the Earth system to counteract human-induced climate change. There are two main types of geoengineering approaches:

• carbon dioxide removal (CDR), and
• solar radiation management (SRM).

Carbon dioxide removal

CDR acts on the cause of global warming by reducing the amount of carbon dioxide in the atmosphere and storing it, thereby reducing the greenhouse effect.  For example, carbon dioxide could be captured and stored by ‘artificial trees’, large-scale planting of biomass or fertilising the ocean.

Solar radiation management

SRM aims to reflect sunlight away from the Earth, thus cooling the planet and counteracting the impact of increased greenhouse gas concentrations. Rather than acting on the cause of the problem, SRM would treat one of its symptoms. Suggested techniques have included putting massive ‘sunshades’ in space, injecting aerosols into the stratosphere, making clouds more reflective or increasing the ability of the Earth to reflect sunlight e.g. with reflective roofs or desert coverings.

Simulations

Simulations using state-of-the-science global general circulation models have demonstrated that SRM techniques have the potential to significantly reduce global average temperatures. Although the results depend on the parameters and assumptions used in the models, they suggest one simple take-home message: no global warming does not equal no climate change. This is because the regional responses in temperature, precipitation, sea-ice, and net primary productivity vary greatly, meaning that some regions are likely to benefit to the detriment of others.

It is therefore clear that geoengineering research cannot be carried out by physical scientists and engineers alone; they need to work with those concerned with areas such as public attitudes and behaviours, ethics, economics, governance and legal issues.

The SPICE project: a geoengineering feasibility study

The SPICE project (Stratospheric Particle Injection for Climate Engineering) is a collaboration between researchers at the Universities of Bristol, Cambridge, Edinburgh and Oxford, together with Marshall Aerospace.

The project will investigate the feasibility of one so-called geoengineering technique: the idea of simulating natural processes that release small particles into the stratosphere, which then reflect a few percent of incoming solar radiation, with the effect of cooling the Earth with relative speed.

Find out more about the SPICE project.

Geoengineering options