Carbon dioxide long ago

In his letter to the editor, Leonard Greiner states that carbon dioxide levels measured at a site in Hawaii have risen from 270 ppm in the 1940s to about 380 ppm now, and with this I have no difficulty (C&EN, Dec. 12, 2005, page 4). Readers need to be aware, however, that carbon dioxide levels globally were around 270 ppm much longer ago than the 1940s. In fact, they were around 270 ppm in New Testament times and farther back than that. This is known from analysis of ancient air trapped in bubbles of known age in the Antarctic ice layer.

Greiner also states that there are "large power plants under consideration in which carbon dioxide is separated from the combustion products for potential storage where it can do no harm." This is simply a description of carbon sequestration, and that is a lot further along than being "under consideration": It is very high on the international agenda for fuel technology and in the action plan for carbon dioxide reductions over the 21st century.

J. C. Jones
University of Aberdeen, Scotland