Jean-Baptiste Joseph Fourier was a renowned physicist and mathematician, having served as Napoleon Bonaparte’s science adviser, when he turned his gaze skyward.

His curiosity helped launch nearly two centuries of climate science that has spurred much of the world to take collective action to slow, stop and reverse a modern-day catastrophe in-the-making: global warming.

Given its size and distance from the sun, Fourier had reasoned, the Earth should be significantly colder, if warmed only by the sun’s rays. He theorized that gases in the Earth’s atmosphere acted as an insulator: a life-sustaining phenomenon we know now as the greenhouse effect.

Today all but one country has pledged to curb its carbon dioxide emissions -- the primary engine fueling dangerous climate change.

The lone outlier is the United States.

Since taking office, the Trump administration has been moving aggressively to avoid taking action to limit carbon pollution – and is actually moving to reverse actions taken by President Obama, which would increase carbon dioxide in the atmosphere. Scott Pruitt, the head of the Environmental Protection Agency, even wants to stage a military-style “red-team/blue-team” national debate on climate science as a way to undermine the international consensus that climate change is hazardous to our health – and our planet.

What a foolhardy and dangerous waste of time that would be. The fundamentals have long been settled.

Fournier’s epiphany in the 1820s eventually led to thousands of research projects, countless peer-reviewed scientific papers and open debate that laid the foundation for our understanding of climate change.

Around the end of the 19th century, Swedish chemist Svante Arrhenius, a Nobel Prize winner, showed that because warmer air holds more water vapors, that combination magnified the greenhouse effect. By 1938, British engineer Guy Callendar, analyzing temperature measurements going back to the previous century, demonstrated clear increases in CO 2 levels.

There were skeptics even back then. But the debate began shifting with the robust post-World War II funding for scientific research into carbon dioxide's role in warming atmospheric temperatures.

Starting in the late 1950s, American chemist Charles David Keeling began taking samples of carbon dioxide around the world and found that atmospheric concentrations of the gas had reached 280 parts per million in 1960. This month, such concentrations reached 409.6 parts per million — higher than at any time in the last 3 million years.

To keep our planet habitable, climate scientists say we must cut those concentrations to 350 parts per million.

By 1965, in a report to the president, Lyndon Johnson’s science advisory committee warned: ''Pollutants have altered on a global scale the carbon dioxide content of the air.'' Johnson relayed the warning to Congress in a special message that declared: “This generation has altered the composition of the atmosphere on a global basis,” a caution that helped pave the way for the 1970 enactment of the Clean Air Act.

In 2007, the Supreme Court ruled that the EPA is obliged under that law to regulate carbon dioxide and other greenhouse gases as pollutants. Two years later, the agency declared in an “endangerment” finding that carbon dioxide and other greenhouse gases ''threaten the public health and welfare of current and future generations.''

It was a section of the Clean Air Act that President Obama in 2015 relied on to issue his Clean Power Plan, a game-changing proposal to significantly limit carbon pollution from power plants, a plan that the Trump administration is moving to undo.

More than a quarter-century ago, under the aegis of the United Nations, the Intergovernmental Panel on Climate Change issued a landmark report -- with tens of thousands of scientists around the world participating -- declaring that CO 2 emissions were greatly increasing the concentration of greenhouse gases in the atmosphere. The fifth and most recent IPCC report, issued in 2014, found with 95-100 percent certainty that humans are the “dominant cause” of global warming.

The numbers tell the story. Of the 18 hottest years on record, 17 have occurred since 2000, and the impact is omnipresent. Sea levels are rising. Croplands are turning to desert. Species are dying off at the fastest rate in 60 million years. Storms, drought, wildfire and floods are taking a mounting toll.

Climate change has become a clear and present danger.

No wonder 97 percent of the world’s climate scientists now say human activities are fueling a steadily warming planet. Public support also is growing for national action to combat climate change.

The Pew Research Center in January found that 46 percent of Americans now believe “dealing with climate change” should be a top priority – a jump of 18 points since 2010. Even among Republicans, that support has risen from 11 percent in 2010 to 18 percent.

The history of climate science is due for a public airing on Wednesday in an unusual setting — a San Francisco courtroom. There, U.S. District Court Judge William Alsup has scheduled a five-hour “tutorial” in a case brought by the cities of Oakland and San Francisco against large oil companies for causing damage related to sea-level rises.

We hope Americans will pay attention.