CBS Newsletter
Winter 1993
pg. 2

A Viewgraph from the Director one foresaw that the new cores would reveal a climatic flickering of great frequency and magnitude...
Art Rosenfeld

Global Warming Warning: Don't Fool with the Climate

I am pleased to be able to bring you this column for the premier issue of our newsletter because it's an opportunity to present the Center's current favorite viewgraph. I hope that readers who decide the information presented here is useful will pass it along to others.

Everything we develop at the Center, from hardware to policy, is aimed at saving energy and money through investments that will pay for themselves in a short time. In a rational market, these ideas sell themselves. But we now know that even before the 1973 oil embargo, when the payback time for improved automobile fuel efficiency was less than a year, the idea attracted monumental disinterest. Many good ideas suffer from this apathy-preventive medicine, gun control, and hundreds of other examples. In the irrational real world, a commitment to energy efficiency is probably awaiting at least two or three hot, dry summers accompanied by significant agricultural losses and wildfires-climate effects that would heighten the sense of urgency to reduce greenhouse-gas emissions.

Until the spring of 1993, climatologists tended to talk more about "global" warming than regional changes, which might manifest themselves as warming or cooling, and as droughts or floods. Our best information on Earth's earlier climates came from a single source: the record of past temperatures locked in the Vostok ice core from Antarctica. The consensus was that the doubling of CO2 would raise the global average temperature by 2-5C, a change comparable to the global cooling of about 4 degrees C during the last ice age. This kind of talk is scary, since that 4 degree difference had great implications: the ice above New York during the last ice age was one to two kilometers thick ("Manhattan, the mile-high city"), Canadian spruce grew along the Caribbean, and if there was land suitable for wheat and corn cultivation it was probably in Mexico.

Reprinted with permission from Nature (364, 203). Copyright 1993 Macmillan Magazines, Ltd.

But now there's even scarier news in an article by J.W.C. White in the 15 July 1993 issue of Nature (364, 186). When ice-core drilling moved from dry Antarctica to snowy Greenland to get better time resolution, no one foresaw that the new cores would reveal a climatic "flickering" of great frequency and magnitude. Temperature changes amounting to plus or minus half the change in temperature of entire the ice age happened in 25 years or less during the last interglacial (the "Eemian"), when-according to Vostok-the climate should have been as stable as it is today. The Greenland Summit and Antarctic Vostok core data are compared in the diagram to the left that depicts oxygen isotope measurements, a close proxy for temperature.

One explanation is that Greenland is on the receiving end of the Gulf Stream, which dominates the climate, and therefore the agriculture of both eastern North America and western Europe. The Gulf Stream seems to have turned on and off, producing in a single decade climate changes comparable to the glacial-interglacial transition.

If Vostok suggested that climate was somewhat stable during interglacial periods in Antarctica, the new Summit core shows that the current interglacial-the time in which we live-is a distinct anomaly. It now looks as if agriculture and Western civilization may have developed during the only known window of climate stability on record. Both the most recent glacial era and the Eemian interglacial era underwent a climate flickering that we would consider catastrophic. To adapt to extreme changes like that, ecosystems and agriculture would have to move an impossible thousands of miles per decade. Of course, we could all move to some warmer, more stable part of the globe, if we could figure out where that will be and if a few billion other people haven't gotten there first. So I tend to agree with J.W.C. White: let's not fool with the fossil fuel-based switch that can turn off climate stability.

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