Recent studies of some of nature's environmental "records" show that global warming can penetrate deep into the ocean faster than scientists have realized. In fact, some such penetration may have already begun.
The record keepers are foraminifera - "forams" for short - creatures so tiny that several could sit together on a pinhead. The mineral composition of their shells reflects the environmental conditions under which they grow. Flavia Nunes and Richard Norris at the Scripps Institution of Oceanography in La Jolla, Calif., reported earlier this month in Nature that the foram record includes a global warming event that provides a warning for our own times. Although it occurred 55 million years ago, they consider it a good analogue for studying the causes and consequences of our own global warming.
Geophysicists call the event the Paleocene/Eocene Thermal Maximum. Several degrees of global warming caused major changes in global ocean circulation patterns. This, in turn, brought warm water into normally frigid deep sea depths. It was accompanied by mass extinctions of bottom-dwelling marine life, according to the fossil record. This massive climate change happened in less than 5,000 years. However, Drs. Nunes and Norris point out that it may have happened even more quickly.
Commenting on this in the Scripps announcement, Nunes said that the key finding is that "the Earth is a system that can change very rapidly." The climate change involved a substantial rise in greenhouse gases such as carbon dioxide and methane. Although there was no human input, this is another example of the important role such gases play in climate change.