Geoengineering is fraught with problems, but research on three approaches could lead to the greatest climate benefits with the smallest chance of unintentional environmental harm.
A few decades ago, the notion of actively controlling Earth’s climate resided primarily in the writings of science fiction authors such as Frank Herbert, Isaac Asimov, and Arthur C. Clarke. Today, planetary engineering is being discussed openly by scientists and policymakers in Congress, the UK House of Commons, and many other settings. Clarke’s advice apparently struck a chord: “Politicians should read science fiction, not westerns and detective stories.”
Geoengineering can be thought of as intentionally manipulating Earth’s climate to offset the warming from greenhouse gas emissions. Its activities can be divided into two loose groups. One set of options cools Earth by removing carbon dioxide (CO2) and other greenhouse gases from air, essentially reversing the process of fossil fuel emissions. The other cools the planet by blocking or reflecting sunlight, offsetting the consequences of increased greenhouse gases for temperature but leaving the buildup of greenhouse gas concentrations unchecked.
Several developments have fueled the rise of geoengineering from fiction to possible reality in a remarkably short period of time. The first is our inability to reduce greenhouse gas emissions in any substantive way. A wealth of scientific evidence shows that Earth’s climate is already changing because of such gases, posing a threat to people and other animals and to plants. A second factor is the concern that some planetary engineering may already be needed to reduce the harmful effects of climate change, even if emissions fall in the future. A third is the hope that geoengineering could be cheaper than cutting emissions, even if it treats only a symptom of climate change, not the root cause.