Factory emissionsMay 4, 1972: The Vancouver-based Don't Make a Wave Committee, formed to oppose U.S. nuclear weapons testing in the Aleutian Islands, officially changes its name to the Greenpeace Foundation.

May 4, 1998: Theodore Kaczynski, the "Unabomber," is sentenced to four life sentences plus 30 years in the deaths of three men and the maiming of two others. From 1978 to 1995, Kaczynski mailed a series of bombs to individuals he thought were responsible for environmental destruction.

May 4, 2007: The Intergovernmental Panel on Climate Change (IPCC) issues a major report calling human-induced climate change "unequivocal," and predicting that average temperatures will rise between 2 and 11.5 degrees Fahrenheit by the year 2100.

May 4, 2012:  The Heartland Institute launches the first of a series of billboards likening advocates of climate change action to villains like the Unabomber, Charles Manson, and Osama bin Laden.  The electronic billboard alongside a Chicago freeway is taken down a few hours later after an uproar that sees Heartland supporters, funders and staffers flee the group.

Photo: Monica McGivern/Flickr

This feature is compiled by Peter Dykstra, an MNN contributor and publisher of Environmental Health News and The Daily Climate.