19th Century Greenhouse Effect
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The "greenhouse effect" refers to the ability of carbon dioxide and other gases to trap heat in the earth's atmosphere. Hi I'm Dave Thurlow, and this is the Weather Notebook.

Scientists have been intensely interested in the greenhouse effect ever since the first evidence of human-induced global warming began to accumulate in the 1970s. But the idea of the greenhouse effect is much older than that. Correspondent Allan Coukell files this report.

Despite its bad press, the greenhouse effect actually keeps our planet warm. Without it, Earth would be a chilly minus 18 degrees celcius. But what happens when humans increase the amount of greenhouse gases in the atmosphere? Believe it or not, that question was first tackled more than a hundred years ago.

Bert Bolin: Svante Arrhenius was a Swedish researcher towards the end of the 19th century. And he was very interested, actually, in trying to see the role of science in society.

The predictions of Svante Arrhenius were amazingly accurate, says fellow Swede and climate scientist Bert Bolin.

Bert Bolin: And he set himself the task to assess "what would a doubling of carbon dioxide in the atmosphere mean in regard to the average temperature of the globe. And it's a remarkable paper hand computations, no direct observations of spectra, but he studied the reflected light from the moon, and deduced that a doubling of carbon dioxide, including the feedback of enhanced water vapour, would be between 5 and 6 degrees celcius.

But then he added that "how wonderful it would be if man's emissions of carbon dioxide into the atmosphere really would increase the climate of the earth that much. We would enjoy it in Sweden!

Unlike Svante Arrenhius, most scientists today believe that, on balance, an increased greenhouse effect will not be beneficial.

That's Allan Coukell of Auckland, New Zealand. The Weather Notebook is a production of the Mount Washington Observatory. Check out more about the greenhouse effect and the mountain with the world's worst weather at www.mountwashington.org.