The silhouettes of emissions are seen rising from stacks of the Duke Energy Corp. Gibson Station power plant at dusk in Owensville, Ind., on July 23. Since the 19th century scientists have known that greenhouse gases like those released from burning fossil fuels affect the global climate. (Luke Sharrett/Bloomberg)

In the biggest change in how we deal with greenhouse gases since we figured out what they were, the Obama administration’s newly unveiled Clean Power Plan is set to enforce unprecedented cuts to emissions of the problematic pollutants.

The new plan is also big news for people who don’t think that greenhouse gas emissions should be restricted. Sen. Ted Cruz (R-Tex.), for example, said Sunday that climate change is an invention of scientists.

[White House set to adopt sweeping curbs on carbon pollution]

“They’re cooking the books. They’re actually adjusting the numbers,” Cruz said at a speech in California, according to Time. Later, he added that the idea of global warming is being used for political purposes to control the economy and the energy industry.

“To any power-greedy politician, this is the perfect theory. It can never, ever, ever be disproven,” Cruz said.

[Foes of clean-air rule plan multiple-front battle]

If climate change really were a conspiracy, it would be a very old, very big one.

The idea predates the airplane, the affordable automobile and every climate change researcher alive today. Scientists have been talking about the effects of burning fossil fuel on the global climate for more than a century, and they have known that greenhouse gases help warm the Earth for nearly two.

[What you need to know about Obama’s biggest global warming move yet — the Clean Power Plan]

It started with the French physicist Joseph Fourier, who in 1824 asked a deceptively simple question: If the Earth is constantly being bombarded by the Sun’s rays, why hasn’t it been getting hotter and hotter over the course of its history?

New developments in physics helped him answer it — scientists knew that heated surfaces emit radiation, so the Earth must be sending most of the solar energy absorbed during the day back into space every night. But that left Fourier with the opposite problem. If the Earth didn’t retain the heat from the Sun, what was keeping it warm?

The answer lay between the Earth’s surface and the Sun, in its atmosphere. Fourier reasoned that the atmosphere must act like a glass covering over the planet, trapping just enough heat to keep our world livable.

Fourier didn’t use the word “greenhouse effect,” in his writing, but it was more or less what he was describing. Forty years later the British physicist John Tyndall refined the theory by explaining how water vapor, carbon dioxide and other atmospheric gases are responsible for trapping heat.

By the turn of the 20th century, the Swedish scientist Svante Arrhenius had quantified exactly how atmospheric carbon dioxide impacts global temperatures. Based on years of complex and tedious number crunching, he reasoned that halving the concentration of CO2 would lower the Earth’s average temperature by five or six degrees Celsius, while doubling the concentration would raise temperatures by the same amount. His calculations weren’t exactly correct — modern scientists believe the global temperature increase would range from 1.5 to 4.5 degrees — but his finding was the foundation of almost all climate science since.

Arrhenius was also the first to propose that humans might be capable of altering atmospheric carbon dioxide levels enough to make the planet warmer, though he wasn’t much bothered by the notion. Indeed, he found the prospect quite agreeable.

“By the influence of the increasing percentage of carbonic acid in the atmosphere, we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the Earth, ages when the Earth will bring forth more abundant crops than at present, for the benefit of a rapidly propagating mankind,” he wrote in his 1908 “Worlds in the Making.”

[What it’s like when your job is to predict the end of humanity]

Not everyone agreed. Alexander Graham Bell (the same guy who invented the telephone), worried about the unchecked burning of fossil fuels and is often credited with coining the term “greenhouse effect.”

The question remained there for the next 50 years or so, while scientists busied themselves with other questions. But the influx of funding for science during the Cold War meant researchers could turn their attention to the atmosphere once more. And what they found there was striking.

In 1956, the physicist Gilbert N. Plass published a paper in American Scientist looking at increases in global temperatures and greenhouse gases since 1900. He found that the world seemed to be warming at a rate of about 1.1 degrees Celsius per century — a number that jibed exactly with the amount of carbon dioxide added to the atmosphere during that time. He concluded that the “carbon dioxide theory” for explaining global temperature increases must be the right one.

Like Arrhenius’s, Plass’s calculations needed refinement, though they more or less captured the trend that climate scientists have been talking about ever since.

But unlike Arrhenius, Plass didn’t think the trend was a positive one.

“The temperature rise from this cause may be so large in several centuries that it will present a serious problem to future generations,” he warned in his conclusion.

The next 60 or so years of climate research would back Plass up. A review of scientific studies conducted by geochemist James Lawrence Powell, who served in the administrations of presidents Ronald Reagan and George H.W. Bush, found only four authors of peer reviewed articles on the issue who did not believe in anthropogenic global warming. That was out of 69,406 studies.

Plass was wrong on one point, though: The problems caused by global temperature increases — severe droughts, melting glaciers, raging wildfires, threats to global health — didn’t take several centuries to develop. They’re happening now.