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When did we discover man-made climate change?


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Arrhenius CO2 study
The title page of Arrhenius's groundbreaking paper on CO2 and atmospheric warming. Photograph: Public domain

Early in the 20th century, the prevailing notion was that people could alter climates locally (for instance, by cutting down forests and ploughing virgin fields) but not globally. Of course, the ice ages and other wrenching climate shifts of the past were topics of research. But few considered them an immediate threat, and hardly anyone thought humans could trigger worldwide climate change. A few pioneering thinkers – such as Swedish chemist Svante Arrhenius in the 1890s – had already seen the potential global impact of fossil-fuel use, but their views were typically dismissed by colleagues.

Starting in 1958, precise measurements of carbon dioxide confirmed its steady increase in the atmosphere. The first computer models of global climate in the 1960s, and more complex ones thereafter, supported the idea floated by mavericks decades before: that the addition of greenhouse gases would indeed warm the climate. Finally, global temperature itself began to rise sharply in the 1980s, which helped raise the issue's profile among the media and the public as well as scientists.

This answer is drawn from The Rough Guide to Climate Change by Robert Henson.

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• This answer last updated: 28.02.2011
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