The year 2020 is ending as it began in some ways -- with politicians sounding the alarm over the "existential threat" of climate change and its allegedly catastrophic impacts.

But, as many have noted, predictions of climate devastation have historically included major flops.

In previous decades, media reports and scientists issued warnings about glaciers disappearing in Montana, carbon concentrations intensifying, heavy snowfalls becoming sparse, and global temperature spiking by 2020.

But according to the right-leaning JunkScience.com, none of those panned out and, in some cases, the polar opposite turned out to be true.

DOOMSDAYS THAT DIDN'T HAPPEN: THINK TANK COMPILES DECADES' WORTH OF DIRE CLIMATE PREDICTIONS

Perhaps the most glaring of failed predictions involved vanishing snow and ice in the north. The Los Angeles Times reported in 2009 on a government ecologist's prediction that all of Montana's glaciers would be gone in 2020. 

The reality? As recently as January, Montana's Glacier National Park was reportedly replacing signs with that very warning.

CNN reported: "In 2017, the park was told by the agency that the complete melting off of the glaciers was no longer expected to take place so quickly due to changes in the forecast model, [park spokeswoman Gina] Kurzmen said. But tight maintenance budgets made it impossible for the park to immediately change the signs."

Other reports relayed predictions that "Snowfalls are now just a thing of the past" (The Independent in 2000), "Snows of Kilimanjaro to Vanish by 2020" (The Vancouver Sun in 2008), and "Arctic summers may be ice free by 2020" (Lancaster Eagle-Gazette in 2013).

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As JunkScience.com's report notes, the Artctic still had plenty of ice in September, and the famous African volcano had defied former Vice President Al Gore's 2006 prediction that "within a decade, there will be no more snows of Kilimanjaro."

Meanwhile, Florida has maintained a sea level rise of less than 4 inches, despite an earlier prediction it could see an increase of 2 feet by 2020. 

In 1987, the Star-Phoenix reported on NASA scientist James Hansen's warning that by the end of the 90s, average global temperature increases would reach between one-half and 1 degree Celsius. 

After quoting Hansen predicting unprecedented warmth in the following decades, the paper said: "If this proves true, by the year 2020 we will experience an average temperature increase of around three degrees, with even greater extremes." It also noted that "more conservative scientists believe a change list this will not happen until the middle of the 21st Century."

While the climate for 2050 is unknown, 2020 has already turned out slightly better than Hansen predicted. Data obtained by JunkScience.com showed the global average temperature was higher by 0.44 degrees Celsius.

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The increase in global CO2 concentration (about 23% from 1978 to 2020) also fell short of a prediction that it would double by 2020. "We learn that if present trends continue, with economics the only limit on the exploitation of fossil fuels, the CO2 concentration will have doubled by 2020," said a 1978 article in The Vancouver Sun.

Predictions like these are often held up as evidence that alarmist predictions about climate change shouldn't be taken seriously. However, these arguments have encountered pushback from critics who argue that some climate models were accurate, and discrepancies can at least partially be attributed to the types of regulations activists are seeking as a response to warming.

It's unclear just how effective those regulations have been. In 2019, the United Nations released a global assessment of environmental rules and noted that poor enforcement hindered their success.

Heartland Institute Director Steve Milloy, who also runs JunkScience.com, told Fox News that the push for policy interventions has failed.

"The world has spent trillions on climate without any obvious benefit — to the environment, climate, public health, or economy," he said.

A study from Yale University, however, argued that environmental regulations have curbed emissions even as the U.S. saw a "substantial increase in manufacturing output" from 1990 to 2008.

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At end of last year, researchers from NASA, the University of California, Berkeley, and the Massachussetts Institute of Technology released a study on climate models published between 1970 and 2007.

"We find that climate models published over the past five decades were generally quite accurate in predicting global warming in the years after publication, particularly when accounting for differences between modeled and actual changes in atmospheric CO2 and other climate drivers," the group said. 

The study specifically looked at 17 models, finding that 10 closely matched observations. That number jumped to 14 when the researchers accounted for differences between modeled and actual changes in carbon dioxide. 

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The Heartland Institute has received criticism over its funding, which has included money from ExxonMobil. The right-leaning think tank does not publicly identify its donors but defends itself by claiming that while donors can influence their research agenda, they "do not surrender control over the peer review process."

It also claims that "[d]uring 2019, The Heartland Institute raised approximately $4.6 million in support from approximately 2,000 individual, foundation, and corporate supporters. Its 2019 income came from the following sources: Foundations 67%, individuals 27%, corporations 5%. Over the years, no corporate donor has contributed more than 5% of Heartland's total receipts."