1.2 Modifying the Earth’s energy budget

Geoengineering techniques aim to modify Earth’s ‘energy budget’. The energy budget is similar to a financial budget. If your income is greater than your outgoings, you save money over time. Currently there is more energy coming in from the Sun than there is going out, so the planet is storing energy. The extra energy has warmed the Earth and led to other changes. The Earth’s energy budget being out of balance is not unusual in itself, only that we are inadvertently helping ‘tip the scales’ with our activities. As this continues, so will the warming.

Geoengineering aims to tip the scales back. If we could bring the energy budget back in balance, the Earth would stop warming. If we could tip them further, so there is more energy going out than coming in, it would begin to cool.

Geoengineering methods are permanent or long-lasting actions that aim to produce long-term climate change. And Geoengineering only applies to changing the Earth (prefix ‘geo-’, from the Greek meaning ‘earth’). This is different to terraforming, much imagined in science fiction, which is the idea of modifying another planet, moon or other body to be more similar to Earth so that it is suitable for human habitation.

Many kinds of geoengineering have been proposed. Some – such as launching giant mirrors into space, or creating artificial volcanic eruptions – seem utterly fantastical, straight from the pages of science fiction. Others have already been tested or are on the brink of widespread adoption.

But before you can look at fixing it, you need to answer the questions: what is ‘climate’, and how does it differ from ‘weather’?