There have been two, maybe three, landmark heat waves in the history of man-made global warming. The first was in 1988. Then as now, the eastern two-thirds of the United States was broiling while relentless drought parched soil and withered crops across the Midwest. But in Washington, the underlying problem was being named for the first time. On June 23, NASA scientist James Hansen testified to the Senate that man-made global warming had begun. The New York Times reported his remarks on Page 1, and the rest of the media at home and abroad followed suit. By year's end, "global warming" had become a common phrase in news bureaus, government ministries and living rooms around the world.

The second landmark heat wave occurred in 2003. It escaped many Americans' notice because it took place in Europe, which suffered the hottest summer on record. By August, corpses were piling up outside morgues in Paris. Initial estimates suggested a death toll of 15,000. But a comprehensive study by the European Union later concluded that, in fact, there had been 71,449 excess deaths.

As 1988 had done in the United States, the 2003 heat wave transformed the conversation about climate change in Europe. David King, the science adviser to the British government, called climate change "the most severe problem we are facing today, more serious even than the threat of terrorism." King cited the finding, reported in Nature, that global warming had been responsible for about half of the excessive temperatures of 2003. It was a historic breakthrough-the first time scientists were able to attribute a carbon fingerprint to a specific weather event. King's advocacy led Prime Minister Tony Blair and other European leaders to endorse stronger action and to press the Bush administration to do the same.

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