Geoengineering

Geoengineering can be described as large-scale manipulation of the climate — the deliberate, large-scale intervention in the Earth's climate system in order to moderate global warming. It is an umbrella term for various techniques that explore ways to ease or counteract the effects of global warming. These techniques are usually divided into two categories: removal of greenhouse gases (carbon dioxide removal) and management of solar radiation.

What is geoengineering?

Innovation in this field is growing and has produced many proposals — which is partly why so many ideas remain largely untested in both theory and practice. One suggested solution is mirrors in space to reflect sunlight back. Other ideas include increasing cloud cover to limit solar radiation, or fertilising the ocean to boost the amount of plankton, which would in turn consume more carbon dioxide.

The risks

Geoengineering also carries negative consequences. Limiting solar radiation, for instance, would be a problem for solar power, slowing the transition to climate-smart energy sources. It also risks locking us into a long-term dependence on geoengineering. Many people are sceptical, because these are extremely complex, global questions about which knowledge is still relatively limited.

Further difficulties arise from controlling the climate, and above all the weather, since the technology is predicted to lead to uneven outcomes — some countries gaining a better climate while others get a worse one. This has been described as "climate colonialism": the needs of the northern hemisphere prioritised over the southern, with richer countries that can afford geoengineering ending up with a better climate than poorer ones.

Lessons from volcanoes

One source of inspiration for geoengineering has been the 1991 eruption of Mount Pinatubo in the Philippines, whose enormous eruption brought the global average temperature down by about half a degree. A similar event was the 1815 eruption of Mount Tambora in Indonesia — the so-called "year without a summer" — after which global temperatures fell sharply. The cooling from these eruptions comes from emissions of sulphate particles, whose increased presence reflects the sun's rays and lowers the global temperature. It is worth noting that weather modification is not the same as geoengineering: it is limited in time, to shorter periods, and in space, to a few square kilometres at a time.

Sources: The Royal Society — Geoengineering the climate: science, governance and uncertainty (2009)