Reports of the National Center for Science Education

Madrid 1995: A sentence to change the world

In this Place & Time article, Spencer Weart pulls back the curtain on the diplomacy and wordsmithing that went into crafting the now-famous climate change statement — "The balance of evidence suggests that there is a discernible human influence on global climate" — by The Intergovernmental Panel on Climate Change.

Houghton, Bolin, and the Madrid conference center.

John Houghton (left), Bert Bolin, and the Madrid conference center. Photos courtesy Wikimedia Commons.

The Palacio Municipal de Congresos in Madrid is a typical convention center, a multi-story labyrinth of hallways and meet- ing rooms of every size, distinguished only by a spectacular mosaic by Joan Miró. Of many important meetings held here, the most epochal convened in November 1995.

The meeting’s path was set in 1988 when climate scientists, worried about future global warming, began to call on the world’s governments to consider restricting greenhouse gas emissions. The scientists admitted that a clear signal of warming might not emerge from the noise of daily weather until the start of the next century. But waiting to act would be costly.

Governments were not about to cramp their most powerful industries because a few obscure scientists were worried. For more solid advice, diplomats devised an Intergovernmental Panel on Climate Change (IPCC), a self-governing body composed of delegates appointed directly by each nation. Decisions would require consensus: any one delegate could veto anything. It looked like a design for inaction, and perhaps was meant to be.

In 1995 when hundreds of delegates assembled for three days of discussion in the huge hall of the Palacio de Congresos, their task was clear. On their desks was a tall stack of reports, drafted by 400 scientists and reviewed by 500 more from 40 countries. Few people would ever read all that. What mattered was a brief “Summary for Policymakers.” The delegates needed a final text that they could all formally approve.

If global warming was coming, the world needed to know it.

The burden lay heavily on the scientist who chaired the discussions, John Houghton, a Welsh meteorologist. A devout evangelical Christian, Houghton was equally devoted to science, “the means by which I would be able to explore and describe God’s creative work.” Unfailingly polite but immovable in his principles, he labored to keep the discussions centered on the scientific evidence. If global warming was coming, the world needed to know it.

That was poison to the representatives of fossil fuel industries who had descended in a swarm upon the conference. Openly served by the delegations from Saudi Arabia and Kuwait, they pounced on any doubt that could be raised about the science or how to describe it. Yet the science was clear. Among other evidence, there was a regional pattern of rising temperatures which neatly matched the pattern that computer models had calculated as a “signature” of the greenhouse effect. Greenhouse warming was a fact. But how certain a fact?

Debate continued until the last hour of the last day ... and beyond, into the evening past the scheduled end. The key sentence was this: “The [???] evidence [???] that there is a [???] human influence on global climate.” Was it the weight or the preponderance of evidence? Under Houghton’s judicious guidance the conference eventually bowed to the Saudis and accepted the weaker balance of evidence. Did that indicate or demonstrate a human influence? A more weaselly word was finally accepted, suggests. But was human influence significant or identifiable or, as the first draft had it, appreciable? As the hours dragged on, consensus seemed out of reach. The dinner break was cancelled and delegates grabbed sandwiches. The exhausted translators went home. Midnight came—the conference center would close in half an hour.

Bert Bolin, the IPCC’s chair and elder statesman, had scarcely spoken. But he circulated through the crowd to hold intimate conversations with every faction. A pioneering Swedish meteorologist, Bolin had deep scientific savvy, but what mattered now were his exceptional diplomatic skills. Like Houghton he was self-effacing, soft-spoken, and universally respected. When the United Kingdom’s delegate mentioned a subtle English word to Bolin, he spoke up to make one last proposal: “The balance of evidence suggests that there is a discernible human influence on global climate.” Desperate and groggy, the delegates applauded vehemently. The Saudis did not dare rise to object. Consensus!

Some of the famished delegates went out for a meal. As they were eating one of them turned to his neighbor and remarked, “This sentence will change the world.” The message was modest but unmistakable: humans must accept responsibility for altering their planet’s climate.

This article has been modified slightly from its original print format.

Spencer Weart
Short Bio

Spencer Weart was Director of the Center for History of Physics at the American Institute of Physics from 1974 to 2009; he is the author of The Discovery of Global  Warming (second edition, 2008) and maintains a website of the same name.