【Watch Psych 2: Lassie Come Home Online】

In 1975,Watch Psych 2: Lassie Come Home Online geologist Wallace Broecker penned a scientific paper warning about the still little-discussed concept of "global warming." Forty-four years later Broecker has died at 87, but not before proving himself a legendary earth scientist, repeatedly underscoring that amassing carbon dioxide in the atmosphere has stoked relentless climate change.

Ancient air trapped in ice cores proves, indisputably, that Earth's carbon dioxide (CO2) concentrations are the highest they've been in at least 800,000 years -- though other measures show that CO2 concentrations are now likely the highest they've been in 15 million years. The planet is responding: 18 of the last 19 years have been the warmest on record.

Broecker, who is now lovingly called the "grandfather of climate science," publicly warned about climate change in a 1975 report published in the academic journal Science entitled "Climatic Change: Are We on the Brink of a Pronounced Global Warming?"

"Of the climatic effects induced by man, only that for CO2 can be conclusively demonstrated to be globally significant," Broecker wrote.

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Broecker's analysis turned out to be largely accurate.

He warned that Earth would soon experience an accelerated warming trend. "It is possible that we are on the brink of a several-decades-long period of rapid warming," Broecker wrote. And over the last 40 years, Earth has indeed experienced a rapid warming trend that has been closely watched and confirmed by NASA, the National Oceanic and Atmospheric Administration (NOAA), and outside agencies and organizations.

"The trends are due almost entirely to us (and specifically the fossil-fuel related increases in CO2)," Gavin Schmidt, the director of the NASA Goddard Institute for Space Studies, told Mashable.

What's more, in the mid-1970s, Broecker predicted that carbon dioxide would become an increasingly dominant influence. He anticipated that naturally-running climate cycles -- which scientists would later pinpoint as decades-long major cooling trends in the Pacific Ocean -- had subdued global average temperatures in the late 1940s through the 1970s but would soon end. (This period has been incorrectly labeled as evidence of long-term "global cooling"). This meant that historically-high carbon dioxide levels would soon show their amassing strength, as the temporary cooling run "bottomed out."

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"Once this happens, the CO2 effect will tend to become a significant factor and by the first decade of the next century we may experience global temperatures warmer than any in the last 1000 years," Broecker wrote.

“We’re playing with an angry beast -- a climate system that has been shown to be very sensitive,” Broecker later told the Associated Press, in 1997.

Now in the second decade of the 21st century, humanity has likely experienced the highest temperatures on Earth since around 120,000 years ago -- back when hippos roamed Europe.

"This period is now the warmest in the history of modern civilization," federal scientists concluded in the congressionally-mandated Fourth National Climate Assessment.

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Today, scientists know that about half of the carbon dioxide emitted into the atmosphere by humans is absorbed by the oceans, forests, and vegetation. That's a good thing. But the looming problem is that these natural "sinks" of carbon are maxed out. The planet can't keep up with amassing carbon emissions, which might not even peak for another decade.

Critically, Broecker noted that Earth's rising temperatures are expected to continue rising, though this rise may slow down or speed up as other natural climate cycles kick in. But these temporary events can't halt a relentless warming trend.

"Future natural cycles would merely modulate this ever-steepening rise," Broecker wrote.

In the end, Broecker was right about the ensuing decades -- and beyond -- of warming, years before reliable Earth-monitoring satellites were launched into space.

"We may be in for a climatic surprise," he said.

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