• General Interest
Nature · 2001


Geoengineering is planetary-scale environmental engineering, particularly engineering aimed at counteracting the undesired side effects of other human activities. The term has usually been applied to proposals for limiting the climatic impact of industrial CO₂ emissions by countervailing measures such as the construction of space-based solar shields. Scale and intent are both central to the common meaning of geoengineering as the following examples demonstrate. First, intent without scale: ornamental gardening is the intentional manipulation of the environment to suit human desires, yet it is not geoengineering because neither the intended nor the realized effect is large-scale. Second, scale without intent: anthropogenic CO₂ emissions will change global climate, yet they are not geoengineering because they are a side effect of the use of fossil fuels to provide energy services. The distinction between geoengineering and more conventional responses to the CO₂–climate problem is fuzzy. Geoengineering has become a label for technologically overreaching proposals that are omitted from serious consideration in climate assessments. For example, few would object to applying the label to the first pair of examples below, but neither proposal rates serious consideration among climate policy-makers. Conversely, the second pair do receive serious consideration but few would call them geoengineering.

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