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decades, the volume of Arctic sea ice has decreased by 40 per cent. And if North Atlantic sinking slows down, less salty Gulf Stream waters flow northward—which exacerbates the situation. In February 2002, at a worldwide meeting of oceanographers, new data on North Atlantic fresh- ening prompted many scientists to say that salinity levels in the North Atlantic are approaching a den- sity very close to the critical point at which the waters will stop sinking. One of my colleagues at Woods Hole, Terry Joyce, put it this way: "I'm in the dark as to how close to an edge or transition to a new ocean and climate regime we might be," he said. "But I know which way we are walking. We are walking toward the cliff." To that sentiment, I would add this: we are walking toward the edge of a cliff—blindfolded. FACING UP TO ABRUPT CLIMATE CHANGE Our ability to understand the potential for future Heat-bearing waters abrupt changes in climate is limited by our lack of understanding of the processes that control them. If too much fresh water enters the North Atlantic, its waters could stop sinking. The Great In the past decades, we have made great strides Conveyor would cease. Heat-bearing Gulf Stream waters (red arrows) would no longer flow . stand; arthte « . ae ati into the North Atlantic, and winters would become more severe. (Illustration by Jack Cook, in understanding Earth's atmospheric circulation WHOI: see WHOI website for animation.) system because we established a global network of thousands of meteorological stations to monitor changing countries, whose populations are often unwelcome in richer atmospheric conditions. No observational network exists to countries. In the 1840s, more than one million Irish people monitor the oceans continuously. If we just had a few more emigrated because of the potato blight. Can you imagine an strategically placed modern instruments in the oceans for an equivalent migration of many millions of people today? Keep extended time, we could understand so much more about how in mind that there were only about one billion people on Earth the oceans can cause abrupt climate changes. then. There are six billion now. At present, there is no national plan for improving our under- I believe that as a society we must face the potential for standing of the issue, and, according to a 2002 National abrupt climate change. Perhaps we can mitigate the changes. Research Council report, no policymaking body is addressing If not, at least we can still take steps to adapt to them. the many concerns raised by the potential for abrupt climate The best way to improve the effectiveness of our response is change. to have more knowledge of what can happen—and how and So here's the situation. We have unequivocal evidence of — when it can happen. Research into the causes, patterns, likeli- repeated, large, widespread, abrupt climate changes on Earth. hood and effects of abrupt climate change can help reduce our It is reasonable to assume that greenhouse warming can exacer- vulnerabilities and increase our ability to adapt. bate the possibility of precipitating large, abrupt and regional or If climate changes come abruptly, we will have less time to global climatic changes. We even have strong evidence that adjust. In other words, the more knowledge we have, the more we may be approaching a dangerous threshold—that we are reliably we can predict changes and the better our chances. squeezing a trigger in the North Atlantic. Maybe over the edge of the cliff there's just a three-inch We could downplay the relevance of past abrupt events and = drop. Or maybe there's a big, fluffy bed full of pillows. My deny the likelihood of future abrupt climate changes. But that worry is that we are indeed approaching this cliff blindfolded. could prove costly. With growing globalisation, the adverse Are you comfortable and secure with this scenario? oo impacts of climate changes are likely to spill across national boundaries—through migration, economic shocks and political About the Author: aftershocks. Robert B. Gagosian, PhD, is President and Director of the Woods Hole Oceanographic Over human his f the maj Institution (WHOI), one of the world's leading oceanographic research and education ver human istory, one of the major institutions. ways that humans have adapted to chang- | py, Gagosian has a Bachelor's degree in Chemistry from Massachusetts Institute of ing environmental and economic fortunes | Technology (1966) and a PhD in Organic Chemistry from Columbia University (1970). has been to migrate from unproductive or | He joined WHOI as an Assistant Scientist in 1972. He has participated in 14 oceano- impacted regions to more productive and | graphic cruises, including seven as Chief Scientist, and four major field programs. He hospitable regions. But today, the world's | has had a distinguished career as a marine geochemist, serving for six years as WHOI population has grown too large. There is | Director of Research and two as Senior Associate Director. He is the author or co-author less usable, unpopulated territory to absorb | of some 85 scientific papers and a number of technical reports. He was appointed to the migrants. position of WHOI Director in 1994 and President and Director in 2001. Dr Gagosian served as Chairman of the Board of Governors of the Consortium for Oceanographic Research and Education (1998-2001). He is also a Fellow of the World Economic Forum (2001-2002). In 2002 he was appointed to the Science Advisory Panel of the US Commission on Ocean Policy. For more information, visit the websites http://www.whoi.edu/home, and http://www.sab.noaa.gov/ Gagosian/20CV.htm. National borders are less open, so it is difficult for people to move to other coun- tries when droughts, floods, famines and wars occur. These boundary effects could be particularly severe for small and poor countries, whose populations are often unwelcome in richer countries. In the 1840s, more than one million Irish people emigrated because of the potato blight. Can you imagine an equivalent migration of many millions of people today? Keep in mind that there were only about one billion people on Earth then. There are six billion now. I believe that as a society we must face the potential for abrupt climate change. Perhaps we can mitigate the changes. If not, at least we can still take steps to adapt to them. The best way to improve the effectiveness of our response is to have more knowledge of what can happen—and how and when it can happen. Research into the causes, patterns, likeli- hood and effects of abrupt climate change can help reduce our vulnerabilities and increase our ability to adapt. If climate changes come abruptly, we will have less time to adjust. In other words, the more knowledge we have, the more reliably we can predict changes and the better our chances. Maybe over the edge of the cliff there's just a three-inch drop. Or maybe there's a big, fluffy bed full of pillows. My worry is that we are indeed approaching this cliff blindfolded. Are you comfortable and secure with this scenario? oo NEXUS #15 FEBRUARY — MARCH 2003 www.nexusmagazine.com