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Updated 11 November 2004

Consequences Vol. 1, No. 2, Summer 1995









Quantitative information, and particularly time series, seem best conveyed in graphical form. These inventions of data graphics, which according to their student and champion Edward Tufte have been around for but about 200 years, put the present nicely in perspective: we can see where we have been and with some imagination, envision where we might be going.

In 1995 the two most common (and I think the most important) graphs that pertain to the environment are the curve of the cumulative population of the world - shown and interpreted in Carl Haub's article in this issue of CONSEQUENCES - and the much-watched and annually-updated curve of average global temperature, depicted below, which relates to the article on agriculture by Cynthia Rosenzweig and Daniel Hillel.

These two curves describe not the possible or the probable but the the fact; not what might happen but what has happened in a century's time in the way of significant global changes. They also tempt an all to simple extrapolation, for at the moment each appears to be headed - like the Dow-Jones average in a stockbroker's dream - out of the range of normal fluctuation and into an ever-upward climb. For population this seems unavoidably the case, at least for the next half-century. For temperature, maybe; or could it be no more than the illusion of a curve too-closely watched, that will soon turn down again, into the noise? To know, for sure, come back in twenty years' time. In the meantime, we must try much harder to understand why these vital series and others - like that of diminishing ozone, discussed in the third summary assessment in this issue - behave as they do. And what their implications are.

Annual values of combined land and sea temperatures for the Earth as a whole, 1860 through 1994, shown as a departure in°C from the mean temperature for the period 1951-1980. The smoothed curve was obtained by applying a 21-year, low-pass filter. Provided by David Parker, Hadley Centre, Met. Office, Bracknell, U.K.

John A. Eddy

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