"Scientists can learn from this study that the general public shouldn't be expected to understand technical terms or be convinced by journal papers written in technical jargon," O'Brien said. "Journalists must explain scientific terms in ways people can understand and thereby ease the movement of those terms into general speech. That can be a slow process. Several words related to climate change diffused into the popular vocabulary over a 30-50 year timeline."

O'Brien's study found that, by 2008, several important terms in the discussion of climate change had entered popular literature from technical obscurity in the early 1900s.

These terms included:

• Biodiversity -- the degree of variation in life forms within a given area
• Holocene -- the current era of Earth's history, which started at the end of the last ice age
• Paleoclimate -the prehistoric climate, often deduced from ice cores, tree rings and pollen trapped in sediments
• Phenology -- the study of how climate and other environmental factors influence the timing of events in organisms' life cycles

Not every term was adopted at the same rate or achieved the same degree of popularity. Biodiversity, for example, came into popular use quickly in only a few years in the late 80s and early 90s. Other terms, like Holocene or phenology, have taken decades and are still relatively uncommon.

"The adoption of words into the popular vocabulary is like the evolution of species," O'Brien said. "A complex process governs why certain terms are successful and adopted into everyday speech, while others fail. For example, the term 'meme' has entered the vernacular, as opposed to the term 'culturgen,' although both refer to a discrete unit of culture, such as a saying transferred from person to person."

To observe the movement of words into popular literature, O'Brien and his colleagues searched the database of 7 million books created by Google. They used the "Ngram" feature of the database to track the number of appearances of climate change keywords in literature since 1800. The usage rate of those climate change terms was compared to the usage of "the," which is the most common word in the English language. Statistical analysis of usage rates was calculated in part by co-author William Brock, a new member of MU's Department of Economics and member of the National Academy of Sciences.

Note: A portion of O'Brien's experiment can be repeated using any computer with internet access.

1. 1. Go to http://books.google.com/ngrams
2. 2. Enter terms such as "climate change," "global warming," or "anthropogenic" and note how they have changed in usage over the past century.

Note: If no author is given, the source is cited instead.

• Language Acquisition
• Child Development

• Climate
• Global Warming

• Environmental Policies
• Popular Culture

• Consensus of scientists regarding global warming
• Temperature record
• Scientific opinion on climate change
• Climate
• Geologic temperature record
• Instrumental temperature record