Informed people now understand that global warming is perhaps the most severe challenge facing the well-being of human society in the coming century. Only a dwindling minority of Americans now denies this (an even smaller fraction believe that we are regularly visited by space aliens). But those who deny it include powerful people, whose interests or ideology are threatened by government regulation of the fossil fuels that are the main source of the danger we face.

History is often used in these arguments. Its role can be direct, as when global-warming denialists assert that not long ago scientists were “spectacularly wrong” in claiming that not warming but a new Ice Age threatened us. So writes, for example, the columnist George Will, quoting from news magazines of the early 1970s. However, when people checked the history they found that Will, following a practice common among denialists, “cherry-picked” a few items that served his purpose from a much larger body of evidence.1 Here’s the real history. In the 1970s scientists discovered that climate can be catastrophically variable; they didn’t agree on what would come next; but they all agreed that they knew too little at the time to make a confident prediction. Any resemblance to the current strong scientific consensus is a fantasy.

A subtler historical fantasy is that the warnings of climate change are a political plot of radical, anti-business environmentalists (so says Michael Crichton’s recent best-selling thriller). In the actual history, concerns arose in the 1950s well before any environmentalist movement. These concerns spread among scientists who were either apolitical or supported by US military agencies. But the most important historical story that people should know is how the concern gave rise to the Intergovernmental Panel on Climate Change (IPCC).

The Reagan administration wanted to forestall pronouncements by self-appointed committees of scientists, fearing they would be “alarmist.” Conservatives promoted the IPCC’s clumsy structure, which consisted of representatives appointed by every government in the world and required to consult all the thousands of experts in repeated rounds of report-drafting in order to reach a consensus. Despite these impediments the IPCC has issued unequivocal statements on the urgent need to act.

Yet perhaps the most important use of history can come through simple explanation. Historians have often worked to illuminate current affairs through their historical descriptions of social and political forces. With a technical subject like the science of climate, history can also clarify the subject itself. Such is the main use of a website I created to describe the history of scientific work on climate change. With a quarter-million words and a thousand references, it is the equivalent of a thick tome. Several hundred visitors come to the site each day. Most are brought by a search engine, either because they entered a general term like “history global warming” or because they sought specific facts about a particular scientist or technical point. Others come through links provided by other climate Websites, blogs, or personal recommendations. What do the visitors want, and do they get it?

A monitoring program shows that many visitors go away quickly, and I presume they either found the specific fact they wanted, or decided the site was too long and scholarly. But many stay for hours, and some read every word. A visitor who reads extensively will come unexpectedly upon a request to answer a brief survey. I’ve gotten only 400-odd responses so far, but these exceptionally motivated readers are worth notice. The majority of respondents are students, typically driven by class assignments; and, indeed, the number of visits to the site exceeds a thousand per day during term-paper periods. Scientists constitute the second largest group of respondents. Most of the visitors, scientists or otherwise, attempt to sort out a subject that they feel they should understand. Some come in search of detailed textbook facts rather than history, and are disappointed. But most say they got what they sought, while others report, as an economist put it, “though I have not found what I'm looking for, I'm enjoying the CO2 history essay, and finding it helpful.”

Not only students and scientists, but also many concerned citizens (describing themselves, for example, as lawyer, physician, engineer, and “unemployed”) wanted enough information to formulate their own opinions.  Environmental activists, teachers and science writers — and a few industrial lobbyists — came not only to inform themselves but also to prepare for explaining or debating the subject. A farmer wondered how warming was affecting the weather; a chemist in Britain wondered if a rising sea level would affect a seaside home. Only a small fraction said they came to find history as such. But a strong majority of respondents said they were getting what they came to find, and many were enthusiastic about the form of presentation.

History, as we all should know, is a great help for presenting complex topics — not just thoroughly but clearly, not just with balance and nuance but with readability and even excitement. Technology lets us do this better than ever.  Historians should note that putting work on the web, with appropriate attention to “marketing” through search-engine placement and the like, can bring a real increase in the social utility of their efforts.