A new ad campaign comparing people who believe in global warming to murderers has foundered, with its conservative sponsor pulling a digital billboard down less than 24 hours after it went up in Chicago.

Drivers cruising along the city’s inbound Eisenhower Expressway on Friday may have been surprised to see Theodore J. Kaczynski, known as the Unabomber, staring at them from a huge billboard. “I still believe in global warming. Do you?” the billboard said. Just below was the Web address www.heartland.org.

The billboard was sponsored by the Heartland Institute, a libertarian organization based in Chicago that describes its chief mission as promoting free-market solutions to social and economic problems. It said it chose to feature “some of the world’s most notorious killers” on the billboards “because what these murderers and madmen have said differs very little from what spokespersons for the United Nations, journalists for the ‘mainstream’ media and liberal politicians say about global warming.”

But late Friday, the organization canceled the ad, which had drawn criticism from some global warming skeptics as well as mainstream climate scientists.