Epstein, P. and E. Mills (eds.). 2005. Published by Harvard Medical School. Sponsored by Swiss Re and the U.N. Development Programme. (Contributing Authors: Pamela Anderson, John Brownstein, Ulisses Confalonieri, Douglas Causey, Nathan Chan, Kristie L. Ebi, Jonathan H. Epstein, J. Scott Greene, Ray Hayes, Eileen Hofmann, Laurence S. Kalkstein, Tord Kjellstrom, Rebecca Lincoln, Anthony J. McMichael, Charles McNeill, David Mills, Avaleigh Milne, Alan D. Perrin, Geetha Ranmuthugala, Christine Rogers, Cynthia Rosenzweig, Colin L. Soskolne, Gary Tabor, Marta Vicarelli, X.B. Yang.)
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"Imagining the unmanageable" was to be the subtitle for the Climate Change Futures report. But the devastating series of intense, immense fall hurricanes besetting the United States displaced it. What were once extreme scenarios for the US have occurred, and the consequences have cascaded across the physical landscape, overwhelming the capacities of health, ecological and economic systems to absorb, adapt to and manage the change.

Hurricane Katrina killed over 1,000 people, displaced over a million people, and spread oil, toxins, microorganisms and deep losses throughout the US Gulf Coast. It revealed deep-seated inequities and vulnerabilities, and the shock waves have reverberated through all sectors of society. The need for prevention has become embedded into our future political landscape.

While no one event is diagnostic of climate change, the relentless pace of unusually severe weather since 2001 — prolonged droughts, heat waves of extraordinary intensity, violent windstorms and more frequent "100-year" floods — is descriptive of a changing climate. The reasons for the changed weather patterns are well understood. Five years ago, Levitus and colleagues at the US Department of Commerce's National Oceanic and Atmospheric Administration reported that the world's oceans had warmed to a depth of two miles in five decades. This year Barnett and colleagues at the Scripps Institution of Oceanography reported that the oceans had absorbed 84% of the globe's warming and that the warming pattern is unmistakably attributable to human activities.

Because of the natural cycles on which global warming is superimposed, the overall frequency of hurricanes ebbs and flows. But, since the 1970s, tropical storm destructiveness (peak winds and duration) (Emanuel 2005) and the frequency of category 4 and 5 storms (Webster et al. 2005) have essentially doubled. These observations are correlated with warming tropical seas, and the scientists project that continued warming will likely enhance the frequency of large storms still further.

Warm sea surfaces evaporate quickly and, with the deep ocean warming, the water replenishing that which evaporates is also warm and fuels subsequent storms. A warmer atmosphere also holds more water vapor, and the accelerated water cycle generates more droughts and more floods (Trenberth 2005).

This fall's succession of megastorms is, at the very least, a harbinger of what we can expect more of in a changing climate (Kerr 2005). The series may also mark a turning point in our understanding of how an energized climate system is exaggerating natural phenomena and of just how rapidly climate has changed.

This multidimensional assessment of climate change includes trends, case studies and scenarios — with a focus on health, ecological and economic dimensions. One surprise is the vulnerability of the energy sector — the primary source of increased heat in Earth systems. The risks to oil production compound the threats to the electricity grid from heat waves and the instabilities of pipelines grounded in thawing tundra.

At the same time, recovery, adaptation and prevention open the door to enormous opportunities. Developing a diversified portfolio of safe, well-distributed and nonpolluting energy sources, with hybrids and complementing technologies, can fortify energy security, bolster public health, promote economic activity and help stabilize the climate. Bold initiatives and innovative measures spearheading a well-funded, well-insured clean energy transition may be just the components needed to build a sustainable engine of growth for the 21st century.