The guys over at the Competitive Enterprise Institute have assembled a big stack of predictions of environmental doom over the past five decades: Paul Ehrlich’s predictions of a global famine by 1975, new ice ages “coming fast,” rising seas obliterating nations by the year 2000, children forgetting what snow is, an ice-free Arctic, U.K. prime minister Gordon Brown’s 2009 declaration that the planet had less than 90 days to prevent catastrophe, and so on.

In 2007, Al Gore accepted the Nobel Peace Prize and warned that the complete melting of the polar caps “could happen in as little as seven years.” While many remain worried about the rate of the ice cap melt, and it is on a gradual downward slope, it still had 1.6 million miles of frozen ice, tying all-time low measurements in 2007 and 2016. Some of the Arctic water will refreeze through fall and winter.

I have another to toss on the pile. The late climate scientist John Firor was highly regarded in his field and in 2002, he wrote The Crowded Greenhouse. He described a world that took climate change seriously after its effects became near-apocalyptic at the end of the first decade of the 21st century:

In the years 2010 and 2011, a sudden acceleration of global warming and the natural variability of the climate combined to produce a year with no winter in the United States. In the summer, 60 days exceeded 90 days throughout the country, and Washington D.C. saw thirty days with temperatures over 100 degrees – all while Congress was in session. Serious droughts occurred in the midwestern and western United States. The U.S. wheat crop was small, and the corn crop failed completely. The Mississippi River dried up. The Colorado River had dwindled to a trickle years before, despite policies designed to maintain some flow to Mexico.

Global surface temperatures for 2010 tied for the warmest year on record, but the only mass extinction seen that year was among House Democrats.

The point is not that Firor didn’t know what he’s talking about. He, like many other people trying to persuade the public about climate change, chose to portray the consequences of what he feared in as nightmarish a way as possible, and to communicate the urgency, he picked a date just eight years after his book’s publication date for environmental doomsday to arrive. Of course, reality unfolded nowhere nearly as direly as he envisioned.

Climate-change activists will insist this sort of dramatic license is necessary to stir a naturally apathetic public. But the metronomic regularity of doomsday predictions like these are part of why the public is so apathetic — they’ve heard it all before, and life went on. The people hearing the latest predictions of underwater coastal cities also may remember the panic over the Y2K bug, the predictions about the Mayan calendar predicting the end of the world, Pat Robertson predicting the world would end in 1982, and so on.

You don’t have to be one of those loons blocking traffic in Washington, D.C. today to see bigger fights over water rights in the Western states, that gradual decline in polar ice cap area, a gradual but irregular climb in hot days in summer, and other potential effects of climate change. But if the activists wonder why so many people tune them out, their perpetual claims of impending apocalypse are probably working against them. Most people tune out the nutty guy on the corner holding up the “THE END IS NEAR” sign.