Climate change activism is warming up this week with climate strikes, a U.N. summit, plus extra media coverage. Naturally, the apocalyptic rhetoric is warming up, too. To take only two examples among many: “2020 could be your last chance to stop an apocalypse,” warned a Los Angeles Times editorial last Sunday. What's more, Rep. Alexandria Ocasio-Cortez responded to criticism that her Green New Deal is unrealistic by saying, “What’s not realistic is Miami not existing in a few years.”

Before anyone is tempted to start believing any of these predictions, it’s worth recalling that similar predictions of impending environmental doom have been made regularly for the past half-century. They have been made by leading scientific experts as well as journalists and politicians.

Although the cause of looming disaster has changed over the decades, one thing hasn’t changed: Every prediction with a date attached has not happened. Most have been spectacularly wrong. Here are a few examples.

Young Stanford biologist Paul Ehrlich, who became famous with publication of The Population Bomb in 1968, regularly predicted global mass starvation by the 1970s and 1980s because of overpopulation and resource depletion. In 1970, Ehrlich predicted that the oceans would be dead in less than a decade, that Americans would face water rationing by 1974 and food rationing by 1980.

Ehrlich, by the way, is older but not wiser. He’s still making similar predictions with the dates changed to a few years into the future.

The next wave of doommongers focused on global cooling and the next ice age. The Guardian reported in January 1974, “Space satellites show new Ice Age coming fast.” Time got around to reporting the same news in July the same year. In 1976, the New York Times reviewed a book by young climate scientist Stephen Schneider about how to prepare for lower food production caused by global cooling. Some years later Schneider became a leading advocate of global warming alarmism.

Cooling was so '70s. By the late 1980s all the really cool people were predicting imminent catastrophes caused by global warming. James Hansen of NASA’s Goddard Institute of Space Studies beginning in 1988 predicted major droughts and up to six feet of sea level rise in the 1990s. One reporter recalled that in the late 1980s, he asked Hansen in his Manhattan office whether anything in the window would look different in 20 years. Hansen replied, “The West Side Highway [which runs along the Hudson River] will be under water. And there will be tape across the windows across the street because of high winds.”

The doommongers have made countless predictions of imminent climate catastrophes in the three decades since Hansen’s debut. Let’s focus on just one: the melting Arctic Ocean icecap.

Al Gore predicted in 2009 that the North Pole would be completely ice free in five years. A U.S. Navy scientist in 2013 concluded that the Arctic’s summer sea ice cover would all be melted by 2016.

Bogus predictions confidently made are not always harmless. The Maritime Bulletin reported that on Sept. 3, 16 “climate change warriors” making a documentary film on the melting polar icecap had to be rescued by helicopter from their ship because it was stuck in the ice halfway between Norway and the North Pole.

The Competitive Enterprise Institute has compiled copies of news clips of these wrong predictions and many more. Most of them are hilarious in hindsight, but they raise a serious question.

After 50 years of misinformed, misguided, and mistaken predictions, is there any reason to believe that the current prophecies of global warming apocalypse are likely to come true?

Myron Ebell is director of the Center for Energy and Environment at the Competitive Enterprise Institute, a free market think tank.