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Here are two recent articles (1999) which echo some major fundamental assertions long made in these pages. Among them the reality of very sudden climatic change; the "band jumps" of climates between different modes of operation - exactly as described here originally as climates switching between different "strata of stability"; and the recognition of "threshold dynamics". |
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Please note that these articles were written in 1999, whereas I had first brought up these concepts in 1985, fully 14 years before these articles.
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Original Abstracts:
GLOBAL CLIMATE CHANGE
Studies of past climate changes indicate that the Earth system has experienced greater and more rapid changes over larger areas that was generally believed possible, with jumping between fundamentally different modes of operation in as little as a few years. Most of the last 100,000 years or longer has been characterized by large and abrupt regional-to-global climate changes, and agriculture and industry have developed during anomalously stable climatic conditions. New high-resolution analysis of sediment cores indicates these past changes have been caused by "*band jumps" between modes of operation of the climate system. Recurrence of such band jumps is possible and might be affected by human activities.
R.B. Alley et al: Global climate change.
(Proc. Natl. Acad. Sci. US 31 Aug 99 96:9987)
QY: Richard B. Alley [ralley@essc.psu.edu]
ON THE POSSIBILITY OF RAPID CLIMATE CHANGE
Over the course of geologic history, the environment on Earth has been far from static. Geologic evidence suggests that 600 million years ago the atmosphere lacked sufficient oxygen to support animal life. More recently, as indicated by sediments recording conditions over the past 500,000 years, the climate of the planet varied between at least two different states.
The record from the past 150,000 years is particularly well-preserved, offering details concerning repeated climate changes. Between approximately 131,000 and 114,000 years ago, a warm period similar to the climate of today occurred. This was followed by what is called the "Wisconsin ice age", which ended approximately 12,000 years ago when the current relatively warm Holocene period began. Kendrick Taylor (Desert Research Institute, US) presents a review of the research of a large project to develop a climate record for the past 110,000 years, the author making the following points:
The author reports that by examining ice cores from Greenland, he and his colleagues have determined that climate changes large enough to have extensive impacts on our society have occurred in a time-frame of less than 10 years (my emphasis). The author suggests that the climate of Earth could change significantly during a lifetime, that we are still a long way from being able to predict such a change, but we are getting closer to an understanding of how it might occur. A pressing concern is whether anthropogenic changes in the atmosphere of the planet might perturb climate stability.
The author points out that climate is the result of the exchange of heat and mass between the land, ocean, atmosphere, ice sheets, and space. As long as changes to the land, ocean, atmosphere, and ice sheets stay below certain thresholds, climate changes will occur slowly. But climate will change rapidly if those thresholds are crossed. *Greenhouse warming, for example, by altering ocean circulation and the flow of tropical heat to the North Atlantic, could lead to rapid cooling in eastern North America, Europe and Scandinavia. Altered ocean circulation could lead to much larger changes. We have no experience predicting climate switches between stable modes.
The author suggests human ingenuity would most likely allow us to adapt to a rapid change in climate, but we would pay a larger price than our civilization has ever known. The author poses a scenario: "Imagine the economic and social cost of moving, in a 20-year period, most of our agricultural activities 500 miles south of their current locations. Imagine the social cost and famine if agriculture could not be relocated quickly enough."
Kendrick Taylor: Rapid climate change. (American Scientist Jul/Aug 1999 87:320); QY: Kendrick Taylor [kendrick@dri.edu]
Also see a synopsis of the powerful breakthrough article "What Drives Glacial Cycles" in REFERENCES in the "Biosphere" section.
Article excerpt from SCIENCE WEEK, Dec. 4. '98 (www.scienceweek.com).
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